WorldWideScience

Sample records for brown dwarf kinematics

  1. Atmospheres of Brown Dwarfs

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarfs are the coolest class of stellar objects known to date. Our present perception is that Brown Dwarfs follow the principles of star formation, and that Brown Dwarfs share many characteristics with planets. Being the darkest and lowest mass stars known makes Brown Dwarfs also the coolest stars known. This has profound implication for their spectral fingerprints. Brown Dwarfs cover a range of effective temperatures which cause brown dwarfs atmospheres to be a sequence that gradually changes from a M-dwarf-like spectrum into a planet-like spectrum. This further implies that below an effective temperature of < 2800K, clouds form already in atmospheres of objects marking the boundary between M-Dwarfs and brown dwarfs. Recent developments have sparked the interest in plasma processes in such very cool atmospheres: sporadic and quiescent radio emission has been observed in combination with decaying Xray-activity indicators across the fully convective boundary.

  2. THE BROWN DWARF KINEMATICS PROJECT (BDKP). IV. RADIAL VELOCITIES OF 85 LATE-M AND L DWARFS WITH MagE

    Energy Technology Data Exchange (ETDEWEB)

    Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Logsdon, Sarah E. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Gagné, Jonathan [Institute for Research on Exoplanets (iREx), Université de Montréal, Département de Physique, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada); Bochanski, John J. [Rider University, 2083 Lawrenceville Road, Lawrenceville, NJ 08648 (United States); Faherty, Jaqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue Boston, MA 02215 (United States); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Schmidt, Sarah J. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Cruz, Kelle L., E-mail: aburgasser@ucsd.edu [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States)

    2015-09-15

    Radial velocity measurements are presented for 85 late M- and L-type very low-mass stars and brown dwarfs obtained with the Magellan Echellette spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2–3 km s{sup −1}, and combined these with astrometric and spectrophotometric data to calculate UVW velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2 ± 0.2 Gyr for sources within 20 pc. We find signficantly different kinematic ages between late-M dwarfs (4.0 ± 0.2 Gyr) and L dwarfs (6.5 ± 0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric U velocity distribution with a net inward flow, similar to gradients recently detected in local stellar samples. Simulations incorporating brown dwarf evolution and Galactic orbital dynamics are unable to reproduce the velocity asymmetry, suggesting non-axisymmetric perturbations or two distinct L dwarf populations. We also find the L dwarfs to have a kinematic age-activity correlation similar to more massive stars. We identify several sources with low surface gravities, and two new substellar candidate members of nearby young moving groups: the astrometric binary DENIS J08230313–4912012AB, a low-probability member of the β Pictoris Moving Group; and 2MASS J15104786–2818174, a moderate-probability member of the 30–50 Myr Argus Association.

  3. The Brown Dwarf Kinematics Project (BDKP). IV. Radial Velocities of 85 Late-M and L dwarfs with MagE

    CERN Document Server

    Burgasser, Adam J; Gagne, Jonathan; Bochanski, John J; Faherty, Jaqueline K; West, Andrew A; Mamajek, Eric E; Schmidt, Sarah J; Cruz, Kelle L

    2015-01-01

    Radial velocity measurements are presented for 85 late M- and L-type very low mass stars and brown dwarfs obtained with the Magellan Echellette (MagE) spectrograph. Targets primarily have distances within 20 pc of the Sun, with more distant sources selected for their unusual spectral energy distributions. We achieved precisions of 2--3 km/s, and combined these with astrometric and spectrophotometric data to calculate $UVW$ velocities. Most are members of the thin disk of the Galaxy, and velocity dispersions indicate a mean age of 5.2$\\pm$0.2 Gyr for sources within 20 pc. We find significantly different kinematic ages between late-M dwarfs (4.0$\\pm$0.2 Gyr) and L dwarfs (6.5$\\pm$0.4 Gyr) in our sample that are contrary to predictions from prior simulations. This difference appears to be driven by a dispersed population of unusually blue L dwarfs which may be more prevalent in our local volume-limited sample than in deeper magnitude-limited surveys. The L dwarfs exhibit an asymmetric $U$ velocity distribution w...

  4. Irradiated brown dwarfs

    CERN Document Server

    Casewell, S L; Lawrie, K A; Maxted, P F L; Dobbie, P D; Napiwotzki, R

    2014-01-01

    We have observed the post common envelope binary WD0137-349 in the near infrared $J$, $H$ and $K$ bands and have determined that the photometry varies on the system period (116 min). The amplitude of the variability increases with increasing wavelength, indicating that the brown dwarf in the system is likely being irradiated by its 16500 K white dwarf companion. The effect of the (primarily) UV irradiation on the brown dwarf atmosphere is unknown, but it is possible that stratospheric hazes are formed. It is also possible that the brown dwarf (an L-T transition object) itself is variable due to patchy cloud cover. Both these scenarios are discussed, and suggestions for further study are made.

  5. Searching for Brown Dwarf Outflows

    CERN Document Server

    Whelan, E T; Bacciotti, F; Randich, S; Natta, A

    2009-01-01

    As outflow activity in low mass protostars is strongly connected to ac- cretion it is reasonable to expect accreting brown dwarfs to also be driving out- flows. In the last three years we have searched for brown dwarf outflows using high quality optical spectra obtained with UVES on the VLT and the technique of spectro-astrometry. To date five brown dwarf outflows have been discovered. Here the method is discussed and the results to date outlined.

  6. A New Benchmark Brown Dwarf

    CERN Document Server

    Tinney, C G; Forveille, T; Delfosse, Xavier

    1997-01-01

    We present optical spectroscopy of three brown dwarf candidates identified in the first 1% of the DENIS sky survey. Low resolution spectra from 6430--9000A show these objects to have similar spectra to the uncertain brown dwarf candidate GD 165B. High resolution spectroscopy shows that one of the objects -- DBD 1228-1547 -- has a strong EW=2.3+-0.05A absorption line of Li I 6708A, and is therefore a brown dwarf with mass below 0.065 Msol. DBD 1228-1547 can now be the considered proto-type for objects JUST below the hydrogen burning limit.

  7. The rotation of brown dwarfs

    CERN Document Server

    Scholz, Aleks

    2016-01-01

    One of the characteristic features of low-mass stars is their propensity to shed large amounts of angular momentum throughout their evolution. This distinguishs them from brown dwarfs which remain fast rotators over timescales of gigayears. Brown dwarfs with rotation periods longer than a couple of days have only been found in star forming regions and young clusters. This is a useful constraint on the mass dependency of mechanisms for angular momentum regular in stars. Rotational braking by disks and winds become highly inefficient in the substellar regime. In this short review I discuss the observational evidence for the fast rotation in brown dwarfs, the implications, and the link to the spin-mass relation in planets.

  8. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing...... masses of the brown dwarf companions are 0.02 ± 0.01 M⊙ and 0.019 ± 0.002 M⊙ for MOA-2011-BLG-104/OGLE-2011-BLG-0172 and MOA-2011-BLG-149, respectively, and both companions are orbiting low-mass M dwarf host stars. More microlensing brown dwarfs are expected to be detected as the number of lensing events...

  9. Microlensing, Brown Dwarfs and GAIA

    CERN Document Server

    Evans, N W

    2014-01-01

    The GAIA satellite can precisely measure the masses of nearby brown dwarfs and lower main sequence stars by the microlensing effect. The scientific yield is maximised if the microlensing event is also followed with ground-based telescopes to provide densely sampled photometry. There are two possible strategies. First, ongoing events can be triggered by photometric or astrometric alerts by GAIA. Second, events can be predicted using known high proper motion stars as lenses. This is much easier, as the location and time of an event can be forecast. Using the GAIA source density, we estimate that the sample size of high proper motion ($>300$ mas yr$^{-1}$) brown dwarfs needed to provide predictable events during the 5 year mission lifetime is surprisingly small, only of the order of a hundred. This is comparable to the number of high proper motion brown dwarfs already known from the work of the UKIDSS Large Area Survey and the all-sky WISE satellite. Provided the relative parallax of the lens and the angular Ein...

  10. The Structure of Brown Dwarf Circumstellar Disks

    OpenAIRE

    Walker, Christina; Wood, Kenneth; Lada, C. J.; Robitaille, Thomas; Bjorkman, J. E.; Whitney, Barbara

    2004-01-01

    We present synthetic spectra for circumstellar disks that are heated by radiation from a central brown dwarf. Under the assumption of vertical hydrostatic equilibrium, our models yield scaleheights for brown dwarf disks in excess of three times those derived for classical T Tauri (CTTS) disks. If the near-IR excess emission observed from brown dwarfs is indeed due to circumstellar disks, then the large scaleheights we find could have a significant impact on the optical and near-IR detectabili...

  11. Microlensing Binaries with Candidate Brown Dwarf Companions

    DEFF Research Database (Denmark)

    Shin, I.-G; Han, C.; Gould, A.;

    2012-01-01

    Brown dwarfs are important objects because they may provide a missing link between stars and planets, two populations that have dramatically different formation histories. In this paper, we present the candidate binaries with brown dwarf companions that are found by analyzing binary microlensing ...

  12. Disks, accretion and outflows of brown dwarfs

    CERN Document Server

    Joergens, V; Liu, Y; Pascucci, I; Whelan, E; Alcala, J; Biazzo, K; Costigan, G; Gully-Santiago, M; Henning, Th; Natta, A; Rigliaco, E; Rodriguez-Ledesma, V; Sicilia-Aguilar, A; Tottle, J; Wolf, S

    2012-01-01

    Characterization of the properties of young brown dwarfs are important to constraining the formation of objects at the extreme low-mass end of the IMF. While young brown dwarfs share many properties with solar-mass T Tauri stars, differences may be used as tests of how the physics of accretion/outflow and disk chemistry/dissipation depend on the mass of the central object. This article summarizes the presentations and discussions during the splinter session on 'Disks, accretion and outflows of brown dwarfs' held at the CoolStars17 conference in Barcelona in June 2012. Recent results in the field of brown dwarf disks and outflows include the determination of brown dwarf disk masses and geometries based on Herschel far-IR photometry (70-160 um), accretion properties based on X-Shooter spectra, and new outflow detections in the very low-mass regime.

  13. The Brown Dwarf-Exoplanet Connection

    CERN Document Server

    Burgasser, Adam J

    2009-01-01

    Brown dwarfs are commonly regarded as easily-observed templates for exoplanet studies, with comparable masses, physical sizes and atmospheric properties. There is indeed considerable overlap in the photospheric temperatures of the coldest brown dwarfs (spectral classes L and T) and the hottest exoplanets. However, the properties and processes associated with brown dwarf and exoplanet atmospheres can differ significantly in detail; photospheric gas pressures, elemental abundance variations, processes associated with external driving sources, and evolutionary effects are all pertinent examples. In this contribution, I review some of the basic theoretical and empirical properties of the currently known population of brown dwarfs, and detail the similarities and differences between their visible atmospheres and those of extrasolar planets. I conclude with some specific results from brown dwarf studies that may prove relevant in future exoplanet observations.

  14. Young Brown Dwarfs as Giant Exoplanet Analogs

    CERN Document Server

    Faherty, Jacqueline K; Rice, Emily L; Riedel, Adric

    2013-01-01

    Young brown dwarfs and directly-imaged exoplanets have enticingly similar photometric and spectroscopic characteristics, indicating that their cool, low gravity atmospheres should be studied in concert. Similarities between the peculiar shaped H band, near and mid-IR photometry as well as location on color magnitude diagrams provide important clues about how to extract physical properties of planets from current brown dwarf observations. In this proceeding we discuss systems newly assigned to 10-150 Myr nearby moving groups, highlight the diversity of this uniform age-calibrated brown dwarf sample, and reflect on their implication for understanding current and future planetary data.

  15. Giant planet and brown dwarf formation

    CERN Document Server

    Chabrier, G; Janson, M; Rafikov, R

    2014-01-01

    Understanding the dominant brown dwarf and giant planet formation processes, and finding out whether these processes rely on completely different mechanisms or share common channels represents one of the major challenges of astronomy and remains the subject of heated debates. It is the aim of this review to summarize the latest developments in this field and to address the issue of origin by confronting different brown dwarf and giant planet formation scenarios to presently available observational constraints. As examined in the review, if objects are classified as "Brown Dwarfs" or "Giant Planets" on the basis of their formation mechanism, it has now become clear that their mass domains overlap and that there is no mass limit between these two distinct populations. Furthermore, while there is increasing observational evidence for the existence of non-deuterium burning brown dwarfs, some giant planets, characterized by a significantly metal enriched composition, might be massive enough to ignite deuterium bur...

  16. Radial Velocity Variability of Field Brown Dwarfs

    CERN Document Server

    Prato, L; Rice, E L; McLean, I S; Kirkpatrick, J D; Burgasser, A J; Kim, S S

    2015-01-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity precision of ~2 km/s, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1 sigma upper limit for very low mass binary frequency is 18%. Our targets included 7 known, wide brown dwarf binary systems. No significant radial velocity variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant ...

  17. Microlensing Planet Around Brown-Dwarf

    CERN Document Server

    Han, C; Udalski, A; Sumi, T; Gaudi, B S; Gould, A; Bennett, D P; Tsapras, Y; Szymański, M K; Kubiak, M; Pietrzyński, G; Soszyński, I; Skowron, J; Kozłowski, S; Poleski, R; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Abe, F; Bond, I A; Botzler, C S; Chote, P; Freeman, M; Fukui, A; Furusawa, K; Harris, P; Itow, Y; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Ohnishi, K; Rattenbury, N J; Saito, To; Sullivan, D J; Sweatman, W L; Suzuki, D; Tristram, P J; Wada, K; Yock, P C M; Batista, V; Christie, G; Choi, J -Y; DePoy, D L; Dong, Subo; Hwang, K -H; Kavka, A; Lee, C -U; Monard, L A G; Natusch, T; Ngan, H; Park, H; Pogge, R W; Porritt, I; Shin, I -G; Tan, T G; Yee, J C; Alsubai, K A; Bramich, D M; Browne, P; Dominik, M; Horne, K; Hundertmark, M; Ipatov, S; Kains, N; Liebig, C; Snodgrass, C; Steele, I A; Street, R A

    2013-01-01

    Observations of accretion disks around young brown dwarfs have led to the speculation that they may form planetary systems similar to normal stars. While there have been several detections of planetary-mass objects around brown dwarfs (2MASS 1207-3932 and 2MASS 0441-2301), these companions have relatively large mass ratios and projected separations, suggesting that they formed in a manner analogous to stellar binaries. We present the discovery of a planetary-mass object orbiting a field brown dwarf via gravitational microlensing, OGLE-2012-BLG-0358Lb. The system is a low secondary/primary mass ratio (0.080 +- 0.001), relatively tightly-separated (~0.87 AU) binary composed of a planetary-mass object with 1.9 +- 0.2 Jupiter masses orbiting a brown dwarf with a mass 0.022 M_Sun. The relatively small mass ratio and separation suggest that the companion may have formed in a protoplanetary disk around the brown dwarf host, in a manner analogous to planets.

  18. Shaping the Brown Dwarf Desert: Predicting the Primordial Brown Dwarf Binary Distributions from Turbulent Fragmentation

    CERN Document Server

    Jumper, Peter H

    2013-01-01

    The formation of brown dwarfs (BDs) poses a key challenge to star formation theory. The observed dearth of nearby ($\\leq 5$ AU) brown dwarf companions to solar-mass stars, known as the brown dwarf desert, as well as the tendency for low-mass binary systems to be more tightly-bound than stellar binaries, have been cited as evidence for distinct formation mechanisms for brown dwarfs and stars. In this paper, we explore the implications of the minimal hypothesis that brown dwarfs in binary systems originate via the same fundamental fragmentation mechanism as stars, within isolated, turbulent giant molecular cloud cores. We demonstrate analytically that the scaling of specific angular momentum with turbulent core mass naturally gives rise to the brown dwarf desert, as well as wide brown-dwarf binary systems. Further, we demonstrate analytically that the turbulent core fragmentation model also naturally predicts that very low-mass (VLM) binary and BD/BD systems are more tightly-bound than stellar systems. In addit...

  19. The Luminosities of the Coldest Brown Dwarfs

    CERN Document Server

    Tinney, C G; Kirkpatrick, J Davy; Cushing, Mike; Morley, Caroline V; Wright, Edward L

    2014-01-01

    In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant planets of our own Solar System (at around 130K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures of in the range 1500-1000K). Distance measurements for these objects deliver absolute magnitudes that make critical tests of our understanding of very cool atmospheres. Here we report new distances for nine Y dwarfs and seven very-late T dwarfs. These reveal that Y dwarfs do indeed represent a continuation of the T dwarf sequence to both fainter luminosities and cooler temperatures. They also show that the coolest objects display a large range in absolute magnitude for a given photometric colour. The latest atmospheric models show good agreement with the majority of these ...

  20. A Very Cool Pair of Brown Dwarfs

    Science.gov (United States)

    2011-03-01

    Observations with the European Southern Observatory's Very Large Telescope, along with two other telescopes, have shown that there is a new candidate for the coldest known star: a brown dwarf in a double system with about the same temperature as a freshly made cup of tea - hot in human terms, but extraordinarily cold for the surface of a star. This object is cool enough to begin crossing the blurred line dividing small cold stars from big hot planets. Brown dwarfs are essentially failed stars: they lack enough mass for gravity to trigger the nuclear reactions that make stars shine. The newly discovered brown dwarf, identified as CFBDSIR 1458+10B, is the dimmer member of a binary brown dwarf system located just 75 light-years from Earth [1]. The powerful X-shooter spectrograph on ESO's Very Large Telescope (VLT) was used to show that the composite object was very cool by brown dwarf standards. "We were very excited to see that this object had such a low temperature, but we couldn't have guessed that it would turn out to be a double system and have an even more interesting, even colder component," said Philippe Delorme of the Institut de planétologie et d'astrophysique de Grenoble (CNRS/Université Joseph Fourier), a co-author of the paper. CFBDSIR 1458+10 is the coolest brown dwarf binary found to date. The dimmer of the two dwarfs has now been found to have a temperature of about 100 degrees Celsius - the boiling point of water, and not much different from the temperature inside a sauna [2]. "At such temperatures we expect the brown dwarf to have properties that are different from previously known brown dwarfs and much closer to those of giant exoplanets - it could even have water clouds in its atmosphere," said Michael Liu of the University of Hawaii's Institute for Astronomy, who is lead author of the paper describing this new work. "In fact, once we start taking images of gas-giant planets around Sun-like stars in the near future, I expect that many of them

  1. Brown dwarfs as close companions to white dwarfs

    Science.gov (United States)

    Stringfellow, Guy S.; Bodenheimer, Peter; Black, David C.

    1990-01-01

    The influence of the radiation flux emitted by a white dwarf primary on the evolution of a closely orbiting brown dwarf (BD) companion is investigated. Full stellar evolutionary calculations are presented for both isolated and thermal bath cases, including effects of large variations in the atmospheric grain opacities. High grain opacities significantly increase the radii of the BDs, but the thermal bath does not. The major influence of the thermal bath is to increase substantially the surface temperature and luminosity of the BD at a given age. These results are compared with the observational properties of the possible BD companion of the white dwarf G29-38. Inclusion of both physical effects, high grain opacities and thermal bath, increases the mass range (0.034-0.063 solar masses) of viable models significantly, yet the final determination of whether the object is indeed a BD requires improvements in the observations of the system's properties.

  2. Spectroscopy of Putative Brown Dwarfs in Taurus

    CERN Document Server

    Luhman, K L

    2010-01-01

    Quanz and coworkers have reported the discovery of the coolest known member of the Taurus star-forming complex (L2+/-0.5) and Barrado and coworkers have identified a possible protostellar binary brown dwarf in the same region. We have performed infrared spectroscopy on the former and the brighter component of the latter to verify their substellar nature. The resulting spectra do not exhibit the strong steam absorption bands that are expected for cool objects, demonstrating that they are not young brown dwarfs. The optical magnitudes and colors for these sources are also indicative of background stars rather than members of Taurus. Although the fainter component of the candidate protostellar binary lacks spectroscopy, we conclude that it is a galaxy rather than a substellar member of Taurus based on its colors and the constraints on its proper motion.

  3. Comparison of cloud models for Brown Dwarfs

    CERN Document Server

    Helling, Ch; Allard, F; Dehn, M; Hauschildt, P; Homeier, D; Lodders, K; Marley, M; Rietmeijer, F; Tsuji, T; Woitke, P

    2007-01-01

    A test case comparison is presented for different dust cloud model approaches applied in brown dwarfs and giant gas planets. We aim to achieve more transparency in evaluating the uncertainty inherent to theoretical modelling. We show in how far model results for characteristic dust quantities vary due to different assumptions. We also demonstrate differences in the spectral energy distributions resulting from our individual cloud modelling in 1D substellar atmosphere simulations

  4. Astrometry of brown dwarfs with Gaia

    CERN Document Server

    de Bruijne, J H J

    2014-01-01

    Europe's Gaia spacecraft will soon embark on its five-year mission to measure the absolute parallaxes of the complete sample of 1,000 million objects down to 20 mag. It is expected that thousands of nearby brown dwarfs will have their astrometry determined with sub-milli-arcsecond standard errors. Although this level of accuracy is comparable to the standard errors of the relative parallaxes that are now routinely obtained from the ground for selected, individual objects, the absolute nature of Gaia's astrometry, combined with the sample increase from one hundred to several thousand sub-stellar objects with known distances, ensures the uniqueness of Gaia's legacy in brown-dwarf science for the coming decade(s). We shortly explore the gain in brown-dwarf science that could be achieved by lowering Gaia's faint-end limit from 20 to 21 mag and conclude that two spectral-type sub-classes could be gained in combination with a fourfold increase in the solar-neighbourhood-volume sampled by Gaia and hence in the numbe...

  5. Brown Dwarfs From Mythical to Ubiquitous

    CERN Document Server

    Liebert, J

    1998-01-01

    Astrophysical objects below the stellar mass limit but well above the mass of Jupiter eluded discovery for nearly three decades after Kumar first proposed their existence, and for two decades after Tarter proposed the name "brown dwarfs." The first unambiguous discoveries of planetary (51 Peg B) and brown dwarf (Gliese 229B) companions occurred about three years ago. Yet while extrasolar planets are now being discovered at a breathtaking rate, brown dwarf companions to ordinary stars are apparently rare; likewise imaging surveys show that GL229B is still unique as a distant companion to a low mass star. On the other hand, the deep imaging studies of the Pleiades and several imbedded young clusters show that the mass function (ie. of single objects) extends in substantial numbers down to at least 40 Jupiter masses. The high mass / stellar density Orion Nebula Cluster may have relatively fewer low mass objects. In the field of the solar neighborhood, the infrared sky surveys DENIS and especially 2MASS show that...

  6. Parallax measurements of cool brown dwarfs

    CERN Document Server

    Manjavacas, E; Reffert, S; Henning, T

    2013-01-01

    Accurate parallax measurements allow us to determine physical properties of brown dwarfs, and help us to constrain evolutionary and atmospheric models, break the age-mass degeneracy and reveal unresolved binaries. We measured absolute trigonometric parallaxes and proper motions of 6 cool brown dwarfs using background galaxies to establish an absolute reference frame. We derive the absolute J-mag. The six T brown dwarfs in our sample have spectral types between T2.5 and T7.5 and magnitudes in J between 13.9 and 18.0, with photometric distances below 25 pc. The observations were taken in the J-band with the Omega-2000 camera on the 3.5 m telescope at Calar Alto, during a time period of 27 months, between March 2011 and June 2013. The number of epochs varied between 11 and 12 depending on the object. The reduction of the astrometric measurements was carried out with respect to the field stars. The relative parallax and proper motions were transformed into absolute measurements using the background galaxies in ou...

  7. Forming isolated brown dwarfs by turbulent fragmentation

    Science.gov (United States)

    Lomax, O.; Whitworth, A. P.; Hubber, D. A.

    2016-05-01

    We use Smoothed Particle Hydrodynamics to explore the circumstances under which an isolated very low mass pre-stellar core can be formed by colliding turbulent flows and collapse to form a brown dwarf. Our simulations suggest that the flows need not be very fast, but do need to be very strongly convergent, i.e. the gas must flow in at comparable speeds from all sides, which seems rather unlikely. We therefore revisit the object Oph-B11, which André et al. have identified as a pre-stellar core with mass between ˜0.020 M⊙ and ˜0.030 M⊙. We re-analyse the observations using a Markov-chain Monte Carlo method that allows us (i) to include the uncertainties on the distance, temperature and dust mass opacity, and (ii) to consider different Bayesian prior distributions of the mass. We estimate that the posterior probability that Oph-B11 has a mass below the hydrogen-burning limit at ˜0.075 M⊙, is between 0.66 and 0.86 . We conclude that, if Oph-B11 is destined to collapse, it probably will form a brown dwarf. However, the flows required to trigger this appear to be so contrived that it is difficult to envisage this being the only way, or even a major way, of forming isolated brown dwarfs. Moreover, Oph-B11 could easily be a transient, bouncing, prolate core, seen end-on; there could, indeed should, be many such objects masquerading as very low mass pre-stellar cores.

  8. Extrasolar Giant Planet and Brown Dwarf Models

    CERN Document Server

    Burrows, A; Lunine, J I; Guillot, M P; Saumon, D S; Freedman, R S

    1997-01-01

    With the discovery of the companions of 51 Peg, 55 Cnc, $\\tau$ Boo, gas giants and/or brown dwarfs with masses from 0.3 through 60 times that of Jupiter assume a new and central role in the emerging field of extrasolar planetary studies. In this contribution, we describe the structural, spectral, and evolutionary characteristics of such exotic objects, as determined by our recent theoretical calculations. These calculations can be used to establish direct search strategies via SIRTF, ISO, and HST (NICMOS), and via various ground--based adaptive optics and interferometric platforms planned for the near future.

  9. Explaining millimeter-sized particles in brown dwarf disks

    NARCIS (Netherlands)

    P. Pinilla; T. Birnstiel; M. Benisty; L. Ricci; A. Natta; C.P. Dullemond; C. Dominik; L. Testi

    2013-01-01

    Context. Planets have been detected around a variety of stars, including low-mass objects, such as brown dwarfs. However, such extreme cases are challenging for planet formation models. Recent sub-millimeter observations of disks around brown dwarf measured low spectral indices of the continuum emis

  10. Investigating the magnetism of brown dwarfs

    CERN Document Server

    Kuzmychov, O; Harrington, D; Kuhn, J

    2013-01-01

    We model the spectra of two brown dwarfs observed with the low resolution spectropolarimeter LRIS (Keck observatory) during several rotational phases in order to infer their magnetic properties. The spectra modeled include the intensity signal (Stokes I/Ic) as well as the polarimetric signals (Stokes Q/Ic, U/Ic, and V/Ic), all coming from the 0-0 vibrational band of the CrH molecule at approx. 8610 A. In order to model the Stokes profiles, we solve a set of the radiative transfer equations for the CrH transitions in the presence of an external magnetic field. We present the upper limits for the magnetic field strengths for the objects observed, based on the modeling of the intensity signal I/Ic and the signal-to-noise information only. The proper modeling of the polarimetric signals, that requires more careful data reduction, is underway. Nevertheless, our preliminary results show a hint for kG magnetic fields for both brown dwarfs, that is in a good agreement with the result obtained from the simultaneous ra...

  11. Population Properties of Brown Dwarf Analogs to Exoplanets

    Science.gov (United States)

    Faherty, Jacqueline K.; Riedel, Adric R.; Cruz, Kelle L.; Gagne, Jonathan; Filippazzo, Joseph C.; Lambrides, Erini; Fica, Haley; Weinberger, Alycia; Thorstensen, John R.; Tinney, C. G.; Baldassare, Vivienne; Lemonier, Emily; Rice, Emily L.

    2016-07-01

    We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 18 new parallaxes (including 10 for comparative field objects), 38 new radial velocities, and 19 new proper motions. We also add low- or moderate-resolution near-infrared spectra for 43 sources confirming their low surface gravity features. Among the full sample, we find 39 objects to be high-likelihood or new bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. Using this age-calibrated sample, we investigate trends in gravity classification, photometric color, absolute magnitude, color-magnitude, luminosity, and effective temperature. We find that gravity classification and photometric color clearly separate 5-130 Myr sources from >3 Gyr field objects, but they do not correlate one to one with the narrower 5-130 Myr age range. Sources with the same spectral subtype in the same group have systematically redder colors, but they are distributed between 1 and 4σ from the field sequences and the most extreme outlier switches between intermediate- and low-gravity sources either confirmed in a group or not. The absolute magnitudes of low-gravity sources from the J band through W3 show a flux redistribution when compared to equivalently typed field brown dwarfs that is correlated with spectral subtype. Low-gravity, late-type L dwarfs are fainter at J than the field sequence but brighter by W3. Low-gravity M dwarfs are >1 mag brighter than field dwarfs in all bands from J through W3. Clouds, which are a far more dominant opacity source for L dwarfs, are the likely cause. On color-magnitude diagrams, the latest-type, low-gravity L dwarfs drive the elbow of the L/T transition up to 1 mag redder and 1 mag fainter than field dwarfs at M J but are consistent with or brighter than the elbow at M W1 and M W2. We conclude that low-gravity dwarfs carry an extreme version of the cloud conditions of field objects to lower temperatures

  12. Global HI Kinematics in Dwarf Galaxies

    CERN Document Server

    Stilp, Adrienne M; Warren, Steven R; Skillman, Evan; Ott, Juergen; Koribalski, Baerbel

    2013-01-01

    HI line widths are typically interpreted as a measure of ISM turbulence, which is potentially driven by star formation. In an effort to better understand the possible connections between line widths and star formation, we have characterized \\hi{} kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce an average, global \\hi{} line profile. These "superprofiles" are composed of a central narrow peak (~6-10 km/s) with higher-velocity wings to either side that contain ~10-15% of the total flux. The superprofiles are all very similar, indicating a universal global HI profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of star formation (SF), with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical proper...

  13. Discovery of Nearest Known Brown Dwarf

    Science.gov (United States)

    2003-01-01

    Bright Southern Star Epsilon Indi Has Cool, Substellar Companion [1] Summary A team of European astronomers [2] has discovered a Brown Dwarf object (a 'failed' star) less than 12 light-years from the Sun. It is the nearest yet known. Now designated Epsilon Indi B, it is a companion to a well-known bright star in the southern sky, Epsilon Indi (now "Epsilon Indi A"), previously thought to be single. The binary system is one of the twenty nearest stellar systems to the Sun. The brown dwarf was discovered from the comparatively rapid motion across the sky which it shares with its brighter companion : the pair move a full lunar diameter in less than 400 years. It was first identified using digitised archival photographic plates from the SuperCOSMOS Sky Surveys (SSS) and confirmed using data from the Two Micron All Sky Survey (2MASS). Follow-up observations with the near-infrared sensitive SOFI instrument on the ESO 3.5-m New Technology Telescope (NTT) at the La Silla Observatory confirmed its nature and has allowed measurements of its physical properties. Epsilon Indi B has a mass just 45 times that of Jupiter, the largest planet in the Solar System, and a surface temperature of only 1000 °C. It belongs to the so-called 'T dwarf' category of objects which straddle the domain between stars and giant planets. Epsilon Indi B is the nearest and brightest T dwarf known. Future studies of the new object promise to provide astronomers with important new clues as to the formation and evolution of these exotic celestial bodies, at the same time yielding interesting insights into the border zone between planets and stars. TINY MOVING NEEDLES IN GIANT HAYSTACKS ESO PR Photo 03a/03 ESO PR Photo 03a/03 [Preview - JPEG: 400 x 605 pix - 92k [Normal - JPEG: 1200 x 1815 pix - 1.0M] Caption: PR Photo 03a/03 shows Epsilon Indi A (the bright star at far right) and its newly discovered brown dwarf companion Epsilon Indi B (circled). The upper image comes from one of the SuperCOSMOS Sky

  14. Accretion and Outflow Activity in Brown Dwarfs

    CERN Document Server

    Riaz, B

    2013-01-01

    An investigation of the magnetospheric accretion and outflow signatures in sub-stellar objects is a natural extension of similar studies conducted on classical T Tauri stars (CTTS), and helps understand if brown dwarfs (BDs) follow the same formation mechanism as stars. Over the past decade, evidence for accretion in very low-mass stars (VLMs) and BDs has been accumulated using various techniques, which indicates that the overall accretion characteristics are continuous across the sub-stellar boundary. Outflow activity in VLMs and BDs has been confirmed based on spectro-astrometry of forbidden emission lines observed in the optical, and in millimetre continuum images of CO J=2-1 emission. This review summarizes the past and current state of observational work on accretion and outflow activity in VLMs and BDs, particularly with the advent of new instruments such as VLT/X-Shooter which has allowed the study of several accretion and outflow indicators over a wider wavelength range.

  15. New Light on Dark Stars Red Dwarfs, Low-Mass Stars, Brown Dwarfs

    CERN Document Server

    Reid, I. Neill

    2005-01-01

    There has been very considerable progress in research into low-mass stars, brown dwarfs and extrasolar planets during the past few years, particularly since the fist edtion of this book was published in 2000. In this new edtion the authors present a comprehensive review of both the astrophysical nature of individual red dwarf and brown dwarf stars and their collective statistical properties as an important Galactic stellar population. Chapters dealing with the observational properies of low-mass dwarfs, the stellar mass function and extrasolar planets have been completely revised. Other chapters have been significantly revised and updated as appropriate, including important new material on observational techniques, stellar acivity, the Galactic halo and field star surveys. The authors detail the many discoveries of new brown dwarfs and extrasolar planets made since publication of the first edition of the book and provide a state-of-the-art review of our current knowledge of very low-mass stars, brown dwarfs a...

  16. GLOBAL H I KINEMATICS IN DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Stilp, Adrienne M.; Dalcanton, Julianne J. [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Warren, Steven R.; Skillman, Evan [Minnesota Institute for Astrophysics, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Ott, Juergen [National Radio Astronomy Observatory, P.O. Box O, 1003 Lopezville Road, Socorro, NM 87801 (United States); Koribalski, Baerbel [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping, NSW 1710 (Australia)

    2013-03-10

    H I line widths are typically interpreted as a measure of interstellar medium turbulence, which is potentially driven by star formation (SF). In an effort to better understand the possible connections between line widths and SF, we have characterized H I kinematics in a sample of nearby dwarf galaxies by co-adding line-of-sight spectra after removing the rotational velocity to produce average global H I line profiles. These ''superprofiles'' are composed of a central narrow peak ({approx}6-10 km s{sup -1}) with higher-velocity wings to either side that contain {approx}10%-15% of the total flux. The superprofiles are all very similar, indicating a universal global H I profile for dwarf galaxies. We compare characteristics of the superprofiles to various galaxy properties, such as mass and measures of SF, with the assumption that the superprofile represents a turbulent peak with energetic wings to either side. We use these quantities to derive average scale heights for the sample galaxies. When comparing to physical properties, we find that the velocity dispersion of the central peak is correlated with ({Sigma}{sub HI}). The fraction of mass and characteristic velocity of the high-velocity wings are correlated with measures of SF, consistent with the picture that SF drives surrounding H I to higher velocities. While gravitational instabilities provide too little energy, the SF in the sample galaxies does provide enough energy through supernovae, with realistic estimates of the coupling efficiency, to produce the observed superprofiles.

  17. The formation of low-mass stars and brown dwarfs

    CERN Document Server

    Stamatellos, Dimitris

    2013-01-01

    It is estimated that ~60% of all stars (including brown dwarfs) have masses below 0.2Msun. Currently, there is no consensus on how these objects form. I will briefly review the four main theories for the formation of low-mass objects: turbulent fragmentation, ejection of protostellar embryos, disc fragmentation, and photo-erosion of prestellar cores. I will focus on the disc fragmentation theory and discuss how it addresses critical observational constraints, i.e. the low-mass initial mass function, the brown dwarf desert, and the binary statistics of low-mass stars and brown dwarfs. I will examine whether observations may be used to distinguish between different formation mechanisms, and give a few examples of systems that strongly favour a specific formation scenario. Finally, I will argue that it is likely that all mechanisms may play a role in low-mass star and brown dwarf formation.

  18. Brown dwarfs forming in discs: Where to look for them?

    Directory of Open Access Journals (Sweden)

    Stamatellos D.

    2011-07-01

    Full Text Available A large fraction of the observed brown dwarfs may form by gravitational fragmentation of unstable discs. This model reproduces the brown dwarf desert, and provides an explanation for the existence of planetary-mass objects and for the binary properties of low-mass objects. We have performed an ensemble of radiative hydrodynamic simulations and determined the statistical properties of the low-mass objects produced by gravitational fragmentation of discs. We suggest that there is a population of brown dwarfs loosely bound on wide orbits (100–5000 AU around Sun-like stars that surveys of brown dwarf companions should target. Our simulations also indicate that planetary-mass companions to Sun-like stars are unlikely to form by disc fragmentation.

  19. Brown dwarfs forming in discs: where to look for them?

    CERN Document Server

    Stamatellos, Dimitris

    2009-01-01

    A large fraction of the observed brown dwarfs may form by gravitational fragmentation of unstable discs. This model reproduces the brown dwarf desert, and provides an explanation the existence of planetary-mass objects and for the binary properties of low-mass objects. We have performed an ensemble of radiative hydrodynamic simulations and determined the statistical properties of the low-mass objects produced by gravitational fragmentation of discs. We suggest that there is a population of brown dwarfs loosely bound on wide orbits (100-5000 AU) around Sun-like stars that surveys of brown dwarf companions should target. Our simulations also indicate that planetary-mass companions to Sun-like stars are unlikely to form by disc fragmentation.

  20. Direct detection of brown dwarf companions of nearby stars

    Science.gov (United States)

    Oppenheimer, Ben R.

    This thesis presents the first direct detection of a substellar companion of a star other than the Sun. This object, a brown dwarf called Gliese 229B, presented a unique opportunity to characterize low-temperature brown dwarfs for the first time. The discovery and initial spectrum of Gliese 229B show that the object must be substellar based on its intrinsic luminosity of 6.4×10-6Lsolar and its cool surface temperature, 900 K. Detailed study of Gliese 229B includes extensive photometric measurements from 0.5 to 12 μm, high signal-to-noise ratio spectroscopy from 0.84 to 5.0 μm and the detection of 0'' t; yr-1 of orbital motion. These results are presented in Chapters 2 and 3. A detailed review of brown dwarf science leads to a complete and scientifically meaningful definition of the classes ``planet'' and ``brown dwarf''' in Chapter 1. After the discovery of Gliese 229B, which was found in a survey for companions of young stars, we began an extensive search for brown dwarf companions in orbit about all known stars within 8 pc of the Sun and with δ > -35°. The search includes optical coronagraphic and infrared direct imaging of these stars, conducted on the Palomar 60' and 200' telescopes respectively. The search was designed to find companions of each star without color bias. While the search revealed no other brown dwarf companions of these stars, it did uncover 6 new stellar companions. The sensitivity limits of the survey permit the detection of brown dwarfs up to four magnitudes fainter than Gliese 229B around 90% of the stars. The sensitivity is, however, not uniform spatially or from star to star. This limits our ability to make strong statements about the prevalence of brown dwarf companions of nearby stars. The survey does have sensitivity to all stellar companions between 3 and 30' from the survey stars, however. Chapter 5 describes related work on very low-mass stars in the Pleiades star cluster. This optical spectroscopy involved trying to find a

  1. Relation between Brown Dwarfs and Exoplanets

    CERN Document Server

    Torres, Lauren Melissa Flor; Schröeder, Klauss-Peter; Caretta, César A; Jack, Dennis

    2016-01-01

    One of the most debated subjects in Astronomy since the discovery of exoplanets is how can we distinguish the most massive of such objects from very-low mass stars like Brown Dwarfs (BDs)? We have been looking for evidences of a difference in physical characteristics that could be related to different formation processes. Using a new diagnostic diagram that compares the baryonic gravitational potential (BGP) with the distances from their host stars, we have classified a sample of 355 well-studied exoplanets according to their possible structures. We have then compared the exoplanets to a sample of 87 confirmed BDs, identifying a range in BGP that could be common to both objects. By analyzing the mass-radius relations (MRR) of the exoplanets and BDs in those different BGP ranges, we were able to distinguish different characteristic behaviors. By comparing with models in the literature, our results suggest that BDs and massive exoplanets might have similar structures dominated by liquid metallic hydrogen (LMH).

  2. Tidal evolution of planets around brown dwarfs

    CERN Document Server

    Bolmont, Emeline; Leconte, Jérémy

    2011-01-01

    The tidal evolution of planets orbiting brown dwarfs (BDs) presents an interesting case study because BDs' terrestrial planet forming region is located extremely close-in. In fact, the habitable zones of BDs range from roughly 0.001 to 0.03 AU and for the lowest-mass BDs are located interior to the Roche limit. In contrast with stars, BDs spin up as they age. Thus, the corotation distance moves inward. This has important implications for the tidal evolution of planets around BDs. We used a standard equilibrium tidal model to compute the orbital evolution of a large ensemble of planet-BD systems. We tested the effect of numerous parameters such as the initial semi-major axis and eccentricity, the rotation period of the BD, the masses of both the BD and planet, and the tidal dissipation factors. We find that all planets that form at or beyond the corotation distance and with initial eccentricities smaller than \\sim 0.1 are repelled from the BD. Some planets initially interior to corotation can survive if their ...

  3. Forming isolated brown dwarfs by turbulent fragmentation

    CERN Document Server

    Lomax, O; Hubber, D A

    2016-01-01

    We use Smoothed Particle Hydrodynamics to explore the circumstances under which an isolated very-low-mass prestellar core can be formed by colliding turbulent flows and collapse to form a brown-dwarf. Our simulations suggest that the flows need not be very fast, but do need to be very strongly convergent, i.e. the gas must flow in at comparable speeds from all sides, which seems rather unlikely. We therefore revisit the object Oph-B11, which Andre, Ward-Thompson and Greaves (2012) have identified as a prestellar core with mass between $\\sim 0.020\\,\\mathrm{M_\\odot}$ and $\\sim 0.030\\,\\mathrm{M_\\odot}$. We reanalyse the observations using a Markov-chain Monte Carlo method that allows us (i) to include the uncertainties on the distance, temperature and dust mass opacity, and (ii) to consider different Bayesian prior distributions of the mass. We estimate that the posterior probability that Oph-B11 has a mass below the hydrogen burning limit at $\\sim 0.075\\,\\mathrm{M_\\odot}$, is between 0.66 and 0.86. We conclude ...

  4. WISE Y Dwarfs As Probes of the Brown Dwarf-Exoplanet Connection

    CERN Document Server

    Beichman, C; Kirkpatrick, J Davy; Cushing, Michael C; Dodson-Robinson, Sally; Marley, Mark S; Morley, Caroline V; Wright, E L

    2014-01-01

    We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (6 T8-9 and 9 Y dwarfs) using the Keck II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we derive parallactic and proper motions for these objects which put the majority within 15 parsecs. For ages greater than a few Gyr, as suggested from kinematic considerations, we find masses of 10-30 M$_{Jup}$ based on standard models for the evolution of low mass objects with a range of mass estimates for individual objects depending on the model in question. Three of the coolest objects have effective temperatures $\\sim$ 350 K and inferred masses of 10-15 M$_{Jup}$. Our parallactic distances confirm earlier photometric estimates (Kirkpatrick et al. 2012) and direct measurements (Marsh et al. 2013, Beichman et al. 2013, Dupuy and Krauss 2013) and suggest that the number of objects with masses below about 15 M$_{Jup}$ must be flat or declining relative to higher mass objects....

  5. A resolved outflow of matter from a Brown Dwarf

    CERN Document Server

    Whelan, E T; Bacciotti, F; Natta, A; Testi, L; Randich, S; Whelan, Emma T.; Ray, Thomas P.; Bacciotti, Francesca; Natta, Antonella; Testi, Leonardo; Randich, Sofia

    2005-01-01

    The birth of stars involves not only accretion but also, counter-intuitively, the expulsion of matter in the form of highly supersonic outflows. Although this phenomenon has been seen in young stars, a fundamental question is whether it also occurs amongst newborn brown dwarfs: these are the so-called 'failed stars', with masses between stars and planets, that never manage to reach temperatures high enough for normal hydrogen fusion to occur. Recently, evidence for accretion in young brown dwarfs has mounted, and their spectra show lines that are suggestive of outflows. Here we report spectro-astrometric data that spatially resolve an outflow from a brown dwarf. The outflow's characteristics appear similar to, but on a smaller scale than, outflows from normal young stars. This result suggests that the outflow mechanism is universal, and perhaps relevant even to the formation of planets.

  6. A resolved outflow of matter from a brown dwarf.

    Science.gov (United States)

    Whelan, Emma T; Ray, Thomas P; Bacciotti, Francesca; Natta, Antonella; Testi, Leonardo; Randich, Sofia

    2005-06-01

    The birth of stars involves not only accretion but also, counter-intuitively, the expulsion of matter in the form of highly supersonic outflows. Although this phenomenon has been seen in young stars, a fundamental question is whether it also occurs among newborn brown dwarfs: these are the so-called 'failed stars', with masses between stars and planets, that never manage to reach temperatures high enough for normal hydrogen fusion to occur. Recently, evidence for accretion in young brown dwarfs has mounted, and their spectra show lines that are suggestive of outflows. Here we report spectro-astrometric data that spatially resolve an outflow from a brown dwarf. The outflow's characteristics appear similar to, but on a smaller scale than, outflows from normal young stars. This result suggests that the outflow mechanism is universal, and perhaps relevant even to the formation of planets.

  7. Detectability of dirty dust grains in brown dwarf atmospheres

    CERN Document Server

    Helling, C H; Thi, W F; Woitke, P; Helling, CH.

    2006-01-01

    Dust clouds influence the atmospheric structure of brown dwarfs, and they affect the heat transfer and change the gas-phase chemistry. However, the physics of their formation and evolution is not well understood. In this letter, we predict dust signatures and propose a potential observational test of the physics of dust formation in brown dwarf atmosphere based on the spectral features of the different solid components predicted by dust formation theory. A momentum method for the formation of dirty dust grains (nucleation, growth, evaporation, drift) is used in application to a static brown dwarf atmosphere structure to compute the dust grain properties, in particular the heterogeneous grain composition and the grain size. Effective medium and Mie theory are used to compute the extinction of these spherical grains. Dust formation results in grains whose composition differs from that of grains formed at equilibrium. Our kinetic model predicts that solid amorphous SiO2[s] (silica) is one of the most abundant so...

  8. Gaia, Non-Single Stars, Brown Dwarfs, and Exoplanets

    CERN Document Server

    Sozzetti, A

    2014-01-01

    In its all-sky survey, Gaia will monitor astrometrically and photometrically millions of main-sequence stars with sufficient sensitivity to brown dwarf companions within a few AUs from their host stars and to transiting brown dwarfs on very short periods, respectively. Furthermore, thousands of detected ultra-cool dwarfs in the backyard of the Sun will have direct (absolute) distance estimates from Gaia, and for these Gaia astrometry will be of sufficient precision to reveal any orbiting companions with masses as low as that of Jupiter. Gaia observations thus bear the potential for critical contributions to many important questions in brown dwarfs astrophysics (how do they form in isolation and as companions to stars? Can planets form around them? What are their fundamental parameters such as ages, masses, and radii? What is their atmospheric physics?), and their connection to stars and planets. The full legacy potential of Gaia in the realm of brown dwarf science will be realized when combined with other det...

  9. Brown Dwarfs: A New Class of Stellar Lighthouse

    Science.gov (United States)

    2007-04-01

    Brown dwarfs, thought just a few years ago to be incapable of emitting any significant amounts of radio waves, have been discovered putting out extremely bright "lighthouse beams" of radio waves, much like pulsars. A team of astronomers made the discovery using the National Science Foundation's Very Large Array (VLA) radio telescope. Artist's Conception of Brown Dwarf Artist's conception of "mini-aurorae" at poles of brown dwarf, producing beams of strong radio emission. CREDIT: Hallinan et al., NRAO/AUI/NSF Click on image for page of graphics and full information "These beams rotate with the brown dwarf, and we see them when the beam passes over the Earth. This is the same way we see pulses from pulsars," said Gregg Hallinan of the National University of Ireland Galway. "We now think brown dwarfs may be a missing link between pulsars and planets in our own Solar System, which also emit, but more weakly," he added. Brown dwarfs are enigmatic objects that are too small to be stars but too large to be planets. They are sometimes called "failed stars" because they have too little mass to trigger hydrogen fusion reactions at their cores, the source of the energy output in larger stars. With roughly 15 to 80 times the mass of Jupiter, the largest planet in our Solar System, brown dwarfs were long thought to exist. However, it was not until 1995 that astronomers were able to actually find one. A few dozen now are known. In 2001, a group of summer students at the National Radio Astronomy Observatory used the VLA to observe a brown dwarf, even though they had been told by seasoned astronomers that brown dwarfs are not observable at radio wavelengths. Their discovery of a strong flare of radio emission from the object surprised astronomers and the students' scientific paper on the discovery was published in the prestigous scientific journal Nature. Hallinan and his team observed a set of brown dwarfs with the VLA last year, and found that three of the objects emit extremely

  10. Non-equilibrium chemistry in the atmospheres of brown dwarfs

    CERN Document Server

    Saumon, D S; Freedman, R S; Lodders, K

    2002-01-01

    Carbon monoxide and ammonia have been detected in the spectrum of Gl 229B at abundances that differ substantially from those obtained from chemical equilibrium. Vertical mixing in the atmosphere is a mechanism that can drive slowly reacting species out of chemical equilibrium. We explore the effects of vertical mixing as a function of mixing efficiency and effective temperature on the chemical abundances in the atmospheres of brown dwarfs and on their spectra. The models compare favorably with the observational evidence and indicate that vertical mixing plays an important role in brown dwarf atmospheres.

  11. Forward and Inverse Modeling of Brown Dwarf Atmospheres

    Science.gov (United States)

    Fortney, Jonathan

    Ultracool dwarfs (UCDs), here defined as the L, T, and Y spectral classes, consist of the lowest mass stars and the substellar brown dwarfs. Over 1200 are currently known, from effective temperatures of 2400 K down to "room temperature" objects of 300 K. Observations of UCDs show tremendous diversity in their spectral characteristics. However, factors such as metallicity, non-solar C/O ratios, surface gravity, vertical mixing efficiency, cloud levels, and cloud thickness remain largely unexplored within atmosphere models. This leads to a very limited understanding of the physical and chemical causes of brown dwarf diversity. One of the main motivations of this proposal is to greatly expand the kinds of modeling efforts that we envision for UCD science to obtain fundamentally new insights from the spectra of several hundred objects. First, we will expand our self-consistent grids of combined atmosphere and evolution models. With this traditional approach we can test the sensitivity of synthetic spectra of changes in parameters like surface gravity, cloud thickness, partial cloudiness, cloud particle size, and vertical mixing efficiency. Second, we will use powerful retrieval techniques to invert the model-to-data comparison problem. These Bayesian techniques allow the inference of P-T profile structure and molecular abundances, directly from the data. The first target populations are benchmark brown dwarfs, which have a well-studied main sequence companion, and where metallicity, age, and even mass can be independently constrained. The second is the 500+ UCDs across all spectral types that have NIR spectra already in hand in the SpeX spectral library. The third population is brown dwarfs that are variable in emission. This work is directly relevant to the NASA Astrophysics Theory (ATP) program. The proposed falls within the ATP scope of "Stellar Astrophysics and Exoplanets," which specifically includes brown dwarfs. The current proposal both facilitates "the

  12. DISCOVERY OF AN UNUSUALLY RED L-TYPE BROWN DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Gizis, John E.; Castro, Philip J. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Faherty, Jacqueline K. [Department of Astronomy, Universidad de Chile, Cerro Calan, Camino El Observatorio 1515, Las Condes (Chile); Liu, Michael C.; Aller, Kimberly M. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Shaw, John D. [Department of Physics, West Chester University, West Chester, PA 19383 (United States); Vrba, Frederick J.; Harris, Hugh C. [U.S. Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001 (United States); Deacon, Niall R. [Max-Planck-Institut fur Astronomie, Konigstuhl 17 D-69117, Heidelberg (Germany)

    2012-10-01

    We report the discovery of an unusually red brown dwarf found in a search for high proper motion objects using WISE and 2MASS data. WISEP J004701.06+680352.1 is moving at 0.''44 yr{sup -1} and lies relatively close to the Galactic plane (b = 5.{sup 0}2). Near-infrared photometry and spectroscopy reveals that this is one of the reddest (2MASS J - K{sub s} 2.55 {+-} 0.08 mag) field L dwarfs yet detected, making this object an important member of the class of unusually red L dwarfs. We discuss evidence for thick condensate clouds and speculate on the age of the object. Although models by different research groups agree that thick clouds can explain the red spectrum, they predict dramatically different effective temperatures, ranging from 1100 K to 1600 K. This brown dwarf is well suited for additional studies of extremely dusty substellar atmospheres because it is relatively bright (K{sub s} = 13.05 {+-} 0.03 mag), which should also contribute to an improved understanding of young gas-giant planets and the transition between L and T brown dwarfs.

  13. Habitable Planets Eclipsing Brown Dwarfs: Strategies for Detection and Characterization

    CERN Document Server

    Belu, Adrian R; Raymond, Sean N; Pallé, Enric; Street, Rachel; Sahu, D K; Von Braun, Kaspar; Bolmont, Emeline; Figueira, Pedro; Anupama, G C; Ribas, Ignasi

    2013-01-01

    Given the very close proximity of their habitable zones, brown dwarfs represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper we develop search strategies to find habitable planets transiting brown dwarfs depending on their maximum habitable orbital period (PHZ out). Habitable planets with PHZ out shorter than the useful duration of a night (e.g. 8-10 hrs) can be screened with 100 percent completeness from a single location and in a single night (near-IR). More luminous brown dwarfs require continuous monitoring for longer duration, e.g. from space or from a longitude-distributed network (one test scheduling achieved - 3 telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known brown dwarfs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5 +5.6-1.4 and 56 +31-13 percent, depending on our assumptions. We calculate that bro...

  14. BROWN DWARF BINARIES FROM DISINTEGRATING TRIPLE SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Reipurth, Bo [Institute for Astronomy and NASA Astrobiology Institute University of Hawaii, 640 N. Aohoku Place, Hilo, HI 96720 (United States); Mikkola, Seppo, E-mail: reipurth@ifa.hawaii.edu, E-mail: Seppo.Mikkola@utu.fi [Tuorla Observatory, University of Turku, Väisäläntie 20, Piikkiö (Finland)

    2015-04-15

    Binaries in which both components are brown dwarfs (BDs) are being discovered at an increasing rate, and their properties may hold clues to their origin. We have carried out 200,000 N-body simulations of three identical stellar embryos with masses drawn from a Chabrier IMF and embedded in a molecular core. The bodies are initially non-hierarchical and undergo chaotic motions within the cloud core, while accreting using Bondi–Hoyle accretion. The coupling of dynamics and accretion often leads to one or two dominant bodies controlling the center of the cloud core, while banishing the other(s) to the lower-density outskirts, leading to stunted growth. Eventually each system transforms either to a bound hierarchical configuration or breaks apart into separate single and binary components. The orbital motion is followed for 100 Myr. In order to illustrate 200,000 end-states of such dynamical evolution with accretion, we introduce the “triple diagnostic diagram,” which plots two dimensionless numbers against each other, representing the binary mass ratio and the mass ratio of the third body to the total system mass. Numerous freefloating BD binaries are formed in these simulations, and statistical properties are derived. The separation distribution function is in good correspondence with observations, showing a steep rise at close separations, peaking around 13 AU and declining more gently, reaching zero at separations greater than 200 AU. Unresolved BD triple systems may appear as wider BD binaries. Mass ratios are strongly peaked toward unity, as observed, but this is partially due to the initial assumptions. Eccentricities gradually increase toward higher values, due to the lack of viscous interactions in the simulations, which would both shrink the orbits and decrease their eccentricities. Most newborn triple systems are unstable and while there are 9209 ejected BD binaries at 1 Myr, corresponding to about 4% of the 200,000 simulations, this number has grown to

  15. NTT Observations Indicate that Brown Dwarfs Form Like Stars

    Science.gov (United States)

    2001-06-01

    Dusty Disks Detected around Very Young Substellar Objects in the Orion Nebula Summary An international team of astronomers [2] is announcing today the discovery of dusty disks surrounding numerous very faint objects that are believed to be recently formed Brown Dwarfs in the Orion Nebula [3]. This finding is based on detailed observations with SOFI, a specialised infrared-sensitive instrument at the ESO 3.5-m New Technology Telescope at the La Silla Observatory. It is of special interest because it sheds light on the origin and nature of substellar objects, known as "Brown Dwarfs" . In particular, these results suggest that Brown Dwarfs share a common origin with stars and that Brown Dwarfs are more similar in nature to stars than to planets and, like stars, have the potential to form with accompanying systems of planets. Moreover, the presence of dusty protoplanetary disks around the faintest objects in the Orion Nebula cluster confirms both the membership of these faint stars in the cluster and their nature as bona-fide substellar objects, making this the largest population of Brown Dwarf objects yet known . These important results are being reported today to the American Astronomical Society Meeting in Pasadena (California, USA). PR Photo 22a/01 : Infrared picture of the Orion Nebula (NTT + SOFI). PR Photo 22b/01 : "Finding Chart" for Very Young Brown Dwarfs in the Orion Nebula. PR Photo 22c/01 : Animated GIF presentation of PR Photos 22a+b/01. Faint substellar objects in the Milky Way Over the past 5 years, several groups of astronomers have identified a type of very faint, substellar objects within our Milky Way galaxy. These gaseous objects have very low masses and will never shine like normal stars because they cannot achieve central temperatures high enough for sustained thermal nuclear reactions to occur in their cores. Such objects weigh less than about 7% of our Sun and have been variously called "Brown Dwarfs" , "Failed Stars" or "Super Planets

  16. Accretion-ejection connection in the young brown dwarf candidate ISO-Cha1 217

    CERN Document Server

    Whelan, E T; Bacciotti, F; Nisini, B; Bonito, R; Antoniucci, S; Stelzer, B; Biazzo, K; D'Elia, V; Ray, T P

    2014-01-01

    As the number of observed brown dwarf outflows is growing it is important to investigate how these outflows compare to the well studied jets from young stellar objects. A key point of comparison is the relationship between outflow and accretion activity and in particular the ratio between the mass outflow and accretion rates ($\\dot{M}_{out}$/$\\dot{M}_{acc}$). The brown dwarf candidate ISO-ChaI 217 was discovered by our group, as part of a spectro-astrometric study of brown dwarfs, to be driving an asymmetric outflow with the blue-shifted lobe having a position angle of $\\sim$ 20$^{\\circ}$. The aim here is to further investigate the properties of ISO-ChaI 217, the morphology and kinematics of its outflow, and to better constrain ($\\dot{M}_{out}$/$\\dot{M}_{acc}$). The outflow is spatially resolved in the $[SII]\\lambda \\lambda 6716,6731$ lines and is detected out to $\\sim$ 1\\farcs6 in the blue-shifted lobe and ~ 1" in the red-shifted lobe. The asymmetry between the two lobes is confirmed although the velocity as...

  17. SHAPING THE BROWN DWARF DESERT: PREDICTING THE PRIMORDIAL BROWN DWARF BINARY DISTRIBUTIONS FROM TURBULENT FRAGMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    Jumper, Peter H.; Fisher, Robert T., E-mail: robert.fisher@umassd.edu [University of Massachusetts Dartmouth, 285 Old Westport Road, N. Dartmouth, MA 02747-2300 (United States)

    2013-05-20

    The formation of brown dwarfs (BDs) poses a key challenge to star formation theory. The observed dearth of nearby ({<=}5 AU) BD companions to solar mass stars, known as the BD desert, as well as the tendency for low-mass binary systems to be more tightly bound than stellar binaries, has been cited as evidence for distinct formation mechanisms for BDs and stars. In this paper, we explore the implications of the minimal hypothesis that BDs in binary systems originate via the same fundamental fragmentation mechanism as stars, within isolated, turbulent giant molecular cloud cores. We demonstrate analytically that the scaling of specific angular momentum with turbulent core mass naturally gives rise to the BD desert, as well as wide BD binary systems. Further, we show that the turbulent core fragmentation model also naturally predicts that very low mass binary and BD/BD systems are more tightly bound than stellar systems. In addition, in order to capture the stochastic variation intrinsic to turbulence, we generate 10{sup 4} model turbulent cores with synthetic turbulent velocity fields to show that the turbulent fragmentation model accommodates a small fraction of binary BDs with wide separations, similar to observations. Indeed, the picture which emerges from the turbulent fragmentation model is that a single fragmentation mechanism may largely shape both stellar and BD binary distributions during formation.

  18. Using Narrow Band Photometry to Classify Stars and Brown Dwarfs

    CERN Document Server

    Mainzer, A K; Sievers, J L; Young, E T; Lean, Ian S. Mc

    2004-01-01

    We present a new system of narrow band filters in the near infrared that can be used to classify stars and brown dwarfs. This set of four filters, spanning the H band, can be used to identify molecular features unique to brown dwarfs, such as H2O and CH4. The four filters are centered at 1.495 um (H2O), 1.595 um (continuum), 1.66 um (CH4), and 1.75 um (H2O). Using two H2O filters allows us to solve for individual objects' reddenings. This can be accomplished by constructing a color-color-color cube and rotating it until the reddening vector disappears. We created a model of predicted color-color-color values for different spectral types by integrating filter bandpass data with spectra of known stars and brown dwarfs. We validated this model by making photometric measurements of seven known L and T dwarfs, ranging from L1 - T7.5. The photometric measurements agree with the model to within +/-0.1 mag, allowing us to create spectral indices for different spectral types. We can classify A through early M stars to...

  19. A non-uniform distribution of the nearest brown dwarfs

    CERN Document Server

    Bihain, G

    2016-01-01

    The census of solar neighbours is still complemented by new discoveries, mainly of very low-mass, faint dwarfs, close to or within the substellar domain. These discoveries contribute to a better understanding of the field population; its origin in terms of Galactic dynamics and (sub)stellar formation and evolution. Also, the nearest stars and brown dwarfs at any given age allow the most precise direct characterization, including the search for planetary companions. We aim to further assess the substellar census on the Galactic plane. We projected the 136 stars and 26 brown dwarfs known at <6.5 pc on the Galactic plane and evaluated their distributions. Stars present a uniform- and brown dwarfs a non-uniform distribution, with 21 objects behind the Sun and only five ahead relative to the direction of rotation of the Galaxy. This substellar configuration has a probability of 0.098$^{+10.878}_{-0.098}$% relative to uniformity. The helio- and geocentric nature of the distribution suggests it might result in pa...

  20. CLOUDS search for variability in brown dwarf atmospheres

    CERN Document Server

    Goldman, B; Marley, M S; Artigau, É; Baliyan, K S; Béjar, V J S; Caballero, J A; Chanover, N; Connelley, M; Doyon, R; Forveille, T; Ganesh, S; Gelino, C R; Hammel, H B; Holtzman, J; Joshi, S; Joshi, U C; Leggett, S K; Liu, M C; Martín, E L; Mohan, V; Nadeau, D; Sagar, R; Stephens, D

    2008-01-01

    Context: L-type ultra-cool dwarfs and brown dwarfs have cloudy atmospheres that could host weather-like phenomena. The detection of photometric or spectral variability would provide insight into unresolved atmospheric heterogeneities, such as holes in a global cloud deck. Aims: It has been proposed that growth of heterogeneities in the global cloud deck may account for the L- to T-type transition as brown dwarf photospheres evolve from cloudy to clear conditions. Such a mechanism is compatible with variability. We searched for variability in the spectra of five L6 to T6 brown dwarfs in order to test this hypothesis. Methods: We obtained spectroscopic time series using VLT/ISAAC, over 0.99-1.13um, and IRTF/SpeX for two of our targets, in J, H and K bands. We search for statistically variable lines and correlation between those. Results: High spectral-frequency variations are seen in some objects, but these detections are marginal and need to be confirmed. We find no evidence for large amplitude variations in s...

  1. Structure and Kinematics of the Nearby Dwarf Galaxy UGCA 105

    CERN Document Server

    Schmidt, Philip; Gentile, Gianfranco; Oh, Se-Heon; Schuberth, Ylva; Bekhti, Nadya Ben; Winkel, Benjamin; Klein, Uli

    2013-01-01

    Owing to their shallow stellar potential, dwarf galaxies possess thick gas disks, which makes them good candidates for studies of the galactic vertical kinematical structure. We present 21 cm line observations of the isolated nearby dwarf irregular galaxy UGCA 105, taken with the Westerbork Synthesis Radio Telescope (WSRT), and analyse the geometry of its neutral hydrogen (HI) disk and its kinematics. The galaxy shows a fragmented HI distribution. It is more extended than the optical disk, and hence allows one to determine its kinematics out to very large galacto-centric distances. The HI kinematics and morphology are well-ordered and symmetric for an irregular galaxy. The HI is sufficiently extended to observe a substantial amount of differential rotation. Moreover, UGCA 105 shows strong signatures for the presence of a kinematically anomalous gas component. Performing tilted-ring modelling by use of the least-squares fitting routine TiRiFiC, we found that the HI disk of UGCA 105 has a moderately warped and ...

  2. Exploration of the brown dwarf regime around solar-like stars by CoRoT

    CERN Document Server

    Csizmadia, Szilárd

    2016-01-01

    Aims. A summary of the CoRoT brown dwarf investigations are presented. Methods. Transiting brown dwarfs around solar like stars were studied by using the photometric time-series of CoRoT, and ground based radial velocity measurements. Results. CoRoT detected three transiting brown dwarfs around F and G dwarf stars. The occurence rate of brown dwarfs was found to be 0.20 +/- 0.15% around solar-like stars which is compatible with the value obtained by Kepler-data.

  3. a Faint and Lonely Brown Dwarf in the Solar Vicinity

    Science.gov (United States)

    1997-04-01

    Discovery of KELU-1 Promises New Insights into Strange Objects Brown Dwarfs are star-like objects which are too small to become real stars, yet too large to be real planets. Their mass is too small to ignite those nuclear processes which are responsible for the large energies and high temperatures of stars, but it is much larger than that of the planets we know in our solar system. Until now, very few Brown Dwarfs have been securely identified as such. Two are members of double-star systems, and a few more are located deep within the Pleiades star cluster. Now, however, Maria Teresa Ruiz of the Astronomy Department at Universidad de Chile (Santiago de Chile), using telescopes at the ESO La Silla observatory, has just discovered one that is all alone and apparently quite near to us. Contrary to the others which are influenced by other objects in their immediate surroundings, this new Brown Dwarf is unaffected and will thus be a perfect object for further investigations that may finally allow us to better understand these very interesting celestial bodies. It has been suggested that Brown Dwarfs may constitute a substantial part of the unseen dark matter in our Galaxy. This discovery may therefore also have important implications for this highly relevant research area. Searching for nearby faint stars The story of this discovery goes back to 1987 when Maria Teresa Ruiz decided to embark upon a long-term search (known as the Calan-ESO proper-motion survey ) for another type of unusual object, the so-called White Dwarfs , i.e. highly evolved, small and rather faint stars. Although they have masses similar to that of the Sun, such stars are no larger than the Earth and are therefore extremely compact. They are particularly interesting, because they most probably represent the future end point of evolution of our Sun, some billions of years from now. For this project, the Chilean astronomer obtained large-field photographic exposures with the 1-m ESO Schmidt telescope at

  4. Interactions between brown-dwarf binaries and Sun-like stars

    CERN Document Server

    Kaplan, M; Whitworth, A P

    2012-01-01

    Several mechanisms have been proposed for the formation of brown dwarfs, but there is as yet no consensus as to which -- if any -- are operative in nature. Any theory of brown dwarf formation must explain the observed statistics of brown dwarfs. These statistics are limited by selection effects, but they are becoming increasingly discriminating. In particular, it appears (a) that brown dwarfs that are secondaries to Sun-like stars tend to be on wide orbits, $a\\ga 100\\,{\\rm AU}$ (the Brown Dwarf Desert), and (b) that these brown dwarfs have a significantly higher chance of being in a close ($a\\la 10\\,{\\rm AU}$) binary system with another brown dwarf than do brown dwarfs in the field. This then raises the issue of whether these brown dwarfs have formed {\\it in situ}, i.e. by fragmentation of a circumstellar disc; or have formed elsewhere and subsequently been captured. We present numerical simulations of the purely gravitational interaction between a close brown-dwarf binary and a Sun-like star. These simulatio...

  5. Flash ionisation signature in coherent cyclotron emission from Brown Dwarfs

    CERN Document Server

    Vorgul, Irena

    2016-01-01

    Brown dwarfs form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in form of lightning resulting in a substantial sudden increase of local ionisation. Brown dwarfs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionisation events (flash ionisation) can be imprinted on a pre-existing radiation. Detection of such flash ionisation events will open investigations into the ionisation state and atmospheric dynamics. Such ionisation events can also result from explosion shock waves, bursts or eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionisation events like lightning. Our conductivity model reproduces the conductivity function derived from observations of Terrestrial Gamma Ray Flashes, and is applicable to astrophysical objects with strong temporal variations in the loca...

  6. A search for rocky planets transiting brown dwarfs

    CERN Document Server

    Triaud, Amaury H M J; Selsis, Franck; Winn, Joshua N; Demory, Brice-Olivier; Artigau, Etienne; Laughlin, Gregory P; Seager, Sara; Helling, Christiane; Mayor, Michel; Albert, Loic; Anderson, Richard I; Bolmont, Emeline; Doyon, Rene; Forveille, Thierry; Hagelberg, Janis; Leconte, Jeremy; Lendl, Monika; Littlefair, Stuart; Raymond, Sean; Sahlmann, Johannes

    2013-01-01

    Exoplanetary science has reached a historic moment. The James Webb Space Telescope will be capable of probing the atmospheres of rocky planets, and perhaps even search for biologically produced gases. However this is contingent on identifying suitable targets before the end of the mission. A race therefore, is on, to find transiting planets with the most favorable properties, in time for the launch. Here, we describe a realistic opportunity to discover extremely favorable targets - rocky planets transiting nearby brown dwarfs - using the Spitzer Space Telescope as a survey instrument. Harnessing the continuous time coverage and the exquisite precision of Spitzer in a 5,400 hour campaign monitoring nearby brown dwarfs, we will detect a handful of planetary systems with planets as small as Mars. The survey we envision is a logical extension of the immense progress that has been realized in the field of exoplanets and a natural outcome of the exploration of the solar neighborhood to map where the nearest habitab...

  7. The First Spectrum of the Coldest Brown Dwarf

    CERN Document Server

    Skemer, Andrew; Allers, Katelyn; Geballe, Thomas; Marley, Mark; Fortney, Jonathan; Faherty, Jacqueline; Bjoraker, Gordon; Lupu, Roxana

    2016-01-01

    The recently discovered brown dwarf WISE 0855 presents our first opportunity to directly study an object outside the Solar System that is nearly as cold as our own gas giant planets. However the traditional methodology for characterizing brown dwarfs---near infrared spectroscopy---is not currently feasible as WISE 0855 is too cold and faint. To characterize this frozen extrasolar world we obtained a 4.5-5.2 $\\mu$m spectrum, the same bandpass long used to study Jupiter's deep thermal emission. Our spectrum reveals the presence of atmospheric water vapor and clouds, with an absorption profile that is strikingly similar to Jupiter. The spectrum is high enough quality to allow the investigation of dynamical and chemical processes that have long been studied in Jupiter's atmosphere, but now on an extrasolar world.

  8. How Dry is the Brown Dwarf Desert?: Quantifying the Relative Number of Planets, Brown Dwarfs and Stellar Companions around Nearby Sun-like Stars

    CERN Document Server

    Grether, D; Grether, Daniel; Lineweaver, Charles H.

    2004-01-01

    Sun-like stars have stellar, brown dwarf and planetary companions. To help constrain their formation and migration scenarios, we analyse the close companions (orbital period 2 M_Solar respectively. However, we find no evidence that companion mass scales with host mass in general. Approximately 16% of Sun-like stars have close (P < 5 years) companions more massive than Jupiter: 11% are stellar, 1% are brown dwarf and 4% are giant planets. The companion mass function in the brown dwarf and stellar mass range, has a different shape than the initial mass function of individual stars and free-floating brown dwarfs. This suggests either a different spectrum of gravitational fragmentation in the formation environment or post-formation migratory processes disinclined to leave brown dwarfs in close orbits.

  9. Eclipse Observations of a Temperate Transiting Brown Dwarf

    Science.gov (United States)

    Beatty, Thomas; Curtis, Jason; Montet, Benjamin; Vanderberg, Andrew

    2016-08-01

    We wish to use 15.7 hours of Spitzer time to observe two eclipses, one each at 3.6 um and 4.5 um of a newly discovered transiting brown dwarf, which we refer to as R147-BD. R147-BD is a 36 MJ object on a 5.3 day orbit about a K=10.666, 5800K solar analog. Uniquely, R147-BD and its host star are both members of the 3.0 Gyr old open cluster Ruprecht 147. R147-BD is thus one of the only transiting brown dwarfs for which we have a robust isochronal age that is not dependent upon brown dwarf evolutionary models. These models predict that a field object with the mass and age of R147-BD should have an effective temperature of about 800K due to internal heat. The zero-albedo blackbody equilibrium temperature for R147-BD, based only on its host star's insolation, is 1125K. This makes R147-BD the first observationally accessible sub-stellar object for which the internal and external energy fluxes are approximately equal, and it can serve as a unique laboratory to test the effect of stellar irradiation on the vertical pressure-temperature structure and clouds of giant planets. Specifically, we wish to investigate three different questions with these observations. First, how does the measured mass, radius, age and emission of R147-BD compare to brown dwarf evolution models, and how have these been altered by stellar irradiation? Second, does R147-BD's dayside atmosphere resemble its isolated field equivalent, or is it closer to hot Jupiters at similar temperatures? Third, can we constrain the cloud properties of R147-BD's dayside? Besides these particular science questions, observations of R147-BD allow us to scout-out future JWST observations of temperate giant planets, which also will have roughly equal amounts of stellar irradiation and internal heat.

  10. Luminosity functions for very low mass stars and brown dwarfs

    Science.gov (United States)

    Laughlin, Gregory; Bodenheimer, Peter

    1993-01-01

    A theoretical investigation of the luminosity function for low-mass objects to constrain the stellar initial mass function at the low-mass end is reported. The ways in which luminosity functions for low-mass stars are affected by star formation histories, brown dwarf and premain-sequence cooling rates and main-sequence mass luminosity relations, and the IMF are examined. Cooling rates and the mass-luminosity relation are determined through a new series of evolutionary calculations for very low mass stars and brown dwarfs in the range 0.05-0.50 solar mass. Model luminosity functions are constructed for specific comparison with the results of four recent observational surveys. The likelihood that the stellar mass function in the solar neighborhood is increasing at masses near the bottom of the main sequence and perhaps at lower masses is confirmed. In the most optimistic case, brown dwarfs contribute half of the local missing disk mass. The actual contribution is likely to be considerably less.

  11. Near Infrared Spectroscopy of Young Brown Dwarfs in Upper Scorpius

    CERN Document Server

    Dawson, P; Ray, T P; Peterson, D E; Rodgers-Lee, D; Geers, V

    2014-01-01

    Spectroscopic follow-up is a pre-requisite for studies of the formation and early evolution of brown dwarfs. Here we present IRTF/SpeX near-infrared spectroscopy of 30 candidate members of the young Upper Scorpius association, selected from our previous survey work. All 24 high confidence members are confirmed as young very low mass objects with spectral types from M5 to L1, 15-20 of them are likely brown dwarfs. This high yield confirms that brown dwarfs in Upper Scorpius can be identified from photometry and proper motions alone, with negligible contamination from field objects (<4%). Out of the 6 candidates with lower confidence, 5 might still be young very low mass members of Upper Scorpius, according to our spectroscopy. We demonstrate that some very low mass class II objects exhibit radically different near infrared (0.6 - 2.5micron) spectra from class III objects, with strong excess emission increasing towards longer wavelengths and partially filled in features at wavelengths shorter than 1.25micron...

  12. A homogeneous analysis of disks around brown dwarfs

    CERN Document Server

    Liu, Y; Bayo, A; Nielbock, M; Wang, H

    2015-01-01

    We re-analyzed the Herschel/PACS data of a sample of 55 brown dwarfs (BDs) and very low mass stars with spectral types ranging from M5.5 to L0. We investigated the dependence of disk structure on the mass of the central object in the substellar regime based on a homogeneous analysis of Herschel data from flux density measurements to spectral energy distribution (SED) modeling. A systematic comparison between the derived disk properties and those of sun-like stars shows that the disk flaring of BDs and very low mass stars is generally smaller than that of their higher mass counterparts, the disk mass is orders of magnitude lower than the typical value found in T Tauri stars, and the disk scale heights are comparable in both sun-like stars and BDs. We further divided our sample into an early-type brown dwarf (ETBD) group and a late-type brown dwarf (LTBD) group by using spectral type (=M8) as the border criterion. We systematically compared the modeling results from Bayesian analysis between these two groups, a...

  13. Exploring Substellar Evolution with the Coldest Brown Dwarfs

    Science.gov (United States)

    Dupuy, Trent J.

    2017-01-01

    The coldest brown dwarfs are our best analogs to extrasolar gas-giant planets, representing the lowest mass products of star formation. Our view of such objects has been transformed over the last few years as new observations have revealed that the solar neighborhood is populated by much colder objects than previously recognized. At the center of efforts to discover and characterize these coldest substellar objects have been observations from NASA missions (WISE, Spitzer, HST) and the Keck Telescopes. I will review the tremendous progress made in this field over just the last few years thanks to major community efforts to overcome observational challenges in obtaining spectroscopy, photometry, and astrometry of these infrared-faint, optically invisible objects. Spectra from HST and Keck were key in establishing the much anticipated "Y" spectral type, extending the classic stellar classification scheme to atmospheres as cool as 300-400 K. Parallaxes and photometry from Spitzer and Keck have provided absolute fluxes, enabling robust temperature determinations and critical tests of model atmopheres. High-resolution imaging with Keck laser guide star adaptive optics (LGS AO) has been the most prolific resource for revealing tight companions among the coldest brown dwarfs. In fact, with continued orbit monitoring with Keck LGS AO and HST, these binary systems will ultimately provide dynamical masses that will allow the strongest tests of models and reveal if the coldest brown dwarfs are indeed "planetary mass" (less than about 13 Jupiter masses) as is currently thought.

  14. Formation of low-mass stars and brown dwarfs

    CERN Document Server

    Hennebelle, Patrick

    2012-01-01

    These lectures attempt to expose the most important ideas, which have been proposed to explain the formation of stars with particular emphasis on the formation of brown dwarfs and low-mass stars. We first describe the important physical processes which trigger the collapse of a self-gravitating piece of fluid and regulate the star formation rate in molecular clouds. Then we review the various theories which have been proposed along the years to explain the origin of the stellar initial mass function paying particular attention to four models, namely the competitive accretion and the theories based respectively on stopped accretion, MHD shocks and turbulent dispersion. As it is yet unsettled whether the brown dwarfs form as low-mass stars, we present the theory of brown dwarfs based on disk fragmentation stressing all the uncertainties due to the radiative feedback and magnetic field. Finally, we describe the results of large scale simulations performed to explain the collapse and fragmentation of molecular cl...

  15. Formation of Low-Mass Stars and Brown Dwarfs

    Science.gov (United States)

    Hennebelle, P.

    2012-11-01

    These lectures attempt to expose the most important ideas, which have been proposed to explain the formation of stars with particular emphasis on the formation of brown dwarfs and low-mass stars. We first describe the important physical processes which trigger the collapse of a self-gravitating piece of fluid and regulate the star formation rate in molecular clouds. Then we review the various theories which have been proposed along the years to explain the origin of the stellar initial mass function paying particular attention to four models, namely the competitive accretion and the theories based respectively on stopped accretion, MHD shocks and turbulent dispersion. As it is yet unsettled whether the brown dwarfs form as low-mass stars, we present the theory of brown dwarfs based on disk fragmentation stressing all the uncertainties due to the radiative feedback and magnetic field. Finally, we describe the results of large scale simulations performed to explain the collapse and fragmentation of molecular clouds.

  16. CONFIRMATION OF ONE OF THE COLDEST KNOWN BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Luhman, K. L.; Bochanski, J. J. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); Burgasser, A. J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Labbe, I.; Monson, A. J.; Persson, S. E. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Saumon, D. [Los Alamos National Laboratory, P.O. Box 1663, MS F663, Los Alamos, NM 87545 (United States); Marley, M. S., E-mail: kluhman@astro.psu.edu [Space Science and Astrobiology Division, NASA Ames Research Center, Mail Stop 245-3, Moffett Field, CA 94035 (United States)

    2012-01-10

    Using two epochs of 4.5 {mu}m images from the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope, we recently identified a common proper motion companion to the white dwarf WD 0806-661 that is a candidate for the coldest known brown dwarf. To verify its cool nature, we have obtained images of this object at 3.6 {mu}m with IRAC, at J with the High Acuity Wide-field K-band Imager (HAWK-I) on the Very Large Telescope, and in a filter covering the red half of J with FourStar on Magellan. WD 0806-661 B is detected by IRAC but not HAWK-I or FourStar. From these data we measure colors of [3.6] - [4.5] = 2.77 {+-} 0.16 and J - [4.5] > 7.0 (S/N < 3). Based on these colors and its absolute magnitudes, WD 0806-661 B is the coldest companion directly imaged outside of the solar system and is a contender for the coldest known brown dwarf with the Y dwarf WISEP J1828+2650. It is unclear which of these two objects is colder given the available data. A comparison of its absolute magnitude at 4.5 {mu}m to the predictions of theoretical spectra and evolutionary models suggests that WD 0806-661 B has T{sub eff} = 300-345 K.

  17. Polarimetric Detection of Exoplanets Transiting T- and L- Brown Dwarfs

    CERN Document Server

    Sengupta, Sujan

    2016-01-01

    While scattering of light by atoms and molecules yields large amount of polarization at the B-band of both T- and L-dwarfs, scattering by dust grains in cloudy atmosphere of L-dwarfs gives rise to significant polarization at the far-optical and infra-red wavelengths where these objects are much brighter. However, the observable disk averaged polarization should be zero if the clouds are uniformly distributed and the object is spherically symmetric. Therefore, in order to explain the observed large polarization of several L-dwarfs, rotation-induced oblateness or horizontally inhomogeneous cloud distribution in the atmosphere is invoked. On the other hand, when an extra-solar planet of Earth-size or larger transits the brown dwarf along the line of sight, the asymmetry induced during the transit gives rise to a net non-zero, time dependent polarization. Employing atmospheric models for a range of effective temperature and surface gravity appropriate for T- and L-dwarfs, I derive the time dependent polarization ...

  18. A Brown Dwarf Census from the SIMP Survey

    CERN Document Server

    Robert, Jasmin; Artigau, Étienne; Lafrenière, David; Nadeau, Daniel; Doyon, René; Malo, Lison; Albert, Loïc; Simard, Corinne; Gagliuffi, Daniella C Bardalez; Burgasser, Adam J

    2016-01-01

    We have conducted a near-infrared (NIR) proper motion survey, the Sondage Infrarouge de Mouvement Propre (SIMP), in order to discover field ultracool dwarfs (UCD) in the solar neighborhood. The survey was conducted by imaging $\\sim28\\%$ of the sky with the Camera PAnoramique Proche-InfraRouge (CPAPIR) both in the southern hemisphere at the Cerro Tololo Inter-American Observatory (CTIO) 1.5-m telescope, and in the northern hemisphere at the Observatoire du Mont-M\\'egantic (OMM) 1.6-m telescope and comparing the source positions from these observations with the Two Micron All-Sky Survey Point Source Catalog (2MASS PSC). Additional color criteria were used to further discriminate unwanted astrophysical sources. We present the results of a NIR spectroscopic follow-up of 169 M, L and T dwarfs. Among the sources discovered are two young field brown dwarfs, six unusually red M and L dwarfs, twenty-five unusually blue M and L dwarfs, two candidate unresolved L+T binaries and twenty-four peculiar UCDs. Additionally, w...

  19. S Ori 70: Just a Foreground Field Brown Dwarf?

    CERN Document Server

    Burgasser, A J; McGovern, M R; McLean, I S; Prato, L; Reid, I N; Burgasser, Adam J.; Govern, Mark R. Mc; Lean, Ian S. Mc

    2004-01-01

    We examine recent claims that the T-type brown dwarf S Ori 053810.1-203626 (S Ori 70) is a spectroscopically verified low mass (3$^{+5}_{-1}$ M$_{Jup}$) member of the 1--8 Myr $\\sigma$ Orionis cluster. Comparative arguments by Mart{\\'{i}}n & Zapatero Osorio asserting that S Ori 70 exhibits low surface gravity spectral features indicative of youth and low mass are invalidated by the fact that their comparison object was not the field T dwarf 2MASS 0559$-$1404 but rather a nearby background star. Instead, we find that the 1--2.5 $\\micron$ spectra of S Ori 70 are well-matched to older (age $\\sim$ few Gyr) field T6--T7 dwarfs. Moreover, we find that spectral model fits to late-type field T dwarf spectra tend to yield low surface gravities ($\\log{g}$ = 3.0--3.5), and thus young ages ($\\lesssim$ 5 Myr) and low masses ($\\lesssim$ 3 M$_{Jup}$), inconsistent with expected and/or empirical values. Finally, we show that the identification of one T dwarf in the field imaged by Zapatero Osorio et al. is statistically ...

  20. A Brown Dwarf Joins the Jet-Set

    Science.gov (United States)

    2007-05-01

    Jets of matter have been discovered around a very low mass 'failed star', mimicking a process seen in young stars. This suggests that these 'brown dwarfs' form in a similar manner to normal stars but also that outflows are driven out by objects as massive as hundreds of millions of solar masses down to Jupiter-sized objects. The brown dwarf with the name 2MASS1207-3932 is full of surprises [1]. Its companion, a 5 Jupiter-mass giant, was the first confirmed exoplanet for which astronomers could obtain an image (see ESO 23/04 and 12/05), thereby opening a new field of research - the direct detection of alien worlds. It was then later found (see ESO 19/06) that the brown dwarf has a disc surrounding it, not unlike very young stars. ESO PR Photo 24/07 ESO PR Photo 24/07 Jets from a Brown Dwarf (Artist's Impression) Now, astronomers using ESO's Very Large Telescope (VLT) have found that the young brown dwarf is also spewing jets, a behaviour again quite similar to young stars. The mass of the brown dwarf is only 24 Jupiter-masses. Hence, it is by far the smallest object known to drive an outflow. "This leads us to the tantalizing prospect that young giant planets could also be associated with outflows," says Emma Whelan, the lead-author of the paper reporting the results. The outflows were discovered using an amazing technique known as spectro-astrometry, based on high resolution spectra taken with UVES on the VLT. Such a technique was required due to the difficulty of the task. While in normal young stars - known as T-Tauri stars for the prototype of their class - the jets are large and bright enough to be seen directly, this is not the case around brown dwarfs: the length scale of the jets, recovered with spectro-astrometry is only about 0.1 arcsecond long, that is, the size of a two Euro coin seen from 40 km away. The jets stretch about 1 billion kilometres and the material is rushing away from the brown dwarf with a speed of a few kilometres per second. The

  1. The Role of Clouds in Brown Dwarf and Extrasolar Giant Planet Atmospheres

    CERN Document Server

    Marley, M S

    2001-01-01

    Clouds and hazes are important throughout our solar system and in the atmospheres of brown dwarfs and extrasolar giant planets. Among the brown dwarfs, clouds control the colors and spectra of the L-dwarfs; the disappearance of clouds helps herald the arrival of the T-dwarfs. The structure and composition of clouds will be among the first remote-sensing results from the direct detection of extrasolar giant planets.

  2. Beyond the T Dwarfs: Theoretical Spectra, Colors, and Detectability of the Coolest Brown Dwarfs

    CERN Document Server

    Burrows, A; Lunine, J; Burrows, Adam; Sudarsky, David; Lunine, Jonathan

    2003-01-01

    We explore the spectral and atmospheric properties of brown dwarfs cooler than the latest known T dwarfs. Our focus is on the yet-to-be-discovered free-floating brown dwarfs in the \\teff range from $\\sim$800 K to $\\sim$130 K and with masses from 25 to 1 \\mj. This study is in anticipation of the new characterization capabilities enabled by the launch of SIRTF and the eventual launch of JWST. We provide spectra from $\\sim$0.4 \\mic to 30 \\mic, highlight the evolution and mass dependence of the dominant H$_2$O, CH$_4$, and NH$_3$ molecular bands, consider the formation and effects of water-ice clouds, and compare our theoretical flux densities with the sensitivities of the instruments on board SIRTF and JWST. The latter can be used to determine the detection ranges from space of cool brown dwarfs. In the process, we determine the reversal point of the blueward trend in the near-infrared colors with decreasing \\teff, the \\teffs at which water and ammonia clouds appear, the strengths of gas-phase ammonia and methan...

  3. Binarity in Brown Dwarfs T Dwarf Binaries Discovered with the Hubble Space Telescope WPFC2

    CERN Document Server

    Burgasser, A J; Reid, I N; Brown, M E; Miskey, C L; Gizis, J E; Burgasser, Adam J.; Brown, Michael E.; Miskey, Cherie L.; Gizis, John E.

    2003-01-01

    (abridged) We present the discovery of two T dwarf binaries, 2MASS 1225-2739AB and 2MASS 1534-2952AB, identified in a sample of ten T dwarfs imaged with the Hubble Space Telescope Wide Field Planetary Camera 2. The separations of the two binary systems are 0{\\farcs}282$\\pm$0{\\farcs}005 and 0{\\farcs}065$\\pm$0{\\farcs}007, implying projected separations of 3.17$\\pm$0.14 and 1.0$\\pm$0.3 AU, respectively. The observed binary fraction of our HST sample, 20$^{+17}_{-7}$%, is consistent with results obtained for late-M and L field dwarfs, and implies a bias-corrected binary fraction of 9$^{+15}_{-4}$% for $a \\gtrsim 1$ AU and $q \\gtrsim 0.4$, significantly lower than the binary fractions of F--G and early-type M dwarf stars. Neither of the T binaries have separations $a \\gtrsim 10$ AU, consistent with results from other brown dwarf binary searches. We conclude that tidal disruption by passing stars or Giant Molecular Clouds, which limits the extent of wide stellar binaries, plays no role in eliminating wide brown dwa...

  4. The Spectral Energy Distribution of the Coldest Known Brown Dwarf

    CERN Document Server

    Luhman, K L

    2016-01-01

    WISE J085510.83-071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf (~250 K) and the fourth closest known system to the Sun (2.2 pc). It has been previously detected only in the J band and two mid-IR bands. To better measure its spectral energy distribution (SED), we have performed deep imaging of WISE 0855-0714 in six optical and near-IR bands with Gemini Observatory, the Very Large Telescope, and the Hubble Space Telescope. Five of the bands show detections, although one detection is marginal (S/N~3). We also have obtained two epochs of images with the Spitzer Space Telescope for use in refining the parallax of the brown dwarf. By combining astrometry from this work and previous studies, we have derived a parallax of 0.449+/-0.008" (2.23+/-0.04 pc). We have compared our photometry for WISE 0855-0714 to data for known Y dwarfs and to the predictions of three suites of models by Saumon et al. (2012) and Morley et al. (2012, 2014) that are defined by the presence or absence of clouds and non-e...

  5. M-dwarf binaries as tracers of star and brown dwarf formation

    CERN Document Server

    Marks, Michael; Kroupa, Pavel; Leigh, Nathan; Thies, Ingo

    2015-01-01

    The separation distribution for M-dwarf binaries in the ASTRALUX survey is narrower and peaking at smaller separations than the distribution for solar-type binaries. This is often interpreted to mean that M-dwarfs constitute a continuous transition from brown dwarfs (BDs) to stars. Here a prediction for the M-dwarf separation distribution is presented, using a dynamical population synthesis (DPS) model in which "star-like" binaries with late-type primaries ($\\lesssim1.5 M_{\\rm sun}$) follow universal initial distribution functions and are dynamically processed in their birth embedded clusters. A separate "BD-like" population has both its own distribution functions for binaries and initial mass function (IMF), which overlaps in mass with the IMF for stars. Combining these two formation modes results in a peak on top of a wider separation distribution for late M-dwarfs consistent with the late ASTRALUX sample. The DPS separation distribution for early M-dwarfs shows no such peak and is in agreement with the M-d...

  6. X-ray emission from the young brown dwarfs of the Taurus molecular cloud

    Science.gov (United States)

    Grosso, N.; Briggs, K. R.; Güdel, M.; Guieu, S.; Franciosini, E.; Palla, F.; Dougados, C.; Monin, J.-L.; Ménard, F.; Bouvier, J.; Audard, M.; Telleschi, A.

    2007-06-01

    Aims:We report the X-ray properties of young (~3 Myr) bona fide brown dwarfs of the Taurus Molecular Cloud (TMC). Methods: The XMM-Newton Extended Survey of the TMC (XEST) is a large program designed to systematically investigate the X-ray properties of young stellar/substellar objects in the TMC. In particular, the area surveyed by 15 XMM-Newton pointings (of which three are archival observations), supplemented with one archival Chandra observation, allows us to study 17 brown dwarfs with M spectral types. Results: Half of this sample (9 out of 17 brown dwarfs) is detected; 7 brown dwarfs are detected here for the first time in X-rays. We observed a flare from one brown dwarf. We confirm several previous findings on brown dwarf X-ray activity: a log-log relation between X-ray and bolometric luminosity for stars (with L* ≤ 10 L_⊙) and brown dwarfs detected in X-rays, which is consistent with a mean X-ray fractional luminosity =-3.5 ± 0.4; for the XEST brown dwarfs, the median of log(L_X/L_*) (including upper limits) is -4.0; a shallow log-log relation between X-ray fractional luminosity and mass; a log-log relation between X-ray fractional luminosity and effective temperature; a log-log relation between X-ray surface flux and effective temperature. We find no significant log-log correlation between the X-ray fractional luminosity and EW(Hα). Accreting and nonaccreting brown dwarfs have a similar X-ray fractional luminosity. The median X-ray fractional luminosity of nonaccreting brown dwarfs is about 4 times lower than the mean saturation value for rapidly rotating low-mass field stars. Our TMC brown dwarfs have higher X-ray fractional luminosity than brown dwarfs in the Chandra Orion Ultradeep Project. Conclusions: The X-ray fractional luminosity declines from low-mass stars to M-type brown dwarfs, and as a sample, the brown dwarfs are less efficient X-ray emitters than low-mass stars. We thus conclude that while the brown dwarf atmospheres observed here are

  7. Fingering convection and cloudless models for cool brown dwarf atmospheres

    CERN Document Server

    Tremblin, P; Mourier, P; Baraffe, I; Chabrier, G; Drummond, B; Homeier, D; Venot, O

    2015-01-01

    This work aims to improve the current understanding of the atmospheres of brown dwarfs, especially cold ones with spectral type T and Y, whose modeling is a current challenge. Silicate and iron clouds are believed to disappear at the photosphere at the L/T transition, but cloudless models fail to reproduce correctly the spectra of T dwarfs, advocating for the addition of more physics, e.g. other types of clouds or internal energy transport mechanisms. We use a one-dimensional (1D) radiative/convective equilibrium code ATMO to investigate this issue. This code includes both equilibrium and out-of-equilibrium chemistry and solves consistently the PT structure. Included opacity sources are H2-H2, H2-He, H2O, CO, CO2, CH4, NH3, K, Na, and TiO, VO if they are present in the atmosphere. We show that the spectra of Y dwarfs can be accurately reproduced with a cloudless model if vertical mixing and NH3 quenching are taken into account. T dwarf spectra still have some reddening in e.g. J - H compared to cloudless mode...

  8. Population Properties of Brown Dwarf Analogs to Exoplanets

    CERN Document Server

    Faherty, Jacqueline K; Cruz, Kelle L; Gagne, Jonathan; Filippazzo, Joseph C; Lambrides, Erini; Fica, Haley; Weinberger, Alycia; Thorstensen, John R; Tinney, C G; Baldassare, Vivienne; Lemonier, Emily; Rice, Emily L

    2016-01-01

    We present a kinematic analysis of 152 low surface gravity M7-L8 dwarfs by adding 8 parallaxes, 38 radial velocities, and 19 proper motions. We find 39 objects to be high-likelihood or bona fide members of nearby moving groups, 92 objects to be ambiguous members and 21 objects that are non-members. We find that gravity classification and photometric color separate 5-150 Myr sources from > 3 Gyr field objects, but they do not correlate one-to-one with the narrower 5 -150 Myr age range. The absolute magnitudes of low-gravity sources from J band through W3 show a flux redistribution when compared to equivalent field sources that is correlated with spectral subtype. Clouds, which are a far more dominant opacity source for L dwarfs, are the likely cause. On CMDs, the latest-type low-gravity L dwarfs drive the elbow of the L/T transition up to 1 mag redder and 1 mag fainter than field dwarfs at M_J but are consistent with or brighter than the elbow at M_W1 and M_W2. Furthermore, there is an indication on CMD's (suc...

  9. The First Detailed Look at a Brown Dwarf Disk

    CERN Document Server

    Pascucci, I; Henning, T; Dullemond, C P; Henning, Th.

    2003-01-01

    The combination of mid-infrared and recent submm/mm measurements allows us to set up the first comprehensive spectral energy distribution (SED) of the circumstellar material around a young Brown Dwarf. Simple arguments suggest that the dust is distributed in the form of a disk. We compare basic models to explore the disk parameters. The modeling shows that a flat disk geometry fits well the observations. A flared disk explains the SED only if it has a puffed-up inner rim and an inner gap much larger than the dust sublimation radius. Similarities and differences with disks around T Tauri stars are discussed.

  10. Formation of low-mass stars and brown dwarfs

    OpenAIRE

    Hennebelle, Patrick

    2012-01-01

    These lectures attempt to expose the most important ideas, which have been proposed to explain the formation of stars with particular emphasis on the formation of brown dwarfs and low-mass stars. We first describe the important physical processes which trigger the collapse of a self-gravitating piece of fluid and regulate the star formation rate in molecular clouds. Then we review the various theories which have been proposed along the years to explain the origin of the stellar initial mass f...

  11. Youngest Brown Dwarf Yet in a Multiple Stellar System

    Science.gov (United States)

    2000-07-01

    ... and the Sharpest Optical Image (0.18 arcsec) from the VLT so far...! Astronomers are eager to better understand the formation of stars and planets - with an eye on the complex processes that lead to the emergence of our own solar system some 4600 million years ago. Brown Dwarfs (BDs) play a special role in this context. Within the cosmic zoo, they represent a class of "intermediate" objects. While they are smaller than normal stars, they shine by their own energy for a limited time, in contrast to planets. Recent observations with the ESO Very Large Telescope (VLT) of a "young" Brown Dwarf in a multiple stellar system are taking on a particular importance in this connection. An evaluation of the new data by an international team of astronomers [1] shows that it is by far the youngest of only four such objects found in a stellar system so far. The results are now providing new insights into the stellar formation process. This small object is known as TWA-5 B and with a mass of only 15 - 40 times that of Jupiter, it is near the borderline between planets and Brown Dwarfs, cf. the explanatory Appendix to this Press Release. However, visible and infrared VLT spectra unambiguously classify it in the latter category. Accurate positional measurements with the Hubble Space Telescope (HST) and the VLT hint that it is orbiting the central, much heavier and brighter star in this system, TWA-5 A (itself a close double star of which each component presumably has a mass of 0.75 solar masses), with a period that may be as long as 900 years. And, by the way, an (I-band) image of the TWA-5 system is the sharpest delivered by the VLT so far, with an image size of only 0.18 arcsec [2]! Brown Dwarfs: a cool subject In current astronomical terminology, Brown Dwarfs (BDs) are objects whose masses are below those of normal stars - the borderline is believed to be about 8% of the mass of our Sun - but larger than those of planets, cf. [3]. Unlike normal stars, Brown Dwarfs are unable

  12. Photometric brown-dwarf classification. I. A method to identify and accurately classify large samples of brown dwarfs without spectroscopy

    Science.gov (United States)

    Skrzypek, N.; Warren, S. J.; Faherty, J. K.; Mortlock, D. J.; Burgasser, A. J.; Hewett, P. C.

    2015-02-01

    Aims: We present a method, named photo-type, to identify and accurately classify L and T dwarfs onto the standard spectral classification system using photometry alone. This enables the creation of large and deep homogeneous samples of these objects efficiently, without the need for spectroscopy. Methods: We created a catalogue of point sources with photometry in 8 bands, ranging from 0.75 to 4.6 μm, selected from an area of 3344 deg2, by combining SDSS, UKIDSS LAS, and WISE data. Sources with 13.0 0.8, were then classified by comparison against template colours of quasars, stars, and brown dwarfs. The L and T templates, spectral types L0 to T8, were created by identifying previously known sources with spectroscopic classifications, and fitting polynomial relations between colour and spectral type. Results: Of the 192 known L and T dwarfs with reliable photometry in the surveyed area and magnitude range, 189 are recovered by our selection and classification method. We have quantified the accuracy of the classification method both externally, with spectroscopy, and internally, by creating synthetic catalogues and accounting for the uncertainties. We find that, brighter than J = 17.5, photo-type classifications are accurate to one spectral sub-type, and are therefore competitive with spectroscopic classifications. The resultant catalogue of 1157 L and T dwarfs will be presented in a companion paper.

  13. EROS 2 proper motion survey a field brown dwarf and an L dwarf companion to LHS 102

    CERN Document Server

    Goldman, B; Forveille, T; Afonso, C; Alard, C; Albert, J N; Andersen, J; Ansari, R; Aubourg, E; Bareyre, P; Bauer, F; Beaulieu, J P; Borsenberger, J; Bouquet, A; Char, S; Charlot, X; Couchot, F; Coutures, C; Derue, F; Ferlet, R; Fouqué, P; Glicenstein, J F; Gould, A; Graff, D S; Gros, M H; Haïssinski, J; Hamilton, J C; Hardin, D P; De Kat, J; Kim, A; Lasserre, T; Lesquoy, E; Loup, C; Magneville, C; Mansoux, B; Marquette, J B; Martín, E L; Maurice, E; Milshtein, A I; Moniez, M; Palanque-Delabrouille, Nathalie; Perdereau, O; Prévôt, L; Regnault, N; Rich, J; Spiro, Michel; Vidal-Madjar, A; Virgoux, L; Zylberajch, S

    1999-01-01

    We report the discovery of two L dwarfs (the new spectral class defined for dwarfs cooler than the M type) in a two-epoch CCD proper motion survey of 413 square degrees, complemented by infrared photometry from DENIS. One of them has a strong lithium line and is therefore a brown dwarf. The other is a common proper motion companion to the mid-M dwarf LHS 102 (GJ 1001), which has a well determined trigonometric parallax. LHS 102B is thus the coolest L dwarf of known distance and luminosity. Its infrared absolute photometry are very well reproduced by the Allard et al DUSTY models.

  14. The First Brown Dwarf/Planetary-Mass Object in the 32 Orionis Group

    CERN Document Server

    Burgasser, Adam J; Mamajek, Eric E; Gagne, Jonathan; Faherty, Jacqueline K; Tallis, Melisa; Choban, Caleb; Escala, Ivanna; Aganze, Christian

    2016-01-01

    The 32 Orionis group is a co-moving group of roughly 20 young (24 Myr) M3-B5 stars 100 pc from the Sun. Here we report the discovery of its first substellar member, WISE J052857.69+090104.2. This source was previously reported to be an M giant star based on its unusual near-infrared spectrum and lack of measurable proper motion. We re-analyze previous data and new moderate-resolution spectroscopy from Magellan/FIRE to demonstrate that this source is a young near-infrared L1 brown dwarf with very low surface gravity features. Spectral model fits indicate T$_{eff}$ = 1880$^{+150}_{-70}$ K and $\\log{g}$ = 3.8$^{+0.2}_{-0.2}$ (cgs), consistent with a 15-22 Myr object with a mass near the deuterium-burning limit. Its sky position, estimated distance, kinematics (both proper motion and radial velocity), and spectral characteristics are all consistent with membership in 32 Orionis, and its temperature and age imply a mass (M = 14$^{+4}_{-3}$ M$_{Jup}$) that straddles the brown dwarf/planetary-mass object boundary. T...

  15. Microlensing Discovery of a Population of Very Tight, Very Low-mass Binary Brown Dwarfs

    CERN Document Server

    Choi, J -Y; Udalski, A; Sumi, T; Gaudi, B S; Gould, A; Bennett, D P; Dominik, M; Beaulieu, J -P; Tsapras, Y; Bozza, V; Abe, F; Bond, I A; Botzler, C S; Chote, P; Freeman, M; Fukui, A; Furusawa, K; Itow, Y; Ling, C H; Masuda, K; Matsubara, Y; Miyake, N; Muraki, Y; Ohnishi, K; Rattenbury, N J; Saito, To; Sullivan, D J; Suzuki, K; Sweatman, W L; Suzuki, D; Takino, S; Tristram, P J; Wada, K; Yock, P C M; Szymański, M K; Kubiak, M; Pietrzyński, G; Soszyński, I; Skowron, J; Kozłowski, S; Poleski, R; Ulaczyk, K; Wyrzykowski, Ł; Pietrukowicz, P; Almeida, L A; DePoy, D L; Dong, Subo; Gorbikov, E; Jablonski, F; Henderson, C B; Hwang, K -H; Janczak, J; Jung, Y -K; Kaspi, S; Lee, C -U; Malamud, U; Maoz, D; McGregor, D; Munoz, J A; Park, B -G; Park, H; Pogge, R W; Shvartzvald, Y; Shin, I -G; Yee, J C; Alsubai, K A; Browne, P; Burgdorf, M J; Novati, S Calchi; Dodds, P; Fang, X -S; Finet, F; Glitrup, M; Grundahl, F; Gu, S -H; Hardis, S; Harpsøe, K; Hinse, T C; Hornstrup, A; Hundertmark, M; Jessen-Hansen, J; Jørgensen, U G; Kains, N; Kerins, E; Liebig, C; Lund, M N; Lundkvist, M; Maier, G; Mancini, L; Mathiasen, M; Penny, M T; Rahvar, S; Ricci, D; Scarpetta, G; Skottfelt, J; Snodgrass, C; Southworth, J; Surdej, J; Tregloan-Reed, J; Wambsganss, J; Wertz, O; Zimmer, F; Albrow, M D; Bachelet, E; Batista, V; Brillant, S; Cassan, A; Cole, A A; Coutures, C; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Greenhill, J; Kubas, D; Marquette, J -B; Menzies, J W; Sahu, K C; Zub, M; Bramich, D M; Horne, K; Steele, I A; Street, R A

    2013-01-01

    Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs are poorly understood. The multiplicity properties and minimum mass of the brown-dwarf mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low-mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 Msun and 0.034 Msun, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field brown-dwarf binaries known. The discovery of a population of such binaries indicates that brown dwarf binaries can robustly form at least down to masses of ~0.02 Msun. Future microlensing surveys will measure a mass-selected sample of brown-dwarf binary systems, which can then be directly compared to similar samples of stellar binaries.

  16. MOA-2007-BLG-197: Exploring the brown dwarf desert

    CERN Document Server

    Ranc, C; Albrow, M D; Kubas, D; Bond, I A; Batista, V; Beaulieu, J -P; Bennett, D P; Dominik, M; Dong, Subo; Fouqué, P; Gould, A; Greenhill, J; Jørgensen, U G; Kains, N; Menzies, J; Sumi, T; Bachelet, E; Coutures, C; Dieters, S; Prester, D Dominis; Donatowicz, J; Gaudi, B S; Han, C; Hundertmark, M; Horne, K; Kane, S R; Lee, C -U; Marquette, J -B; Park, B -G; Pollard, K R; Sahu, K C; Street, R; Tsapras, Y; Wambsganss, J; Williams, A; Zub, M; Abe, F; Fukui, A; Itow, Y; Masuda, K; Matsubara, Y; Muraki, Y; Ohnishi, K; Rattenbury, N; Saito, To; Sullivan, D J; Sweatman, W L; Tristram, P J; Yock, P C M; Yonehara, A

    2015-01-01

    We present the analysis of MOA-2007-BLG-197Lb, the first brown dwarf companion to a Sun-like star detected through gravitational microlensing. The event was alerted and followed-up photometrically by a network of telescopes from the PLANET, MOA, and uFUN collaborations, and observed at high angular resolution using the NaCo instrument at the VLT. From the modelling of the microlensing light curve, we derived the binary lens separation in Einstein radius units (s~1.13) and a mass ratio of (4.732+/-0.020)x10^{-2}. Annual parallax, lens orbital motion and finite source effects were included in the models. To recover the lens system's physical parameters, we combined the resulting light curve best-fit parameters with (J,H,Ks) magnitudes obtained with VLT NaCo and calibrated using IRSF and 2MASS data. We derived a lens total mass of 0.86+/-0.04 Msun and a lens distance of 4.2+/-0.3 kpc. We find that the companion of MOA-2007-BLG-197L is a brown dwarf of 41+/-2 Mjup observed at a projected separation of 4.3+/-0.1 A...

  17. Chemically reacting fluid flow in exoplanet and brown dwarf atmospheres

    Science.gov (United States)

    Bordwell, Baylee; Brown, Benjamin P.; Oishi, Jeffrey S.

    2016-11-01

    In the past few decades, spectral observations of planets and brown dwarfs have demonstrated significant deviations from predictions in certain chemical abundances. Starting with Jupiter, these deviations were successfully explained to be the effect of fast dynamics on comparatively slow chemical reactions. These dynamical effects are treated using mixing length theory in what is known as the "quench" approximation. In these objects, however, both radiative and convective zones are present, and it is not clear that this approximation applies. To resolve this issue, we solve the fully compressible equations of fluid dynamics in a matched polytropic atmosphere using the state-of-the-art pseudospectral simulation framework Dedalus. Through the inclusion of passive tracers, we explore the transport properties of convective and radiative zones, and verify the classical eddy diffusion parameterization. With the addition of active tracers, we examine the interactions between dynamical and chemical processes using abstract chemical reactions. By locating the quench point (the point at which the dynamical and chemical timescales are the same) in different dynamical regimes, we test the quench approximation, and generate prescriptions for the exoplanet and brown dwarf communities.

  18. The disk around the brown dwarf KPNO Tau 3

    CERN Document Server

    Broekhoven-Fiene, Hannah; Duchene, Gaspard; Di Francesco, James; Scholz, Aleks; Chrysostomou, Antonio; Jayawardhana, Ray

    2014-01-01

    We present submillimeter observations of the young brown dwarfs KPNO Tau 1, KPNO Tau 3, and KPNO Tau 6 at 450 micron and 850 micron taken with the Submillimeter Common-User Bolometer Array on the James Clerke Maxwell Telescope. KPNO Tau 3 and KPNO Tau 6 have been previously identified as Class II objects hosting accretion disks, whereas KPNO Tau 1 has been identified as a Class III object and shows no evidence of circumsubstellar material. Our 3 sigma detection of cold dust around KPNO Tau 3 implies a total disk mass of (4.0 +/- 1.1) x 10^{-4} Msolar (assuming a gas to dust ratio of 100:1). We place tight constraints on any disks around KPNO Tau 1 or KPNO Tau 6 of <2.1 x 10^{-4} Msolar and <2.7 x 10^{-4} Msolar, respectively. Modeling the spectral energy distribution of KPNO Tau 3 and its disk suggests the disk properties (geometry, dust mass, and grain size distribution) are consistent with observations of other brown dwarf disks and low-mass T-Tauri stars. In particular, the disk-to-host mass ratio fo...

  19. Analytic Models of Brown Dwarfs and The Substellar Mass Limit

    CERN Document Server

    Auddy, Sayantan; Valluri, S R

    2016-01-01

    We present the current status of the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main sequence stars. In the spirit of a simplified analytic theory we also introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal non-relativistic Fermi gas at a finite temperature, therefore allowing for non-zero values of the degeneracy parameter ($\\psi = \\frac{kT}{\\mu_{F}}$, where $\\mu_{F}$ is the Fermi energy). We review the derivation of surface luminosity using an entropy matching condition and the first-order phase transition between the molecular hydrogen in the outer envelope and the partially-ionized hydrogen in the inner region. We also discuss the results of modern simulations of the plasma phase transition, which illustrate the uncertainties in determining its critical temperature. Based on the existing models and with some simple modification we find the maximum mass for a brown dwarf to be in the range $0.064M_\\odot...

  20. Model Atmospheres From Very Low Mass Stars to Brown Dwarfs

    CERN Document Server

    Allard, F; Freytag, B

    2010-01-01

    Since the discovery of brown dwarfs in 1994, and the discovery of dust cloud formation in the latest Very Low Mass Stars (VLMs) and Brown Dwarfs (BDs) in 1996, the most important challenge in modeling their atmospheres as become the understanding of cloud formation and advective mixing. For this purpose, we have developed radiation hydrodynamic 2D model atmosphere simulations to study the formation of forsterite dust in presence of advection, condensation, and sedimentation across the M-L-T VLMs to BDs sequence (Teff = 2800 K to 900 K, Freytag et al. 2010). We discovered the formation of gravity waves as a driving mechanism for the formation of clouds in these atmospheres, and derived a rule for the velocity field versus atmospheric depth and Teff , which is relatively insensitive to gravity. This rule has been used in the construction of the new model atmosphere grid, BT-Settl, to determine the microturbulence velocity, the diffusion coefficient, and the advective mixing of molecules as a function of depth. ...

  1. NEOWISE-R observation of the coolest known brown dwarf

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Edward L. [UCLA Astronomy, P.O. Box 951547, Los Angeles, CA 90095-1547 (United States); Mainzer, Amy; Bauer, James; Eisenhardt, Peter R. M. [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Davy Kirkpatrick, J.; Masci, Frank; Fajardo-Acosta, Sergio; Gelino, Christopher R.; Beichman, Charles A.; Cutri, Roc [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C. [Department of Physics and Astronomy, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606-3328 (United States); Skrutskie, M. F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Grav, T., E-mail: wright@astro.ucla.edu [Planetary Science Institute, Tucson, AZ 85719 (United States)

    2014-11-01

    The Wide-field Infrared Survey Explorer (WISE) spacecraft has been reactivated as NEOWISE-R to characterize and search for near-Earth objects. The brown dwarf WISE J085510.83–071442.5 has now been re-observed by NEOWISE-R, and we confirm the results of Luhman, who found a very low effective temperature (≈250 K), a very high proper motion (8.''1 ± 0.''1 yr{sup –1}), and a large parallax (454 ± 45 mas). The large proper motion has separated the brown dwarf from the background sources that influenced the 2010 WISE data, allowing a measurement of a very red WISE color of W1 – W2 >3.9 mag. A re-analysis of the 2010 WISE astrometry using only the W2 band, combined with the new NEOWISE-R 2014 position, gives an improved parallax of 448 ± 33 mas and a proper motion of 8.''08 ± 0.''05 yr{sup –1}. These are all consistent with values from Luhman.

  2. Indications of Water Clouds in the Coldest Known Brown Dwarf

    CERN Document Server

    Faherty, Jacqueline K; Skemer, Andrew; Monson, Andrew J

    2014-01-01

    We present a deep near-infrared image of the newly discovered brown dwarf WISE J085510.83-071442.5 (W0855) using the FourStar imager at Las Campanas Observatory. Our detection of J3=24.8+0.33 -0.53 (J_MKO=25.0+0.33-0.53) at 2.6sigma -- or equivalently an upper limit of J3 > 23.8 (J_MKO > 24.0) at 5sigma makes W0855 the reddest brown dwarf ever categorized (J_MKO - W2 = 10.984+0.33 - 0.53 at 2.6sigma -- or equivalently an upper limit of J_MKO - W2 > 9.984 at 5sigma) and refines its position on color magnitude diagrams. Comparing the new photometry with chemical equilibrium model atmosphere predictions, we demonstrate that W0855 is 4.5sigma from models using a cloudless atmosphere and well reproduced by partly cloudy models (50%) containing sulfide and water ice clouds. Non-equilibrium chemistry or non-solar metallicity may change predictions, however using currently available model approaches, this is the first candidate outside our own solar system to have direct evidence for water clouds.

  3. Flared Disks and Silicate Emission in Young Brown Dwarfs

    CERN Document Server

    Mohanty, S; Natta, A; Fujiyoshi, T; Tamura, M; Barrado y Navascués, D; Mohanty, Subhanjoy; Jayawardhana, Ray; Natta, Antonella; Fujiyoshi, Takuya; Tamura, Motohide; Navascues, David Barrado y

    2004-01-01

    We present mid-infrared photometry of three very young brown dwarfs located in the $\\rho$ Ophiuchi star-forming region -- GY5, GY11 and GY310 --obtained with the Subaru 8-meter telescope. All three sources were detected at 8.6 and 11.7$\\mu$m, confirming the presence of significant mid-infrared excess arising from optically thick dusty disks. The spectral energy distributions of both GY310 and GY11 exhibit strong evidence of flared disks; flat disks can be ruled out for these two brown dwarfs. The data for GY5 show large scatter, and are marginally consistent with both flared and flat configurations. Inner holes a few substellar radii in size are indicated in all three cases (and especially in GY11), in agreement with magnetospheric accretion models. Finally, our 9.7$\\mu$m flux for GY310 implies silicate emission from small grains on the disk surface (though the data do not completely preclude larger grains with no silicate feature). Our results demonstrate that disks around young substellar objects are analog...

  4. Search for exoplanets and brown dwarfs with VLBI

    Science.gov (United States)

    Katarzyński, K.; Gawroński, M.; Goździewski, K.

    2016-09-01

    The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter's magnetic field (˜9 G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI. However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies. We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different emission scenarios, and found that the radiation induced by moons (process similar to Jupiter-Io interactions) appears to be less efficient than the emission generated by a stellar wind on a planetary magnetosphere. We also estimated hypothetical emission of planets and brown dwarfs located around relatively young and massive main-sequence A-type stars. Our results show that the emission produced by stellar winds could be detected by currently operating VLBI networks.

  5. 2MASS J035523.37+113343.7: A YOUNG, DUSTY, NEARBY, ISOLATED BROWN DWARF RESEMBLING A GIANT EXOPLANET

    Energy Technology Data Exchange (ETDEWEB)

    Faherty, Jacqueline K. [Department of Astronomy, Universidad de Chile Cerro Calan, Las Condes (Chile); Rice, Emily L.; Cruz, Kelle L.; Nunez, Alejandro [Department of Astrophysics , American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States); Mamajek, Eric E., E-mail: jfaherty17@gmail.com, E-mail: jfaherty@amnh.org [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile)

    2013-01-01

    We present parallax and proper motion measurements, near-infrared spectra, and Wide-field Infrared Survey Explorer photometry for the low surface gravity L5{gamma} dwarf 2MASS J035523.37+113343.7 (2M0355). We use these data to evaluate photometric, spectral, and kinematic signatures of youth as 2M0355 is the reddest isolated L dwarf yet classified. We confirm its low-gravity spectral morphology and find a strong resemblance to the sharp triangular shaped H-band spectrum of the {approx}10 Myr planetary-mass object 2M1207b. We find that 2M0355 is underluminous compared to a normal field L5 dwarf in the optical and Mauna Kea Observatory J, H, and K bands and transitions to being overluminous from 3 to 12 {mu}m, indicating that enhanced photospheric dust shifts flux to longer wavelengths for young, low-gravity objects, creating a red spectral energy distribution. Investigating the near-infrared color-magnitude diagram for brown dwarfs confirms that 2M0355 is redder and underluminous compared to the known brown dwarf population, similar to the peculiarities of directly imaged exoplanets 2M1207b and HR8799bcd. We calculate UVW space velocities and find that the motion of 2M0355 is consistent with young disk objects (<2-3 Gyr) and it shows a high likelihood of membership in the AB Doradus association.

  6. Limits on the infrared photometric monitoring of brown dwarfs

    CERN Document Server

    Bailer-Jones, C A L

    2003-01-01

    Recent monitoring programs of ultra cool field M and L dwarfs (low mass stars or brown dwarfs) have uncovered low amplitude photometric I-band variations which may be associated with an inhomogeneous distribution of photospheric condensates. Further evidence hints that this distribution may evolve on very short timescales, specifically of order a rotation period or less. In an attempt to study this behaviour in more detail, we have carried out a pilot program to monitor three L dwarfs in the near infrared where these objects are significantly brighter than at shorter wavelengths. We present a robust data analysis method for improving the precision and reliability of infrared photometry. No significant variability was detected in either the J or Km bands in 2M1439 and SDSS1203 above a peak-to-peak amplitude of 0.04 mag (0.08 mag for 2M1112). The main limiting factor in achieving lower detection limits is suspected to be second order extinction effects in the Earth's atmosphere, on account of the very different...

  7. The Spectral Energy Distribution of the Coldest Known Brown Dwarf

    Science.gov (United States)

    Luhman, K. L.; Esplin, T. L.

    2016-09-01

    WISE J085510.83-071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf (˜250 K) and the fourth-closest known system to the Sun (2.2 pc). It has been previously detected only in the J band and two mid-IR bands. To better measure its spectral energy distribution (SED), we have performed deep imaging of WISE 0855-0714 in six optical and near-IR bands with Gemini Observatory, the Very Large Telescope, and the Hubble Space Telescope. Five of the bands show detections, although one detection is marginal (S/N ˜ 3). We also have obtained two epochs of images with the Spitzer Space Telescope for use in refining the parallax of the brown dwarf. By combining astrometry from this work and previous studies, we have derived a parallax of 0.449 ± 0.008″ (2.23 ± 0.04 pc). We have compared our photometry for WISE 0855-0714 to data for known Y dwarfs and to the predictions of three suites of models by Saumon et al. and Morley et al. that are defined by the presence or absence of clouds and nonequilibrium chemistry. Our estimates of Y - J and J - H for WISE 0855-0714 are redder than colors of other Y dwarfs, confirming a predicted reversal of near-IR colors to redder values at temperatures below 300-400 K. In color-magnitude diagrams, no single suite of models provides a clearly superior match to the sequence formed by WISE 0855-0714 and other Y dwarfs. Instead, the best-fitting model changes from one diagram to the next. Similarly, all of the models have substantial differences from the SED of WISE 0855-0714. As a result, we are currently unable to constrain the presence of clouds or nonequilibrium chemistry in its atmosphere. Based on observations made with the Spitzer Space Telescope, the NASA/ESA Hubble Space Telescope, Gemini Observatory, and the ESO Telescopes at Paranal Observatory.

  8. Photometric brown-dwarf classification. I. A method to identify and accurately classify large samples of brown dwarfs without spectroscopy

    CERN Document Server

    Skrzypek, Nathalie; Faherty, Jacqueline K; Mortlock, Daniel J; Burgasser, Adam J; Hewett, Paul C

    2014-01-01

    Aims. We present a method, named photo-type, to identify and accurately classify L and T dwarfs onto the standard spectral classification system using photometry alone. This enables the creation of large and deep homogeneous samples of these objects efficiently, without the need for spectroscopy. Methods. We created a catalogue of point sources with photometry in 8 bands, ranging from 0.75 to 4.6 microns, selected from an area of 3344 deg^2, by combining SDSS, UKIDSS LAS, and WISE data. Sources with 13.0 0.8, were then classified by comparison against template colours of quasars, stars, and brown dwarfs. The L and T templates, spectral types L0 to T8, were created by identifying previously known sources with spectroscopic classifications, and fitting polynomial relations between colour and spectral type. Results. Of the 192 known L and T dwarfs with reliable photometry in the surveyed area and magnitude range, 189 are recovered by our selection and classification method. We have quantified the accuracy of th...

  9. The First Hundred Brown Dwarfs Discovered by the Wide-Field Infrared Survey Explorer (WISE)

    Science.gov (United States)

    Kirkpatrick, J. Davy; Cushing, Michael C.; Gelino, Christopher R.; Griffith, Roger L.; Skrutskie, Michael F.; Marsh, Kenneth A.; Wright, Edward L.; Mainzer, Amanda K.; Eisenhardt, Peter R.; McLean, Ian S.; Bauer, James M.; Benford, Dominic J.; Lake, Sean E.; Petty, Sara M.; Tsai, Chao-Wei; Beichman, Charles; Stapelfeldt, Karl R.; Stern, Daniel; Vacca, William D.

    2011-01-01

    We present ground-based spectroscopic verification of six Y dwarfs also Cushing et al.), eighty-nine T dwarfs, eight L dwarfs, and one M dwarf identified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these are cold brown dwarfs with spectral types > or =T6, six of which have been announced earlier in Mainzer et al. and I3urgasser et al. We present color-color and colortype diagrams showing the locus of M, L, T, and Y dwarfs in WISE color space. "

  10. Hot methane line lists for exoplanet and brown dwarf atmospheres

    CERN Document Server

    Hargreaves, R J; Michaux, L; Irfan, M; Bernath, P F

    2013-01-01

    We present comprehensive experimental line lists of methane (CH4) at high temperatures obtained by recording Fourier transform infrared emission spectra. Calibrated line lists are presented for the temperatures 300 - 1400 degC at twelve 100 degC intervals spanning the 960 - 5000 cm-1 (2.0 - 10.4 microns) region of the infrared. This range encompasses the dyad, pentad and octad regions, i.e., all fundamental vibrational modes along with a number of combination, overtone and hot bands. Using our CH4 spectra, we have estimated empirical lower state energies (Elow in cm-1) and our values have been incorporated into the line lists along with line positions (cm-1) and calibrated line intensities (S' in cm molecule-1). We expect our hot CH4 line lists to find direct application in the modeling of planetary atmospheres and brown dwarfs.

  11. Bayesian fitting of Taurus brown dwarf spectral energy distributions

    CERN Document Server

    Mayne, N J; Rowe, John; Acreman, David M

    2012-01-01

    We present derived stellar and disc parameters for a sample of Taurus brown dwarfs both with and without evidence of an associated disc. These parameters have been derived using an online fitting tool (http://bd-server.astro.ex.ac.uk/), which includes a statistically robust derivation of uncertainties, an indication of pa- rameter degeneracies, and a complete treatment of the input photometric and spectroscopic observations. The observations of the Taurus members with indications of disc presence have been fitted using a grid of theoretical models including detailed treatments of physical processes accepted for higher mass stars, such as dust sublimation, and a simple treatment of the accretion flux. This grid of models has been designed to test the validity of the adopted physical mechanisms, but we have also constructed models using parameterisation, for example semi-empirical dust sublimation radii, for users solely interested in parameter derivation and the quality of the fit. The parameters derived for t...

  12. Bok Prize Lecture (shared) The Brown Dwarf Radial Velocity Survey

    Science.gov (United States)

    Charbonneau, Dave

    2004-03-01

    The swarm of nearby brown dwarfs and very low mass stars is an attractive sample for radial velocity monitoring. Such work is best conducted with an echelle spectrograph operating at infrared wavelengths where these objects(i) are most luminous, (ii) have a forest of molecular features, providing an excellent velocity metric, and {iii) are superimposed on the telluric spectrum, which yields the requisite wavelength calibration. I will present first results from such a survey, with a precision sufficient to detect Jupiter-mass planets with orbital periods of less than a year. Should such systems be uncovered, the planets would be amenable to direct study, due to system proximity, and the favorable contrast ratio between the planet and parent object.

  13. Bayesian fitting of Taurus brown dwarf spectral energy distributions

    Science.gov (United States)

    Mayne, N. J.; Harries, Tim J.; Rowe, John; Acreman, David M.

    2012-06-01

    We present derived stellar and disc parameters for a sample of Taurus brown dwarfs both with and without evidence of an associated disc. These parameters have been derived using an online fitting tool (), which includes a statistically robust derivation of uncertainties, an indication of parameter degeneracies and a complete treatment of the input photometric and spectroscopic observations. The observations of the Taurus members with indications of disc presence have been fitted using a grid of theoretical models including detailed treatments of physical processes accepted for higher mass stars, such as dust sublimation, and a simple treatment of the accretion flux. This grid of models has been designed to test the validity of the adopted physical mechanisms, but we have also constructed models using parametrization, for example semi-empirical dust sublimation radii, for users solely interested in parameter derivation and the quality of the fit. The parameters derived for the naked and disc brown dwarf systems are largely consistent with literature observations. However, our inner disc edge locations are consistently closer to the star than previous results and we also derive elevated accretion rates over non-spectral energy distribution based accretion rate derivations. For inner edge locations, we attribute these differences to the detailed modelling we have performed of the disc structure, particularly at the crucial inner edge where departures in geometry from the often adopted vertical wall due to dust sublimation (and therefore accretion flux) can compensate for temperature (and therefore distance) changes to the inner edge of the dust disc. In the case of the elevated derived accretion rates, in some cases, this may be caused by the intrinsic stellar luminosities of the targets exceeding that predicted by the isochrones we have adopted.

  14. The formation of brown dwarfs in discs: Physics, numerics, and observations

    CERN Document Server

    Stamatellos, Dimitris

    2010-01-01

    A large fraction of brown dwarfs and low-mass stars may form by gravitational fragmentation of relatively massive (a few 0.1 Msun), extended (a few hundred AU) discs around Sun-like stars. We present an ensemble of radiative hydrodynamic simulations that examine the conditions for disc fragmentation. We demonstrate that this model can explain the low-mass IMF, the brown dwarf desert, and the binary properties of low-mass stars and brown dwarfs. Observing discs that are undergoing fragmentation is possible but very improbable, as the process of disc fragmentation is short lived (discs fragment within a few thousand years).

  15. CFBDS J111807-064016: A new L/T transition brown dwarf in a binary system

    CERN Document Server

    Reylé, C; Artigau, É; Delfosse, X; Albert, L; Forveille, T; Rajpurohit, A S; Allard, F; Homeier, D; Robin, A C

    2013-01-01

    Stellar-substellar binary systems are quite rare, and provide interesting benchmarks. They constrain the complex physics of substellar atmospheres, because several physical parameters of the substellar secondary can be fixed from the much better characterized main sequence primary. We report the discovery of CFBDS J111807-064016, a T2 brown dwarf companion to 2MASS J111806.99-064007.8, a low-mass M4.5-M5 star. The brown-dwarf was identified from the Canada France Brown Dwarf Survey. At a distance of 50-120 pc, the 7.7 arcsec angular separation corresponds to projected separations of 390-900 AU. The primary displays no Halpha emission, placing a lower limit on the age of the system of about 6 Gyr. The kinematics is also consistent with membership in the old thin disc. We obtained near-infrared spectra, which together with recent atmosphere models allow us determine the effective temperature and gravity of both components. From these parameters and the age constraint, evolutionary models estimate masses of 0.10...

  16. Kinematics of nearby K-M dwarfs: first results .

    Science.gov (United States)

    Upgren, A. R.; Boyle, R. P.; Sperauskas, J.; Bartašiūtė, S.

    The lists of stars selected spectroscopically by Vyssotsky at the McCormick Observatory and the 4th version of the Catalogue of Nearby Stars (CNS4) are two major sources of nearby K-M dwarfs, which complement each other and provide a kinematically unbiased sample of about 1400 such stars. With the addition of Hipparcos and Tycho astrometry, this stellar sample offers perhaps best insight on the kinematical properties of the lower main sequence stars in the immediate solar neighborhood. Until recently, however, the main limitation in observational data for this sample was the lack of well determined radial velocities, especially for fainter magnitude stars. Therefore our first goal was to perform radial velocity observations for one-third of the sample stars which had no accurate or any radial velocity data. Using the CORAVEL spectrometer of Vilnius University Observatory, attached to the 1.5-m NASA and 1.6-m Kuiper telescopes at Steward Observatory, US, and the 1.6-m telescope at Molėtai Observatory, Lithuania, radial velocities have been recently measured for 475 K-M dwarfs. These observations, together with previous radial-velocity data and available astrometry, are used to derive complete kinematical information on the sample stars. Preliminary analysis shows the presence of different age populations which dominate in different regions of the asymmetric drift: from the young disk component, showing no lag behind the rotational motion of the Sun, to the thick disk stars which make up an extended asymmetric tail. Assuming that the U and W velocity components have zero motion relative to the LSR, and that the asymmetric drift is proportional to sigma 2_U, we find the peculiar motion of the Sun relative to the LSR (U_⊙, V_⊙, W_⊙)= (9.3± 1.3, 5.9± 0.8, 6.9±0.7) km s-1. No attempt was made at this stage of work to determine V_⊙ directly from the mean V-motion of the young disk stars. After completion of the radial-velocity program, the next step will be to

  17. 2MASSJ035523.51+113337.4: A Young, Dusty, Nearby, Isolated Brown Dwarf Resembling A Giant Exoplanet

    CERN Document Server

    Faherty, Jacqueline K; Cruz, Kelle L; Mamajek, Eric E; Núñez, Alejandro

    2012-01-01

    We present parallax and proper motion measurements, near-infrared spectra, and WISE photometry for the low surface gravity L5gamma dwarf 2MASSJ035523.51+113337.4 (2M0355). We use these data to evaluate photometric, spectral, and kinematic signatures of youth. We confirm low-gravity spectral morphology and find a strong resemblance to the sharp triangular shaped H-band spectrum of the ~10 Myr planetary-mass object 2MASSJ1207b. We find that 2M0355 is underluminous compared to a normal field L5 dwarf in the optical and MKO J,H, and K bands and transitions to being overluminous from 3-12 microns indicating that enhanced photospheric dust shifts flux to longer wavelengths for young, low-gravity objects, creating a red spectral energy distribution. Investigating the near-infrared color magnitude diagram for brown dwarfs confirms that 2M0355 is redder and underluminous compared to the known brown dwarf population, similar to the peculiarities of directly imaged exoplanets 2MASSJ1207b and HR8799bcd. We calculate UVW ...

  18. Pleiades low-mass brown dwarfs: the cluster L dwarf sequence

    CERN Document Server

    Bihain, G; Béjar, V J S; Caballero, J A; Bailer-Jones, C A L; Mundt, R; Acosta-Pulido, J A; Torres, A M

    2006-01-01

    We present a search for low-mass brown dwarfs in the Pleiades open cluster. The identification of Pleiades members fainter and cooler than those currently known allows us to constrain evolutionary models for L dwarfs and to extend the study of the cluster mass function to lower masses. We conducted a 1.8 deg^2 near-infrared J-band survey at the 3.5m Calar Alto Telescope, with completeness J~19.0. The detected sources were correlated with those of previously available optical I-band images (completeness I~22). Using a J versus I-J colour-magnitude diagram, we identified 18 faint red L-type candidates, with magnitudes 17.43.2. If Pleiades members, their masses would span ~0.040-0.020 M_Sol. We performed follow-up HKs-band imaging to further confirm their cluster membership by photometry and proper motion. Out of 11 IJ candidates with proper motion measurements, we find six cluster members, two non-members and three whose membership is uncertain and depends on the intrinsic velocity dispersion of Pleiades brown ...

  19. Spitzer Trigonometric Parallaxes of the Solar Neighborhood's Coldest Brown Dwarfs, Part 2

    Science.gov (United States)

    Kirkpatrick, J. Davy; Gelino, Christopher; Beichman, Charles; Martin, Emily; Smart, Richard; Faherty, Jacqueline; Tinney, Christopher; Cushing, Michael; Schneider, Adam; Wright, Edward; Lowrance, Patrick

    2016-08-01

    Objects in the immediate solar neighborhood serve as touchstones of stellar populations throughout the rest of the Milky Way and the Universe in general. A detailed accounting and characterization of these objects is therefore of fundamental importance to many fields of astrophysics. One of the most fundamental properties is distance, which directly determines absolute luminosity and space density and aids in the decipherment of radius, kinematics, age, the mass function, etc. The Gaia mission is soon poised to revolutionize our understanding of the solar neighborhood through micro-arcsecond astrometric monitoring. Its sensitivity, however, is limited to objects that emit strongly at wavelengths shorter than 1 micron; Gaia will be unable to detect any objects as cool as late-T and Y dwarfs (250-1100K). Nevertheless, these very cold objects are critically important not only to our understanding of the star formation process at the lowest masses, but also in our comprehension of the physical mechanisms present in cold, exoplanet-like atmospheres. In this proposal, we extend our distance determinations to objects colder than those Gaia can probe by continuing to measure parallaxes, as begun in our Cycle 9-10 program 90007, for all T6 and later brown dwarfs within 20 pc of the Sun.

  20. HST Spectral Mapping of L/T Transition Brown Dwarfs Reveals Cloud Thickness Variations

    CERN Document Server

    Apai, Daniel; Buenzli, Esther; Burrows, Adam; Reid, Iain N; Jayawardhana, Ray

    2013-01-01

    Most directly imaged giant exoplanets are fainter than brown dwarfs with similar spectra. To explain their relative underluminosity unusually cloudy atmospheres have been proposed. However, with multiple parameters varying between any two objects, it remained difficult to observationally test this idea. We present a new method, sensitive time-resolved Hubble Space Telescope near-infrared spectroscopy, to study two rotating L/T transition brown dwarfs (2M2139 and SIMP0136). The observations provide spatially and spectrally resolved mapping of the cloud decks of the brown dwarfs. The data allow the study of cloud structure variations while other parameters are unchanged. We find that both brown dwarfs display variations of identical nature: J- and H-band brightness variations with minimal color and spectral changes. Our light curve models show that even the simplest surface brightness distributions require at least three elliptical spots. We show that for each source the spectral changes can be reproduced with ...

  1. First limits on the occurrence rate of short-period planets orbiting brown dwarfs

    CERN Document Server

    He, Matthias Y; Gillon, Michaël

    2016-01-01

    Planet formation theories predict a large but still undetected population of short-period terrestrial planets orbiting brown dwarfs. Should specimens of this population be discovered transiting relatively bright and nearby brown dwarfs, the Jupiter-size and the low luminosity of their hosts would make them exquisite targets for detailed atmospheric characterisation with JWST and future ground-based facilities. The eventual discovery and detailed study of a significant sample of transiting terrestrial planets orbiting nearby brown dwarfs could prove to be useful not only for comparative exoplanetology but also for astrobiology, by bringing us key information on the physical requirements and timescale for the emergence of life. In this context, we present a search for transit-signals in archival time-series photometry acquired by the Spitzer Space Telescope for a sample of 44 nearby brown dwarfs. While these 44 targets were not particularly selected for their brightness, the high precision of their Spitzer ligh...

  2. Toward the End of Stars: Discovering the Galaxy's Coldest Brown Dwarfs

    CERN Document Server

    Burgasser, Adam J; Cruz, Kelle; Cushing, Michael; Leggett, Sandy; Lodders, Katharina; Mainzer, Amanda; Marley, Mark; Metchev, Stanimir; Mohanty, Subhanjoy; Oppenheimer, Ben; West, Andrew

    2009-01-01

    This White Paper to the National Academy of Sciences Astro2010 Decadal Review Committee highlights cross-disciplinary science opportunities over the next decade with cold brown dwarfs, sources defined here as having photospheric temperatures less than ~1000 K.

  3. Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

    NARCIS (Netherlands)

    Toloba, E.; Boselli, A.; Cenarro, A. J.; Peletier, R. F.; Gorgas, J.; Gil de Paz, A.; Munoz-Mateos, J. C.

    2011-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy

  4. Kinematics and chemistry of faint high latitude dwarf carbon stars

    Science.gov (United States)

    Yoon, Jinmi; Beers, Timothy C.; Dietz, Sarah; Lee, Young Sun; Placco, Vinicius M.

    2017-01-01

    The diffuse halo system of the Milky Way is complex, and has been shown to comprise at least two main components: a near-zero net rotation inner-halo and a more rapidly rotating outer-halo component. Studies of the ancient, very metal-poor stars in the Galactic halo system are crucial for understanding its early formation history. The so-called carbon-enhanced metal-poor (CEMP) stars are an important subset of the stars in the halo system, which exhibit distinctive kinematic and chemical signatures that can be used to constrain the star-formation histories and assembly of the various Galactic components.We have examined the sample of main-sequence dwarf and other faint high Galactic latitude carbon-enhanced stars from the Sloan Digital Sky Survey studied by Green (2013). As noted by Green, many of these starsexhibit high proper motions, which have been later claimed to be related to possible binary ejection models Plant et al. (2016). By use of the CEMP sub-classification approach of Yoon et al. (2016), we investigate whether the kinematics of these stars might instead result from their membership in the inner/outer halo populations of the Galaxy.ReferencesGreen, P. 2013, ApJ, 765, 12Plant, K. et al. 2016, AAS 227.34115Yoon, J. et al. 2016, ApJ, in pressAcknowledgementThis work was supported in part by the National Science Foundation under Grant No. PHY-1430152 (JINA Center for the Evolution of the Elements).

  5. Brown dwarf disks with ALMA: evidence for truncated dust disks in Ophiuchus

    CERN Document Server

    Testi, L; Scholz, A; Tazzari, M; Ricci, L; Monsalvo, I de Gregorio

    2016-01-01

    The study of the properties of disks around young brown dwarfs can provide important clues on the formation of these very low mass objects and on the possibility of forming planetary systems around them. The presence of warm dusty disks around brown dwarfs is well known, based on near- and mid-infrared studies. High angular resolution observations of the cold outer disk are limited, we used ALMA to attempt a first survey of young brown dwarfs in the rho-Ophiuchi star forming region with ALMA. All 17 young brown dwarfs in our sample were observed at 890 um in the continuum at ~0.5" angular resolution. The sensitivity of our observations was chosen to detect ~0.5 MEarth of dust. We detect continuum emission in 11 disks (65% of the total), the estimated mass of dust in the detected disks ranges from ~0.5 to ~6 MEarth. These disk masses imply that planet formation around brown dwarfs may be relatively rare and that the supra-Jupiter mass companions found around some brown dwarfs are probably the result of a binar...

  6. Kinematics of the Galactic disk from LAMOST Dwarf sample

    CERN Document Server

    Jing, Yingjie; Gu, Jiayin; Jia, Yunpeng; Peng, Xiyan; Chen, Yuqin; Wu, Zhenyu; Ma, Jun; Zhou, Xu; Cao, Zihuang; Hou, Yonghui; Wang, Yuefei; Zhang, Yong

    2016-01-01

    Based on the LAMOST survey and Sloan Digital Sky Survey (SDSS), we use low-resolution spectra of 130,043 F/G-type dwarf stars to study the kinematics and metallicity properties of the Galactic disk. Our study shows that the stars with poorer metallicity and larger vertical distance from Galactic plane tend to have larger eccentricity and velocity dispersion. After separating the sample stars into likely thin-disk and thick-disk sub-sample, we find that there exits a negative gradient of rotation velocity $V_{\\phi}$ with metallicity [Fe/H] for the likely thin-disk sub-sample, and the thick-disk sub-sample exhibit a larger positive gradient of rotation velocity with metallicity. By comparing with model prediction, we consider the radial migration of stars appears to have influenced on the thin-disk formation. In addition, our results shows that the observed thick-disk stellar orbital eccentricity distribution peaks at low eccentricity ($e \\sim 0.2$) and extends to a high eccentricity ($e \\sim 0.8$). We compare ...

  7. DISCOVERY OF THREE DISTANT, COLD BROWN DWARFS IN THE WFC3 INFRARED SPECTROSCOPIC PARALLELS SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Masters, D.; Siana, B. [Department of Physics and Astronomy, University of California, Riverside, CA 92521 (United States); McCarthy, P.; Hathi, N. P.; Dressler, A. [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States); Burgasser, A. J. [Center for Astrophysics and Space Science, University of California, San Diego, La Jolla, CA 92093 (United States); Malkan, M.; Ross, N. R. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States); Scarlata, C. [Astronomy Department, University of Minnesota, Minneapolis, MN 55455 (United States); Henry, A. [Department of Physics, University of California, Santa Barbara, CA 93106 (United States); Colbert, J.; Atek, H. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Rafelski, M.; Teplitz, H. [Infrared Processing and Analysis Center, Caltech, Pasadena, CA 91125 (United States); Bunker, A. [Department of Physics, University of Oxford, Oxford (United Kingdom)

    2012-06-10

    We present the discovery of three late-type ({>=}T4.5) brown dwarfs, including a probable Y dwarf, in the WFC3 Infrared Spectroscopic Parallels (WISP) survey. We use the G141 grism spectra to determine the spectral types of the dwarfs and derive distance estimates based on a comparison with nearby T dwarfs with known parallaxes. These are the most distant spectroscopically confirmed T/Y dwarfs, with the farthest at an estimated distance of {approx}400 pc. We compare the number of cold dwarfs found in the WISP survey with simulations of the brown dwarf mass function. The number found is generally consistent with an initial stellar mass function dN/dM{proportional_to}M{sup -{alpha}} with {alpha} = 0.0-0.5, although the identification of a Y dwarf is somewhat surprising and may be indicative of either a flatter absolute magnitude/spectral-type relation than previously reported or an upturn in the number of very-late-type brown dwarfs in the observed volume.

  8. Discovery of Three Distant, Cold Brown Dwarfs in the WFC3 Infrared Spectroscopic Parallels Survey

    CERN Document Server

    Masters, Daniel; Burgasser, Adam J; Hathi, Nimish P; Malkan, Matthew; Ross, Nathaniel R; Siana, Brian; Scarlata, Claudia; Henry, Alaina; Colbert, James; Atek, Hakim; Rafelski, Marc; Teplitz, Harry; Bunker, Andrew; Dressler, Alan

    2012-01-01

    We present the discovery of three late type (>T4) brown dwarfs, including a probable Y dwarf, in the WFC3 Infrared Spectroscopic Parallels (WISP) Survey. We use the G141 grism spectra to determine the spectral types of the dwarfs and derive distance estimates based on a comparison with nearby T dwarfs with known parallaxes. These are the most distant spectroscopically confirmed T/Y dwarfs, with the farthest at an estimated distance of ~400 pc. We compare the number of cold dwarfs found in the WISP survey with simulations of the brown dwarf mass function. The number found is generally consistent with an initial stellar mass function dN/dM \\propto M^{-\\alpha} with \\alpha = 0.0--0.5, although the identification of a Y dwarf is somewhat surprising and may be indicative of either a flatter absolute magnitude/spectral type relation than previously reported or an upturn in the number of very late type brown dwarfs in the observed volume.

  9. An irradiated brown-dwarf companion to an accreting white dwarf

    CERN Document Server

    Santisteban, Juan V Hernández; Littlefair, Stuart P; Breton, Rene P; Dhillon, Vikram S; Gänsicke, Boris T; Marsh, Thomas R; Pretorius, Magaretha L; Southworth, John; Hauschildt, Peter H

    2016-01-01

    Brown dwarfs and giant planets orbiting close to a host star are subjected to significant irradiation that can modify the properties of their atmospheres. In order to test the atmospheric models that are used to describe these systems, it is necessary to obtain accurate observational estimates of their physical properties (masses, radii, temperatures, albedos). Interacting compact binary systems provide a natural laboratory for studying strongly irradiated sub-stellar objects. As the mass-losing secondary in these systems makes a critical, but poorly understood transition from the stellar to the sub-stellar regime, it is also strongly irradiated by the compact accretor. In fact, the internal and external energy fluxes are both expected to be comparable in these objects, providing access to an unexplored irradiation regime. However, the atmospheric properties of such donors have so far remained largely unknown. Here, we report the direct spectroscopic detection and characterisation of an irradiated sub-stellar...

  10. Search for exoplanets and brown dwarfs with VLBI

    CERN Document Server

    Katarzynski, K; Gozdziewski, K

    2016-01-01

    The main aim of this work is to estimate possible radio GHz emission of extrasolar planets and brown dwarfs and to check if such radiation can be detected by Very Large Baseline Interferometers (VLBI). In the estimation we assume that the emission may originate in processes similar to those observed in the Jupiter system. The frequency of the radio emission that is produced in this system depends mostly on the magnetic field strength. Jupiter's magnetic field ($\\sim 9$ G on average) allows for radiation from kHz frequencies up to 40 MHz. This is well below the frequency range of VLBI. However, it was demonstrated that the magnetic field strength in massive and young object may be up to two orders of magnitude higher than for Jupiter, which is especially relevant for planets around short-lived A type stars. This should extend the range of the emission up to GHz frequencies. We calculated expected flux densities of radio emission for a variety of hypothetical young planetary systems. We analysed two different e...

  11. A new parallax measurement for the coldest known brown dwarf

    Energy Technology Data Exchange (ETDEWEB)

    Luhman, K. L.; Esplin, T. L., E-mail: kluhman@astro.psu.edu [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-11-20

    WISE J085510.83–071442.5 was recently discovered as the coldest known brown dwarf based on four epochs of images from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope. We have improved the accuracy of its parallax measurement by obtaining two additional epochs of Spitzer astrometry. We derive a parallactic distance of 2.31 ± 0.08 pc, which continues to support its rank as the fourth closest known system to the Sun when compared to WISE J104915.57–531906.1 AB (2.02 ± 0.02 pc) and Wolf 359 (2.386 ± 0.012 pc). The new constraint on the absolute magnitude at 4.5 μm indicates an effective temperature of 235-260 K based on four sets of theoretical models. We also show the updated positions of WISE J085510.83–071442.5 in two color-magnitude diagrams. Whereas Faherty and coworkers cited its location in M {sub W2} versus J – W2 as evidence of water clouds, we find that those data can be explained instead by cloudless models that employ non-equilibrium chemistry.

  12. A New Parallax Measurement for the Coldest Known Brown Dwarf

    CERN Document Server

    Luhman, K L

    2014-01-01

    WISE J085510.83-071442.5 was recently discovered as the coldest known brown dwarf based on four epochs of images from the Wide-field Infrared Survey Explorer and the Spitzer Space Telescope. We have improved the accuracy of its parallax measurement by obtaining two additional epochs of Spitzer astrometry. We derive a parallactic distance of 2.31+/-0.08 pc, which continues to support its rank as the fourth closest known system to the Sun when compared to WISE J104915.57-531906.1 AB (2.02+/-0.02 pc) and Wolf 359 (2.386+/-0.012 pc). The new constraint on the absolute magnitude at 4.5um indicates an effective temperature of 235-260 K based on four sets of theoretical models. We also show the updated positions of WISE J085510.83-071442.5 in two color-magnitude diagrams. Whereas Faherty and coworkers cited its location in MW2 versus J-W2 as evidence of water clouds, we find that those data can be explained instead by cloudless models that employ non-equilibrium chemistry.

  13. Protoplanetary Disk Masses from Stars to Brown Dwarfs

    CERN Document Server

    Mohanty, Subhanjoy; Mortlock, Daniel; Pascucci, Ilaria; Scholz, Aleks; Thompson, Mark; Apai, Daniel; Lodato, Giuseppe; Looper, Dagny

    2013-01-01

    We present SCUBA-2 850um observations for 7 very low mass stars (VLMS) and brown dwarfs (BDs): 3 in Taurus, 4 in the TWA, and all classical T Tauri (cTT) analogs. We detect 2 of the 3 Taurus disks, but none of the TWA ones. Our 3sigma limits correspond to a dust mass of 1.2 MEarth in Taurus and a mere 0.2 MEarth in the TWA (3--10x deeper than previous work). We combine our data with other sub-mm/mm surveys of Taurus, rho Oph and the TWA to investigate trends in disk mass and grain growth during the cTT phase. We find : (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is 100 AU for intermediate-mass stars, solar-types and VLMS, and 20 AU for BDs. (2) While the upper envelope of disk masses increases with Mstar from BDs to VLMS to solar-types, no increase is seen from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate masses. (3) Many disks around Taurus and rho Oph intermediate-mass and solar-type stars evin...

  14. HABITABLE PLANETS ECLIPSING BROWN DWARFS: STRATEGIES FOR DETECTION AND CHARACTERIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Belu, Adrian R.; Selsis, Franck; Raymond, Sean N.; Bolmont, Emeline [Universite de Bordeaux, LAB, UMR 5804, F-33270, Floirac (France); Palle, Enric [Instituto de Astrofisica de Canarias, E-38205 La Laguna (Spain); Street, Rachel [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Sahu, D. K.; Anupama, G. C. [Indian Institute of Astrophysics, Koramangala, Bangalore 560034 (India); Von Braun, Kaspar [NASA Exoplanet Science Institute, California Institute of Technology, MC 100-22, Pasadena, CA 91125 (United States); Figueira, Pedro [Centro de Astrofisica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Ribas, Ignasi, E-mail: belu@obs.u-bordeaux1.fr [Institut de Ciencies de l' Espai (CSIC-IEEC), Campus UAB, Facultat de Ciencies, Torre C5, parell, 2a pl., E-08193 Bellaterra (Spain)

    2013-05-10

    Given the very close proximity of their habitable zones, brown dwarfs (BDs) represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper, we develop search strategies to find habitable planets transiting BDs depending on their maximum habitable orbital period (P{sub HZ{sub out}}). Habitable planets with P{sub HZ{sub out}} shorter than the useful duration of a night (e.g., 8-10 hr) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous BDs require continuous monitoring for longer duration, e.g., from space or from a longitude-distributed network (one test scheduling achieved three telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known BDs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5{sup +5.6}{sub -1.4}% and 56{sup +31}{sub -13}%, depending on our assumptions. We calculate that BDs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using {approx}1% of a five-year mission's lifetime spread over a contiguous segment only one-fifth to one-tenth of this duration.

  15. Chemical abundances of stars with brown-dwarf companions

    CERN Document Server

    Sánchez, D Mata; Israelian, G; Santos, N C; Sahlmann, J; Udry, S

    2014-01-01

    It is well-known that stars with giant planets are on average more metal-rich than stars without giant planets, whereas stars with detected low-mass planets do not need to be metal-rich. With the aim of studying the weak boundary that separates giant planets and brown dwarfs (BDs) and their formation mechanism, we analyze the spectra of a sample of stars with already confirmed BD companions both by radial velocity and astrometry. We employ standard and automatic tools to perform an EW-based analysis and to derive chemical abundances from CORALIE spectra of stars with BD companions. We compare these abundances with those of stars without detected planets and with low-mass and giant-mass planets. We find that stars with BDs do not have metallicities and chemical abundances similar to those of giant-planet hosts but they resemble the composition of stars with low-mass planets. The distribution of mean abundances of $\\alpha$-elements and iron peak elements of stars with BDs exhibit a peak at about solar abundance...

  16. Discovery of a Wide Binary Brown Dwarf Born in Isolation

    CERN Document Server

    Luhman, K L; Allen, P R; Muench, A A; Finkbeiner, D P

    2009-01-01

    During a survey for stars with disks in the Taurus star-forming region using the Spitzer Space Telescope, we have discovered a pair of young brown dwarfs, FU Tau A and B, in the Barnard 215 dark cloud. They have a projected angular separation of 5.7", corresponding to 800 AU at the distance of Taurus. To assess the nature of these two objects, we have obtained spectra of them and have constructed their spectral energy distributions. Both sources are young (~1 Myr) according to their Halpha emission, gravity-sensitive spectral features, and mid-IR excess emission. The proper motion of FU Tau A provides additional evidence of its membership in Taurus. We measure spectral types of M7.25 and M9.25 for FU Tau A and B, respectively, which correspond to masses of ~0.05 and ~0.015 Msun according to the evolutionary models of Chabrier and Baraffe. FU Tau A is significantly overluminous relative to an isochrone passing through FU Tau B and relative to other members of Taurus near its spectral type, which may indicate t...

  17. Deep search for companions to probable young brown dwarfs

    CERN Document Server

    Chauvin, G; Boccaletti, A; Cruz, K; Lagrange, A -M; Zuckerman, B; Bessell, M S; Beuzit, J -L; Bonnefoy, M; Dumas, C; Lowrance, P; Mouillet, D; Song, I

    2012-01-01

    We have obtained high contrast images of four nearby, faint, and very low mass objects 2MASSJ04351455-1414468, SDSSJ044337.61+000205.1, 2MASSJ06085283-2753583 and 2MASSJ06524851-5741376 (here after 2MASS0435-14, SDSS0443+00, 2MASS0608-27 and 2MASS0652-57), identified in the field as probable isolated young brown dwarfs. Our goal was to search for binary companions down to the planetary mass regime. We used the NAOS-CONICA adaptive optics instrument (NACO) and its unique capability to sense the wavefront in the near-infrared to acquire sharp images of the four systems in Ks, with a field of view of 28"*28". Additional J and L' imaging and follow-up observations at a second epoch were obtained for 2MASS0652-57. With a typical contrast DKs= 4.0-7.0 mag, our observations are sensitive down to the planetary mass regime considering a minimum age of 10 to 120 Myr for these systems. No additional point sources are detected in the environment of 2MASS0435-14, SDSS0443+00 and 2MASS0608-27 between 0.1-12" (i.e about 2 t...

  18. Habitable Planets Eclipsing Brown Dwarfs: Strategies for Detection and Characterization

    Science.gov (United States)

    Belu, Adrian R.; Selsis, Franck; Raymond, Sean N.; Pallé, Enric; Street, Rachel; Sahu, D. K.; von Braun, Kaspar; Bolmont, Emeline; Figueira, Pedro; Anupama, G. C.; Ribas, Ignasi

    2013-05-01

    Given the very close proximity of their habitable zones, brown dwarfs (BDs) represent high-value targets in the search for nearby transiting habitable planets that may be suitable for follow-up occultation spectroscopy. In this paper, we develop search strategies to find habitable planets transiting BDs depending on their maximum habitable orbital period (P HZ out). Habitable planets with P HZ out shorter than the useful duration of a night (e.g., 8-10 hr) can be screened with 100% completeness from a single location and in a single night (near-IR). More luminous BDs require continuous monitoring for longer duration, e.g., from space or from a longitude-distributed network (one test scheduling achieved three telescopes, 13.5 contiguous hours). Using a simulated survey of the 21 closest known BDs (within 7 pc) we find that the probability of detecting at least one transiting habitable planet is between 4.5^{+5.6}_{-1.4}% and 56^{+31}_{-13}%, depending on our assumptions. We calculate that BDs within 5-10 pc are characterizable for potential biosignatures with a 6.5 m space telescope using ~1% of a five-year mission's lifetime spread over a contiguous segment only one-fifth to one-tenth of this duration.

  19. New light on dark stars red dwarfs, low-mass stars, brown dwarfs

    CERN Document Server

    Reid, I Neill

    2000-01-01

    Perhaps the most common question that a child asks when he or she sees the night sky from a dark site for the first time is: 'How many stars are there?' This happens to be a question which has exercised the intellectual skills of many astronomers over the course of most of the last century, including, for the last two decades, one of the authors of this text. Until recently, the most accurate answer was 'We are not certain, but there is a good chance that almost all of them are M dwarfs. ' Within the last three years, results from new sky-surveys - particularly the first deep surveys at near­ infrared wavelengths - have provided a breakthrough in this subject, solidifying our census of the lowest-mass stars and identifying large numbers of the hitherto almost mythical substellar-mass brown dwarfs. These extremely low-luminosity objects are the central subjects of this book, and the subtitle should be interpreted accordingly. The expression 'low-mass stars' carries a wide range of meanings in the astronomical...

  20. Ultracool Field Brown Dwarf Candidates Selected at 4.5 microns

    CERN Document Server

    Eisenhardt, Peter R M; Stern, Daniel; Wright, Edward L; Ashby, Matthew L N; Brodwin, Mark; Brown, Michael J I; Bussmann, R S; Dey, Arjun; Ghez, A M; Glikman, Eilat; Gonzalez, Anthony H; Kirkpatrick, J Davy; Konopacky, Quinn; Mainzer, Amy; Vollbach, David; Wright, Shelley A

    2010-01-01

    We have identified a sample of cool field brown dwarf candidates using IRAC data from the Spitzer Deep, Wide-Field Survey (SDWFS). The candidates were selected from 400,000 SDWFS sources with [4.5] = 1.5 and [4.5] - [8.0] 70 pc. The reddest brown dwarf candidate (SDWFS J143356.62+351849.2) has [3.6] - [4.5]=2.24 and H - [4.5] > 5.7, redder than any published brown dwarf in these colors, and may be the first example of the elusive Y-dwarf spectral class. Models from Burrows et al. (2003) predict larger numbers of cool brown dwarfs should be found for a Chabrier (2003) mass function. Suppressing the model [4.5] flux by a factor of two, as indicated by previous work, brings the Burrows models and observations into reasonable agreement. The recently launc hed Wide-field Infrared Survey Explorer (WISE) will probe a volume ~40x larger and should find hundreds of brown dwarfs cooler than T7.

  1. Deriving the true mass of an unresolved Brown Dwarf companion to an M-Dwarf with AO aided astrometry*

    Directory of Open Access Journals (Sweden)

    Kürster M.

    2011-07-01

    Full Text Available From radial velocity (RV detections alone one does not get all orbital parameters needed to derive the true mass of a non-transiting, unresolved substellar companion to a star. Additional astrometric measurements are needed to calculate the inclination and the longitude of the ascending node. Until today only few true substellar companion masses have been determined by this method with the HST fine guidance sensor [1, 2]. We aim to derive the true mass of a brown dwarf candidate companion to an early M 2.5V dwarf with groundbased high-resolution astrometry aided by adaptive optics. We found this unique brown dwarf desert object, whose distance to the host star is only 0.42 AU, in our UVES precision RV survey of M dwarfs, inferring a minimum companion mass of 27 Jupiter masses [3]. Combining the data with HIPPARCOS astrometry, we found a probability of only 2.9% that the companion is stellar. We therefore observed the host star together with a reference star within a monitoring program with VLT/NACO to derive the true mass of the companion and establish its nature (brown dwarf vs. star. Simultaneous observations of a reference field in a globular cluster are performed to determine the stability of the adaptive optics (AO plus detector system and check its suitability for such high-precision astrometric measurements over several epochs which are needed to find and analyse extrasolar planet systems.

  2. Disc Frequencies for Brown Dwarfs in the Upper Scorpius OB Association: Implications for Brown Dwarf Formation Theories

    CERN Document Server

    Riaz, B; Goodwin, S; Stamatellos, D; Thompson, M

    2011-01-01

    We have investigated the brown dwarf (BD) and stellar disc fractions in the Upper Scorpius OB Association (USco) and compared them with several other young regions. We have compiled the most complete sample of of all spectroscopically confirmed BDs in USco, and have made use of the WISE catalog to identify the disc candidates. We report on the discovery of 12 new BD discs in USco, with spectral type (SpT) between M6 and M8.5. The WISE colors for the new discs are similar to the primordial (transition) discs earlier detected in USco. Combining with previous surveys, we find the lowest inner disc fractions (~20-25%) for a wide range in stellar masses (~0.01-4.0 Msun) in the USco association. The low disc fractions for high-mass stars in USco (and the other clusters) are consistent with an evolutionary decline in inner disc frequency with age. However, BD disc fractions are higher than those for the stars in 1-3 Myr clusters, but very low in the ~5 Myr old USco. Also, primordial BD discs are still visible in the...

  3. A Keck LGS AO Search for Brown Dwarf and Planetary Mass Companions to Upper Scorpius Brown Dwarfs

    CERN Document Server

    Biller, Beth; Liu, Michael; Close, Laird; Dupuy, Trent

    2011-01-01

    We searched for binary companions to 20 young brown dwarfs in the Upper Scorpius association (145 pc, 5 Myr, nearest OB association) with the the Laser Guide Star adaptive optics system and the facility infrared camera NIRC2 on the 10 m Keck II telescope. We discovered a 0.14" companion (20.9+-0.4 AU) to the <0.1 MJup object SCH J16091837-20073523. From spectral deconvolution of integrated-light near-IR spectroscopy of SCH1609 using the SpeX spectrograph (Rayner et al. 2003), we estimate primary and secondary spectral types of M6+-0.5 and M7+-1.0, corresponding to masses of 79+-17 MJup and 55+-25 MJup at an age of 5 Myr and masses of 84+-15 MJup and 60+-25 MJup at an age of 10 Myr. For our survey objects with spectral types later than M8, we find an upper limit on the binary fraction of <9% (1-sigma) at separations of 10 -- 500 AU. We combine the results of our survey with previous surveys of Upper Sco and similar young regions to set the strongest constraints to date on binary fraction for young subste...

  4. The role of convection, overshoot, and gravity waves for the transport of dust in M dwarf and brown dwarf atmospheres

    CERN Document Server

    Freytag, Bernd; Ludwig, Hans-Guenter; Homeier, Derek; Steffen, Matthias

    2010-01-01

    Observationally, spectra of brown dwarfs indicate the presence of dust in their atmospheres while theoretically it is not clear what prevents the dust from settling and disappearing from the regions of spectrum formation. Consequently, standard models have to rely on ad hoc assumptions about the mechanism that keeps dust grains aloft in the atmosphere. We apply hydrodynamical simulations to develop an improved physical understanding of the mixing properties of macroscopic flows in M dwarf and brown dwarf atmospheres, in particular of the influence of the underlying convection zone. We performed 2D radiation hydrodynamics simulations including a description of dust grain formation and transport with the CO5BOLD code. The simulations cover the very top of the convection zone and the photosphere including the dust layers for effective temperatures between 900K and 2800K, all with logg=5 assuming solar chemical composition. Convective overshoot occurs in the form of exponentially declining velocities with small s...

  5. Multiwaveband photometry of the irradiated brown dwarf WD0137-349B

    CERN Document Server

    Casewell, S L; Maxted, P F L; Marley, M S; Fortney, J J; Rimmer, P B; Littlefair, S P; Wynn, G; Burleigh, M R; Helling, Ch

    2014-01-01

    WD0137-349 is a white dwarf-brown dwarf binary system in a 116 minute orbit. We present radial velocity observations and multiwaveband photometry from V, R and I in the optical, to J, H and Ks in the near-IR and [3.6], [4.5], [5.8] and [8.0] microns in the mid-IR. The photometry and lightcurves show variability in all wavebands, with the amplitude peaking at [4.5] microns, where the system is also brightest. Fluxes and brightness temperatures were computed for the heated and unheated atmosphere of the brown dwarf (WD0137-349B) using synthetic spectra of the white dwarf using model atmosphere simulations. We show that the flux from the brown dwarf dayside is brighter than expected in the Ks and [4.5] micron bands when compared to models of irradiated brown dwarfs with full energy circulation and suggest this over-luminosity may be attributed to H2 fluorescence or H3+ being generated in the atmosphere by the UV irradiation.

  6. Flash ionization signature in coherent cyclotron emission from brown dwarfs

    Science.gov (United States)

    Vorgul, I.; Helling, Ch.

    2016-05-01

    Brown dwarfs (BDs) form mineral clouds in their atmospheres, where charged particles can produce large-scale discharges in the form of lightning resulting in substantial sudden increase of local ionization. BDs are observed to emit cyclotron radio emission. We show that signatures of strong transient atmospheric ionization events (flash ionization) can be imprinted on a pre-existing radiation. Detection of such flash ionization events will open investigations into the ionization state and atmospheric dynamics. Such events can also result from explosion shock waves, material outbursts or (volcanic) eruptions. We present an analytical model that describes the modulation of a pre-existing electromagnetic radiation by a time-dependent (flash) conductivity that is characteristic for flash ionization events like lightning. Our conductivity model reproduces the conductivity function derived from observations of terrestrial gamma-ray flashes, and is applicable to astrophysical objects with strong temporal variations in the local ionization, as in planetary atmospheres and protoplanetary discs. We show that the field responds with a characteristic flash-shaped pulse to a conductivity flash of intermediate intensity. More powerful ionization events result in smaller variations of the initial radiation, or in its damping. We show that the characteristic damping of the response field for high-power initial radiation carries information about the ionization flash magnitude and duration. The duration of the pulse amplification or the damping is consistently shorter for larger conductivity variations and can be used to evaluate the intensity of the flash ionization. Our work suggests that cyclotron emission could be probe signals for electrification processes inside BD atmosphere.

  7. SMA and CARMA observations of young brown dwarfs in ρ Ophiuchi and Taurus

    Directory of Open Access Journals (Sweden)

    Lee C.-F.

    2011-07-01

    Full Text Available Molecular outflows provide vital information about the earliest stages in the birth of stars, studying the molecular outflow properties is therefore crucial for understanding how stars form. Brown dwarfs with masses between that of stars and planets are not massive enough to maintain stable hydrogen-burning fusion reactions during most of their lifetime. Their origins are subject to much debate in recent literature because their masses are far below the typical mass where core collapse is expected to occur. Based on Submillimeter Array (SMA and Combined Array for Research in Millimeter-wave Astronomy (CARMA observations, we present the first detections of bipolar molecular outflows from young brown dwarfs in ρ Ophiuchi and Taurus. Our results demonstrate that the bipolar molecular outflow operates down to brown dwarf masses, occurring in brown dwarfs as a scaled-down version of the universal process seen in young low-mass stars. This demonstrates that brown dwarfs and low-mass stars likely share the same formation mechanism.

  8. Hunting for brown dwarf binaries and testing atmospheric models with X-Shooter

    CERN Document Server

    Manjavacas, E; Alcalá, J M; Zapatero-Osorio, M R; Béjar, V J S; Homeier, D; Bonnefoy, M; Smart, R L; Henning, T; Allard, F

    2015-01-01

    The determination of the brown dwarf binary fraction may contribute to the understanding of the substellar formation mechanisms. Unresolved brown dwarf binaries may be revealed through their peculiar spectra or the discrepancy between optical and near-infrared spectral type classification. We obtained medium-resolution spectra of 22 brown dwarfs with these characteristics using the X-Shooter spectrograph at the VLT. We aimed to identify brown dwarf binary candidates, and to test if the BT-Settl 2014 atmospheric models reproduce their observed spectra. To find binaries spanning the L-T boundary, we used spectral indices and compared the spectra of the selected candidates to single spectra and synthetic binary spectra. We used synthetic binary spectra with components of same spectral type to determine as well the sensitivity of the method to this class of binaries. We identified three candidates to be combination of L plus T brown dwarfs. We are not able to identify binaries with components of similar spectral ...

  9. Brown Dwarf Model Atmospheres Based on Multi-Dimensional Radiation Hydrodynamics

    Science.gov (United States)

    Allard, France; Freytag, Bernd

    2010-11-01

    The atmospheres of Brown Dwarfs (BDs) are the site of molecular opacities and cloud formation, and control their cooling rate, radius and brightness evolution. Brown dwarfs evolve from stellar-like properties (magnetic activity, spots, flares, mass loss) to planet-like properties (electron degeneracy of the interior, cloud formation, dynamical molecular transport) while retaining, due to their fully convective interior, larger rotational velocities (≤ 30 km/s i.e. P objects. While the pure gas-phase based NextGen model atmospheres (Allard et al. 1997, Hauschildt et al. 1999) have allowed the understanding of the several populations of Very Low Mass Stars (VLMs), the AMES-Dusty models (Allard et al. 2001) based on equilibrium chemistry have reproduced some near-IR photometric properties of M and L-type brown dwarfs, and played a key role in the determination of the mass of brown dwarfs and Planetary Mass Objects (PMOs) in the eld and in young stellar clusters. In this paper, we present a new model atmosphere grid for VLMs, BDs, PMOs named BT-Settl, which includes a cloud model and dynamical molecular transport based on mixing information from 2D Radiation Hydrodynamic (RHD) simulations (Freytag et al. 2009). We also present the status of our 3D RHD simulations including rotation (Coriolis forces) of a cube on the surface of a brown dwarf. The BT-Settl model atmosphere grid will be available shortly via the Phoenix web simulator (http://phoenix.ens-lyon.fr/simulator/).

  10. A Method for Determining the Physical Properties of the Coldest Known Brown Dwarfs

    CERN Document Server

    Burgasser, A J; Kirkpatrick, J D; Burgasser, Adam J.; Burrows, Adam

    2006-01-01

    We present a method for measuring the physical parameters of the coldest T-type brown dwarfs using low resolution near infrared spectra. By comparing H_2O- and H_2-sensitive spectral ratios between empirical data and theoretical atmosphere models, and calibrating these ratios to measurements for the well-characterized 2-5 Gyr companion brown dwarf Gliese 570D, we derive estimates of the effective temperatures and surface gravities for 13 mid- and late-type field T dwarfs. We also deduce the first quantitative estimate of subsolar metallicity for the peculiar T dwarf 2MASS 0937+2931. Derived temperatures are consistent with prior estimates based on parallax and bolometric luminosity measurements, and examination of possible systematic effects indicate that the results are robust. Two recently discovered late-type T dwarfs, 2MASS 0939-2448 and 2MASS 1114-2618, both appear to be >50 K cooler than the latest-type T dwarf, 2MASS 0415-0935, and are potentially the coldest and least luminous brown dwarfs currently k...

  11. A statistical analysis of seeds and other high-contrast exoplanet surveys: massive planets or low-mass brown dwarfs?

    Energy Technology Data Exchange (ETDEWEB)

    Brandt, Timothy D.; Spiegel, David S. [Institute for Advanced Study, Princeton, NJ (United States); McElwain, Michael W.; Grady, C. A. [Exoplanets and Stellar Astrophysics Laboratory, Goddard Space Flight Center, Greenbelt, MD (United States); Turner, Edwin L. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ (United States); Mede, Kyle; Kuzuhara, Masayuki [University of Tokyo, Tokyo (Japan); Schlieder, Joshua E.; Brandner, W.; Feldt, M. [Max Planck Institute for Astronomy, Heidelberg (Germany); Wisniewski, John P. [HL Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, OK (United States); Abe, L. [Laboratoire Hippolyte Fizeau, Nice (France); Biller, B. [University of Edinburgh, Edinburgh, Scotland (United Kingdom); Carson, J. [College of Charleston, Charleston, SC (United States); Currie, T. [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON (Canada); Egner, S.; Golota, T.; Guyon, O. [Subaru Telescope, Hilo, Hawai' i (United States); Goto, M. [Universitäts-Sternwarte München, Munich (Germany); Hashimoto, J. [National Astronomical Observatory of Japan, Tokyo (Japan); and others

    2014-10-20

    We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars. The stars cover a wide range of ages and spectral types, and include five detections (κ And b, two ∼60 M {sub J} brown dwarf companions in the Pleiades, PZ Tel B, and CD–35 2722B). For some analyses we add a currently unpublished set of SEEDS observations, including the detections GJ 504b and GJ 758B. We conduct a uniform, Bayesian analysis of all stellar ages using both membership in a kinematic moving group and activity/rotation age indicators. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most of the integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis of the distribution function derived from radial-velocity planets, finding model-dependent values of ∼30-100 AU. Finally, we model the entire substellar sample, from massive brown dwarfs to a theoretically motivated cutoff at ∼5 M {sub J}, with a single power-law distribution. We find that p(M, a)∝M {sup –0.65} {sup ±} {sup 0.60} a {sup –0.85} {sup ±} {sup 0.39} (1σ errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M {sub J} companions between 10 and 100 AU. This suggests that many of the directly imaged exoplanets known, including most (if not all) of the low-mass companions in our sample, formed by fragmentation in a cloud or disk, and represent the low-mass tail of the brown dwarfs.

  12. BANYAN. V. A SYSTEMATIC ALL-SKY SURVEY FOR NEW VERY LATE-TYPE LOW-MASS STARS AND BROWN DWARFS IN NEARBY YOUNG MOVING GROUPS

    Energy Technology Data Exchange (ETDEWEB)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Malo, Lison; Artigau, Étienne [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada)

    2015-01-10

    We present the BANYAN All-Sky Survey (BASS) catalog, consisting of 228 new late-type (M4-L6) candidate members of nearby young moving groups (YMGs) with an expected false-positive rate of ∼13%. This sample includes 79 new candidate young brown dwarfs and 22 planetary-mass objects. These candidates were identified through the first systematic all-sky survey for late-type low-mass stars and brown dwarfs in YMGs. We cross-matched the Two Micron All Sky Survey and AllWISE catalogs outside of the galactic plane to build a sample of 98,970 potential ≥M5 dwarfs in the solar neighborhood and calculated their proper motions with typical precisions of 5-15 mas yr{sup –1}. We selected highly probable candidate members of several YMGs from this sample using the Bayesian Analysis for Nearby Young AssociatioNs II tool (BANYAN II). We used the most probable statistical distances inferred from BANYAN II to estimate the spectral type and mass of these candidate YMG members. We used this unique sample to show tentative signs of mass segregation in the AB Doradus moving group and the Tucana-Horologium and Columba associations. The BASS sample has already been successful in identifying several new young brown dwarfs in earlier publications, and will be of great interest in studying the initial mass function of YMGs and for the search of exoplanets by direct imaging; the input sample of potential close-by ≥M5 dwarfs will be useful to study the kinematics of low-mass stars and brown dwarfs and search for new proper motion pairs.

  13. Chemical Tracers of Pre-Brown Dwarf Cores Formed Through Turbulent Fragmentation

    CERN Document Server

    Holdship, Jonathan

    2015-01-01

    A gas-grain time dependent chemical code, UCL\\_CHEM, has been used to investigate the possibility of using chemical tracers to differentiate between the possible formation mechanisms of brown dwarfs. In this work, we model the formation of a pre-brown dwarf core through turbulent fragmentation by following the depth-dependent chemistry in a molecular cloud through the step change in density associated with an isothermal shock and the subsequent freefall collapse once a bound core is produced. Trends in the fractional abundance of molecules commonly observed in star forming cores are then explored to find a diagnostic for identifying brown dwarf mass cores formed through turbulence. We find that the cores produced by our models would be bright in CO and NH$_3$ but not in HCO$^+$. This differentiates them from models using purely freefall collapse as such models produce cores that would have detectable transitions from all three molecules.

  14. Radio signatures of lightning discharges in exoplanets and brown dwarfs

    Science.gov (United States)

    Hodosán, Gabriella; Helling, Christiane; Vorgul, Irena

    2014-05-01

    Lightning related signatures can be found in the whole spectral range from radio to gamma-rays. While for example UV, visible or IR molecular emission (as the lightning discharge causes changes in the local chemistry) depends on the composition of the atmosphere of the extrasolar body, radio signatures do not have this limitation, which means they may give us a universal tool for lightning observations outside the Solar System, both on exoplanets and brown dwarfs. Lightning induced radio signatures have three main types. Sferics emit in the low-frequency (LF) range with a power density peak at 10 kHz on Earth. (Aplin, K. L., 'Electrifying atmospheres', Springer 2013) Whistlers are electromagnetic waves propagating along magnetic field lines and emitting in the very low-frequency (VLF) range. (Desch, S. J. et al. 2002, Rep. Prog. Phys. 65, 955) While Schumann-resonances are VLF lightning discharge-induced electromagnetic oscillations of the earth-ionosphere cavity. (Simões, F. et al. 2012, LPICo 1683, 1052) There are certain factors that limit the observability of radio signatures. Every object with an ionosphere has a low cutoff frequency. This means radio waves with frequencies below this peak-frequency cannot propagate through the atmosphere. For Earth this value is about 5-10 MHz. However, the values for extrasolar atmospheres remain to be determined. Besides that, natural background noises like the galactic radio background or photo-electron noises give a limitation. (Zarka et al. 2012, PSS 74, 156) Putting all together, radio signatures with frequency below 10 MHz might only be observable from space. Waves below 30 kHz would not be able to reach the inner Solar System. (Zarka et al. 2012, PSS 74, 156) We show a general summary of radio signatures and their properties. A table of other lightning discharge signatures that have been observed either on Earth or other Solar System planets is also included. This table, also contains a list of different instruments

  15. Kinematics of dwarf galaxies in gas-rich groups, and the survival and detectability of tidal dwarf galaxies

    CERN Document Server

    Sweet, Sarah M; Meurer, Gerhardt; Kilborn, Virginia; Audcent-Ross, Fiona; Baumgardt, Holger; Bekki, Kenji

    2015-01-01

    We present DEIMOS multi-object spectroscopy (MOS) of 22 star-forming dwarf galaxies located in four gas-rich groups, including six newly-discovered dwarfs. Two of the galaxies are strong tidal dwarf galaxy (TDG) candidates based on our luminosity-metallicity relation definition. We model the rotation curves of these galaxies. Our sample shows low mass-to-light ratios (M/L=0.73$\\pm0.39M_\\odot/L_\\odot$) as expected for young, star-forming dwarfs. One of the galaxies in our sample has an apparently strongly-falling rotation curve, reaching zero rotational velocity outside the turnover radius of $r_{turn}=1.2r_e$. This may be 1) a polar ring galaxy, with a tilted bar within a face-on disk; 2) a kinematic warp. These scenarios are indistinguishable with our current data due to limitations of slit alignment inherent to MOS-mode observations. We consider whether TDGs can be detected based on their tidal radius, beyond which tidal stripping removes kinematic tracers such as H$\\alpha$ emission. When the tidal radius i...

  16. Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition

    CERN Document Server

    Burgasser, A J; Cruz, K L; Reid, I N; Leggett, S K; Liebert, J; Burrows, A; Brown, M E; Burgasser, Adam J.; Cruz, Kelle L.; Leggett, Sandy K.; Liebert, James; Burrows, Adam; Brown, Michael E.

    2006-01-01

    We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0"05-0"35, and companionship is established on the basis of component F110W-F170M colors (indicative of CH4 absorption) and low probabilities of background contamination. Prior ground-based observations show 2MASS 1553+1532AB to be a common proper motion binary. The properties of these systems - low multiplicity fraction (11[+7][-3]% resolved, as corrected for sample selection baises), close projected separations (a = 1.8-5.0 AU) and near-unity mass ratios - are consistent with previous results for field brown dwarf binaries. Three of the binaries have components that span the poorly-understood transition between L dwarfs and T dwarfs. Spectral decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar flux reversal between its components, as its T5 secondary is ~30% brighter at 1.05 and 1.27 micron than its T1 primary. This...

  17. Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Luminous Infrared Galaxy Candidates

    CERN Document Server

    Griffith, Roger L; Eisenhardt, Peter R M; Gelino, Christopher R; Cushing, Michael C; Benford, Dominic; Blain, Andrew; Bridge, Carrie R; Cohen, Martin; Cutri, Roc M; Donoso, Emilio; Jarrett, Thomas H; Lonsdale, Carol; Mace, Gregory; Mainzer, A; Marsh, Ken; Padgett, Deborah; Petty, Sara; Ressler, Michael E; Skrutskie, Michael F; Stanford, Spencer A; Stern, Daniel; Tsai, Chao-Wei; Wright, Edward L; Wu, Jingwen; Yan, Lin

    2012-01-01

    We present Spitzer 3.6 and 4.5 $\\mu$m photometry and positions for a sample of 1510 brown dwarf candidates identified by the WISE all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12); Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify 7 fainter (4.5 $\\mu$m $\\sim$ 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy (HyLIRG) candidates. For this control sample we find another 6 brown dwarf c...

  18. Habitable planets around white and brown dwarfs: the perils of a cooling primary.

    Science.gov (United States)

    Barnes, Rory; Heller, René

    2013-03-01

    White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10(-6). Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 10(4) K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable.

  19. Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf

    CERN Document Server

    Luhman, K L; D'Alessio, Paola; Calvet, Nuria; McLeod, Kim K; Bohac, J; Forrest, William J; Hartmann, Lee; Sargent, B; Watson, Dan M

    2007-01-01

    We present observations of a circumstellar disk that is inclined close to edge-on around a young brown dwarf in the Taurus star-forming region. Using data obtained with SpeX at the NASA Infrared Telescope Facility, we find that the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399 cannot be reproduced with a photosphere reddened by normal extinction. Instead, the slope is consistent with scattered light, indicating that circumstellar material is occulting the brown dwarf. By combining the SpeX data with mid-IR photometry and spectroscopy from the Spitzer Space Telescope and previously published millimeter data from Scholz and coworkers, we construct the spectral energy distribution for 2MASS J04381486+2611399 and model it in terms of a young brown dwarf surrounded by an irradiated accretion disk. The presence of both silicate absorption at 10 um and silicate emission at 11 um constrains the inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional evidence of the h...

  20. First detection of thermal radio jets in a sample of proto-brown dwarf candidates

    CERN Document Server

    Morata, O; González, R F; de Gregorio-Monsalvo, I; Ribas, A; Perger, M; Bouy, H; Barrado, D; Eiroa, C; Bayo, A; Huélamo, N; Morales-Calderón, M; Rodríguez, L F

    2015-01-01

    We observed with the JVLA at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf candidates in Taurus in a search for thermal radio jets driven by the most embedded brown dwarfs. We detected for the first time four thermal radio jets in proto-brown dwarf candidates. We compiled data from UKIDSS, 2MASS, Spitzer, WISE and Herschel to build the Spectral Energy Distribution (SED) of the objects in our sample, which are similar to typical Class~I SEDs of Young Stellar Objects (YSOs). The four proto-brown dwarf candidates driving thermal radio jets also roughly follow the well-known trend of centimeter luminosity against bolometric luminosity determined for YSOs, assuming they belong to Taurus, although they present some excess of radio emission compared to the known relation for YSOs. Nonetheless, we are able to reproduce the flux densities of the radio jets modeling the centimeter emission of the thermal radio jets using the same type of models applied to YSOs, but with corresponding smaller stellar wind velocities a...

  1. New Young Brown Dwarfs in the Orion Molecular Cloud 2/3 Region

    CERN Document Server

    Peterson, Dawn E; Luhman, K L; Pipher, J L; Stauffer, J R; Navascues, D Barrado y; Wilson, J C; Skrutskie, M F; Nelson, M J; Smith, J D

    2008-01-01

    Forty new low mass members with spectral types ranging from M4-M9 have been confirmed in the Orion Molecular Cloud 2/3 region. Through deep, I, z', J, H, K photometry of a 20' x 20' field in OMC 2/3, we selected brown dwarf candidates for follow-up spectroscopy. Low resolution far-red and near-infrared spectra were obtained for the candidates, and 19 young brown dwarfs in the OMC 2/3 region are confirmed. They exhibit spectral types of M6.5-M9, corresponding to approximate masses of 0.075-0.015 M_solar using the evolutionary models of Baraffe et al. (1998). At least one of these bona fide young brown dwarfs has strong Halpha emission, indicating that it is actively accreting. In addition, we confirm 21 new low mass members with spectral types of M4-M6, corresponding to approximate masses of 0.35-0.10 M_solar in OMC 2/3. By comparing pre-main sequence tracks to the positions of the members in the H-R diagram, we find that most of the brown dwarfs are less than 1 Myr, but find a number of low mass stars with in...

  2. PROTOPLANETARY DISK MASSES FROM STARS TO BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Mohanty, Subhanjoy; Mortlock, Daniel [Imperial College London, 1010 Blackett Lab, Prince Consort Rd., London SW7 2AZ (United Kingdom); Greaves, Jane [SUPA, Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Pascucci, Ilaria; Apai, Daniel [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson AZ 85721 (United States); Scholz, Aleks [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); Thompson, Mark [Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Lodato, Giuseppe [Dipartimento di Fisica, Universita Degli Studi di Milano, Via Celoria 16, I-20133 Milano (Italy); Looper, Dagny, E-mail: s.mohanty@imperial.ac.uk [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Dr., Honolulu, HI 96822 (United States)

    2013-08-20

    We present SCUBA-2 850 {mu}m observations of seven very low mass stars (VLMS) and brown dwarfs (BDs). Three are in Taurus and four in the TW Hydrae Association (TWA), and all are classical T Tauri (cTT) analogs. We detect two of the three Taurus disks (one only marginally), but none of the TWA ones. For standard grains in cTT disks, our 3{sigma} limits correspond to a dust mass of 1.2 M{sub Circled-Plus} in Taurus and a mere 0.2 M{sub Circled-Plus} in the TWA (3-10 Multiplication-Sign deeper than previous work). We combine our data with other submillimeter/millimeter (sub-mm/mm) surveys of Taurus, {rho} Oph, and the TWA to investigate the trends in disk mass and grain growth during the cTT phase. Assuming a gas-to-dust mass ratio of 100:1 and fiducial surface density and temperature profiles guided by current data, we find the following. (1) The minimum disk outer radius required to explain the upper envelope of sub-mm/mm fluxes is {approx}100 AU for intermediate-mass stars, solar types, and VLMS, and {approx}20 AU for BDs. (2) While the upper envelope of apparent disk masses increases with M{sub *} from BDs to VLMS to solar-type stars, no such increase is observed from solar-type to intermediate-mass stars. We propose this is due to enhanced photoevaporation around intermediate stellar masses. (3) Many of the disks around Taurus and {rho} Oph intermediate-mass and solar-type stars evince an opacity index of {beta} {approx} 0-1, indicating significant grain growth. Of the only four VLMS/BDs in these regions with multi-wavelength measurements, three are consistent with considerable grain growth, though optically thick disks are not ruled out. (4) For the TWA VLMS (TWA 30A and B), combining our 850 {mu}m fluxes with the known accretion rates and ages suggests substantial grain growth by 10 Myr, comparable to that in the previously studied TWA cTTs Hen 3-600A and TW Hya. The degree of grain growth in the TWA BDs (2M1207A and SSPM1102) remains largely unknown. (5) A

  3. Clouds and Chemistry Brown Dwarf Atmospheric Properties from Optical and Infrared Colors

    CERN Document Server

    Marley, M S; Saumon, D S; Lodders, K; Ackerman, A S; Freedman, R

    2001-01-01

    The optical and infrared colors of L and T dwarfs are sensitive to cloud sedimentation and chemical processes in their atmospheres. In particular the J-K color of a cooling brown dwarf is sensitive to the vertical distribution of condensates in its atmosphere. Only atmosphere models which include sedimentation of condensates are able to reproduce the observed trends in J-K in which objects first become redder, then bluer with falling effective temperature. The Sloan Digital Sky Survey color i'-z' is sensitive to assumptions surrounding the alkali metal chemistry. Chemical equilibrium models which account for cloud sedimentation predict redder colors, by up to 2 magnitudes, than models which neglect sedimentation. The i'-z' vs. J-K color-color diagram is thus interesting for the window it opens into diverse atmospheric processes. In addition, we predict the locus in this color-color diagram of brown dwarfs cooler than yet found.

  4. Discovery of a brown dwarf companion to the A3V star β Circini

    Science.gov (United States)

    Smith, L. C.; Lucas, P. W.; Contreras Peña, C.; Kurtev, R.; Marocco, F.; Jones, H. R. A.; Beamin, J. C.; Napiwotzki, R.; Borissova, J.; Burningham, B.; Faherty, J.; Pinfield, D. J.; Gromadzki, M.; Ivanov, V. D.; Minniti, D.; Stimson, W.; Villanueva, V.

    2015-12-01

    We report the discovery of an L dwarf companion to the A3V star β Circini. VVV J151721.49-585131.5, or β Cir B, was identified in a proper motion and parallax catalogue of the VISTA Variables in the Vía Láctea survey as having near-infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of β Cir. The projected separation of ˜3.6 arcmin corresponds to 6656 au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of 370-500 Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0 ± 0.5 and lacks the typical signatures of low-surface gravity seen in younger brown dwarfs. This suggests that signs of low-surface gravity disappear from the spectra of early L dwarfs by an age of ˜370-500 Myr, as expected from theoretical isochrones. The mass of β Cir B is estimated from the BHAC15 isochrones as 0.056 ± 0.007 M⊙.

  5. Mid-infrared followup of cold brown dwarfs: diversity in age, mass and metallicity

    Energy Technology Data Exchange (ETDEWEB)

    Saumon, Didier [Los Alamos National Laboratory; Leggett, Sandy K [GEMINI OBSERVATORY; Burningham, Ben [HERTFORDSHITE UNIV; Marley, Mark S [NASA AMES; Waren, S J [IMPERIAL COLLEGE LONDON; Jones, H R A [HERTFORDSHIRE U; Pinfield, D J [HERTFORDSHIRE U; Smart, R L [ASTRONOMICAL OBS

    2009-01-01

    We present new Spitzer IRAC [3.6], [4.5], [5.8] and [8.0] photometry of nine very late-type T dwarfs. Combining this with previously published photometry, we investigate trends with type and color that are useful for both the planning and interpretation of infrared surveys designed to discover the coldest T or Y dwarfs. Brown dwarfs with effective temperature (T{sub eff}) below 700 K emit more than half their flux at wavelengths longer than 3 {micro}m, and the ratio of the mid-infrared flux to the near-infrared flux becomes very sensitive to T{sub eff} at these low temperatures. We confirm that the color H (1.6 {micro}m) - [4.5] is a good indicator of T{sub eff} with a relatively weak dependence on metallicity and gravity. Conversely, the colors H - K (2.2 {micro}m) and [4.5] - [5.8] are sensitive to metallicity and gravity. Thus near- and mid-infrared photometry provide useful indicators of the fundamental properties of brown dwarfs, and if temperature and gravity are known, then mass and age can be reliably determined from evolutionary models. There are twelve dwarfs currently known with H - [4.5] > 3.0, and {approx} 500 < T{sub eff} K {approx}< 800, which we examine in detail. The ages of the dwarfs in the sample range from very young (0.1 - 1.0 Gyr) to relatively old (3 - 12 Gyr). The mass range is possibly as low as 5 Jupiter masses to up to 70 Jupiter masses, i.e. near the hydrogen burning limit. The metallicities also span a large range, from [m/H]= -0.3 to [m/H]= +0.2. The small number of T8 - T9 dwarfs found in the UKIRT Infrared Deep Sky Survey to date appear to be predominantly young low-mass dwarfs. Accurate mid-infrared photometry of cold brown dwarfs is essentially impossible from the ground, and extensions to the mid-infrared space missions warm-Spitzer and WISE are desirable in order to obtain the vital mid-infrared data for cold brown dwarfs, and to discover more of these rare objects.

  6. CHARACTERIZING THE BROWN DWARF FORMATION CHANNELS FROM THE INITIAL MASS FUNCTION AND BINARY-STAR DYNAMICS

    Energy Technology Data Exchange (ETDEWEB)

    Thies, Ingo; Pflamm-Altenburg, Jan; Kroupa, Pavel; Marks, Michael [Helmholtz-Institut für Strahlen- und Kernphysik (HISKP), Universität Bonn, Nussallee 14-16, D-53115 Bonn (Germany)

    2015-02-10

    The stellar initial mass function (IMF) is a key property of stellar populations. There is growing evidence that the classical star-formation mechanism by the direct cloud fragmentation process has difficulties reproducing the observed abundance and binary properties of brown dwarfs and very-low-mass stars. In particular, recent analytical derivations of the stellar IMF exhibit a deficit of brown dwarfs compared to observational data. Here we derive the residual mass function of brown dwarfs as an empirical measure of the brown dwarf deficiency in recent star-formation models with respect to observations and show that it is compatible with the substellar part of the Thies-Kroupa IMF and the mass function obtained by numerical simulations. We conclude that the existing models may be further improved by including a substellar correction term that accounts for additional formation channels like disk or filament fragmentation. The term ''peripheral fragmentation'' is introduced here for such additional formation channels. In addition, we present an updated analytical model of stellar and substellar binarity. The resulting binary fraction and the dynamically evolved companion mass-ratio distribution are in good agreement with observational data on stellar and very-low-mass binaries in the Galactic field, in clusters, and in dynamically unprocessed groups of stars if all stars form as binaries with stellar companions. Cautionary notes are given on the proper analysis of mass functions and the companion mass-ratio distribution and the interpretation of the results. The existence of accretion disks around young brown dwarfs does not imply that these form just like stars in direct fragmentation.

  7. A High-Resolution Survey of the Very Youngest Brown Dwarfs

    Science.gov (United States)

    Allers, Katelyn

    2012-10-01

    We propose to image the youngest { 0.5 Myr} brown dwarfs in the nearby Ophiuchus star-forming region {d=125 pc}. These observations will complete our high resolution imaging survey of a well-defined sample of young brown dwarfs and very low mass stars spanning the age range of 0.5-100 Myr {Allers et al. 2009, Allers et al. 2010, Biller et al. 2011}. Our proposed survey will be the culmination of the most extensive high resolution search for companions to young substellar objects conducted to date. We have established a novel, reddening-insensitive approach, which uses imaging in three WFC3 UVIS and IR filters to discern candidate companions from contaminant background stars. Our proposed survey is sensitive enough to discover planetary-mass companions. As only two planetary-mass companions to brown dwarfs are known {Chauvin et al. 2005, Todorov et al. 2010}, such discoveries will provide valuable new benchmark objects for testing atmospheric and evolutionary models of planetary-mass objects. Our survey will put the strongest constraints to date on the primordial binary fraction for brown dwarfs. By comparing results in Ophiuchus with our completed survey of the Upper Sco region {Biller et al. 2011}, we can directly measure how the binary characteristics change with age {i.e. as a cluster dynamically evolves}, providing key inputs for refining models of brown dwarf formation. The proposed observations are only possible with HST WFC3. Because of the high extinction of the Ophiuchus cloud, suitable tip-tilt stars are not available to allow for ground-based LGS AO imaging of our sample.

  8. First limits on the occurrence rate of short-period planets orbiting brown dwarfs

    Science.gov (United States)

    He, Matthias Y.; Triaud, Amaury H. M. J.; Gillon, Michaël

    2017-01-01

    Planet formation theories predict a large but still undetected population of short-period terrestrial planets orbiting brown dwarfs. Should specimens of this population be discovered transiting relatively bright and nearby brown dwarfs, the Jupiter-size and the low luminosity of their hosts would make them exquisite targets for detailed atmospheric characterization with JWST and future ground-based facilities. The eventual discovery and detailed study of a significant sample of transiting terrestrial planets orbiting nearby brown dwarfs could prove to be useful not only for comparative exoplanetology but also for astrobiology, by bringing us key information on the physical requirements and time-scale for the emergence of life. In this context, we present a search for transit-signals in archival time series photometry acquired by the Spitzer Space Telescope for a sample of 44 nearby brown dwarfs. While these 44 targets were not particularly selected for their brightness, the high precision of their Spitzer light curves allows us to reach sensitivities below Earth-sized planets for 75 per cent of the sample and down to Europa-sized planets on the brighter targets. We could not identify any unambiguous planetary signal. Instead, we could compute the first limits on the presence of planets on close-in orbits. We find that within a 1.28 d orbit, the occurrence rate of planets with a radius between 0.75 and 3.25 R⊕ is η TRAPPIST-1b systems would suggest, we estimate that 175 brown dwarfs need to be monitored in order to guarantee (95 per cent) at least one detection.

  9. LHS 6343: Precise Constraints on the Mass and Radius of a Transiting Brown Dwarf Discovered by Kepler

    Science.gov (United States)

    Montet, Benjamin; Johnson, J. A.; Muirhead, P. S.; Shporer, A.; Howard, A.; Baranec, C.; Albert, L.; Robo-AO Collaboration

    2014-01-01

    Despite the discovery of more than 1200 brown dwarfs, only a dozen have both a measured mass and radius. Such systems are fundamental for our understanding of brown dwarf evolution. To this end, we report an updated analysis of the mass and radius of LHS 6343C, a brown dwarf orbiting one member of an M+M binary system in the Kepler field. With visible light adaptive optics data from Robo-AO, we are able to determine the third light contribution in the Kepler bandpass from the B component directly from observations in visible wavelengths. We combine 16 quarters of transit photometry from Kepler with 33 Keck HIRES radial velocity observations to measure the brown dwarf’s mass and radius with 2 percent precision. Tight constraints such as these will be critical for future brown dwarf atmospheric studies as the next generation of theoretical evolutionary models are developed.

  10. On the origin of bursts in blue compact dwarf galaxies: clues from kinematics and stellar populations

    CERN Document Server

    Koleva, M; Zeilinger, W W; Verbeke, R; Schroyen, J; Vermeylen, L

    2014-01-01

    Blue compact dwarf galaxies (BCDs) form stars at, for their sizes, extraordinarily high rates. In this paper, we study what triggers this starburst and what is the fate of the galaxy once its gas fuel is exhausted. We select four BCDs with smooth outer regions, indicating them as possible progenitors of dwarf elliptical galaxies. We have obtained photometric and spectroscopic data with the FORS and ISAAC instruments on the VLT. We analyse their infra-red spectra using a full spectrum fitting technique which yields the kinematics of their stars and ionized gas together with their stellar population characteristics. We find that the_stellar_ velocity to velocity dispersion ratio (v/sigma) of our BCDs is of the order of 1.5, similar to that of dwarf elliptical galaxies. Thus, those objects do not require significant (if any) loss of angular momentum to fade into early type dwarfs. This finding is in discordance with previous studies, which however compared the stellar kinematics of dwarf elliptical galaxies with...

  11. The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE)

    CERN Document Server

    Kirkpatrick, J Davy; Gelino, Christopher R; Griffith, Roger L; Skrutskie, Michael F; Marsh, Kenneth A; Wright, Edward L; Mainzer, Amanda K; Eisenhardt, Peter R; McLean, Ian S; Thompson, Maggie A; Bauer, James M; Benford, Dominic J; Bridge, Carrie R; Lake, Sean E; Petty, Sara M; Stanford, S Adam; Tsai, Chao-Wei; Bailey, Vanessa; Beichman, Charles A; Bochanski, John J; Burgasser, Adam J; Capak, Peter L; Cruz, Kelle L; Hinz, Philip M; Kartaltepe, Jeyhan S; Knox, Russell P; Manohar, Swarnima; Masters, Daniel; Morales-Calderon, Maria; Prato, Lisa A; Rodigas, Timothy J; Salvato, Mara; Schurr, Steven D; Scoville, Nicholas Z; Simcoe, Robert A; Stapelfeldt, Karl R; Stern, Daniel; Stock, Nathan D; Vacca, William D

    2011-01-01

    We present ground-based spectroscopic verification of six Y dwarfs (see Cushing et al), eighty-nine T dwarfs, eight L dwarfs, and one M dwarf identified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these are cold brown dwarfs with spectral types greater than or equal to T6, six of which have been announced earlier in Mainzer et al and Burgasser et al. We present color-color and color-type diagrams showing the locus of M, L, T, and Y dwarfs in WISE color space. Near-infrared classifications as late as early Y are presented and objects with peculiar spectra are discussed. After deriving an absolute WISE 4.6 um (W2) magnitude vs. spectral type relation, we estimate spectrophotometric distances to our discoveries. We also use available astrometric measurements to provide preliminary trigonometric parallaxes to four our discoveries, which have types of L9 pec (red), T8, T9, and Y0; all of these lie within 10 pc of the Sun. The Y0 dwarf, WISE 1541-2250, is the closest at 2.8 (+1.3,-0.6) pc; if this ...

  12. The First Ultra-Cool Brown Dwarf Discovered by the Wide-field Infrared Survey Explorer

    CERN Document Server

    Mainzer, A; Skrutskie, M; Gelino, C R; Kirkpatrick, J Davy; Jarrett, T; Masci, F; Marley, M; Saumon, D; Wright, E; Beaton, R; Dietrich, M; Eisenhardt, P; Garnavich, P; Kuhn, O; Leisawitz, D; Marsh, K; McLean, I; Padgett, D; Rueff, K

    2010-01-01

    We report the discovery of the first new ultra-cool brown dwarf found with the Wide-field Infrared Survey Explorer (WISE). The object's preliminary designation is WISEPC J045853.90+643451.9. Follow-up spectroscopy with the LUCIFER instrument on the Large Binocular Telescope indicates that it is a very late-type T dwarf with a spectral type approximately equal to T9. Fits to an IRTF/SpeX 0.8-2.5 micron spectrum to the model atmospheres of Marley and Saumon indicate an effective temperature of approximately 600 K as well as the presence of vertical mixing in its atmosphere. The new brown dwarf is easily detected by WISE, with a signal-to-noise ratio of ~36 at 4.6 microns. Current estimates place it at a distance of 6 to 10 pc. This object represents the first in what will likely be hundreds of nearby brown dwarfs found by WISE that will be suitable for follow up observations, including those with the James Webb Space Telescope. One of the two primary scientific goals of the WISE mission is to find the coolest, ...

  13. Discovery of a brown dwarf companion to the A3V star \\beta{} Circini

    CERN Document Server

    Smith, L C; Peña, C Contreras; Kurtev, R; Marocco, F; Jones, H R A; Beamin, J C; Napiwotzki, R; Borissova, J; Burningham, B; Faherty, J; Pinfield, D J; Gromadzki, M; Ivanov, V D; Minniti, D; Stimson, W; Villanueva, V

    2015-01-01

    We report the discovery of an L dwarf companion to the A3V star \\beta{} Circini. VVV J151721.49-585131.5, or \\beta{} Cir B, was identified in a proper motion and parallax catalogue of the Vista Variables in the V\\'{i}a L\\'{a}ctea survey as having near infrared luminosity and colour indicative of an early L dwarf, and a proper motion and parallax consistent with that of \\beta{} Cir. The projected separation of $\\sim$3.6' corresponds to $6656$ au, which is unusually wide. The most recent published estimate of the age of the primary combined with our own estimate based on newer isochrones yields an age of $370-500$ Myr. The system therefore serves as a useful benchmark at an age greater than that of the Pleiades brown dwarfs and most other young L dwarf benchmarks. We have obtained a medium resolution echelle spectrum of the companion which indicates a spectral type of L1.0$\\pm$0.5 and lacks the typical signatures of low surface gravity seen in younger brown dwarfs. This suggests that signs of low surface gravit...

  14. The NIRSPEC Brown Dwarf Spectroscopic Survey II: High-Resolution J-Band Spectra of M, L and T Dwarfs

    CERN Document Server

    McLean, I S; McGovern, M R; Burgasser, A J; Kirkpatrick, J D; Rice, E L; Kim, S S; Lean, Ian S. Mc; Govern, Mark R. Mc; Burgasser, Adam J.; Rice, Emily L.; Kim, Sungsoo S.

    2006-01-01

    We present a sequence of high resolution (R~20,000 or 15 km/s) infrared spectra of stars and brown dwarfs spanning spectral types M2.5 to T6. Observations of 16 objects were obtained using eight echelle orders to cover part of the J-band from 1.165-1.323 micron with NIRSPEC on the Keck II telescope. By comparing opacity plots and line lists, over 200 weak features in the J-band are identified with either FeH or H2O transitions. Absorption by FeH attains maximum strength in the mid-L dwarfs, while H2O absorption becomes systematically stronger towards later spectral types. Narrow resolved features broaden markedly after the M to L transition. Our high resolution spectra also reveal that the disappearance of neutral Al lines at the boundary between M and L dwarfs is remarkably abrupt, presumably because of the formation of grains. Neutral Fe lines can be traced to mid-L dwarfs before Fe is removed by condensation. The neutral potassium (K I) doublets that dominate the J-band have pressure broadened wings that c...

  15. Spitzer Photometry of WISE-Selected Brown Dwarf and Hyper-Lumninous Infrared Galaxy Candidates

    Science.gov (United States)

    Griffith, Roger L.; Kirkpatrick, J. Davy; Eisenhardt, Peter R. M.; Gelino, Christopher R.; Cushing, Michael C.; Benford, Dominic; Blain, Andrew; Bridge, Carrie R.; Cohen, Martin; Cutri, Roc M.; Donoso, Emilio; Jarrett, Thomas H.; Lonsdale, Carol; Mace, Gregory; Mainzer, A.; Marsh, Ken; Padgett, Deborah; Petty, Sara; Ressler, Michael E.; Skrutskie, Michael F.; Stanford, Spencer A.; Stern, Daniel; Tsai, Chao-Wei; Wright, Edward L.; Wu, Jingwen

    2012-01-01

    We present Spitzer 3.6 and 4.5 micrometer photometry and positions for a sample of 1510 brown dwarf candidates identified by the Wide-field Infrared Survey Explorer (WISE) all-sky survey. Of these, 166 have been spectroscopically classified as objects with spectral types M(1), L(7), T(146), and Y(12). Sixteen other objects are non-(sub)stellar in nature. The remainder are most likely distant L and T dwarfs lacking spectroscopic verification, other Y dwarf candidates still awaiting follow-up, and assorted other objects whose Spitzer photometry reveals them to be background sources. We present a catalog of Spitzer photometry for all astrophysical sources identified in these fields and use this catalog to identify seven fainter (4.5 m to approximately 17.0 mag) brown dwarf candidates, which are possibly wide-field companions to the original WISE sources. To test this hypothesis, we use a sample of 919 Spitzer observations around WISE-selected high-redshift hyper-luminous infrared galaxy candidates. For this control sample, we find another six brown dwarf candidates, suggesting that the seven companion candidates are not physically associated. In fact, only one of these seven Spitzer brown dwarf candidates has a photometric distance estimate consistent with being a companion to the WISE brown dwarf candidate. Other than this, there is no evidence for any widely separated (greater than 20 AU) ultra-cool binaries. As an adjunct to this paper, we make available a source catalog of 7.33 x 10(exp 5) objects detected in all of these Spitzer follow-up fields for use by the astronomical community. The complete catalog includes the Spitzer 3.6 and 4.5 m photometry, along with positionally matched B and R photometry from USNO-B; J, H, and Ks photometry from Two Micron All-Sky Survey; and W1, W2, W3, and W4 photometry from the WISE all-sky catalog.

  16. Atmospheric Chemistry in Giant Planets, Brown Dwarfs, and Low-Mass Dwarf Stars II. Sulfur and Phosphorus

    CERN Document Server

    Visscher, C

    2005-01-01

    We use thermochemical equilibrium and kinetic calculations to model sulfur and phosphorus chemistry in the atmospheres of giant planets, brown dwarfs, low-mass stars, and extrasolar giant planets (EGPs). The chemical behavior of individual S- and P-bearing gases and condensates is determined as a function of pressure, temperature, and metallicity. Our results are independent of any particular model atmosphere and the behavior of different gases can be used to constrain atmospheric structure and metallicity. Hydrogen sulfide is the dominant sulfur gas in substellar atmospheres and approximately represents the atmospheric sulfur inventory. Depending on the prevailing S and C chemistry, the abundance of minor sulfur gases may constrain atmospheric temperatures or metallicity. Disequilibrium abundances of PH3 are expected in the observable atmospheres of substellar objects, and PH3 is representative of the total P abundance in giant planets and T dwarfs. A number of other phosphorus gases become relatively abunda...

  17. Mid-infrared followup of cold brown dwarfs: Diversity in age, mass and metallicity

    Directory of Open Access Journals (Sweden)

    Pinfield D.J.

    2011-07-01

    Full Text Available We use Spitzer IRAC 3.6–8.0 μm photometry of late-type T dwarfs to investigate various trends which can aid the planning and interpretation of infrared (IR surveys for the coldest T or Y dwarfs. Brown dwarfs with effective temperature (Teff50% of their flux at λ>3 μm, and the ratio of the mid-IR to the near-IR flux becomes very sensitive to Teff. The color H − [4.5] is a good indicator of Teff with a weak dependence on metallicity ([m/H] and gravity (g while H −K and [4.5] − [5.8] are sensitive to [m/H] and g. Thus Teff and g can be constrained and mass and age can then be determined from evolutionary models. There are 12 dwarfs known with H − [4.5] > 3.0 and 500 ≲ Teff K ≲ 800, which we examine in detail. The ages of these dwarfs range from very young (0.1–1.0 Gyr to old (3–12 Gyr. The mass range is possibly as low as 5 MJup to 70 MJup, and [m/H] also spans a large range of ~ −0.3 to ~ +0.3. The T8–T9 dwarfs found so far in the UKIRT IR Deep Sky Survey are unexpectedly young and low-mass. Extensions to the warm Spitzer and WISE space missions are needed to obtain mid-IR data for cold brown dwarfs, and to discover more of these rare objects.

  18. The influence of binary stars on dwarf spheroidal galaxy kinematics

    CERN Document Server

    Hargreaves, J C; Annan, J D

    1995-01-01

    We have completed a Monte-Carlo simulation to estimate the effect of binary star orbits on the measured velocity dispersion in dwarf spheroidal galaxies. This paper analyses previous attempts at this calculation, and explains the simulations which were performed with mass, period and ellipticity distributions similar to that measured for the solar neighbourhood. The conclusion is that with functions such as these, the contribution of binary stars to the velocity dispersion is small. The distributions are consistent with the percentage of binaries detected by observations, although this is quite dependent on the measuring errors and on the number of years over which measurements have been taken. For binaries to be making a significant contribution to the dispersion measured in dSph galaxies, the distributions of the orbital parameters would need to be very different from those of stars in the solar neighbourhood. In particular more smaller period orbits with higher mass secondaries would be required. The shape...

  19. Exoplanets versus brown dwarfs: the CoRoT view and the future

    CERN Document Server

    Schneider, Jean

    2016-01-01

    CoRoT has detected by transit several tens of objects whose radii run from 1.67 Earth radius. Their mass run from less than 5.7 Earth mass (CoRoT-24 b, Alonso et al. 2014) to 63 Jupiter mass (CoRoT-15 b, Bouchy et al. 2011). One could be tempted to think that more massive the object is, the larger it is in size and that there is some limit in mass and/or radius beyond which objects are not planets but very low mass stars below the 80 Jupiter mass limit to trigger nuclear fusion (namely "brown dwarfs" ). CoRoT findings contribute to the planet versus brown dwarf debate since there is no clear mass-radius relation.

  20. Ionisation and discharge in cloud-forming atmospheres of brown dwarfs and extrasolar planets

    CERN Document Server

    Helling, Ch; Rodriguez-Barrera, I M; Wood, Kenneth; Robertson, G B; Stark, C R

    2016-01-01

    Brown dwarfs and giant gas extrasolar planets have cold atmospheres with a rich chemical compositions from which mineral cloud particles form. Their properties, like particle sizes and material composition, vary with height, and the mineral cloud particles are charged due to triboelectric processes in such dynamic atmospheres. The dynamics of the atmospheric gas is driven by the irradiating host star and/or by the rotation of the objects that changes during its lifetime. Thermal gas ionisation in these ultra-cool but dense atmospheres allows electrostatic interactions and magnetic coupling of a substantial atmosphere volume. Combined with a strong magnetic field $\\gg B_{\\rm Earth}$, a chromosphere and aurorae might form as suggested by radio and X-ray observations of brown dwarfs. Non-equilibrium processes like cosmic ray ionisation and discharge processes in clouds will increase the local pool of free electrons in the gas. Cosmic rays and lighting discharges also alter the composition of the local atmospheri...

  1. Expect the unexpected: non-equilibrium processes in brown dwarf atmospheres

    CERN Document Server

    Helling, Christiane

    2014-01-01

    Brown Dwarf atmosphere are a chemically extremely rich, one example being the formation of clouds driven by the phase-non-equilibrium of the atmospheric gas. Cloud formation modelling is an integral part of any atmosphere simulation used to interpret spectral observations of ultra-cool objects and to determine fundamental parameters like log(g) and Teff. This proceeding to the workshop 'GAIA and the Unseen: The Brown Dwarf Question' first summarizes what a model atmosphere simulation is, and then advocates two ideas: A) The use of a multitude of model families to determine fundamental parameters with realistic confidence interval. B) To keep an eye on the unexpected, like for example, ionisation signatures resulting plasma processes

  2. Ionisation in atmospheres of Brown Dwarfs and extrasolar planets I The role of electron avalanche

    CERN Document Server

    Helling, Ch; Witte, S; Diver, D A

    2010-01-01

    Brown Dwarf and extrasolar planet atmospheres form clouds which strongly influence the local chemistry and physics. These clouds are globally neutral obeying dust-gas charge equilibrium which is, on short time scales, inconsistent with the observation of stochastic ionisation events of the solar system planets. We argue that a significant volume of the clouds in Brown Dwarfs and extrasolar planets is susceptible to local discharge events. These are electron avalanches triggered by charged dust grains. Such intra-cloud discharges occur on time scales shorter than the time needed to neutralise the dust grains by collisional processes. An ensemble of discharges is likely to produce enough free charges to suggest a partial and stochastic coupling of the atmosphere to a large-scale magnetic field.

  3. Lightning climatology of exoplanets and brown dwarfs guided by Solar System data

    CERN Document Server

    Hodosán, Gabriella; Asensio-Torres, Rubén; Vorgul, Irena; Rimmer, Paul B

    2016-01-01

    Clouds form on extrasolar planets and brown dwarfs where lightning could occur. Lightning is a tracer of atmospheric convection, cloud formation and ionization processes as known from the Solar System, and may be significant for the formation of prebiotic molecules. We study lightning climatology for the different atmospheric environments of Earth, Venus, Jupiter and Saturn. We present lightning distribution maps for Earth, Jupiter and Saturn, and flash densities for these planets and Venus, based on optical and/or radio measurements from the WWLLN and STARNET radio networks, the LIS/OTD satellite instruments, the Galileo, Cassini, New Horizons and Venus Express spacecraft. We also present flash densities calculated for several phases of two volcano eruptions, Eyjafjallaj\\"okull's (2010) and Mt Redoubt's (2009). We estimate lightning rates for sample, transiting and directly imaged extrasolar planets and brown dwarfs. Based on the large variety of exoplanets, six categories are suggested for which we use the ...

  4. Measuring the Initial Mass Function of Low Mass Stars and Brown Dwarfs

    CERN Document Server

    Jeffries, R D

    2012-01-01

    I review efforts to determine the form and any lower limit to the initial mass function in the Galactic disk, using observations of low-mass stars and brown dwarfs in the field, young clusters and star forming regions. I focus on the methodologies that have been used and the uncertainties that exist due to observational limitations and to systematic uncertainties in calibrations and theoretical models. I conclude that whilst it is possible that the low-mass IMFs deduced from the field and most young clusters are similar, there are too many problems to be sure; there are examples of low-mass cluster IMFs that appear to be very discrepant and the IMFs for brown dwarfs in the field and young clusters have yet to be reconciled convincingly.

  5. Benchmark Transiting Brown Dwarf LHS 6343 C: Spitzer Secondary Eclipse Observations Yield Brightness Temperature and mid-T Spectral Class

    CERN Document Server

    Montet, Benjamin T; Fortney, Jonathan J; Desert, Jean-Michel

    2016-01-01

    There are no field brown dwarf analogs with measured masses, radii, and luminosities, precluding our ability to connect the population of transiting brown dwarfs with measurable masses and radii and field brown dwarfs with measurable luminosities and atmospheric properties. LHS 6343 C, a weakly-irradiated brown dwarf transiting one member of an M+M binary in the Kepler field, provides the first opportunity to probe the atmosphere of a non-inflated brown dwarf with a measured mass and radius. Here, we analyze four Spitzer observations of secondary eclipses of LHS 6343 C behind LHS 6343 A. Jointly fitting the eclipses with a Gaussian process noise model of the instrumental systematics, we measure eclipse depths of 1.06 \\pm 0.21 ppt at 3.6 microns and 2.09 \\pm 0.08 ppt at 4.5 microns, corresponding to brightness temperatures of 1026 \\pm 57 K and 1249 \\pm 36 K, respectively. We then apply brown dwarf evolutionary models to infer a bolometric luminosity log(L_star / L_sun) = -5.16 \\pm 0.04. Given the known physica...

  6. Testing core creation in hydrodynamical simulations using the HI kinematics of field dwarfs

    CERN Document Server

    Papastergis, Emmanouil

    2016-01-01

    The majority of recent hydrodynamical simulations indicate the creation of central "cores" in the mass profiles of low-mass halos, a process that is attributed to star formation-related baryonic feedback. Core creation is regarded as one of the most promising solutions to potential issues faced by LambdaCDM cosmology on small scales. For example, the reduced dynamical mass enclosed by cores can explain the low rotational velocities measured for nearby dwarf galaxies, thus possibly lifting the seeming contradiction with the LambdaCDM expectations (the so-called "too big to fail" problem). Here we test core creation as a solution of cosmological issues by using a sample of dwarfs with measurements of their atomic hydrogen (HI) kinematics extending to large radii. Using the NIHAO hydrodynamical simulation as an example, we show that core creation can successfully reproduce the kinematics of dwarfs with small kinematic radii, R <~ 1.5 kpc. However, the agreement with observations becomes poor once galaxies wit...

  7. Methane, carbon monoxide, and ammonia in brown dwarfs and self-luminous giant planets

    Energy Technology Data Exchange (ETDEWEB)

    Zahnle, Kevin J.; Marley, Mark S., E-mail: Kevin.J.Zahnle@NASA.gov, E-mail: Mark.S.Marley@NASA.gov [NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States)

    2014-12-10

    We address disequilibrium abundances of some simple molecules in the atmospheres of solar composition brown dwarfs and self-luminous extrasolar giant planets using a kinetics-based one-dimensional atmospheric chemistry model. Our approach is to use the full kinetics model to survey the parameter space with effective temperatures between 500 K and 1100 K. In all of these worlds, equilibrium chemistry favors CH{sub 4} over CO in the parts of the atmosphere that can be seen from Earth, but in most disequilibrium favors CO. The small surface gravity of a planet strongly discriminates against CH{sub 4} when compared to an otherwise comparable brown dwarf. If vertical mixing is like Jupiter's, the transition from methane to CO occurs at 500 K in a planet. Sluggish vertical mixing can raise this to 600 K, but clouds or more vigorous vertical mixing could lower this to 400 K. The comparable thresholds in brown dwarfs are 1100 ± 100 K. Ammonia is also sensitive to gravity, but, unlike CH{sub 4}/CO, the NH{sub 3}/N{sub 2} ratio is insensitive to mixing, which makes NH{sub 3} a potential proxy for gravity. HCN may become interesting in high-gravity brown dwarfs with very strong vertical mixing. Detailed analysis of the CO-CH{sub 4} reaction network reveals that the bottleneck to CO hydrogenation goes through methanol, in partial agreement with previous work. Simple, easy to use quenching relations are derived by fitting to the complete chemistry of the full ensemble of models. These relations are valid for determining CO, CH{sub 4}, NH{sub 3}, HCN, and CO{sub 2} abundances in the range of self-luminous worlds we have studied, but may not apply if atmospheres are strongly heated at high altitudes by processes not considered here (e.g., wave breaking).

  8. Parallaxes and Proper Motions of Ultracool Brown Dwarfs of Spectral Types Y and Late T

    CERN Document Server

    Marsh, Kenneth A; Kirkpatrick, J Davy; Gelino, Christopher R; Cushing, Michael C; Griffith, Roger L; Skrutskie, Michael F; Eisenhardt, Peter R

    2012-01-01

    We present astrometric measurements of eleven nearby ultracool brown dwarfs of spectral types Y and late-T, based on imaging observations from a variety of space-based and ground-based telescopes. These measurements have been used to estimate relative parallaxes and proper motions via maximum likelihood fitting of geometric model curves. To compensate for the modest statistical significance (~ 3 pc. In addition, we have obtained significant estimates of Vtan for two of the Y dwarfs; both are <100 km/s, consistent with membership in the thin disk population. Comparison of absolute magnitudes with model predictions as a function of color shows that the Y dwarfs are significantly redder in J-H than predicted by a cloud-free model

  9. ROTATION PERIODS OF YOUNG BROWN DWARFS: K2 SURVEY IN UPPER SCORPIUS

    Energy Technology Data Exchange (ETDEWEB)

    Scholz, Alexander [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS (United Kingdom); Kostov, Veselin [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Jayawardhana, Ray [Faculty of Science, York University, 355 Lumbers Building, 4700 Keele Street, Toronto, ON M3J 1P2 (Canada); Mužić, Koraljka, E-mail: as110@st-andrews.ac.uk [Nucleo de Astronomía, Facultad de Ingeniería, Universidad Diego Portales, Av. Ejercito 441, Santiago (Chile)

    2015-08-20

    We report rotational periods for 16 young brown dwarfs in the nearby Upper Scorpius association, based on 72 days of high-cadence, high-precision photometry from the Keplerspace telescope’s K2 mission. The periods range from a few hours to two days (plus one outlier at five days), with a median just above one day, confirming that brown dwarfs, except at the very youngest ages, are fast rotators. Interestingly, four of the slowest rotators in our sample exhibit mid-infrared excess emission from disks; at least two also show signs of disk eclipses and accretion in the light curves. Comparing these new periods with those for two other young clusters and simple angular momentum evolution tracks, we find little or no rotational braking in brown dwarfs between 1–10 Myr, in contrast to low-mass stars. Our findings show that disk braking, while still at work, is inefficient in the substellar regime, thus providing an important constraint on the mass dependence of the braking mechanism.

  10. Using Narrow Band Photometry to Detect Young Brown Dwarfs in IC348

    CERN Document Server

    Mainzer, A K; Lean, Ian S. Mc

    2003-01-01

    We report the discovery of a population of young brown dwarf candidates in the open star cluster IC348 and the development of a new spectroscopic classification technique using narrow band photometry. Observations were made using FLITECAM, the First Light Camera for SOFIA, at the 3-m Shane Telescope at Lick Observatory. FLITECAM is a new 1-5 micron camera with an 8 arcmin field of view. Custom narrow band filters were developed to detect absorption features of water vapor (at 1.495 microns) and methane (at 1.66 microns) characteristic of brown dwarfs. These filters enable spectral classification of stars and brown dwarfs without spectroscopy. FLITECAM's narrow and broadband photometry was verified by examining the color-color and color-magnitude characteristics of stars whose spectral type and reddening was known from previous surveys. Using our narrow band filter photometry method, it was possible to identify an object measured with a signal-to-noise ratio of 20 or better to within +/-3 spectral class subtyp...

  11. The SOPHIE search for northern extrasolar planets IX. Populating the brown dwarf desert

    CERN Document Server

    Wilson, P A; Santos, N C; Sahlmann, J; Montagnier, G; Astudillo-Defru, N; Boisse, I; Bouchy, F; Rey, J; Arnold, L; Bonfils, X; Bourrier, V; Courcol, B; Deleuil, M; Delfosse, X; Díaz, R F; Ehrenreich, D; Forveille, T; Moutou, C; Pepe, F; Santerne, A; Ségransan, D; Udry, S

    2016-01-01

    Radial velocity planet search surveys of nearby Solar-type stars have shown a strong deficit of brown dwarf companions within $\\sim5\\,\\mathrm{AU}$. There is presently no comprehensive explanation of this lack of brown dwarf companions, therefore, increasing the sample of such objects is crucial to understand their formation and evolution. Based on precise radial velocities obtained using the SOPHIE spectrograph at Observatoire de Haute-Provence we characterise the orbital parameters of $15$ companions to solar-type stars and constrain their true mass using astrometric data from the Hipparcos space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from ~$13$ to $70\\,\\mathrm{M}_{\\mathrm{Jup}}$, and are well distributed across the planet/brown dwarf mass regime, making them an important contribution to the known population of massive companions around solar-type stars. We characterise six companions as stellar in nature with masses ranging from a minimum mass of $76 \\pm 4...

  12. The Discovery of a Second Field Methane Brown Dwarf from Sloan Digital Sky Survey Commissioning Data

    CERN Document Server

    Tsvetanov, Z I

    2000-01-01

    We report the discovery of a second field methane brown dwarf from the commissioning data of the Sloan Digital Sky Survey (SDSS). The object, SDSS J134646.45-003150.4 (SDSS 1346-00), was selected because of its very red color and stellar appearance. Its spectrum between 0.8-2.5 mic is dominated by strong absorption bands of H_2O and CH_4 and closely mimics those of Gliese 229B and SDSS 162414.37+002915.6 (SDSS 1624+00), two other known methane brown dwarfs. SDSS 1346-00 is approximately 1.5 mag fainter than Gliese 229B, suggesting that it lies about 11 pc from the sun. The ratio of flux at 2.1 mic to that at 1.27 mic is larger for SDSS 1346-00 than for Gliese 229B and SDSS 1624+00, which suggests that SDSS 1346-00 has a slightly higher effective temperature than the others. Based on a search area of 130 sq. deg. and a detection limit of z* = 19.8, we estimate a space density of 0.05 pc^-3 for methane brown dwarfs with T_eff ~ 1000 K in the 40 pc^3 volume of our search. This estimate is based on small-sample s...

  13. Methane, Carbon Monoxide, and Ammonia in Brown Dwarfs and Self-Luminous Giant Planets

    CERN Document Server

    Zahnle, Kevin J

    2014-01-01

    We address disequilibrum abundances of some simple molecules in the atmospheres of solar composition brown dwarfs and self-luminous extrasolar giant planets using a kinetics-based 1D atmospheric chemistry model. We employ cloudless atmospheres of approximately solar metallicity. Our approach is to use the complete model to survey the parameter space with effective temperatures between 500 K and 1100 K. In all of these worlds equilibrium chemistry favors CH4 over CO in the parts of the atmosphere that can be seen from Earth. Small surface gravity of planets strongly discriminates against CH4 when compared to an otherwise comparable brown dwarf. If vertical mixing is comparable to Jupiter's, methane becomes more abundant than CO in Jupiter-mass planets cooler than 500 K. Sluggish vertical mixing can raise this threshold to 600 K; but clouds or more vigorous vertical mixing could lower this threshold to 400 K. The comparable threshold in brown dwarfs is 1100 K. Ammonia is also sensitive to gravity, but unlike CH...

  14. EPIC201702477b: A Long Period Transiting Brown Dwarf from K2

    CERN Document Server

    Bayliss, D; Santerne, A; Dragomir, D; Zhou, G; Shporer, A; Colón, K D; Almenara, J; Armstrong, D J; Barrado, D; Barros, S C C; Bento, J; Boisse, I; Bouchy, F; Brown, D J A; Brown, T; Cameron, A; Cochran, W D; Demangeon, O; Deleuil, M; Díaz, R F; Fulton, B; Horne, K; Hébrard, G; Lillo-Box, J; Lovis, C; Mawet, D; Ngo, H; Osborn, H; Palle, E; Petigura, E; Pollacco, D; Santos, N; Sefako, R; Siverd, R; Sousa, S G; Tsantaki, M

    2016-01-01

    We report the discovery of EPIC201702477b, a transiting brown dwarf in a long period (40.73691 +/- 0.00037 day) and eccentric (e=0.2281 +/- 0.0026) orbit. This system was initially reported as a planetary candidate based on two transit events seen in K2 Campaign 1 photometry and later validated as an exoplanet. We confirm the transit and refine the ephemeris with two subsequent ground-based detections of the transit using the LCOGT 1m telescope network. We rule out any transit timing variations above the level of 30s. Using high precision radial velocity measurements from HARPS and SOPHIE we identify the transiting companion as a brown dwarf with a mass, radius, and bulk density of 66.9 +/- 1.7 M$_J$, 0.757 +/- 0.065 R$_J$, and 191+/-51 g.cm$^{-3}$ respectively. EPIC201702477b is the smallest radius brown dwarf yet discovered, with a mass just below the H-burning limit. It has the highest density of any planet, substellar mass object or main-sequence star discovered so far. We find evidence in the set of know...

  15. A submillimeter search for pre- and proto-brown dwarfs in Chamaeleon II

    CERN Document Server

    de Gregorio-Monsalvo, I; Bouy, H; Bayo, A; Palau, Aina; Morales-Calderon, M; Huelamo, N; Morata, O; Merin, B; Eiroa, C

    2015-01-01

    Context. Chamaeleon II molecular cloud is an active star forming region that offers an excellent opportunity for studying the formation of brown dwarfs in the southern hemisphere. Aims. Our aims are to identify a population of pre- and proto- brown dwarfs (5 sigma mass limit threshold of ~0.015 Msun) and provide information on the formation mechanisms of substellar objects. Methods. We performed high sensitivity observations at 870 microns using the LABOCA bolometer at the APEX telescope towards an active star forming region in Chamaeleon II. The data are complemented with an extensive multiwavelength catalogue of sources from the optical to the far-infrared to study the nature of the LABOCA detections. Results. We detect fifteen cores at 870 microns, and eleven of them show masses in the substellar regime. The most intense objects in the surveyed field correspond to the submillimeter counterparts of the well known young stellar objects DK Cha and IRAS 12500-7658. We identify a possible proto-brown dwarf cand...

  16. A new benchmark T8-9 brown dwarf and a couple of new mid-T dwarfs from the UKIDSS DR5+ LAS

    CERN Document Server

    Goldman, B; Henning, T; Clemens, C; Greiner, J

    2010-01-01

    Benchmark brown dwarfs are those objects for which fiducial constraints are available, including effective temperature, parallax, age, metallicity. We searched for new cool brown dwarfs in 186 sq.deg. of the new area covered by the data release DR5+ of the UKIDSS Large Area Survey. Follow-up optical and near-infrared broad-band photometry, and methane imaging of four promising candidates, revealed three objects with distinct methane absorption, typical of mid- to late-T dwarfs, and one possibly T4 dwarf. The latest-type object, classified as T8-9, shares its large proper motion with Ross 458 (BD+13o2618), an active M0.5 binary which is 102" away, forming a hierarchical low-mass star+brown dwarf system. Ross 458C has an absolute J-band magnitude of 16.4, and seems overluminous, particularly in the K band, compared to similar field brown dwarfs. We estimate the age of the system to be less than 1 Gyr, and its mass to be as low as 14 Jupiter masses for the age of 1 Gyr. At 11.4 pc, this new late T benchmark dwar...

  17. Towards Precise Ages and Masses of Free Floating Planetary Mass Brown Dwarfs

    CERN Document Server

    Canty, James; Roche, Patrick; Pinfield, David

    2013-01-01

    Measurement of the substellar initial mass function (IMF) in very young clusters is hampered by the possibility of the age spread of cluster members. This is particularly serious for candidate planetary mass objects (PMOs), which have a very similar location to older and more massive brown dwarfs on the Hertzsprung-Russell Diagram (HRD). This degeneracy can be lifted by the measurement of gravity-sensitive spectral features. To this end we have obtained medium resolution (R~5000) Near-infrared Integral Field Spectrometer (NIFS) K band spectra of a sample of late M- / early L-type dwarfs. The sample comprises old field dwarfs and very young brown dwarfs in the Taurus association and in the Sigma Orionis cluster. We demonstrate a positive correlation between the strengths of the 2.21micron NaI doublet and the objects' ages. We demonstrate a further correlation between these objects' ages and the shape of their K band spectra. We have quantified this correlation in the form of a new index, the H2(K) index. This ...

  18. Comparison of BT Settl Model Spectra in NIR to Brown Dwarfs and Massive Exoplanets

    Science.gov (United States)

    Popinchalk, Mark; Buzard, Cam; Alam, Munazza; Camnasio, Sara; Cruz, Kelle L.; Faherty, Jacqueline K.; Rice, Emily L.

    2017-01-01

    Brown dwarfs and giant exoplanets are difficult to observe, which hampers our understanding of their properties. Model spectra, such as the BT Settl model grid, can provide an opportunity to augment and validate our understanding of these faint objects by serving to contrast and complement our analysis of their observed spectra. We present work from an upcoming paper that leverages this opportunity. The near infrared (NIR) wavelength region is favorable for analysis of low mass brown dwarfs and high mass gaseous companions, in particular the K band (1.97 - 2.40 µm) due to its relatively high resolution and high signal-to-noise ratio wavelength range for spectra of planetary companions. We present a method to analyze two regions of the K band spectral structure (2.03 - 2.10 µm and 2.215 - 2.290 µm), and apply it to a sample of objects with field gravity, low gravity, and planetary mass as well as the BT Settl model grid for a similar range of effective temperatures and surface gravities. A correlation between spectral structure and effective temperature is found for the shorter wavelength region and there is evidence of gravity dependence for the longer wavelength range. This work suggests that the K band has the potential to be an indicator for brown dwarf and exoplanet surface gravity and effective temperature. We also present preliminary analysis from another upcoming paper. We examine equivalent widths of K I absorption lines at 1.1693 µm, 1.1773 µm, 1.2436 µm and 1.2525 µm in a selection of L dwarfs to explore their physical properties by comparing them to equivalent measurements in the BT Settl model grid.

  19. Elucidating the True Binary Fraction of VLM Stars and Brown Dwarfs with Spectral Binaries

    Science.gov (United States)

    Bardalez Gagliuffi, Daniella; Burgasser, Adam J.; Gelino, Christopher R.; SAHLMANN, JOHANNES; Schmidt, Sarah J.; Gagne, Jonathan; Skrzypek, Nathalie

    2017-01-01

    The very lowest-mass (VLM) stars and brown dwarfs are found in abundance in nearly all Galactic environments, yet their formation mechanism(s) remain an open question. One means of testing current formation theories is to use multiplicity statistics. The majority of VLM binaries have been discovered through direct imaging, and current angular resolution limits (0.05”-0.1") are coincident with the 1-4 AU peak in the projected separation distribution of known systems, suggesting an observational bias. I have developed a separation-independent method to detect T dwarf companions to late-M/early-L dwarfs by identifying methane absorption in their unresolved, low-resolution, near-infrared spectra using spectral indices and template fitting. Over 60 spectral binary candidates have been identified with this and comparable methods. I discuss follow-up observations, including laser-guide star adaptive optics imaging with Keck/NIRC2, which have confirmed 9 systems; and radial velocity and astrometric monitoring observations that have confirmed 7 others. The direct imaging results indicate a resolved binary fraction of 18%, coincident with current estimates of the VLM binary fraction; however, our sample contained 5 previously confirmed binaries, raising its true binary fraction to 47%. To more accurately measure the true VLM binary fraction, I describe the construction of an unbiased, volume-limited, near-infrared spectral sample of M7-L5 dwarfs within 25 pc, of which 4 (1%) are found to be spectral binary candidates. I model the complex selection biases of this method through a population simulation, set constraints on the true binary fraction as traced by these systems, and compare to the predictions of current formation theories. I also describe how this method may be applied to conduct a separation-unbiased search for giant exoplanets orbiting young VLM stars and brown dwarfs.

  20. THE FIRST HUNDRED BROWN DWARFS DISCOVERED BY THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE)

    Energy Technology Data Exchange (ETDEWEB)

    Davy Kirkpatrick, J.; Gelino, Christopher R.; Griffith, Roger L.; Marsh, Kenneth A.; Tsai, Chao-Wei; Beichman, Charles A. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C.; Mainzer, A.; Eisenhardt, Peter R.; Bauer, James M. [NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Skrutskie, Michael F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Wright, Edward L.; McLean, Ian S.; Lake, Sean E.; Petty, Sara M. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Thompson, Maggie A. [The Potomac School, 1301 Potomac School Road, McLean, VA 22101 (United States); Benford, Dominic J. [Infrared Astrophysics Branch, NASA-Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States); Bridge, Carrie R. [Division of Physics, Mathematics, and Astronomy, MS 220-6, California Institute of Technology, Pasadena, CA 91125 (United States); Stanford, S. A. [Department of Physics, University of California, Davis, CA 95616 (United States); Bailey, Vanessa, E-mail: davy@ipac.caltech.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); and others

    2011-12-01

    We present ground-based spectroscopic verification of 6 Y dwarfs (see also Cushing et al.), 89 T dwarfs, 8 L dwarfs, and 1 M dwarf identified by the Wide-field Infrared Survey Explorer (WISE). Eighty of these are cold brown dwarfs with spectral types {>=}T6, six of which have been announced earlier by Mainzer et al. and Burgasser et al. We present color-color and color-type diagrams showing the locus of M, L, T, and Y dwarfs in WISE color space. Near-infrared and, in a few cases, optical spectra are presented for these discoveries. Near-infrared classifications as late as early Y are presented and objects with peculiar spectra are discussed. Using these new discoveries, we are also able to extend the optical T dwarf classification scheme from T8 to T9. After deriving an absolute WISE 4.6 {mu}m (W2) magnitude versus spectral type relation, we estimate spectrophotometric distances to our discoveries. We also use available astrometric measurements to provide preliminary trigonometric parallaxes to four of our discoveries, which have types of L9 pec (red), T8, T9, and Y0; all of these lie within 10 pc of the Sun. The Y0 dwarf, WISE 1541-2250, is the closest at 2.8{sup +1.3}{sub -0.6} pc; if this 2.8 pc value persists after continued monitoring, WISE 1541-2250 will become the seventh closest stellar system to the Sun. Another 10 objects, with types between T6 and >Y0, have spectrophotometric distance estimates also placing them within 10 pc. The closest of these, the T6 dwarf WISE 1506+7027, is believed to fall at a distance of {approx}4.9 pc. WISE multi-epoch positions supplemented with positional info primarily from the Spitzer/Infrared Array Camera allow us to calculate proper motions and tangential velocities for roughly one-half of the new discoveries. This work represents the first step by WISE to complete a full-sky, volume-limited census of late-T and Y dwarfs. Using early results from this census, we present preliminary, lower limits to the space density of

  1. The Dawes Review 3: The Atmospheres of Extrasolar Planets and Brown Dwarfs

    CERN Document Server

    Bailey, Jeremy

    2014-01-01

    The last few years has seen a dramatic increase in the number of exoplanets known and in the range of methods for characterising their atmospheric properties. At the same time, new discoveries of increasingly cooler brown dwarfs have pushed down their temperature range which now extends down to Y-dwarfs of <300 K. Modelling of these atmospheres has required the development of new techniques to deal with the molecular chemistry and clouds in these objects. The atmospheres of brown dwarfs are relatively well understood, but some problems remain, in particular the behavior of clouds at the L/T transition. Observational data for exoplanet atmosphere characterization is largely limited to giant exoplanets that are hot because they are near to their star (hot Jupiters) or because they are young and still cooling. For these planets there is good evidence for the presence of CO and H2O absorptions in the IR. Sodium absorption is observed in a number of objects. Reflected light measurements show that some giant exo...

  2. Habitable Planets Around White and Brown Dwarfs: The Perils of a Cooling Primary

    CERN Document Server

    Barnes, Rory

    2012-01-01

    White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time, and hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water, and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10^-6. Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons as their surface temperatures are over 10^4 K. The situation is less clear for brown dwarfs, as observational data do not const...

  3. A Search for Substellar Companions to the Two Nearest Brown Dwarf Systems

    CERN Document Server

    Melso, N D; Luhman, K L

    2015-01-01

    WISE J104915.57-531906.1 A+B and WISE J085510.83-071442.5 were recently discovered as the third and fourth closest known systems to the Sun, respectively (2.0 and 2.3 pc). The former consists of a L8+T0.5 binary and the latter is a probable Y dwarf and is the coldest known brown dwarf (~250 K). We present a search for common proper motion companions to these brown dwarfs using multi-epoch mid-infrared images from the Spitzer Space Telescope. We have also obtained near-infrared adaptive optics images of WISE J104915.57-531906.1 A+B with the Very Large Telescope to search for companions at smaller separations than reached by Spitzer. No new companions are detected in either system. At projected separations of 25-420" (50-840 AU) for WISE J104915.57-531906.1 A+B and 4-420" (9-970 AU) for WISE J085510.83-071442.5, the Spitzer images are sensitive to companions with M_4.5=1 M_Jup for ages of >=1 Gyr and temperatures of >=150 K. The detection limit in the adaptive optics images of WISE J104915.57-531906.1 A+B is dH...

  4. The Brown Dwarf Kinematics Project (BDKP. III. Parallaxes for 70 Ultracool Dwarfs

    Science.gov (United States)

    2012-06-10

    2019 61.2 ± 5.1 −2905.1 ± 3.4 −1953.9 ± 3.4 61.67 ± 2.12 −2906.15 ± 2.41 −1963.12 ± 2.71 A 7 SDSS J1446+0024 46.7 ± 14.6 202.9 ± 10.9 −100.4 ± 10.8...al. 2010; Stumpf et al. 2011). Four known binary sources, 2MASS J0518−2828, 2MASS J1209−1004, 2MASS J1404−3159, and SDSS J2052−1609 had parallax...measurements reported in this work as did one suspected binary SDSS J1511+0607 (Burgasser et al. 2010a; C. R. Gelino et al. in preparation). We list the 9

  5. Ionisation and discharge in cloud-forming atmospheres of brown dwarfs and extrasolar planets

    Science.gov (United States)

    Helling, Ch; Rimmer, P. B.; Rodriguez-Barrera, I. M.; Wood, Kenneth; Robertson, G. B.; Stark, C. R.

    2016-07-01

    Brown dwarfs and giant gas extrasolar planets have cold atmospheres with rich chemical compositions from which mineral cloud particles form. Their properties, like particle sizes and material composition, vary with height, and the mineral cloud particles are charged due to triboelectric processes in such dynamic atmospheres. The dynamics of the atmospheric gas is driven by the irradiating host star and/or by the rotation of the objects that changes during its lifetime. Thermal gas ionisation in these ultra-cool but dense atmospheres allows electrostatic interactions and magnetic coupling of a substantial atmosphere volume. Combined with a strong magnetic field \\gg {{B}\\text{Earth}} , a chromosphere and aurorae might form as suggested by radio and x-ray observations of brown dwarfs. Non-equilibrium processes like cosmic ray ionisation and discharge processes in clouds will increase the local pool of free electrons in the gas. Cosmic rays and lighting discharges also alter the composition of the local atmospheric gas such that tracer molecules might be identified. Cosmic rays affect the atmosphere through air showers in a certain volume which was modelled with a 3D Monte Carlo radiative transfer code to be able to visualise their spacial extent. Given a certain degree of thermal ionisation of the atmospheric gas, we suggest that electron attachment to charge mineral cloud particles is too inefficient to cause an electrostatic disruption of the cloud particles. Cloud particles will therefore not be destroyed by Coulomb explosion for the local temperature in the collisional dominated brown dwarf and giant gas planet atmospheres. However, the cloud particles are destroyed electrostatically in regions with strong gas ionisation. The potential size of such cloud holes would, however, be too small and might occur too far inside the cloud to mimic the effect of, e.g. magnetic field induced star spots.

  6. Multi-band Emission Light Curves of Jupiter: Insights on Brown Dwarfs and Directly Imaged Exoplanets

    Science.gov (United States)

    Zhang, Xi; Ge, Huazhi; Orton, Glenn S.; Fletcher, Leigh N.; Sinclair, James; Fernandes, Joshua; Momary, Thomas W.; Kasaba, Yasumasa; Sato, Takao M.; Fujiyoshi, Takuya

    2016-10-01

    Many brown dwarfs exhibit significant infrared flux variability (e.g., Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750, 105), ranging from several to twenty percent of the brightness. Current hypotheses include temperature variations, cloud holes and patchiness, and cloud height and thickness variations (e.g., Apai et al. 2013, ApJ, 768, 121; Robinson and Marley 2014, ApJ, 785, 158; Zhang and Showman 2014, ApJ, 788, L6). Some brown dwarfs show phase shifts in the light curves among different wavelengths (e.g., Buenzli et al. 2012, ApJ, 760, L31; Yang et al. 2016, arXiv:1605.02708), indicating vertical variations of the cloud distribution. The current observational technique can barely detect the brightness changes on the surfaces of nearby brown dwarfs (Crossfield et al. 2014, Nature, 505, 654) let alone resolve detailed weather patterns that cause the flux variability. The infrared emission maps of Jupiter might shed light on this problem. Using COMICS at Subaru Telescope, VISIR at Very Large Telescope (VLT) and NASA's Infrared Telescope Facility (IRTF), we obtained infrared images of Jupiter over several nights at multiple wavelengths that are sensitive to several pressure levels from the stratosphere to the deep troposphere below the ammonia clouds. The rotational maps and emission light curves are constructed. The individual pixel brightness varies up to a hundred percent level and the variation of the full-disk brightness is around several percent. Both the shape and amplitude of the light curves are significantly distinct at different wavelengths. Variation of light curves at different epochs and phase shift among different wavelengths are observed. We will present principle component analysis to identify dominant emission features such as stable vortices, cloud holes and eddies in the belts and zones and strong emissions in the aurora region. A radiative transfer model is used to simulate those features to get a more quantitative

  7. Optical and NIR Polarimetry of a Core L328 with Proto-Brown Dwarf

    Science.gov (United States)

    Soam, A.; Kwon, J.; Maheswar, G.; Tamura, M.; Lee, C. W.

    2015-12-01

    LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self-gravitating contraction. We present results of our optical and near infrared polarisation observations of regions towards LDN 328. Results from the present study suggest that the magnetic field may be playing a vital role even in the cores that are forming sub-stellar sources.

  8. The Near-infrared Spectrum of the Brown Dwarf Gliese 229B

    OpenAIRE

    Geballe, T. R.; Kulkarni, S.R.; Woodward, C. E.; Sloan, G.C.

    1996-01-01

    A medium resolution 1.0-2.5um spectrum of the brown dwarf, Gliese 229B has been obtained using CGS4 on UKIRT. In addition to the broad spectral structure seen in earlier low resolution observations, the new spectrum reveals a large number of absorption lines, many of which can be identified with water vapor. Water and methane are both shown to be strong absorbers in the near-infrared spectrum of the object. Several spectral features in Gl 229B that are attributable to methane match ones seen ...

  9. Dwarf Galaxy Dark Matter Density Profiles Inferred from Stellar and Gas Kinematics

    CERN Document Server

    Adams, Joshua J; Fabricius, Maximilian H; Bosch, Remco C E van den; Barentine, John C; Bender, Ralf; Gebhardt, Karl; Hill, Gary J; Murphy, Jeremy D; Swaters, R A; Thomas, Jens; van de Ven, Glenn

    2014-01-01

    We present new constraints on the density profiles of dark matter (DM) halos in seven nearby dwarf galaxies from measurements of their integrated stellar light and gas kinematics. The gas kinematics of low mass galaxies frequently suggest that they contain constant density DM cores, while N-body simulations instead predict a cuspy profile. We present a data set of high resolution integral field spectroscopy on seven galaxies and measure the stellar and gas kinematics simultaneously. Using Jeans modeling on our full sample, we examine whether gas kinematics in general produce shallower density profiles than are derived from the stars. Although 2/7 galaxies show some localized differences in their rotation curves between the two tracers, estimates of the central logarithmic slope of the DM density profile, gamma, are generally robust. The mean and standard deviation of the logarithmic slope for the population are gamma=0.67+/-0.10 when measured in the stars and gamma=0.58+/-0.24 when measured in the gas. We als...

  10. An Analysis of the SEEDS High-Contrast Exoplanet Survey: Massive Planets or Low-Mass Brown Dwarfs?

    CERN Document Server

    Brandt, Timothy D; Turner, Edwin L; Mede, Kyle; Spiegel, David S; Kuzuhara, Masayuki; Schlieder, Joshua E; Wisniewski, John P; Abe, L; Brandner, W; Carson, J; Currie, T; Egner, S; Feldt, M; Golota, T; Goto, M; Grady, C A; Guyon, O; Hashimoto, J; Hayano, Y; Hayashi, M; Hayashi, S; Henning, T; Hodapp, K W; Inutsuka, S; Ishii, M; Iye, M; Janson, M; Kandori, R; Knapp, G R; Kudo, T; Kusakabe, N; Kwon, J; Matsuo, T; Miyama, S; Morino, J -I; Moro-Martín, A; Nishimura, T; Pyo, T -S; Serabyn, E; Suto, H; Suzuki, R; Takami, M; Takato, N; Terada, H; Thalmann, C; Tomono, D; Watanabe, M; Yamada, T; Takami, H; Usuda, T; Tamura, M

    2014-01-01

    We conduct a statistical analysis of a combined sample of direct imaging data, totalling nearly 250 stars observed by HiCIAO on the Subaru Telescope, NIRI on Gemini North, and NICI on Gemini South. The stars cover a wide range of ages and spectral types, and include five detections (kap And b, two ~60 M_J brown dwarf companions in the Pleiades, PZ Tel B, and CD-35 2722 B). We conduct a uniform, Bayesian analysis of the ages of our entire sample, using both membership in a kinematic moving group and activity/rotation age indicators, to obtain posterior age distributions. We then present a new statistical method for computing the likelihood of a substellar distribution function. By performing most integrals analytically, we achieve an enormous speedup over brute-force Monte Carlo. We use this method to place upper limits on the maximum semimajor axis beyond which the distribution function for radial-velocity planets cannot extend, finding model-dependent values of ~30--100 AU. Finally, we treat our entire subst...

  11. The Properties of the 500 K Dwarf UGPS J072227.51-054031.2, and a Study of the Far-Red Flux of Cold Brown Dwarfs

    CERN Document Server

    Leggett, S K; Marley, M S; Lodders, K; Canty, J; Lucas, P; Smart, R L; Tinney, C G; Homeier, D; Allard, F; Burningham, Ben; Day-Jones, A; Fegley, B; Ishii, Miki; Jones, H R A; Marocco, F; Pinfield, D J; Tamura, M

    2012-01-01

    We present i and z photometry for 25 T dwarfs and one L dwarf. Combined with published photometry, the data show that the i - z, z - Y and z - J colors of T dwarfs are very red, and continue to increase through to the late-type T dwarfs, with a hint of a saturation for the latest types with T_eff ~ 600 K. We present new 0.7-1.0 um and 2.8-4.2 um spectra for the very late-type T dwarf UGPS J072227.51-054031.2, as well as improved astrometry for this dwarf. Examination of the spectral energy distribution using the new and published data, with Saumon & Marley models, shows that the dwarf has T_eff = 505 +/- 10 K, a mass of 3-11 M_Jupiter and an age between 60 Myr and 1 Gyr. This young age is consistent with the thin disk kinematics of the dwarf. The mass range overlaps with that usually considered to be planetary, despite this being an unbound object discovered in the field near the Sun. This apparently young rapid rotator is also undergoing vigorous atmospheric mixing, as determined by the IRAC and WISE-2 4...

  12. The role of the molecular-metallic transition of hydrogen in the evolution of Jupiter, Saturn, and brown dwarfs

    Science.gov (United States)

    Saumon, Didier; Hubbard, William B.; Chabrier, Gilles; Van Horn, Hugh M.

    1992-01-01

    An equation of state for hydrogen which predicts a molecular-metallic phase transition at finite temperatures has become available recently. The effect of this phase transition on the cooling histories of these two giant planets and of substellar brown dwarfs is studied. The phase transition alters the present age of Jupiter and of Saturn by a few percent. Interestingly, the cooling of brown dwarfs is most strongly affected at the time when the interior adiabat crosses the critical point of the phase transition.

  13. VLT X-shooter spectroscopy of the nearest brown dwarf binary

    CERN Document Server

    Lodieu, N; Rebolo, R; Bejar, V J S; Pavlenko, Y; Perez-Garrido, A

    2015-01-01

    The aim of the project is to characterise both components of the nearest brown dwarf sytem to the Sun, WISE J104915.57-531906.1 (=Luhman16AB) at optical and near-infrared wavelengths. We obtained high signal-to-noise intermediate-resolution (R~6000-11000) optical (600-1000 nm) and near-infrared (1000-2480nm) spectra of each component of Luhman16AB, the closest brown dwarf binary to the Sun, with the X-Shooter instrument on the Very Large Telescope. We classify the primary and secondary of the Luhman16 system as L6-L7.5 and T0+/-1, respectively, in agreement with previous measurements published in the literature. We present measurements of the lithium pseudo-equivalent widths, which appears of similar strength on both components (8.2+/-1.0 Angstroms and 8.4+/-1.5 Angstroms for the L and T components, respectively). The presence of lithium (Lithium 7) in both components imply masses below 0.06 Msun while comparison with models suggests lower limits of 0.04 Msun. The detection of lithium in the T component is th...

  14. Hubble Space Telescope Spectroscopy of Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer

    CERN Document Server

    Schneider, Adam C; Kirkpatrick, J Davy; Gelino, Christopher R; Mace, Gregory N; Wright, Edward L; Eisenhardt, Peter R; Skrutskie, M F; Griffith, Roger L; Marsh, Kenneth A

    2015-01-01

    We present a sample of brown dwarfs identified with the {\\it Wide-field Infrared Survey Explorer} (WISE) for which we have obtained {\\it Hubble Space Telescope} ({\\it HST}) Wide Field Camera 3 (WFC3) near-infrared grism spectroscopy. The sample (twenty-two in total) was observed with the G141 grism covering 1.10$-$1.70 $\\mu$m, while fifteen were also observed with the G102 grism, which covers 0.90$-$1.10 $\\mu$m. The additional wavelength coverage provided by the G102 grism allows us to 1) search for spectroscopic features predicted to emerge at low effective temperatures (e.g.\\ ammonia bands) and 2) construct a smooth spectral sequence across the T/Y boundary. We find no evidence of absorption due to ammonia in the G102 spectra. Six of these brown dwarfs are new discoveries, three of which are found to have spectral types of T8 or T9. The remaining three, WISE J082507.35$+$280548.5 (Y0.5), WISE J120604.38$+$840110.6 (Y0), and WISE J235402.77$+$024015.0 (Y1) are the nineteenth, twentieth, and twenty-first spec...

  15. The radius anomaly in the planet/brown dwarf overlapping mass regime

    Directory of Open Access Journals (Sweden)

    Baraffe I.

    2011-02-01

    Full Text Available The recent detection of the transit of very massive substellar companions (Deleuil et al. 2008; Bouchy et al. 2010; Anderson et al. 2010; Bakos et al. 2010 provides a strong constraint to planet and brown dwarf formation and migration mechanisms. Whether these objects are brown dwarfs originating from the gravitational collapse of a dense molecular cloud that, at the same time, gave birth to the more massive stellar companion, or whether they are planets that formed through core accretion of solids in the protoplanetary disk can not always be determined unambiguously and the mechanisms responsible for their short orbital distances are not yet fully understood. In this contribution, we examine the possibility to constrain the nature of a massive substellar object from the various observables provided by the combination of Radial Velocity and Photometry measurements (e.g. Mp , Rp , M⋆, Age, a, e.... In a second part, developments in the modeling of tidal evolution at high eccentricity and inclination - as measured for HD 80 606 with e = 0.9337 (Naef et al. 2001 , XO-3 with a stellar obliquity ε⋆  > 37.3 ± 3.7 deg (Hébrard et al. 2008; Winn et al. 2009 and several other exoplanets - are discussed along with their implication in the understanding of the radius anomaly problem of extrasolar giant planets.

  16. DISCOVERY OF A ∼250 K BROWN DWARF AT 2 pc FROM THE SUN

    Energy Technology Data Exchange (ETDEWEB)

    Luhman, K. L., E-mail: kluhman@astro.psu.edu [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-05-10

    Through a previous analysis of multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE), I identified WISE J085510.83–071442.5 as a new high proper motion object. By combining astrometry from WISE and the Spitzer Space Telescope, I have measured a proper motion of 8.1 ± 0.1'' yr{sup –1} and a parallax of 0.454 ± 0.045'' (2.20{sub −0.20}{sup +0.24} pc) for WISE J085510.83–071442.5, giving it the third highest proper motion and the fourth largest parallax of any known star or brown dwarf. It is also the coldest known brown dwarf based on its absolute magnitude at 4.5 μm and its color in [3.6]-[4.5]. By comparing M {sub 4.5} with the values predicted by theoretical evolutionary models, I estimate an effective temperature of 225-260 K and a mass of 3-10 M {sub Jup} for the age range of 1-10 Gyr that encompasses most nearby stars.

  17. A Herschel Search For Cold Dust in Brown Dwarf Disks: First Results

    CERN Document Server

    Harvey, Paul M; Menard, Francois; Wolf, Sebastian; Liu, Yao; Cieza, Lucas A; Evans, Neal J; Pascucci, Ilaria; Merin, Bruno; Pinte, Christophe

    2011-01-01

    We report initial results from a {\\it Herschel} program to search for far-infrared emission from cold dust around a statistically significant sample of young brown dwarfs. The first three objects in our survey are all detected at 70\\micron, and we report the first detection of a brown dwarf at 160\\micron. The flux densities are consistent with the presence of substantial amounts of cold dust in the outer disks around these objects. We modeled the SED's with two different radiative transfer codes. We find that a broad range of model parameters provides a reasonable fit to the SED's, but that the addition of our 70\\micron, and especially the 160\\micron\\ detection enables strong lower limits to be placed on the disk masses since most of the mass is in the outer disk. We find likely disk masses in the range of a few $\\times 10^{-6}$ to $10^{-4}$ \\msun. Our models provide a good fit to the SED's and do not require dust settling.

  18. Your Age is Showing: Understanding the Spectral Features of Young Brown Dwarfs

    Science.gov (United States)

    DiTomasso, Victoria; Schwab, Ellianna; Rice, Emily L.; Riedel, Adric R.; Cruz, Kelle L.; Faherty, Jackie

    2017-01-01

    Brown dwarfs are substellar objects that continuously cool, shrink, and fade over billions of years. These physical changes lead us to expect that young objects will have spectral indicators of low gravity. We selected 11 brown dwarfs ranging in spectral type from M7-L7 whose optical and/or low resolution NIR spectroscopy suggest that they are low gravity, hence young, objects. Using high-resolution (R~20,000) near-infrared data from the NIRSPEC instrument at the Keck II telescope in Hawaii, we analyzed J-band (1.1-1.4 μm) spectra of these targets. We calculated their radial velocities and combined those values with previously calculated parallax distances and proper motions to determine their likelihood of membership in nearby young moving groups, successfully placing three of them. We also compared our high-resolution spectra to observations of confirmed young (evaluate the consistency of spectral indicators of youth across spectral type, age, resolution, and wavelength regime.

  19. A census of very-low-mass stars and brown dwarfs in the sigma Orionis cluster

    CERN Document Server

    Lodieu, N; Rebolo, R; Martín, E L; Hambly, N C

    2009-01-01

    (ABRIDGED) We have analysed the near-infrared photometric data from the Fourth Data Release (DR4) of the UKIRT Infrared Deep Sky Suvey (UKIDSS) Galactic Clusters Survey (GCS) to derive the cluster luminosity and mass functions, evaluate the extent of the cluster, and study the distribution and variability of low-mass stars and brown dwarfs down to the deuterium-burning limit. We have recovered most of the previously published members and found a total of 287 candidate members within the central 30 arcmin in the 0.5-0.009 Msun mass range, including new objects not previously reported in the literature. This new catalogue represents a homogeneous dataset of brown dwarf member candidates over the central 30 arcmin of the cluster. The expected photometric contamination by field objects with similar magnitudes and colours to sigma Orionis members is ~15%. We present evidence of variability at the 99.5% confidence level over ~yearly timescales in 10 member candidates that exhibit signs of youth and the presence of ...

  20. Substellar Objects in Nearby Young Clusters (SONYC) V: New brown dwarfs in rho Ophiuchi

    CERN Document Server

    Muzic, Koraljka; Geers, Vincent C; Jayawardhana, Ray; Tamura, Motohide

    2011-01-01

    SONYC - Substellar Objects in Nearby Young Clusters - is a survey program to investigate the frequency and properties of substellar objects with masses down to a few times that of Jupiter in nearby star-forming regions. For the ~1Myr old rho Ophiuchi cluster, in our earlier paper we reported deep, wide-field optical and near-infrared imaging using Subaru, combined with 2MASS and Spitzer photometry, as well as follow-up spectroscopy confirming three likely cluster members, including a new brown dwarf with a mass close to the deuterium-burning limit. Here we present the results of extensive new spectroscopy targeting a total of ~100 candidates in rho Oph, with FMOS at the Subaru Telescope and SINFONI at the ESO's Very Large Telescope. We identify 19 objects with effective temperatures at or below 3200 K, 8 of which are newly identified very-low-mass probable members of rho Oph. Among these eight, six objects have Teff <= 3000 K, confirming their likely substellar nature. These six new brown dwarfs comprise o...

  1. Discovery of a ~250 K Brown Dwarf at 2 pc from the Sun

    CERN Document Server

    Luhman, K L

    2014-01-01

    Through a previous analysis of multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE), I identified WISE J085510.83-071442.5 as a new high proper motion object. By combining astrometry from WISE and the Spitzer Space Telescope, I have measured a proper motion of 8.1+/-0.1"/yr and a parallax of 0.454+/-0.045" (2.20+0.24/-0.20 pc) for WISE J085510.83-071442.5, giving it the third highest proper motion and the fourth largest parallax of any known star or brown dwarf. It is also the coldest known brown dwarf based on its absolute magnitude at 4.5um and its color in [3.6]-[4.5]. By comparing M4.5 with the values predicted by theoretical evolutionary models, I estimate an effective temperature of 225-260 K and a mass of 3-10 Mjup for the age range of 1-10 Gyr that encompasses most nearby stars.

  2. Brown dwarf disks with Herschel: Linking far-infrared and (sub)-mm fluxes

    CERN Document Server

    Daemgen, Sebastian; Scholz, Alexander; Testi, Leonardo; Jayawardhana, Ray; Greaves, Jane; Eastwood, Daniel

    2016-01-01

    Brown dwarf disks are excellent laboratories to test our understanding of disk physics in an extreme parameter regime. In this paper we investigate a sample of 29 well-characterized brown dwarfs and very low mass stars, for which Herschel far-infrared fluxes as well as (sub)-mm fluxes are available. We have measured new Herschel PACS fluxes for 11 objects and complement these with (sub)-mm data and Herschel fluxes from the literature. We analyze their spectral energy distributions in comparison with results from radiative transfer modeling. Fluxes in the far-infrared are strongly affected by the shape and temperature of the disk (and hence stellar luminosity), whereas the (sub)-mm fluxes mostly depend on disk mass. Nevertheless, there is a clear correlation between far-infrared and (sub)-mm fluxes. We argue that the link results from the combination of the stellar mass-luminosity relation and a scaling between disk mass and stellar mass. We find strong evidence of dust settling to the disk midplane. The spect...

  3. Ionization in atmospheres of Brown Dwarfs and extrasolar planets IV. The Effect of Cosmic Rays

    CERN Document Server

    Rimmer, Paul

    2013-01-01

    Cosmic rays provide an important source for free electrons in the Earth's atmosphere and also in dense interstellar regions where they produce a prevailing background ionization. We utilize a Monte Carlo cosmic ray transport model for particle energies of 1 MeV < E < 1 GeV, and an analytic cosmic ray transport model for particle energies of 1 GeV < E < 1 TeV in order to investigate the cosmic ray enhancement of free electrons in substellar atmospheres of free-floating objects. The cosmic ray calculations are applied to Drift-Phoenix model atmospheres of an example brown dwarf with effective temperature Teff = 1500 K, and two example giant gas planets (Teff = 1000 K, 1500 K). For the model brown dwarf atmosphere, the electron fraction is enhanced significantly by cosmic rays when the pressure pgas < 10^-2 bar. Our example giant gas planet atmosphere suggests that the cosmic ray enhancement extends to 10^-4 - 10^-2 bar, depending on the effective temperature. For the model atmosphere of the examp...

  4. Multi-fibre optical spectroscopy of low-mass stars and brown dwarfs in Upper Sco

    CERN Document Server

    Lodieu, N; Hambly, N C

    2011-01-01

    We have obtained multi-fibre intermediate-resolution optical spectroscopy of 94 photometric and proper motion selected low-mass star and brown dwarf candidates in Upper Sco with AAT/AAOmega. We have estimated the spectral types and measured the equivalent widths of youth and gravity diagnostic features to confirm the spectroscopic membership of about 95% of the candidates extracted from 6.5 square degrees in Upper Sco. We also detect lithium in the spectra with the highest signal-to-noise, consolidating our conclusions about their youth. Furthermore, we derive an estimate of our selections using spectroscopic data obtained for a large number of stars falling into the instrument's field-of-view. We have estimated the effective temperatures and masses for each new spectroscopic member using the latest evolutionary models available for low-mass stars and brown dwarfs. Combining the current optical spectroscopy presented here with near-infrared spectroscopy obtained for the faintest photometric candidates, we con...

  5. The minimum mass for star formation, and the origin of binary brown dwarfs

    CERN Document Server

    Stamatellos, A P W D

    2006-01-01

    Our first aim is to calculate the minimum mass for Primary Fragmentation in a variety of potential star-formation scenarios, i.e. (i) hierarchical fragmentation of a 3-D medium; (ii) one-shot, 2-D fragmentation of a shock-compressed layer; (iii) fragmentation of a circumstellar disc. Our second aim is to evaluate the role of H2 dissociation in facilitating Secondary Fragmentation and thereby producing close, low-mass binaries. Results: (i)For contemporary, local star formation, the minimum mass for Primary Fragmentation is in the range 0.001-0.004Msun, irrespective of the scenario considered. (ii)Circumstellar discs are only able to radiate fast enough to undergo Primary Fragmentation in their cool outer parts (R>100AU). Therefore brown dwarfs (BDs) should have difficulty forming by Primary Fragmentation at R100AU could be the source of brown dwarfs in wide orbits, and could explain why massive discs with Rd>100AU are rarely seen.(iii)H2 dissociation can lead to collapse and Secondary Fragmentation, thereby c...

  6. A multi-wavelength characterization of proto-brown dwarf candidates in Serpens

    CERN Document Server

    Riaz, B; Harsono, D; Caselli, P; Tikare, K; Gonzalez-Martin, O

    2016-01-01

    We present results from a deep sub-millimeter survey in the Serpens Main and Serpens/G3-G6 clusters, conducted with the Submillimetre Common-User Bolometer Array (SCUBA-2) at the James Clerk Maxwell Telescope. We have combined Herschel PACS far-infrared photometry, sub-millimeter continuum and molecular gas line observations, with the aim to conduct a detailed multi-wavelength characterization of `proto-brown dwarf' candidates in Serpens. We have performed continuum and line radiative transfer modeling, and have considered various classification schemes to understand the structure and the evolutionary stage of the system. We have identified four proto-brown dwarf candidates, of which the lowest luminosity source has an Lbol ~0.05 Lsun. Two of these candidates show characteristics consistent with Stage 0/I systems, while the other two are Stage I-T/Class Flat systems with tenuous envelopes. Our work has also revealed a ~20% fraction of mis-identified Class 0/I/Flat sources that show characteristics consistent ...

  7. Brown Dwarf Jets: Investigating the Universality of Jet Launching Mechanisms at the Lowest Masses

    CERN Document Server

    Whelan, Emma Teresa; Ray, Tom; Dougados, Catherine

    2010-01-01

    Recently it has become apparent that proto-stellar-like outflow activity extends to the brown dwarf (BD) mass regime. While the presence of accretion appears to be the common ingredient in all objects known to drive jets fundamental questions remain unanswered. The more prominent being the exact mechanism by which jets are launched, and whether this mechanism remains universal among such a diversity of sources and scales. To address these questions we have been investigating outflow activity in a sample of protostellar objects that differ considerably in mass and mass accretion rate. Central to this is our study of brown dwarf jets. To date Classical T Tauri stars (CTTS) have offered us the best touchstone for decoding the launching mechanism. Here we shall summarise what is understood so far of BD jets and the important constraints observations can place on models. We will focus on the comparison between jets driven by objects with central mass < 0.1M \\odot and those driven by CTTSs. In particular we wish...

  8. Two candidate brown dwarf companions around core helium-burning stars

    CERN Document Server

    Schaffenroth, V; Nagel, K; Geier, S; Koen, C; Heber, U; Edelmann, H

    2014-01-01

    Hot subdwarf stars of spectral type B (sdBs) are evolved, core helium-burning objects. The formation of those objects is puzzling, because the progenitor star has to lose almost its entire hydrogen envelope in the red-giant phase. Binary interactions have been invoked, but single sdBs exist as well. We report the discovery of two close hot subdwarf binaries with small radial velocity amplitudes. Follow-up photometry revealed reflection effects originating from cool irradiated companions, but no eclipses. The lower mass limits for the companions of CPD-64$^{\\circ}$481 ($0.048\\,M_{\\rm \\odot}$) and PHL\\,457 ($0.027\\,M_{\\rm \\odot}$) are significantly below the stellar mass limit. Hence they could be brown dwarfs unless the inclination is unfavourable. Two very similar systems have already been reported. The probability that none of them is a brown dwarf is very small, 0.02%. Hence we provide further evidence that substellar companions with masses that low are able to eject a common envelope and form an sdB star. ...

  9. The Coldest Brown Dwarf (Or Free Floating Planet)?: The Y Dwarf WISE 1828+2650

    CERN Document Server

    Beichman, Charles A; Kirkpatrick, J Davy; Barman, Travis S; Marsh, Kenneth A; Cushing, Michael C; Wright, E L

    2013-01-01

    We have monitored the position of the cool Y dwarf WISEPA J182831.08+265037.8 using a combination of ground- and space-based telescopes and have determined its distance to be 11.2$_{-1.0}^{+1.3}$ pc. Its absolute H magnitude, M$_H=22.21^{+0.25}_{-0.22}$ mag, suggests a mass in the range 0.5-20 M$_{Jup}$ for ages of 0.1-10 Gyr with an effective temperature in the range 250-400 K. The broad range in mass is due primarily to the unknown age of the object. Since the high tangential velocity of the object, 51$\\pm5$ km s$^{-1}$, is characteristic of an old disk population, a plausible age range of 2-4 Gyr leads to a mass range of 3-6 M$_{Jup}$ based on fits to the (highly uncertain) COND evolutionary models. The range in temperature is due to the fact that no single model adequately represents the 1-5 $\\mu$m spectral energy distribution (SED) of the source, failing by factors of up to 5 at either the short or long wavelength portions of the spectral energy distribution. The appearance of this very cold object may b...

  10. Astrometric discovery of GJ 802b : in the Brown Dwarf Oasis?

    Science.gov (United States)

    Pravdo, Steven H.; Shaklan, Stuart B.; Lloyd, James

    2005-01-01

    The Stellar Planet Survey is an ongoing astrometric search for giant planets and brown dwarfs around a sample of 30 M dwarfs. We have discovered several low-mass companions by measuring the motion of our target stars relative to their reference frames. The lowest mass discovery thus far is GJ 802b, a companion to the M5 dwarf GJ 802A. The orbital period is 3.14 +/-0:03 yr, the system mass is 0:214 +/- 0:045 M(circled dot operator), and the semimajor axis is 1:28+/- 0:10 AU or 81 + 6 mas. Imaging observations indicate that GJ 802b is likely to be a brow with the astrometrically determined mass 0:058 +/- 0:021 M(circled dot operator) (1 (sigma) limits). The remaining uncertainty in the orbit is the eccentricity that is now loosely constrained. We dis the system age limits the mass and the prospects of further narrowing the mass range when e is more precisely determined.

  11. Brown Dwarfs in Young Moving Groups from Pan-STARRS1. I. AB Doradus

    CERN Document Server

    Aller, Kimberly M; Magnier, Eugene A; Best, William M J; Kotson, Michael C; Burgett, William S; Chambers, Kenneth C; Hodapp, Klaus W; Flewelling, Heather; Kaiser, Nick; Metcalf, Nigel; Tonry, John L; Wainscoat, Richard J; Waters, Christopher

    2016-01-01

    Substellar members of young ($\\lesssim$150 Myr) moving groups are valuable benchmarks to empirically define brown dwarf evolution with age and to study the low-mass end of the initial mass function. We have combined Pan-STARRS1 (PS1) proper motions with optical$-$IR photometry from PS1, 2MASS and $\\textit{WISE}$ to search for substellar members of the AB Dor Moving Group within $\\approx$50 pc and with spectral types of late-M to early-L, corresponding to masses down to $\\approx$30 M$_{Jup}$ at the age of the group ($\\approx$125 Myr). Including both photometry and proper motions allows us to better select candidates by excluding field dwarfs whose colors are similar to young AB~Dor Moving Group members. Our near-IR spectroscopy has identified six ultracool dwarfs (M6$-$L4; $\\approx$30$-$100 M$_{Jup}$) with intermediate surface gravities (INT-G) as candidate members of the AB Dor Moving Group. We find another two candidate members with spectra showing hints of youth but consistent with field gravities. We also ...

  12. WD0837+185: THE FORMATION AND EVOLUTION OF AN EXTREME MASS-RATIO WHITE-DWARF-BROWN-DWARF BINARY IN PRAESEPE

    Energy Technology Data Exchange (ETDEWEB)

    Casewell, S. L.; Burleigh, M. R.; Wynn, G. A.; Alexander, R. D.; Lawrie, K. A.; Jameson, R. F. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Napiwotzki, R. [Science and Technology Research Institute, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Dobbie, P. D. [School of Mathematics and Physics, University of Tasmania, Hobart, Tasmania 7001 (Australia); Hodgkin, S. T., E-mail: slc25@le.ac.uk [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom)

    2012-11-10

    There is a striking and unexplained dearth of brown dwarf companions in close orbits (<3 AU) around stars more massive than the Sun, in stark contrast to the frequency of stellar and planetary companions. Although rare and relatively short-lived, these systems leave detectable evolutionary end points in the form of white-dwarf-brown-dwarf binaries and these remnants can offer unique insights into the births and deaths of their parent systems. We present the discovery of a close (orbital separation {approx}0.006 AU) substellar companion to a massive white dwarf member of the Praesepe star cluster. Using the cluster age and the mass of the white dwarf, we constrain the mass of the white dwarf progenitor star to lie in the range 3.5-3.7 M{sub Sun} (B9). The high mass of the white dwarf means the substellar companion must have been engulfed by the B star's envelope while it was on the late asymptotic giant branch (AGB). Hence, the initial separation of the system was {approx}2 AU, with common envelope evolution reducing the separation to its current value. The initial and final orbital separations allow us to constrain the combination of the common envelope efficiency ({alpha}) and binding energy parameters ({lambda}) for the AGB star to {alpha}{lambda} {approx} 3. We examine the various formation scenarios and conclude that the substellar object was most likely captured by the white dwarf progenitor early in the life of the cluster, rather than forming in situ.

  13. Uncovering the Outflow Driven by the Brown Dwarf LS-RCr A1: H-alpha as a Tracer of Outflow Activity in Brown Dwarfs

    CERN Document Server

    Whelan, E T; Bacciotti, F

    2009-01-01

    It is now apparent that classical T Tauri-like outflows commonly accompany the formation of young brown dwarfs. To date two optical outflows have been discovered and results presented in this paper increase this number to three. Using spectro-astrometry the origin of the LS-RCrA 1 forbidden emission lines in a blue-shifted outflow is confirmed. The non-detection of the red-shifted component of the outflow in forbidden lines, along with evidence for some separation between low and high velocity outflow components, do not support the hypothesis that LS-RCrA 1 has an edge-on accretion disk. The key result of this analysis is the discovery of an outflow component to the H-alpha line. The H-alpha line profile has blue and red-shifted features in the wings which spectro-astrometry reveals to also originate in the outflow. The discovery that H-alpha emission in BDs can have a significant contribution from an outflow suggests the use of H-alpha line widths as a proxy of mass accretion in BDs is not clear-cut. This me...

  14. Further Defining Spectral Type "Y" and Exploring the Low-mass End of the Field Brown Dwarf Mass Function

    CERN Document Server

    Kirkpatrick, J Davy; Cushing, Michael C; Mace, Gregory N; Griffith, Roger L; Skrutskie, Michael F; Marsh, Kenneth A; Wright, Edward L; Eisenhardt, Peter R; McLean, Ian S; Mainzer, Amanda K; Burgasser, Adam J; Tinney, C G; Parker, Stephen; Salter, Graeme

    2012-01-01

    We present the discovery of another seven Y dwarfs from the Wide-field Infrared Survey Explorer (WISE). Using these objects, as well as the first six WISE Y dwarf discoveries from Cushing et al., we further explore the transition between spectral types T and Y. We find that the T/Y boundary roughly coincides with the spot where the J-H colors of brown dwarfs, as predicted by models, turn back to the red. Moreover, we use preliminary trigonometric parallax measurements to show that the T/Y boundary may also correspond to the point at which the absolute H (1.6 um) and W2 (4.6 um) magnitudes plummet. We use these discoveries and their preliminary distances to place them in the larger context of the Solar Neighborhood. We present a table that updates the entire stellar and substellar constituency within 8 parsecs of the Sun, and we show that the current census has hydrogen-burning stars outnumbering brown dwarfs by roughly a factor of six. This factor will decrease with time as more brown dwarfs are identified wi...

  15. Spectroscopy of brown dwarf candidates in IC 348 and the determination of its substellar IMF down to planetary masses

    CERN Document Server

    de Oliveira, C Alves; Bouvier, J; Duchene, G; Bouy, H; Maschberger, T; Hudelot, P

    2012-01-01

    Context. Brown dwarfs represent a sizable fraction of the stellar content of our Galaxy and populate the transition between the stellar and planetary mass regime. There is however no agreement on the processes responsible for their formation. Aims. We have conducted a large survey of the young, nearby cluster IC 348, to uncover its low-mass brown dwarf population and study the cluster properties in the substellar regime. Methods. Deep optical and near-IR images taken with MegaCam and WIRCam at the Canada-France-Hawaii Telescope (CFHT) were used to select photometric candidate members. A spectroscopic follow-up of a large fraction of the candidates was conducted to assess their youth and membership. Results. We confirmed spectroscopically 16 new members of the IC 348 cluster, including 13 brown dwarfs, contributing significantly to the substellar census of the cluster, where only 30 brown dwarfs were previously known. Five of the new members have a L0 spectral type, the latest-type objects found to date in thi...

  16. The TRENDS High-Contrast Imaging Survey. VI. Discovery of a Mass, Age, and Metallicity Benchmark Brown Dwarf

    CERN Document Server

    Crepp, Justin R; Bechter, Eric B; Montet, Benjamin T; Johnson, John Asher; Piskorz, Danielle; Howard, Andrew W; Isaacson, Howard

    2016-01-01

    The mass and age of substellar objects are degenerate parameters leaving the evolutionary state of brown dwarfs ambiguous without additional information. Theoretical models are normally used to help distinguish between old, massive brown dwarfs and young, low mass brown dwarfs but these models have yet to be properly calibrated. We have carried out an infrared high-contrast imaging program with the goal of detecting substellar objects as companions to nearby stars to help break degeneracies in inferred physical properties such as mass, age, and composition. Rather than using imaging observations alone, our targets are pre-selected based on the existence of dynamical accelerations informed from years of stellar radial velocity (RV) measurements. In this paper, we present the discovery of a rare benchmark brown dwarf orbiting the nearby ($d=18.69\\pm0.19$ pc), solar-type (G9V) star HD 4747 ([Fe/H]=$-0.22\\pm0.04$) with a projected separation of only $\\rho=11.3\\pm0.2$ AU ($\\theta \\approx$ 0.6''). Precise Doppler m...

  17. Spitzer and z' secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b

    Energy Technology Data Exchange (ETDEWEB)

    Beatty, Thomas G.; Gaudi, B. Scott [Department of Astronomy, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210 (United States); Collins, Karen A.; Kielkopf, John F. [Department of Physics and Astronomy, University of Louisville, Louisville, KY 40292 (United States); Fortney, Jonathan [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Knutson, Heather [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Bruns, Jacob M. [Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States); Showman, Adam P. [Lunar and Planetary Laboratory, 1629 E. University Blvd., University of Arizona, Tucson, AZ (United States); Eastman, Jason [Las Cumbres Observatory Global Telescope Network, 6740 Cortona Dr., Suite 102, Santa Barbara, CA 93117 (United States); Pepper, Joshua [Department of Physics, Lehigh University, Bethlehem, PA 18015 (United States); Siverd, Robert J.; Stassun, Keivan G., E-mail: tbeatty@astronomy.ohio-state.edu [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States)

    2014-03-10

    We present secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b. These observations represent the first constraints on the atmospheric dynamics of a highly irradiated brown dwarf, the atmospheres of irradiated giant planets at high surface gravity, and the atmospheres of brown dwarfs that are dominated by external, rather than internal, energy. Using the Spitzer Space Telescope, we measure secondary eclipse depths of 0.195% ± 0.010% at 3.6 μm and 0.200% ± 0.012% at 4.5 μm. We also find tentative evidence for the secondary eclipse in the z' band with a depth of 0.049% ± 0.023%. These measured eclipse depths are most consistent with an atmosphere model in which there is a strong substellar hotspot, implying that heat redistribution in the atmosphere of KELT-1b is low. While models with a more mild hotspot or even with dayside heat redistribution are only marginally disfavored, models with complete heat redistribution are strongly ruled out. The eclipse depths also prefer an atmosphere with no TiO inversion layer, although a model with TiO inversion is permitted in the dayside heat redistribution case, and we consider the possibility of a day-night TiO cold trap in this object. For the first time, we compare the IRAC colors of brown dwarfs and hot Jupiters as a function of effective temperature. Importantly, our measurements reveal that KELT-1b has a [3.6] – [4.5] color of 0.07 ± 0.11, identical to that of isolated brown dwarfs of similarly high temperature. In contrast, hot Jupiters generally show redder [3.6] – [4.5] colors of ∼0.4, with a very large range from ∼0 to ∼1. Evidently, despite being more similar to hot Jupiters than to isolated brown dwarfs in terms of external forcing of the atmosphere by stellar insolation, KELT-1b appears to have an atmosphere most like that of other brown dwarfs. This suggests that surface gravity is very important in controlling the atmospheric systems of substellar mass bodies.

  18. Formation and evolution of dwarf early-type galaxies in the Virgo cluster I. Internal kinematics

    CERN Document Server

    Toloba, E; Cenarro, A J; Peletier, R F; Gorgas, J; de Paz, A Gil; Munoz-Mateos, J C

    2010-01-01

    We present new medium resolution kinematic data for a sample of 21 dwarf early-type galaxies (dEs) mainly in the Virgo cluster, obtained with the WHT and INT telescopes at the Roque de los Muchachos Observatory (La Palma, Spain). These data are used to study the origin of the dwarf elliptical galaxy population inhabiting clusters. We confirm that dEs are not dark matter dominated galaxies, at least up to the half-light radius. We also find that the observed galaxies in the outer parts of the cluster are mostly rotationally supported systems with disky morphological shapes. Rotationally supported dEs have rotation curves similar to those of star forming galaxies of similar luminosity and follow the Tully-Fisher relation. This is expected if dE galaxies are the descendant of low luminosity star forming systems which recently entered the cluster environment and lost their gas due to a ram pressure stripping event, quenching their star formation activity and transforming into quiescent systems, but conserving the...

  19. A LOFAR mini-survey for low-frequency radio emission from the nearest brown dwarfs

    CERN Document Server

    Burningham, Ben; Nichols, J D; Casewell, S L; Littlefair, S P; Stark, C; Burleigh, M R; Metchev, S; Tannock, M E; van Weeren, R J; Williams, W L; Wynn, G A

    2016-01-01

    We have conducted a mini-survey for low-frequency radio emission from some of the closest brown dwarfs to the Sun with rapid rotation rates: SIMP J013656.5+093347, WISEPC J150649.97+702736.0, and WISEPA J174124.26+255319.5. We have placed robust 3-sigma upper limits on the flux density in the 111 - 169 MHz frequency range for these targets: WISE 1506: < 0.72 mJy; WISE 1741: < 0.87 mJy; SIMP 0136: < 0.66 mJy. At 8 hours of integration per target to achieve these limits, we find that systematic and detailed study of this class of object at LOFAR frequencies will require a substantial dedication of resources.

  20. Atomic and Molecular Opacities for Brown Dwarf and Giant Planet Atmospheres

    CERN Document Server

    Sharp, C M; Sharp, Christopher M.; Burrows, Adam

    2006-01-01

    We present a comprehensive description of the theory and practice of opacity calculations from the infrared to the ultraviolet needed to generate models of the atmospheres of brown dwarfs and extrasolar giant planets. Methods for using existing line lists and spectroscopic databases in disparate formats are presented and plots of the resulting absorptive opacities versus wavelength for the most important molecules and atoms at representative temperature/pressure points are provided. Electronic, ro-vibrational, bound-free, bound-bound, free-free, and collision-induced transitions and monochromatic opacities are derived, discussed, and analyzed. The species addressed include the alkali metals, iron, heavy metal oxides, metal hydrides, $H_2$, $H_2O$, $CH_4$, $CO$, $NH_3$, $H_2S$, $PH_3$, and representative grains. [Abridged

  1. MICROLENSING DISCOVERY OF A POPULATION OF VERY TIGHT, VERY LOW MASS BINARY BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Choi, J.-Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Gaudi, B. S.; Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bennett, D. P. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556-5670 (United States); Dominik, M. [SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS (United Kingdom); Beaulieu, J.-P. [Institut dAstrophysique de Paris, UMR7095 CNRS-Universite Pierre and Marie Curie, 98 bis boulevard Arago, F-75014 Paris (France); Tsapras, Y. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Drive, Goleta, CA 93117 (United States); Bozza, V. [INFN, Sezione di Napoli, I-80126 Napoli (Italy); Abe, F.; Furusawa, K.; Itow, Y. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Bond, I. A.; Ling, C. H. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland 0745 (New Zealand); Botzler, C. S.; Freeman, M. [Department of Physics, University of Auckland, Private Bag 92-019, Auckland 1001 (New Zealand); Chote, P. [School of Chemical and Physical Sciences, Victoria University, Wellington 6140 (New Zealand); Fukui, A. [Okayama Astrophysical Observatory, National Astronomical Observatory of Japan, Asakuchi, Okayama 719-0232 (Japan); Collaboration: MOA Collaboration; OGLE Collaboration; muFUN Collaboration; MiNDSTEp Consortium; PLANET Collaboration; RoboNet Collaboration; and others

    2013-05-10

    Although many models have been proposed, the physical mechanisms responsible for the formation of low-mass brown dwarfs (BDs) are poorly understood. The multiplicity properties and minimum mass of the BD mass function provide critical empirical diagnostics of these mechanisms. We present the discovery via gravitational microlensing of two very low mass, very tight binary systems. These binaries have directly and precisely measured total system masses of 0.025 M{sub Sun} and 0.034 M{sub Sun }, and projected separations of 0.31 AU and 0.19 AU, making them the lowest-mass and tightest field BD binaries known. The discovery of a population of such binaries indicates that BD binaries can robustly form at least down to masses of {approx}0.02 M{sub Sun }. Future microlensing surveys will measure a mass-selected sample of BD binary systems, which can then be directly compared to similar samples of stellar binaries.

  2. First Ultraviolet Spectrum of a Brown Dwarf: Evidence for H_2 Fluorescence and Accretion

    CERN Document Server

    Gizis, J E; Harvin, J A; Gizis, John E.; Shipman, Harry L.; Harvin, James A.

    2005-01-01

    We analyze an HST/STIS ultraviolet spectrum of the young brown dwarf 2MASSW J1207334-393254, a member of the ten million-year old TW Hya Association that has a planetary-mass companion. We detect and identify numerous emission lines. CIV and other ions are seen that arise in hot gas. We identify a series of lines with Lyman-pumped H_2 molecular lines, indicating that cool gas is also present. Overall, this substellar object shows many of the same characteristics as classical T Tauri stars. We interpret our results as direct evidence of accretion from a circumstellar gas disk, consistent with previous claims. The lack of SiIV emission from the accreting gas indicates that silicon has been depleted into grains.

  3. A search for mass segregation of stars and brown dwarfs in \\rho\\ Ophiuchi

    CERN Document Server

    Parker, Richard J; de Oliveira, Catarina Alves

    2012-01-01

    We apply two different algorithms to search for mass segregation to a recent observational census of the rho Ophiuchi star forming region. Firstly, we apply the Lambda_MSR method, which compares the minimum spanning tree (MST) of a chosen subset of stars to MSTs of random subsets of stars in the cluster, and determine the mass segregation ratio, Lambda_MSR. Secondly, we apply the m-Sigma method, which calculates the local stellar surface density around each star and determines the statistical significance of the average surface density for a chosen mass bin, compared to the average surface density in the whole cluster. Using both methods, we find no indication of mass segregation (normal or inverse) in the spatial distribution of stars and brown dwarfs in rho Ophiuchi. Although rho Ophiuchi suffers from high visual extinction, we show that a significant mass segregation signature would be detectable, albeit slightly diluted, despite dust obscuration of centrally located massive stars.

  4. Ionisation in atmospheres of Brown Dwarfs and extrasolar planets III. Breakdown conditions for mineral clouds

    CERN Document Server

    Helling, Ch; Stark, C; Diver, D

    2013-01-01

    Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in Brown Dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from ou...

  5. Strong brightness variations signal cloudy-to-clear transition of brown dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Radigan, Jacqueline [Space Telescope Science Institute, 3700 San Martin Drive Baltimore, MD 21218 (United States); Lafrenière, David; Artigau, Etienne [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-Ville, Montréal, QC H3C 3J7 (Canada); Jayawardhana, Ray, E-mail: radigan@stsci.edu [Department of Astronomy and Astrophysics, University of Toronto, Toronto, ON M5S 3H4 (Canada)

    2014-10-01

    We report the results of a J-band search for cloud-related variability in the atmospheres of 62 L4-T9 dwarfs using the Du Pont 2.5 m telescope at Las Campanas Observatory and the Canada-France-Hawaii Telescope on Mauna Kea. We find 9 of 57 objects included in our final analysis to be significantly variable with >99% confidence, 5 of which are new discoveries. In our study, strong signals (peak-to-peak amplitudes >2%) are confined to the L/T transition (4/16 objects with L9-T3.5 spectral types and 0/41 objects for all other spectral types). The probability that the observed occurrence rates for strong variability inside and outside the L/T transition originate from the same underlying true occurrence rate is excluded at >99.7% confidence. Based on a careful assessment of our sensitivity to astrophysical signals, we infer that 39{sub −14}{sup +16}% of L9-T3.5 dwarfs are strong variables on rotational timescales. If we consider only L9-T3.5 dwarfs with 0.8 < J – K {sub s} < 1.5, and assume an isotropic distribution of spin axes for our targets, we find that 80{sub −19}{sup +18}% would be strong variables if viewed edge-on; azimuthal symmetry and/or binarity may account for non-variable objects in this group. These observations suggest that the settling of condensate clouds below the photosphere in brown dwarf (BD) atmospheres does not occur in a spatially uniform manner. Rather, the formation and sedimentation of dust grains at the L/T transition is coupled to atmospheric dynamics, resulting in highly contrasting regions of thick and thin clouds and/or clearings. Outside the L/T transition we identify five weak variables (peak-to-peak amplitudes of 0.6%-1.6%). Excluding L9-T3.5 spectral types, we infer that 60{sub −18}{sup +22}% of targets vary with amplitudes of 0.5%-1.6%, suggesting that surface heterogeneities are common among L and T dwarfs. Our survey establishes a significant link between strong variability and L/T transition spectral types, providing

  6. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. IV. THE EFFECT OF COSMIC RAYS

    Energy Technology Data Exchange (ETDEWEB)

    Rimmer, P. B.; Helling, Ch., E-mail: pr33@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom)

    2013-09-10

    Cosmic rays provide an important source for free electrons in Earth's atmosphere and also in dense interstellar regions where they produce a prevailing background ionization. We utilize a Monte Carlo cosmic ray transport model for particle energies of 10{sup 6} eV brown dwarf with effective temperature T{sub eff} = 1500 K, and two example giant gas planets (T{sub eff} = 1000 K, 1500 K). For the model brown dwarf atmosphere, the electron fraction is enhanced significantly by cosmic rays when the pressure p{sub gas} < 10{sup -2} bar. Our example giant gas planet atmosphere suggests that the cosmic ray enhancement extends to 10{sup -4}-10{sup -2} bar, depending on the effective temperature. For the model atmosphere of the example giant gas planet considered here (T{sub eff} = 1000 K), cosmic rays bring the degree of ionization to f{sub e} {approx}> 10{sup -8} when p{sub gas} < 10{sup -8} bar, suggesting that this part of the atmosphere may behave as a weakly ionized plasma. Although cosmic rays enhance the degree of ionization by over three orders of magnitude in the upper atmosphere, the effect is not likely to be significant enough for sustained coupling of the magnetic field to the gas.

  7. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. III. BREAKDOWN CONDITIONS FOR MINERAL CLOUDS

    Energy Technology Data Exchange (ETDEWEB)

    Helling, Ch.; Jardine, M.; Stark, C. [SUPA, School of Physics and Astronomy, University of St. Andrews, St. Andrews KY16 9SS (United Kingdom); Diver, D., E-mail: ch@leap2010.eu [SUPA, School of Physics and Astronomy, University of Glasgow, Glasgow G12 8QQ (United Kingdom)

    2013-04-20

    Electric discharges were detected directly in the cloudy atmospheres of Earth, Jupiter, and Saturn, are debatable for Venus, and indirectly inferred for Neptune and Uranus in our solar system. Sprites (and other types of transient luminous events) have been detected only on Earth, and are theoretically predicted for Jupiter, Saturn, and Venus. Cloud formation is a common phenomenon in ultra-cool atmospheres such as in brown dwarf and extrasolar planetary atmospheres. Cloud particles can be expected to carry considerable charges which may trigger discharge events via small-scale processes between individual cloud particles (intra-cloud discharges) or large-scale processes between clouds (inter-cloud discharges). We investigate electrostatic breakdown characteristics, like critical field strengths and critical charge densities per surface, to demonstrate under which conditions mineral clouds undergo electric discharge events which may trigger or be responsible for sporadic X-ray emission. We apply results from our kinetic dust cloud formation model that is part of the DRIFT-PHOENIX model atmosphere simulations. We present a first investigation of the dependence of the breakdown conditions in brown dwarf and giant gas exoplanets on the local gas-phase chemistry, the effective temperature, and primordial gas-phase metallicity. Our results suggest that different intra-cloud discharge processes dominate at different heights inside mineral clouds: local coronal (point discharges) and small-scale sparks at the bottom region of the cloud where the gas density is high, and flow discharges and large-scale sparks near, and maybe above, the cloud top. The comparison of the thermal degree of ionization and the number density of cloud particles allows us to suggest the efficiency with which discharges will occur in planetary atmospheres.

  8. Lightning climatology of exoplanets and brown dwarfs guided by Solar system data

    Science.gov (United States)

    Hodosán, G.; Helling, Ch.; Asensio-Torres, R.; Vorgul, I.; Rimmer, P. B.

    2016-10-01

    Clouds form on extrasolar planets and brown dwarfs where lightning could occur. Lightning is a tracer of atmospheric convection, cloud formation and ionization processes as known from the Solar system, and may be significant for the formation of prebiotic molecules. We study lightning climatology for the different atmospheric environments of Earth, Venus, Jupiter and Saturn. We present lightning distribution maps for Earth, Jupiter and Saturn, and flash densities for these planets and Venus, based on optical and/or radio measurements from the World Wide Lightning Location Network and Sferics Timing and Ranging Network radio networks, the Lightning Imaging Sensor/Optical Transient Detector satellite instruments, the Galileo, Cassini, New Horizons and Venus Express spacecraft. We also present flash densities calculated for several phases of two volcano eruptions, Eyjafjallajökull's (2010) and Mt Redoubt's (2009). We estimate lightning rates for sample, transiting and directly imaged extrasolar planets and brown dwarfs. Based on the large variety of exoplanets, six categories are suggested for which we use the lightning occurrence information from the Solar system. We examine lightning energy distributions for Earth, Jupiter and Saturn. We discuss how strong stellar activity may support lightning activity. We provide a lower limit of the total number of flashes that might occur on transiting planets during their full transit as input for future studies. We find that volcanically very active planets might show the largest lightning flash densities. When applying flash densities of the large Saturnian storm from 2010/11, we find that the exoplanet HD 189733b would produce high lightning occurrence even during its short transit.

  9. Brown dwarfs and planetary mass objects in star-forming regions. (Spanish Title: Enanas marrones y objetos de masas planetarias en regiones de formación estelar)

    Science.gov (United States)

    Gómez, M.

    In this contribution we present the properties of substellar mass objects and discuss the different formation mechanisms of brown dwarfs. In particular we analyze the so-called T Tauri formation mode, with disks and jets, and its implications for the existence of planetary systems associated with subestellar mass objects or brown dwarfs. We also briefly discuss the properties of planemos (planetary mass objects). Finally we consider the contribution of these objects to the Initial Mass Function (IMF). Although brown dwarfs and planetary mass objects seem to be as common as stars in the Galaxy, their precise contribution to the IMF still remains uncertain.

  10. DE0823$-$49 is a juvenile binary brown dwarf at 20.7 pc

    CERN Document Server

    Sahlmann, J; Martín, E L; Lazorenko, P F; Gagliuffi, D C Bardalez; Mayor, M; Ségransan, D; Queloz, D; Udry, S

    2015-01-01

    Astrometric monitoring of the nearby early-L dwarf DE0823$-$49 has revealed a low-mass companion in a 248-day orbit that was announced in an earlier work. Here, we present new astrometric and spectroscopic observations that allow us to characterise the system in detail. The optical spectrum shows LiI-absorption indicative of a young age and/or substellar mass for the primary component. The near-infrared spectrum is best reproduced by a binary system of brown dwarfs with spectral types of L1.5 $+$ L5.5 and effective temperatures of $2150\\pm100$ K and $1670\\pm140$ K. To conform with the photocentric orbit size measured with astrometry and the current understanding of substellar evolution, the system must have an age in the 80--500 Myr range. Evolutionary models predict component masses in the ranges of $M_1\\simeq0.028-0.063\\,M_\\odot$ and $M_2\\simeq0.018-0.045\\,M_\\odot$ with a mass ratio of $q\\simeq0.64-0.74$. Multi-epoch radial velocity measurements unambiguously establish the three-dimensional orbit of the sys...

  11. Strong Brightness Variations Signal Cloudy-to-Clear Transition of Brown Dwarfs

    CERN Document Server

    Radigan, Jacqueline; Jayawardhana, Ray; Artigau, Etienne

    2014-01-01

    We report the results of a $J$ band search for cloud-related variability in the atmospheres of 62 L4-T9 dwarfs using the Du Pont 2.5-m telescope at Las Campanas Observatory and the Canada France Hawaii Telescope on Mauna Kea. We find 9 of 57 objects included in our final analysis to be significantly variable with >99% confidence, 5 of which are new discoveries. In our study, strong variability (peak-to-peak amplitudes >2%) are confined to the L/T transition (4/16 objects with L9-T3.5 spectral types and 0/41 objects for all other spectral types). The probability that the observed occurrence rates for strong variability inside and outside the L/T transition originate from the same underlying true occurrence rate is excluded with >99.7% confidence. These observations suggest that the settling of condensate clouds below the photosphere in brown dwarf atmospheres does not occur in a spatially uniform manner. Rather, the formation and sedimentation of dust grains at the L/T transition is coupled to atmospheric dyna...

  12. Effects of Latent Heating on Atmospheres of Brown Dwarfs and Directly Imaged Planets

    Science.gov (United States)

    Tan, Xianyu; Showman, Adam P.

    2017-02-01

    The growing number of observations of brown dwarfs (BDs) has provided evidence for strong atmospheric circulation on these objects. Directly imaged planets share similar observations and can be viewed as low-gravity versions of BDs. Vigorous condensate cycles of chemical species in their atmospheres are inferred by observations and theoretical studies, and latent heating associated with condensation is expected to be important in shaping atmospheric circulation and influencing cloud patchiness. We present a qualitative description of the mechanisms by which condensational latent heating influences circulation, and then illustrate them using an idealized general circulation model that includes a condensation cycle of silicates with latent heating and molecular weight effect due to the rainout of the condensate. Simulations with conditions appropriate for typical T dwarfs exhibit the development of localized storms and east–west jets. The storms are spatially inhomogeneous, evolving on a timescale of hours to days and extending vertically from the condensation level to the tropopause. The fractional area of the BD covered by active storms is small. Based on a simple analytic model, we quantitatively explain the area fraction of moist plumes and show its dependence on the radiative timescale and convective available potential energy (CAPE). We predict that if latent heating dominates cloud formation processes, the fractional coverage area of clouds decreases as the spectral type goes through the L/T transition from high to lower effective temperature. This is a natural consequence of the variation of the radiative timescale and CAPE with the spectral type.

  13. Ionization in Atmospheres of Brown Dwarfs and Extrasolar Planets V: Alfv\\'{e}n Ionization

    CERN Document Server

    Stark, Craig R; Diver, Declan A; Rimmer, Paul B

    2013-01-01

    Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbour localized plasmas in their atmospheric environments. For low-mass objects, the degree of thermal ionization is insufficient to qualify the ionized component as a plasma, posing the question: what ionization processes can efficiently produce the required plasma that is the source of the radiation? We propose Alfv\\'{e}n ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization ($\\geq10^{-7}$) that they constitute plasmas. We outline the criteria required for Alfv\\'{e}n ionization and demonstrate it's applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs and M-dwarfs for both solar and sub-solar metallicities. We find that Alfv\\'{e}n ionization is most efficient at mid to low atmospheric pressures where a seed plasma is easier to magnetize and the pressure gradients needed to drive the required neut...

  14. A Chandra Observation of the TW Hydrae Association Brown Dwarf 2MASSW J1139511-315921

    CERN Document Server

    Castro, Philip J; Gagné, Marc

    2011-01-01

    We report on a sequence of Chandra X-ray Observatory observations of the TW Hydrae brown dwarf (BD) 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3-sigma confidence level. We find an X-ray luminosity of L_X = 1.4^(+2.7)_(-1.0) x 10^26 ergs s^-1 or log(L_X/L_bol) = -4.8 +/- 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have H-alpha emission, both show no signatures of accretion, and both have comparable ages and spectral types. TWA 5B was previously detected in X-rays with a luminosity of L_X = 4 x 10^27 ergs s^-1 or log(L_X/L_bol) = -3.4, an order of magnitude more luminous in X-rays than 2M1139. We find that the discrepancy between the X-ray luminosity of 2M1139 and TWA 5B is consistent with the spread in X-ray luminosity in the Orion Nebula Cluster (ONC) for BDs of similar spectral types. Though rotation may play a role in the X-ray activity of ultracool dwarfs like 2M1139 and TWA 5B, the discrepancy cannot be expla...

  15. PROPERTIES OF THE NEARBY BROWN DWARF WISEP J180026.60+013453.1

    Energy Technology Data Exchange (ETDEWEB)

    Gizis, John E. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Vrba, Frederick J. [US Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001 (United States)

    2015-12-15

    We present new spectroscopy and astrometry to characterize the nearby brown dwarf WISEP J180026.60+013453.1. The optical spectral type, L7.5, is in agreement with the previously reported near-infrared spectral type. The preliminary trigonometric parallax places it at a distance of 8.01 ± 0.21 pc, confirming that it is the fourth closest known late-L (L7–L9) dwarf. The measured luminosity, our detection of lithium, and the lack of low surface gravity indicators indicates that WISEP J180026.60+013453.1 has a mass 0.03 < M < 0.06 M{sub ⊙} and an age between 300 million and 1.5 billion years according to theoretical substellar evolution models. The low space motion is consistent with this young age. We have measured the rotational broadening (v sin i = 13.5 ± 0.5 km s{sup −1}), and use it to estimate a maximum rotation period of 9.3 hr.

  16. Three new cool brown dwarfs discovered with the wide-field infrared survey explorer (WISE) and an improved spectrum of the Y0 dwarf wise J041022.71+150248.4

    Energy Technology Data Exchange (ETDEWEB)

    Cushing, Michael C. [Department of Physics and Astronomy, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Kirkpatrick, J. Davy; Gelino, Christopher R. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Mace, Gregory N. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States); Skrutskie, Michael F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Gould, Andrew, E-mail: michael.cushing@utoledo.edu [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States)

    2014-05-01

    As part of a larger search of Wide-field Infrared Survey Explorer (WISE) data for cool brown dwarfs with effective temperatures less than 1000 K, we present the discovery of three new cool brown dwarfs with spectral types later than T7. Using low-resolution, near-infrared spectra obtained with the NASA Infrared Telescope Facility and the Hubble Space Telescope, we derive spectral types of T9.5 for WISE J094305.98+360723.5, T8 for WISE J200050.19+362950.1, and Y0: for WISE J220905.73+271143.9. The identification of WISE J220905.73+271143.9 as a Y dwarf brings the total number of spectroscopically confirmed Y dwarfs to 17. In addition, we present an improved spectrum (i.e., higher signal-to-noise ratio) of the Y0 dwarf WISE J041022.71+150248.4 that confirms the Cushing et al. classification of Y0. Spectrophotometric distance estimates place all three new brown dwarfs at distances less than 12 pc, with WISE J200050.19+362950.1 lying at a distance of only 3.9-8.0 pc. Finally, we note that brown dwarfs like WISE J200050.19+362950.1 that lie in or near the Galactic plane offer an exciting opportunity to directly measure the mass of a brown dwarf via astrometric microlensing.

  17. Juvenile Ultracool Dwarfs

    CERN Document Server

    Rice, Emily L; Cruz, Kelle; Barman, Travis; Looper, Dagny; Malo, Lison; Mamajek, Eric E; Metchev, Stanimir; Shkolnik, Evgenya L

    2011-01-01

    Juvenile ultracool dwarfs are late spectral type objects (later than ~M6) with ages between 10 Myr and several 100 Myr. Their age-related properties lie intermediate between very low mass objects in nearby star-forming regions (ages 1-5 Myr) and field stars and brown dwarfs that are members of the disk population (ages 1-5 Gyr). Kinematic associations of nearby young stars with ages from ~10-100 Myr provide sources for juvenile ultracool dwarfs. The lowest mass confirmed members of these groups are late-M dwarfs. Several apparently young L dwarfs and a few T dwarfs are known, but they have not been kinematically associated with any groups. Normalizing the field IMF to the high mass population of these groups suggests that more low mass (mainly late-M and possibly L dwarf) members have yet to be found. The lowest mass members of these groups, along with low mass companions to known young stars, provide benchmark objects with which spectroscopic age indicators for juvenile ultracool dwarfs can be calibrated and...

  18. The Searches and Observational Characteristics of Brown Dwarfs%褐矮星的观测特征和搜寻

    Institute of Scientific and Technical Information of China (English)

    王有芬; 邵正义

    2013-01-01

    褐矮星是亚恒星天体,内核没有稳定的氢燃烧,其质量一般在13至75倍木星质量之间.本质上,褐矮星的内核物理演化过程不同于行星和恒星,观测上我们根据褐矮星不同于行星和恒星的测光和光谱特征来区别证认它们.由于质量小、温度低,在光学波段,它们测光特征表现为光度暗,颜色红;在近红外波段,受大气尘埃、金属丰度等影响,它们有不同寻常的星等、颜色.根据褐矮星的光谱形态与特征谱线,它们可以被分为M、L、T和Y矮星.现在己发现的全部T与Y矮星都是褐矮星,但不是所有的M与L矮星都是褐矮星.介绍了L、T和Y矮星的特征吸收线和光谱分类方法,回顾了早期在星团和双星系统中褐矮星的搜寻,以及现阶段用大视场、长波段深度巡天数据在近邻场区中褐矮星的搜寻.对目前己发现的晚型M和L、T、Y矮星的总数目、温度范围、距离及测量其年龄的方法等做了小结.最后讨论了如何判断L矮星是否为褐矮星,重力、金属丰度和大气尘埃对近红外波段光谱形状的影响,光谱型-J波段绝对星等图上L、T交接处“大鼓包”的形成原因等热点问题.%Brown dwarfs are substellar objects which have masses in between the most massive planets and the least massive stars. There are no stable hydrogen fusion in their interiors, although large mass brown dwarf might have instant hydrogen fusion in their core. All brown dwarfs have deuterium burning in their interiors. The L, T and Y dwarfs are cooler than M dwarfs. A small part of late M, most of the L, all of the T and all of the up to date discovered Y dwarfs are brown dwarfs. The hallmarks of L dwarfs in optical band are prominent absorption lines from neutral alkali atoms and alkali hydrides like KI, Nal, FeH etc. In near infrared band, the hallmarks of T dwarfs are strong H2O, CH4 absorption lines. The Y dwarfs have NH3 absorption lines in near infrared H band. The

  19. Atmospheric circulation of brown dwarfs and directly imaged extrasolar giant planets with active clouds

    Science.gov (United States)

    Tan, Xianyu; Showman, Adam

    2016-10-01

    Observational evidence have suggested active meteorology in the atmospheres of brown dwarfs (BDs) and directly imaged extrasolar giant planets (EGPs). In particular, a number of surveys for brown dwarfs showed that near-IR brightness variability is common for L and T dwarfs. Directly imaged EGPs share similar observations, and can be viewed as low-gravity versions of BDs. Clouds are believed to play the major role in shaping the thermal structure, dynamics and near-IR flux of these atmospheres. So far, only a few studies have been devoted to atmospheric circulation and the implications for observations of BDs and directly EGPs, and yet no global model includes a self-consistent active cloud formation. Here we present preliminary results from the first global circulation model applied to BDs and directly imaged EGPs that can properly treat absorption and scattering of radiation by cloud particles. Our results suggest that horizontal temperature differences on isobars can reach up to a few hundred Kelvins, with typical horizontal length scale of the temperature and cloud patterns much smaller than the radius of the object. The combination of temperature anomaly and cloud pattern can result in moderate disk-integrated near-IR flux variability. Wind speeds can reach several hundred meters per second in cloud forming layers. Unlike Jupiter and Saturn, we do not observe stable zonal jet/banded patterns in our simulations. Instead, our simulated atmospheres are typically turbulent and dominated by transient vortices. The circulation is sensitive to the parameterized cloud microphysics. Under some parameter combinations, global-scale atmospheric waves can be triggered and maintained. These waves induce global-scale temperature anomalies and cloud patterns, causing large (up to several percent) disk-integrated near-IR flux variability. Our results demonstrate that the commonly observed near-IR brightness variability for BDs and directly imaged EGPs can be explained by the

  20. Signatures of cloud, temperature, and gravity from spectra of the closest brown dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Beletsky, Yuri; Osip, David J. [Las Campanas Observatory, Carnegie Institution of Washington, Colina el Pino, Casilla 601 La Serena (Chile); Burgasser, Adam J. [Center of Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, CA 92093 (United States); Tinney, Chris [University of New South Wales, Sydney, New South Wales (Australia); Filippazzo, Joseph C. [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States); Simcoe, Robert A., E-mail: jfaherty@ciw.edu [MIT-Kavli Institute for Astrophysics and Space Research, 70 Vassar Street, Cambridge, MA 02139 (United States)

    2014-08-01

    We present medium-resolution optical (λ/Δλ ∼ 4000) and near-infrared (λ/Δλ ∼ 8000) spectral data for components of the newly discovered WISE J104915.57-531906.1AB (Luhman 16AB) brown dwarf binary. The optical spectra reveal strong 6708 Å Li I absorption in both Luhman 16A (8.0 ± 0.4 Å) and Luhman 16B (3.8 ± 0.4 Å) confirming their substellar mass. Interestingly, this is the first detection of Li I absorption in a T dwarf. In the near-infrared data, we find strong K I absorption at 1.168, 1.177, 1.243, and 1.254 μm in both components. Neither the optical nor the near-infrared alkali lines show low surface gravity signatures. Along with the Li I absorption detection, we can broadly constrain the system age to 0.1-3 Gyr or the mass to 20-65 M{sub Jup} for each component. Compared to the strength of K I line absorption in equivalent spectral subtype brown dwarfs, Luhman 16A is weaker while Luhman 16B is stronger. Analyzing the spectral region around each doublet in distance scaled flux units and comparing the two sources, we confirm the J-band flux reversal and find that Luhman 16B has a brighter continuum in the 1.17 μm and 1.25 μm regions than Luhman 16A. Converting flux units to a brightness temperature we interpret this to mean that the secondary is ∼50 K warmer than the primary in regions dominated by condensate grain scattering. One plausible explanation for this difference is that Luhman 16B has thinner clouds or patchy holes in its atmosphere allowing us to see to deeper, hotter regions. We also detect comparably strong FeH in the 0.9896 μm Wing-Ford band for both components. Traditionally, a signpost of changing atmosphere conditions from late-type L to early T, the persistence and similarity of FeH at 0.9896 μm in both Luhman 16A and Luhman 16B is an indication of homogenous atmosphere conditions. We calculate bolometric luminosities from observed data supplemented with best fit models for longer wavelengths and find the components are

  1. Dust in the atmospheres of brown dwarfs and young planets: the effects of gravitational settling and convective overshoot

    Science.gov (United States)

    Homeier, D.; Ludwig, H.-G.; Allard, F.; Hauschildt, P.; Dehn, M.

    Dwarfs of the spectral types late-M, L and T span mass regimes from very-low-mass stars through brown dwarfs down to young planetary objects. They all show massive molecular line-blanketing and the condensation of refractory species with decreasing T_{eff}, leading to changes in chemical equilibrium composition and absorption due to dust grains. The spectral evolution from late-M through L to mid- and late-T classes is now understood as chiefly due to increasing amounts of condensates in the visible photosphere up to mid-L types, and the settling of dust clouds into deeper regions at the transition from L to T, resulting in a depletion of condensable elements in the upper atmosphere. The ensuing photospheric cooling also drives a change in carbon chemistry leading to the hallmark methane absorption features of T dwarfs.Recent observations of brown dwarfs in the L-T spectral sequence and model atmosphere calculations have shown that these changes in spectral features reveal differences in the efficiency of cloud removal that seem to be triggered by an additional parameter besides effective temperature. We present models describing the settling of particle clouds as an equilibrium process between condensation, gravitational sedimentation and convective and turbulent mixing, based on 3D-hydrodynamical simulations for the description of the velocity field. These calculations predict a strong dependence of the settling on gravity, and can therefore explain observed differences between the spectral energy distributions of brown dwarfs of equal luminosity as an effect of different mass. Based on these calculations we would expect even stronger deviations in the colours of young brown dwarfs of very low mass from those commonly observed in the field. Such predictions seem to be in aggreement with the first observations of candidate planetary-mass objects, and would imply that extrasolar planets at very young ages have spectral energy distributions significantly different

  2. Kinematics and energetics of swimming performance during acute warming in brown trout Salmo trutta.

    Science.gov (United States)

    Lea, J M D; Keen, A N; Nudds, R L; Shiels, H A

    2016-01-01

    This study examined how acute warming of water temperature affects the mechanical efficiency of swimming and aerobic capabilities of the brown trout Salmo trutta. Swimming efficiency was assessed using the relationship between swimming kinematics and forward speed (U), which is thought to converge upon an optimum range of a dimensionless parameter, the Strouhal number (St ). Swim-tunnel intermittent stopped-flow respirometry was used to record kinematics and measure oxygen consumption (ṀO2) of S. trutta during warming and swimming challenges. Salmo trutta maintained St between 0·2 and 0·3 at any given U over a range of temperatures, irrespective of body size. The maintenance of St within the range for maximum efficiency for oscillatory propulsion was achieved through an increase in tail-beat frequency (ftail) and a decrease in tail-beat amplitude (A) as temperature increased. Maintenance of efficient steady-state swimming was fuelled by aerobic metabolism, which increased as temperature increased up to 18° C but declined above this temperature, decreasing the apparent metabolic scope. As St was maintained over the full range of temperatures whilst metabolic scope was not, the results may suggest energetic trade-offs at any given U at temperatures above thermal optima.

  3. The white dwarfs within 25 pc of the Sun: Kinematics and spectroscopic subtypes

    Energy Technology Data Exchange (ETDEWEB)

    Sion, Edward M.; McCook, George P.; Wasatonic, Richard; Myszka, Janine [Department of Astronomy and Astrophysics, Villanova University, Villanova, PA 19085 (United States); Holberg, J. B. [Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 75201 (United States); Oswalt, Terry D., E-mail: edward.sion@villanova.edu, E-mail: george.mccook@villanova.edu, E-mail: richard.wasatonic@villanova.edu, E-mail: janine.myszka@villanova.edu, E-mail: holberg@vega.lpl.arizona.edu, E-mail: toswalt@fit.edu [Department of Physics and Space Sciences, Florida Institute of Technology, Melbourne, FL 19085 (United States)

    2014-06-01

    We present the fractional distribution of spectroscopic subtypes, range and distribution of surface temperatures, and kinematical properties of the white dwarfs (WDs) within 25 pc of the Sun. There is no convincing evidence of halo WDs in the total 25 pc sample of 224 WDs. There is also little to suggest the presence of genuine thick disk subcomponent members within 25 pc. It appears that the entire 25 pc sample likely belongs to the thin disk. We also find no significant kinematic differences with respect to spectroscopic subtypes. The total DA to non-DA ratio of the 25 pc sample is 1.8, a manifestation of deepening envelope convection, which transforms DA stars with sufficiently thin H surface layers into non-DAs. We compare this ratio with the results of other studies. We find that at least 11% of the WDs within 25 pc of the Sun (the DAZ and DZ stars) have photospheric metals that likely originate from accretion of circumstellar material (debris disks) around them. If this interpretation is correct, then it suggests the possibility that a similar percentage have planets, asteroid-like bodies, or debris disks orbiting them. Our volume-limited sample reveals a pileup of DC WDs at the well-known cutoff in DQ WDs at T {sub eff} ∼ 6000 K. Mindful of small number statistics, we speculate on its possible evolutionary significance. We find that the incidence of magnetic WDs in the 25 pc sample is at least 8% in our volume-limited sample, dominated by cool WDs. We derive approximate formation rates of DB and DQ degenerates and present a preliminary test of the evolutionary scenario that all cooling DB stars become DQ WDs via helium convective dredge-up with the diffusion tail of carbon extending upward from their cores.

  4. AN ACTIVITY–ROTATION RELATIONSHIP AND KINEMATIC ANALYSIS OF NEARBY MID-TO-LATE-TYPE M DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    West, Andrew A.; Weisenburger, Kolby L. [Department of Astronomy, Boston University, 725 Commonwealth Ave, Boston, MA 02215 (United States); Irwin, Jonathan; Charbonneau, David; Dittmann, Jason [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Berta-Thompson, Zachory K. [MIT, Kavli Institute for Astrophysics and Space Research, 77 Massachusetts Ave., Bldg. 37, Cambridge, MA 02139 (United States); Pineda, J. Sebastian, E-mail: aawest@bu.edu [California Institute of Technology, Department of Astronomy, 1200 E. California Ave, Pasadena, CA 91125 (United States)

    2015-10-10

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by Hα emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that v sin i measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, late-type, slowly rotating stars present in our sample. Additionally, we find that all M dwarfs with rotation periods shorter than 26 days (early-type; M1–M4) and 86 days (late-type; M5–M8) are magnetically active. This potential mismatch suggests that the physical mechanisms that connect stellar rotation to chromospheric heating may be different in fully convective stars. A kinematic analysis suggests that the magnetically active, rapidly rotating stars are consistent with a kinematically young population, while slow-rotators are less active or inactive and appear to belong to an older, dynamically heated stellar population.

  5. Probing Cloud-Driven Variability on Two of the Youngest, Lowest-Mass Brown Dwarfs in the Solar Neighborhood

    Science.gov (United States)

    Schneider, Adam; Cushing, Michael; Kirkpatrick, J. Davy

    2016-08-01

    Young, late-type brown dwarfs share many properties with directly imaged giant extrasolar planets. They therefore provide unique testbeds for investigating the physical conditions present in this critical temperature and mass regime. WISEA 1147-2040 and 2MASS 1119-1137, two recently discovered late-type (~L7) brown dwarfs, have both been determined to be members of the ~10 Myr old TW Hya Association (Kellogg et al. 2016, Schneider et al. 2016). Each has an estimated mass of 5-6 MJup, making them two of the youngest and lowest-mass free floating objects yet found in the solar neighborhood. As such, these two planetary mass objects provide unparalleled laboratories for investigating giant planet-like atmospheres far from the contaminating starlight of a host sun. Condensate clouds play a critical role in shaping the emergent spectra of both brown dwarfs and gas giant planets, and can cause photometric variability via their non-uniform spatial distribution. We propose to photometrically monitor WISEA 1147-2040 and 2MASS 1119-1137 in order to search for the presence of cloud-driven variability to 1) investigate the potential trend of low surface gravity with high-amplitude variability in a previously unexplored mass regime and 2) explore the angular momentum evolution of isolated planetary mass objects.

  6. Disk Sizes and Grain Growth across the Brown Dwarf Boundary from the Taurus Boundary of Stellar/Substellar (TBOSS) Survey

    Science.gov (United States)

    Patience, Jenny; Ward-Duong, Kimberly; Bulger, Joanna; van der Plas, Gerrit; Menard, Francois; Pinte, Christophe; Bryden, Geoffrey; Turner, Neal J.; Jackson, Alan Patrick; Harvey, Paul M.; Hales, Antonio

    2017-01-01

    With a combination of submm/mm observations from ALMA, CSO, and PdBI, we are investigating the properties of disks around low mass stars and brown dwarfs in the Taurus star-forming region. Disk sizes and spectral slopes are important properties to assess the formation scenarios for brown dwarfs and the viability of planet formation in the disks. The ALMA maps have a beam size of approximately 0.3arcseconds and a number of the sources are spatially resolved in the continuum and CO(3-2) line measurements. For most of the resolved systems, the gas disks are more extended than the dust disks, similar to previous results from observations of more massive stars. From the multi-wavelength data, we are measuring the spectral slope of the emission to search for the signature of initial grain growth that is encoded in the slope of the spectral energy distribution in order to test the hypothesis of enhanced radial drift in disks around substellarobjects. Theoretical studies have suggested that fast radial drift could prevent the growth of dust particles up to large bodies in brown dwarf disks, and our program is designed to obtain a set of measurements for objects across the stellar/substellar transition.

  7. Structural and compositional properties of brown dwarf disks: the case of 2MASS J04442713+2512164

    CERN Document Server

    Bouy, H; Pinte, C; Olofsson, J; Navascues, D Barrado y; Martín, E L; Pantin, E; Monin, J -L; Basri, G; Augereau, J -C; Ménard, F; Duvert, G; Duchêne, G; Marchis, F; Bayo, A; Bottinelli, S; Lefort, B; Guieu, S

    2008-01-01

    In order to improve our understanding of substellar formation, we have performed a compositional and structural study of a brown dwarf disk. We present the result of photometric, spectroscopic and imaging observations of 2MASS J04442713+2512164, a young brown dwarf (M7.25) member of the Taurus association. Our dataset, combined with results from the literature, provides a complete coverage of the spectral energy distribution from the optical to the millimeter including the first photometric measurement of a brown dwarf disk at 3.7mm, and allows us to perform a detailed analysis of the disk properties. The target was known to have a disk. High resolution optical spectroscopy shows that it is intensely accreting, and powers a jet and an outflow. The disk structure is similar to that observed for more massive TTauri stars. Spectral decomposition models of Spitzer/IRS spectra suggest that the mid-infrared emission from the optically thin disk layers is dominated by grains with intermediate sizes (1.5micron). Crys...

  8. Rotation periods and astrometric motions of the Luhman 16AB brown dwarfs by high-resolution lucky-imaging monitoring

    CERN Document Server

    Mancini, L; Littlefair, S P; Southworth, J; Bozza, V; Damasso, M; Dominik, M; Hundertmark, M; Jorgensen, U G; Juncher, D; Popovas, A; Rabus, M; Rahvar, S; Schmidt, R W; Skottfelt, J; Snodgrass, C; Sozzetti, A; Alsubai, K; Bramich, D M; Novati, S Calchi; Ciceri, S; D'Ago, G; Jaimes, R Figuera; Galianni, P; Gu, S -H; Harpsoe, K; Haugbolle, T; Henning, Th; Hinse, T C; Kains, N; Korhonen, H; Scarpetta, G; Starkey, D; Surdej, J; Wang, X -B; Wertz, O

    2015-01-01

    Context. Photometric monitoring of the variability of brown dwarfs can provide useful information about the structure of clouds in their cold atmospheres. The brown-dwarf binary system Luhman 16AB is an interesting target for such a study, as its components stand at the L/T transition and show high levels of variability. Luhman 16AB is also the third closest system to the Solar system, allowing precise astrometric investigations with ground-based facilities. Aims. The aim of the work is to estimate the rotation period and study the astrometric motion of both components. Methods. We have monitored Luhman 16AB over a period of two years with the lucky-imaging camera mounted on the Danish 1.54m telescope at La Silla, through a special i+z long-pass filter, which allowed us to clearly resolve the two brown dwarfs into single objects. An intense monitoring of the target was also performed over 16 nights, in which we observed a peak-to-peak variability of 0.20 \\pm 0.02 mag and 0.34 \\pm 0.02 mag for Luhman 16A and 1...

  9. Kinematic properties as probes of the evolution of dwarf galaxies in the Virgo cluster

    CERN Document Server

    Toloba, E; Gorgas, J; Peletier, R F; Cenarro, A J; Gadotti, D A; de Paz, A Gil; Pedraz, S; Yildiz, U

    2009-01-01

    We present new observational results on the kinematical, morphological, and stellar population properties of a sample of 21 dEs located both in the Virgo cluster and in the field, which show that 52% of the dEs i) are rotationally supported, ii) exhibit structural signs of typical rotating systems such as discs, bars or spiral arms, iii) are younger (~3 Gyr) than non-rotating dEs, and iv) are preferentially located either in the outskirts of Virgo or in the field. This evidence is consistent with the idea that rotationally supported dwarfs are late type spirals or irregulars that recently entered the cluster and lost their gas through a ram pressure stripping event, quenching their star formation and becoming dEs through passive evolution. We also find that all, but one, galaxies without photometric hints for hosting discs are pressure supported and are all situated in the inner regions of the cluster. This suggests a different evolution from the rotationally supported systems. Three different scenarios for t...

  10. WISEP J004701.06+680352.1: An intermediate surface gravity, dusty brown dwarf in the AB Dor Moving Group

    CERN Document Server

    Gizis, John E; Liu, Michael C; Harris, Hugh C; Faherty, Jacqueline K; Burgasser, Adam J; Kirkpatrick, J Davy

    2014-01-01

    We present spectroscopy, astrometry, and photometry of the brown dwarf WISEP J004701.06+680352.1 (W0047+68), an unusually red field L dwarf at a distance of $12.2 \\pm 0.4$ parsecs. The three-dimensional space motion identifies it as a member of the AB Dor Moving Group, an identification supported by our classification of W0047+68 as intermediate surface gravity (INT-G) using the Allers \\& Liu (2013) near-infrared classification system. This moving group membership implies near-solar metallicity, age $\\sim 100-125$ Myr, $M \\approx 0.018~M_\\odot$, and $\\log g \\approx 4.5$; the thick condensate clouds needed to explain the infrared spectrum are therefore a result of the lower surface gravity than ordinary field brown dwarfs. From the observed luminosity and evolutionary model radius, we find $T_{eff} \\approx 1300 $K, a temperature normally associated with early T dwarfs. Thick clouds are also used to explain the spectral properties of directly imaged giant planets, and we discuss the successes and challenges...

  11. Discovery of a Brown Dwarf Companion to Gliese 570ABC A 2MASS T Dwarf Significantly Cooler than Gliese 229B

    CERN Document Server

    Burgasser, A J; Cutri, R M; McCallon, H; Kopan, G; Gizis, J E; Liebert, J; Reid, I N; Brown, M E; Monet, D G; Dahn, C C; Beichman, C A; Skrutskie, M F

    2000-01-01

    We report the discovery of a widely separated (258$\\farcs3\\pm0\\farcs$4) T dwarf companion to the Gl 570ABC system. This new component, Gl 570D, was initially identified from the Two Micron All Sky Survey (2MASS). Its near-infrared spectrum shows the 1.6 and 2.2 $\\micron$ CH$_4$ absorption bands characteristic of T dwarfs, while its common proper motion with the Gl 570ABC system confirms companionship. Gl 570D (M$_J$ = 16.47$\\pm$0.07) is nearly a full magnitude dimmer than the only other known T dwarf companion, Gl 229B, and estimates of L = (2.8$\\pm$0.3)x10$^{-6}$ L$_{\\sun}$ and T$_{eff}$ = 750$\\pm$50 K make it significantly cooler and less luminous than any other known brown dwarf companion. Using evolutionary models by Burrows et al. and an adopted age of 2-10 Gyr, we derive a mass estimate of 50$\\pm$20 M$_{Jup}$ for this object.

  12. Chemistry and Kinematics of the Late-forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG

    Science.gov (United States)

    Kirby, Evan N.; Rizzi, Luca; Held, Enrico V.; Cohen, Judith G.; Cole, Andrew A.; Manning, Ellen M.; Skillman, Evan D.; Weisz, Daniel R.

    2017-01-01

    We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies—but especially Leo A and Aquarius—share in common delayed star formation histories (SFHs) relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating H i gas. The velocity dispersions indicate that all three galaxies are dark-matter-dominated, with dark-to-baryonic mass ratios ranging from {4.4}-0.8+1.0 (SagDIG) to {9.6}-1.8+2.5 (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were further along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a closed or leaky box model of chemical evolution, suggesting that the galaxy was pre-enriched or acquired external gas during star formation. The metallicities of stars increased steadily for all three galaxies, but possibly at different rates. The [α/Fe] ratios at a given [Fe/H] are lower than that of the Sculptor dwarf spheroidal galaxy, which indicates more extended SFHs than Sculptor, consistent with photometrically derived SFHs. Overall, the bulk kinematic and chemical properties for the late-forming dwarf galaxies do not diverge significantly from those of less delayed dwarf galaxies, including dwarf spheroidal galaxies. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  13. On the Cool Side: Modeling the Atmospheres of Brown Dwarfs and Giant Planets

    Science.gov (United States)

    Marley, M. S.; Robinson, T. D.

    2015-08-01

    The atmosphere of a brown dwarf or extrasolar giant planet controls the spectrum of radiation emitted by the object and regulates its cooling over time. Although the study of these atmospheres has been informed by decades of experience modeling stellar and planetary atmospheres, the distinctive characteristics of these objects present unique challenges to forward modeling. In particular, complex chemistry arising from molecule-rich atmospheres, molecular opacity line lists (sometimes running to 10 billion absorption lines or more), multiple cloud-forming condensates, and disequilibrium chemical processes all combine to create a challenging task for any modeling effort. This review describes the process of incorporating these complexities into one-dimensional radiative-convective equilibrium models of substellar objects. We discuss the underlying mathematics as well as the techniques used to model the physics, chemistry, radiative transfer, and other processes relevant to understanding these atmospheres. The review focuses on methods for creating atmosphere models and briefly presents some comparisons of model predictions to data. Current challenges in the field and some comments on the future conclude the review.

  14. Detection of brown dwarf-like objects in the core of NGC3603

    CERN Document Server

    Spezzi, Loredana; De Marchi, Guido; Young, Erick T; Paresce, Francesco; Dopita, Michael A; Andersen, Morten; Panagia, Nino; Balick, Bruce; Bond, Howard E; Calzetti, Daniela; Carollo, C Marcella; Disney, Michael J; Frogel, Jay A; Hall, Donald N B; Holtzman, Jon A; Kimble, Randy A; McCarthy, Patrick J; O'Connell, Robert W; Saha, Abhijit; Silk, Joseph I; Trauger, John T; Walker, Alistair R; Whitmore, Bradley C; Windhorst, Rogier A

    2011-01-01

    We use near-infrared data obtained with the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope to identify objects having the colors of brown dwarfs (BDs) in the field of the massive galactic cluster NGC 3603. These are identified through use of a combination of narrow and medium band filters spanning the J and H bands, and which are particularly sensitive to the presence of the 1.3-1.5{\\mu}m H2O molecular band - unique to BDs. We provide a calibration of the relationship between effective temperature and color for both field stars and for BDs. This photometric method provides effective temperatures for BDs to an accuracy of {\\pm}350K relative to spectroscopic techniques. This accuracy is shown to be not significantly affected by either stellar surface gravity or uncertainties in the interstellar extinction. We identify nine objects having effective temperature between 1700 and 2200 K, typical of BDs, observed J-band magnitudes in the range 19.5-21.5, and that are strongly clustered towards the luminous...

  15. A Venus-Mass Planet Orbiting a Brown Dwarf: Missing Link between Planets and Moons

    CERN Document Server

    Udalski, A; Han, C; Gould, A; Kozlowski, S; Skowron, J; Poleski, R; Soszyński, I; Pietrukowicz, P; Mróz, P; Szymański, M K; Wyrzykowski, Ł; Ulaczyk, K; Pietrzyński, G; Shvartzvald, Y; Maoz, D; Kaspi, S; Gaudi, B S; Hwang, K -H; Choi, J -Y; Shin, I -G; Park, H; Bozza, V

    2015-01-01

    The co-planarity of solar-system planets led Kant to suggest that they formed from an accretion disk, and the discovery of hundreds of such disks around young stars as well as hundreds of co-planar planetary systems by the {\\it Kepler} satellite demonstrate that this formation mechanism is extremely widespread. Many moons in the solar system, such as the Galilean moons of Jupiter, also formed out of the accretion disks that coalesced into the giant planets. We report here the discovery of an intermediate system OGLE-2013-BLG-0723LB/Bb composed of a Venus-mass planet orbiting a brown dwarf, which may be viewed either as a scaled down version of a planet plus star or as a scaled up version of a moon plus planet orbiting a star. The latter analogy can be further extended since they orbit in the potential of a larger, stellar body. For ice-rock companions formed in the outer parts of accretion disks, like Uranus and Callisto, the scaled masses and separations of the three types of systems are similar, leading us ...

  16. Classical T Tauri-like Outflow Activity in the Brown Dwarf Mass Regime

    CERN Document Server

    Whelan, E T; Podio, L; Bacciotti, F; Randich, S

    2009-01-01

    Over the last number of years spectroscopic studies have strongly supported the assertion that protostellar accretion and outflow activity persists to the lowest masses. In this paper we present the results of our latest investigation of brown dwarf (BD) outflow activity and report on the discovery of two new outflows. Here ISO-Oph 32 is shown to drive a blue-shifted outflow with a radial velocity of 10-20 km/s and spectro-astrometric analysis constrains the position angle of this outflow to 240 +/- 7 degrees. The BD candidate ISO-Cha1 217 is found to have a bipolar outflow bright in several key forbidden lines (radial velocity = -20 km/s, +40 km/s) and with a PA of 190-210 degrees. A striking feature of the ISO-Cha1 217 outflow is the strong asymmetry between the red and blue-shifted lobes. This asymmetry is revealed in the relative brightness of the two lobes (red-shifted lobe is brighter), the factor of two difference in radial velocity (the red-shifted lobe is faster) and the difference in the electron de...

  17. Characterizing the Cool KOIs. VII. Refined Physics Properties of the Eclipsing Brown Dwarf LHS 6343 C

    CERN Document Server

    Montet, Benjamin T; Muirhead, Philip S; Villar, Ashley; Vassallo, Corinne; Baranec, Christoph; Law, Nicholas M; Riddle, Reed; Marcy, Geoffrey W; Howard, Andrew W; Isaacson, Howard

    2014-01-01

    We present an updated analysis of LHS 6343, a triple system in the Kepler field which consists of a brown dwarf eclipsing one member of a widely-separated M+M binary system. By analyzing the full Kepler dataset and 34 Keck/HIRES radial velocity observations, we measure both the observed eclipse depth and Doppler semiamplitude to 0.5% precision. With Robo-AO and Palomar/PHARO adaptive optics imaging as well as TripleSpec spectroscopy, we measure a model-dependent mass for LHS 6343 C of 62.1 +/- 1.2 M_Jup and a radius of 0.783 +/- 0.011 R_Jup. We detect the secondary eclipse in the Kepler data at 3.5 sigma, measuring e cos omega = 0.0228 +/- 0.0008. We also derive a method to measure the mass and radius of a star and transiting/eclipsing companion directly, without any reliance on stellar models. The mass and radius of both objects depend only on the orbital period, stellar density, reduced semimajor axis, Doppler semiamplitude, eccentricity, and inclination. With this method, we calculate a model-independent m...

  18. X-shooter observations of the accreting brown dwarf J053825.4-024241

    CERN Document Server

    Rigliaco, E; Randich, S; Testi, L; Covino, E; Herczeg, G; Alcala', J M

    2010-01-01

    We present the first observations of a probable brown dwarf, obtained with the new spectrograph X-shooter mounted on the UT2@VLT. The target (2MASS J053825.4-024241) is a 0.06 Msun object in the star-formation region sigma Orionis. The X-shooter spectrum covers simultaneously the whole range from UV to NIR (300-2500 nm). The J053825.4-024241 spectrum is rich in emission lines that are typical of accreting young object and clearly shows the Balmer jump. Moreover, many photospheric atomic and molecular absorption lines yield the spectral type and confirm that the object is young. We compute the mass accretion rate from all available observed accretion diagnostics. We find that there is a large spread in the Macc values (up to a factor 40) that is not caused by variability; some of this spread may be intrinsic, i.e., owing to different physical conditions of the emitting region for the same Macc. However, within the large error bars all Macc measurements agree, and the mean value is logMacc ~ -9.86 +- 0.45 Myr. ...

  19. Spectroscopy across the brown dwarf/planetary mass boundary - I. Near-infrared JHK spectra

    CERN Document Server

    Patience, J; De Rosa, R J; Vigan, A; Witte, S; Rice, E; Helling, Ch; Hauschildt, P

    2012-01-01

    With a uniform VLT SINFONI data set of nine targets, we have developed an empirical grid of J,H,K spectra of the atmospheres of objects estimated to have very low substellar masses of \\sim5-20 MJup and young ages of \\sim1-50 Myr. Most of the targets are companions, objects which are especially valuable for comparison with atmosphere and evolutionary models, as they present rare cases in which the age is accurately known from the primary. Based on the sample youth, all objects are expected to have low surface gravity, and this study investigates the critical early phases of the evolution of substellar objects. The spectra are compared with grids of five different theoretical atmosphere models. This analysis represents the first systematic model comparison with infrared spectra of young brown dwarfs. The fits to the full JHK spectra of each object result in a range of best fit effective temperatures of +/-150-300K whether or not the full model grid or a subset restricted to lower log(g) values is used. This eff...

  20. Neptune's Dynamic Atmosphere from Kepler K2 Observations: Implications for Brown Dwarf Light Curve Analyses

    CERN Document Server

    Simon, Amy A; Gaulme, Patrick; Hammel, Heidi B; Casewell, Sarah L; Fortney, Jonathan J; Gizis, John E; Lissauer, Jack J; Morales-Juberias, Raul; Orton, Glenn S; Wong, Michael H; Marley, Mark S

    2015-01-01

    Observations of Neptune with the Kepler Space Telescope yield a 49-day light curve with 98% coverage at a 1-minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-meter telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired 9 months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune's zonal wind profile, and confirms observed cloud feature variability. Although Neptune's clouds vary in location and intensity on short and long time scales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extras...

  1. Lucky Imaging Adaptive Optics of the brown dwarf binary GJ569Bab

    CERN Document Server

    Femenía, Autors: B; Pérez-Prieto, J A; Hildebrandt, S R; Labadie, L; Pérez-Garrido, A; Béjar, V J S; Díaz-Sánchez, A; Villó, I; Oscoz, A; López, R; Rodríguez, L F; Piqueras, J

    2010-01-01

    The potential of combining Adaptive Optics (AO) and Lucky Imaging (LI) to achieve high precision astrometry and differential photometry in the optical is investigated by conducting observations of the close 0\\farcs1 brown dwarf binary GJ569Bab. We took 50000 $I$-band images with our LI instrument FastCam attached to NAOMI, the 4.2-m William Herschel Telescope (WHT) AO facility. In order to extract the most of the astrometry and photometry of the GJ569Bab system we have resorted to a PSF fitting technique using the primary star GJ569A as a suitable PSF reference which exhibits an $I$-band magnitude of $7.78\\pm0.03$. The AO+LI observations at WHT were able to resolve the binary system GJ569Bab located at $4\\farcs 92 \\pm 0\\farcs05$ from GJ569A. We measure a separation of $98.4 \\pm 1.1$ mas and $I$-band magnitudes of $13.86 \\pm 0.03$ and $14.48 \\pm 0.03$ and $I-J$ colors of 2.72$\\pm$0.08 and 2.83$\\pm$0.08 for the Ba and Bb components, respectively. Our study rules out the presence of any other companion to GJ569A...

  2. The properties of discs around planets and brown dwarfs as evidence for disc fragmentation

    CERN Document Server

    Stamatellos, Dimitris

    2015-01-01

    Direct imaging searches have revealed many very low-mass objects, including a small number of planetary mass objects, as wide-orbit companions to young stars. The formation mechanism of these objects remains uncertain. In this paper we present the predictions of the disc fragmentation model regarding the properties of the discs around such low-mass objects. We find that the discs around objects that have formed by fragmentation in discs hosted by Sun-like stars (referred to as 'parent' discs and 'parent' stars) are more massive than expected from the ${M}_{\\rm disc}-M_*$ relation (which is derived for stars with masses $M_*>0.2 {\\rm M}_{\\odot}$). Accordingly, the accretion rates onto these objects are also higher than expected from the $\\dot{M}_*-M_*$ relation. Moreover there is no significant correlation between the mass of the brown dwarf or planet with the mass of its disc nor with the accretion rate from the disc onto it. The discs around objects that form by disc fragmentation have larger than expected m...

  3. A Pulsation Search Among Young Brown Dwarfs and Very Low Mass Stars

    CERN Document Server

    Cody, Ann Marie

    2014-01-01

    In 2005, Palla & Baraffe proposed that brown dwarfs (BDs) and very low mass stars (VLMSs; <0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of 1-4 hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters $\\sigma$ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to obs...

  4. Temperature constraints on the coldest brown dwarf known WISE 0855-0714

    CERN Document Server

    Beamín, J C; Bayo, A; Mužić, K; Boffin, H M J; Allard, F; Homeier, D; Minniti, D; Gromadzki, M; Kurtev, R; Lodieu, N; Martin, E L; Mendez, R A

    2014-01-01

    Context. Nearby isolated planetary mass objects are beginning to be discovered, but their individual properties are poorly constrained because their low surface temperatures and strong molecular self-absorption make them extremely faint. Aims. We aimed to detect the near infrared emission of the coldest brown dwarf (BD) found so far WISE0855$-$0714, located $\\sim$2.2 pc away, and to improve its temperature estimate (T$_{\\rm eff}$= 225-260 K) from a comparison with state of the art models of BD atmospheres. Methods. We observed the field containing WISE0855-0714 with HAWK-I at the VLT in the $Y$ band. For BDs with T$_{\\rm eff}24.4 mag at 3-$\\sigma$ level, leading to Y-[4.5]>10.5. Combining this limit with previous detections and upper limits at other wavelengths, WISE0855-0714 is confirmed as the reddest BD detected. We applied spectral energy distribution fitting with collections of models from two independent groups for extremely cool BD atmospheres leading to an effective temperature of T$_{\\rm eff}<$250...

  5. A pulsation search among young brown dwarfs and very-low-mass stars

    Energy Technology Data Exchange (ETDEWEB)

    Cody, Ann Marie; Hillenbrand, Lynne A., E-mail: amc@ipac.caltech.edu [California Institute of Technology, Department of Astrophysics, MC 249-17, Pasadena, CA 91125 (United States)

    2014-12-01

    In 2005, Palla and Baraffe proposed that brown dwarfs (BDs) and very-low-mass stars (VLMSs; < 0.1 solar masses) may be unstable to radial oscillations during the pre-main-sequence deuterium burning phase. With associated periods of one to four hours, this potentially new class of pulsation offers unprecedented opportunities to probe the interiors and evolution of low-mass objects in the 1-15 million year age range. Following up on reports of short-period variability in young clusters, we designed a high-cadence photometric monitoring campaign to search for deuterium-burning pulsation among a sample of 348 BDs and VLMSs in the four young clusters σ Orionis, Chamaeleon I, IC 348, and Upper Scorpius. In the resulting light curves we achieved sensitivity to periodic signals of amplitude several millimagnitudes, on timescales from 15 minutes to two weeks. Despite the exquisite data quality, we failed to detect any periodicities below seven hours. We conclude that D-burning pulsations are not able to grow to observable amplitudes in the early pre-main sequence. In spite of the nondetection, we did uncover a rich set of variability behavior—both periodic and aperiodic—on day to week timescales. We present new compilations of variable sources from our sample, as well as three new candidate cluster members in Chamaeleon I.

  6. WISE/2MASS-SDSS Brown Dwarfs candidates using Virtual Observatory tools

    CERN Document Server

    Aberasturi, M; Martin, E L

    2011-01-01

    Massive imaging surveys in different passbands are the main contributors to the discovery of brown dwarfs (BDs). The Virtual Observatory (VO) represents an adequate framework to efficiently handle these vast datasets and filter them out according to specific requirements. Having an statistically significant number of BDs is mandatory to better understand their general properties as well as to identify peculiar objects. WISE, an all-sky survey in the infrared, provides an excellent opportunity to significantly increase the number of BDs, in particular those at the lower end of the temperature scale. The main aim of this work is to demonstrate that VO tools are efficient to identify BDs by cross correlating public catalogues released by large imaging surveys. Using VO tools we have performed a cross-match of the WISE Preliminary Release, the 2MASS Point Source and SDSS Data Release 7 catalogues over the whole area of sky that they have in common. Photometric and proper motion criteria were used to obtain a list...

  7. One more neighbor: The first brown dwarf in the VVV survey

    CERN Document Server

    Beamín, J C; Gromadzki, M; Kurtev, R; Ivanov, V D; Beletsky, Y; Lucas, P; Saito, R K; Borissova, J

    2013-01-01

    Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and young star clusters has helped to constraint the low-mass end of the stellar mass function and the initial mass function. We use data of the Vista Variables in the V\\'ia L\\'actea (VVV), a near-infrared (NIR) multiwavelength (Z Y J H Ks) multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern Galactic plane to search for nearby BDs. Aims. The ultimate aim of the project is to improve the completeness of the census of nearby stellar and substellar objects towards the Galactic bulge and inner disk regions. Methods. Taking advantage of the homogeneous sample of VVV multi-epoch data, we identified stars with high proper motion (> 0.1"/yr), and then selected low-mass objects using NIR colors. We searched for a possible parallax signature using the all available Ks band epochs. We set some constraints on the month-to-year scale Ks band variability of our candidates, and even searched for possible transiting companions. We ...

  8. EPIC 219388192 b - an inhabitant of the brown dwarf desert in the Ruprecht 147 open cluster

    CERN Document Server

    Nowak, Grzegorz; Gandolfi, Davide; Dai, Fei; Lanza, Antonino F; Hirano, Teruyuki; Barragán, Oscar; Fukui, Akihiko; Bruntt, Hans; Endl, Michael; Cochran, William D; Prieto-Arranz, Jorge; Kiilerich, Amanda; Nespral, David; Hatzes, Artie P; Albrecht, Simon; Deeg, Hans; Winn, Joshua N; Yu, Liang; Kuzuhara, Masayuki; Grziwa, Sascha; Smith, Alexis M S; Moroni, Pier G Prada; Guenther, Eike W; Van Eylen, Vincent; Csizmadia, Szilard; Fridlund, Malcolm; Cabrera, Juan; Eigmüller, Philipp; Erikson, Anders; Korth, Judith; Narita, Norio; Pätzold, Martin; Rauer, Heike; Ribas, Ignasi

    2016-01-01

    We report the discovery of EPIC 219388192 b, a transiting brown dwarf in a 5.3-day orbit around a member star of Ruprecht-147, the oldest nearby open cluster association, which was photometrically monitored by K2 during its Campaign 7. We combine the K2 time-series data with ground-based adaptive optics imaging and high resolution spectroscopy to rule out false positive scenarios and determine the main parameters of the system. EPIC 219388192 b has a radius of $R_\\mathrm{b}$=$0.937\\pm0.042$~$\\mathrm{R_{Jup}}$ and mass of $M_\\mathrm{b}$=$36.50\\pm0.09$~$\\mathrm{M_{Jup}}$, yielding a mean density of $59.0\\pm8.1$~$\\mathrm{g\\,cm^{-3}}$. The host star is nearly a Solar twin with mass $M_\\star$=$0.99\\pm0.05$~$\\mathrm{M_{\\odot}}$, radius $R_\\star$=$1.01\\pm0.04$~$\\mathrm{R_{\\odot}}$, effective temperature $\\mathrm{T_{eff}}$=$5850\\pm85$~K and iron abundance [Fe/H]=$0.03\\pm0.08$~dex. Its age, spectroscopic distance, and reddening are consistent with those of Ruprecht-147, corroborating its cluster membership. EPIC 21938...

  9. A molecular outflow driven by the brown dwarf binary FU Tau

    CERN Document Server

    Monin, J -L; Lefloch, B; Dougados, C; de Oliveira, C Alves

    2013-01-01

    We report the detection of a molecular outflow driven by the brown dwarf binary FU Tau. Using the IRAM 30 m telescope we observed the $^{12}$CO(2-1) (CO) emission in the vicinity of FU Tau and detected a bipolar outflow by examining the wings of the CO(2-1) line as we moved away from the source position. An integrated map of the wing emission between 3 kms$^{-1}$ and 5 kms$^{-1}$ reveals a blue-shifted lobe at a position of $\\sim$ 20 \\arcsec\\ from the FU Tau system and at a position angle of $\\sim$ 20$^{\\circ}$. The beam size of the observations is $11\\arcsec$\\ hence it is not possible to distinguish between the two components of the FU Tau binary. However as optical forbidden emission, a strong tracer of the shocks caused by outflow activity, has been detected in the spectrum of FU Tau A we assume this component to be the driving source of the molecular outflow. We estimate the mass and mass outflow rate of the outflow at 4 $\\times$ 10$^{-6}$ \\Msun\\ and 6 $\\times$ 10$^{-10}$ \\Msun/yr respectively. These resu...

  10. The SONYC survey: Towards a complete census of brown dwarfs in star forming regions

    CERN Document Server

    Muzic, K; Geers, V C; Jayawardhana, R; Tamura, M; Dawson, P; Ray, T P

    2013-01-01

    SONYC, short for "Substellar Objects in Nearby Young Clusters", is a survey program to provide a census of the substellar population in nearby star forming regions. We have conducted deep optical and near-infrared photometry in five young regions (NGC1333, rho Ophiuchi, Chamaeleon-I, Upper Sco, and Lupus-3), combined with proper motions, and followed by extensive spectroscopic campaigns with Subaru and VLT, in which we have obtained more than 700 spectra of candidate low-mass objects. We have identified and characterized more than 60 new substellar objects, among them a handful of objects with masses close to, or below the Deuterium burning limit. Through SONYC and surveys by other groups, the substellar IMF is now well characterized down to ~ 5 - 10 MJup, and we find that the ratio of the number of stars with respect to brown dwarfs lies between 2 and 6. A comprehensive survey of NGC 1333 reveals that, down to ~5MJup, free-floating objects with planetary masses are 20-50 times less numerous than stars, i.e. ...

  11. New Low-Mass Stars and Brown Dwarfs with Disks in Lupus

    CERN Document Server

    Allen, P R; Myers, P C; Megeath, S T; Allen, L E; Hartmann, L; Fazio, G G

    2007-01-01

    Using the Infrared Array Camera and the Multiband Imaging Photometer aboard the {\\it Spitzer Space Telescope}, we have obtained images of the Lupus 3 star-forming cloud at 3.6, 4.5, 5.8, 8.0, and 24 \\micron. We present photometry in these bands for the 41 previously known members that are within our images. In addition, we have identified 19 possible new members of the cloud based on red 3.6-8.0 \\micron colors that are indicative of circumstellar disks. We have performed optical spectroscopy on 6 of these candidates, all of which are confirmed as young low-mass members of Lupus 3. The spectral types of these new members range from M4.75 to M8, corresponding to masses of 0.2-0.03 $M_\\odot$ for ages of $\\sim1$ Myr according to theoretical evolutionary models. We also present optical spectroscopy of a candidate disk-bearing object in the vicinity of the Lupus 1 cloud, 2M 1541-3345, which Jayawardhana & Ivanov recently classified as a young brown dwarf ($M\\sim0.03$ $M_\\odot$) with a spectral type of M8. In co...

  12. Finding benchmark brown dwarfs to probe the IMF as a function of time

    CERN Document Server

    Pinfield, D J; Day-Jones, A C; Folkes, S L; Jones, H R A; Kendall, T R; Lucas, P W; Steele, I A

    2006-01-01

    Using a simulated disk brown dwarf (BD) population, we find that new large area infrared surveys are expected to identify enough BDs covering wide enough mass--age ranges to potentially measure the mass function down to ~0.03Mo, and the BD formation history out to 10 Gyr, at a level capable of establishing if BD formation follows star formation. We suggest these capabilities are best realised by spectroscopic calibration of BD properties (Teff, g and [M/H]) which, when combined with a measured luminosity and an evolutionary model can give BD mass and age relatively independent of BD atmosphere models. Such calibration requires an empirical understanding of how BD spectra are affected by variations in these properties, and thus the identification and study of "benchmark BDs" whose age and composition can be established independently. We identify the best sources of benchmark BDs as young open cluster members, moving group members, and wide (>1000AU) BD companions to both subgiant stars and high mass white dwar...

  13. Rotational studies in the Orion Nebula Cluster: from solar mass stars to brown dwarfs

    CERN Document Server

    Rodriguez-Ledesma, Maria Victoria; Eislöffel, Jochen

    2009-01-01

    Rotational studies at a variety of ages and masses are important for constraining the angular momentum evolution of young stellar objects (YSO). Of particular interest are the very low mass (VLM) stars and brown dwarfs (BDs), because of the significant lack of known rotational periods in that mass range. We provide for the first time information on rotational periods for a large sample of young VLM stars and BDs. This extensive rotational period study in the 1 Myr old Orion Nebula Cluster (ONC) is based on a deep photometric monitoring campaign using the Wide Field Imager (WFI) camera on the ESO/MPG 2.2m telescope on La Silla, Chile. Accurate I-band photometry of 2908 stars was obtained, extending three magnitudes deeper than previous studies in the ONC. We found 487 periodic variables with estimated masses between 0.5 Msun and 0.015 Msun, 124 of which are BD candidates. This is by far the most extensive and complete rotational period data set for young VLM stars and BDs. In addition, 808 objects show non-per...

  14. VizieR Online Data Catalog: Hydrogen and Helium EOS in brown dwarfs (Becker+, 2014)

    Science.gov (United States)

    Becker, A.; Lorenzen, W.; Fortney, J. J.; Nettelmann, N.; Schottler, M.; Redmer, R.

    2015-02-01

    We present new equations of state (EOSs) for hydrogen and helium covering a wide range of temperatures from 60K to 107K and densities from 10-10g/cm3 to 103g/cm3. They include an extended set of ab initio EOS data for the strongly correlated quantum regime with an accurate connection to data derived from other approaches for the neighboring regions. We compare linear mixing isotherms based on our EOS tables with available real mixture data. A first important astrophysical application of this new EOS data is the calculation of interior models for Jupiter and comparison with recent results. Second, mass-radius relations are calculated for Brown Dwarfs (BDs) which we compare with predictions derived from the widely used EOS of Saumon, Chabrier, and van Horn. Furthermore, we calculate interior models for typical BDs with different masses, namely, Corot-3b, Gliese-229b, and Corot-15b, and the giant planet KOI-889b. The predictions for the central pressures and densities differ by up to 10% dependent on the EOS used. (2 data files).

  15. A Hybrid Scenario for the Formation of Brown Dwarfs and Very Low Mass Stars

    CERN Document Server

    Basu, Shantanu

    2012-01-01

    We present a calculation of protostellar disk formation and evolution in which gaseous clumps (essentially, the first Larson cores formed via disk fragmentation) are ejected from the disk during the early stage of evolution. This is a universal process related to the phenomenon of ejection in multiple systems of point masses. However, it occurs in our model entirely due to the interaction of compact, gravitationally-bound gaseous clumps and is free from the smoothing-length uncertainty that is characteristic of models using sink particles. Clumps that survive ejection span a mass range of 0.08--0.35 $M_\\odot$, and have ejection velocities $0.8 \\pm 0.35$ km s$^{-1}$, which are several times greater than the escape speed. We suggest that, upon contraction, these clumps can form substellar or low-mass stellar objects with notable disks, or even close-separation very-low-mass binaries. In this hybrid scenario, allowing for ejection of clumps rather than finished protostars/proto--brown-dwarfs, disk formation and ...

  16. New Brown Dwarfs and an Updated Initial Mass Function in Taurus

    CERN Document Server

    Luhman, K L

    2004-01-01

    I have performed a search for young low-mass stars and brown dwarfs (BDs) in 2 regions encompassing a total area of 4 deg^2 in the Taurus star-forming region, discovering 15 new members of Taurus. In addition, I present 7 new members outside of these areas from the initial stage of a survey of all of Taurus. These 22 objects exhibit spectral types of M4.5-M9.25 and masses of 0.3-0.015 M_sun according to the theoretical evolutionary models of Baraffe and Chabrier, 7 of which are likely to be BDs. Emission in H(alpha), He I, Ca II, [O I], and [S II] and excess emission in optical and near-IR bands among some of these objects suggest the presence of accretion, outflows, and circumstellar disks. The results from the 4 deg^2 survey have been combined with previous studies of Taurus to arrive at an IMF for a total area of 12.4 deg^2. As in the previous IMFs for Taurus, the updated IMF peaks at a higher mass (0.8 M_sun) than the mass functions in IC 348 and Orion (0.1-0.2 M_sun). Meanwhile, the deficit of BDs in Tau...

  17. Determination of the globular cluster and halo stellar mass functions and stellar and brown dwarf densities

    CERN Document Server

    Chabrier, G; Chabrier, Gilles; Méra, Dominique

    1997-01-01

    We use recent low-mass star models, which reproduce accurately the observed sequences of various globular clusters, to convert the observed luminosity functions into bolometric luminosity functions and mass functions down to the bottom of the main sequence. These mass functions are well describedby a slowly rising power-law $dN/dm\\propto m^{-\\alpha}$, with $0.5\\wig < \\alpha \\wig < 1.5$, down to $\\sim 0.1 \\msol$, independently of the metallicity, suggesting a rather universal behaviour of the cluster initial mass functions. We predict luminosity functions in the NICMOS filters in the stellar and in the brown dwarf domains for different mass functions and metallicities. We apply these calculations to the determination, slope and normalization, of the mass function of the Galactic halo (spheroid and dark halo). The spheroid mass function is well described by the afore-mentioned power-law function with function below $\\sim 0.15 \\msol$ can not be excluded with the data presently available. Comparison with th...

  18. New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data

    CERN Document Server

    Lodieu, N; Jameson, R F; Hodgkin, S T; Carraro, G; Kendall, T R

    2006-01-01

    We present first results from a deep (J = 18.7), wide-field (6.5 square degrees) infrared (ZYJHK) survey in the Upper Sco association conducted within the science verification phase of the UKIRT Infrared Deep Sky Survey Galactic Cluster Survey (GCS). Cluster members define a sequence well separated from field stars in the (Z-J,Z) colour-magnitude diagram. We have selected a total of 164 candidates with J = 10.5-18.7 mag from the (Z-J,Z) and (Y-J,Y) diagrams. We further investigated the location of those candidates in the other colour-magnitude and colour-colour diagrams to weed out contaminants. The cross-correlation of the GCS catalogue with the 2MASS database confirms the membership of 116 photometric candidates down to 20 Jupiter masses as they lie within a 2 sigma circle centred on the association mean motion. The final list of cluster members contains 129 sources with masses between 0.3 and 0.007 Msun. We extracted a dozen new low-mass brown dwarfs below 20 Mjup, the limit of previous surveys in the regi...

  19. Small hydrocarbon molecules in cloud-forming Brown Dwarf and giant gas planet atmospheres

    CERN Document Server

    Bilger, Camille; Helling, Christiane

    2013-01-01

    We study the abundances of complex carbon-bearing molecules in the oxygen-rich dust- forming atmospheres of Brown Dwarfs and giant gas planets. The inner atmospheric re- gions that form the inner boundary for thermochemical gas-phase models are investigated. Results from Drift-phoenix atmosphere simulations, which include the feedback of phase- non-equilibrium dust cloud formation on the atmospheric structure and the gas-phase abun- dances, are utilised. The resulting element depletion leads to a shift in the carbon-to-oxygen ratio such that several hydrocarbon molecules and cyanopolycyanopolyynene molecules can be present. An increase in surface gravity and/or a decrease in metallicity support the increase in the partial pressures of these species. CO, CO2, CH4, and HCN contain the largest fraction of carbon. In the upper atmosphere of low-metallicity objects, more carbon is contained in C4H than in CO, and also CH3 and C2H2 play an increasingly important role as carbon-sink. We determine chemical relaxation...

  20. Photometric Monitoring of the Coldest Known Brown Dwarf with the {\\it Spitzer Space Telescope}

    CERN Document Server

    Esplin, Taran; Cushing, Michael; Hardegree-Ullman, Kevin; Trucks, Jessica; Burgasser, Adam; Schneider, Adam

    2016-01-01

    Because WISE J085510.83$-$071442.5 (hereafter WISE 0855-0714) is the coldest known brown dwarf ($\\sim250$ K) and one of the Sun's closest neighbors (2.2 pc), it offers a unique opportunity for studying a planet-like atmosphere in an unexplored regime of temperature. To detect and characterize inhomogeneities in its atmosphere (e.g., patchy clouds, hot spots), we have performed time-series photometric monitoring of WISE 0855-0714 at 3.6 and 4.5 micron with the Spitzer Space Telescope during two 23~hr periods that were separated by several months. For both bands, we have detected variability with peak-to-peak amplitudes of 4-5% and 3-4% in the first and second epochs, respectively. The light curves are semi-periodic in the first epoch for both bands, but are more irregular in the second epoch. Models of patchy clouds have predicted a large increase in mid-IR variability amplitudes (for a given cloud covering fraction) with the appearance of water ice clouds at $T_{\\rm eff}<$375 K, so if such clouds are respo...

  1. Extended Transiting Disks and Rings Around Planets and Brown Dwarfs: Theoretical Constraints

    CERN Document Server

    Zanazzi, J J

    2016-01-01

    Newly formed planets (or brown dwarfs) may possess disks or rings that occupy an appreciable fraction of the planet's Hill sphere and extend beyond the Laplace radius, where the tidal torque from the host star dominates over the torque from the oblate planet. Such a disk/ring can exhibit unique, detectable transit signatures, provided that the disk/ring is significantly misaligned with the orbital plane of the planet. There exists tentative evidence for an extended ring system around the young K5 star 1 SWASP J140747-354542. We present a general theoretical study of the inclination (warp) profile of circumplanetary disks under the combined influences of the tidal torque from the central star, the torque from the oblate planet and the self-gravity of the disk. We calculate the steady-state warp profile ("generalized Laplace Surface") and investigate the condition for coherent precession of the disk. We find that to maintain non-negligible misalignment between the extended outer disk and the planet's orbital pl...

  2. Water Clouds in the Atmosphere of a Jupiter-Like Brown Dwarf

    Science.gov (United States)

    Kohler, Susanna

    2016-07-01

    Lying a mere 7.2 light-years away, WISE 0855 is the nearest known planetary-mass object. This brown dwarf, a failed star just slightly more massive than Jupiter, is also the coldest known compact body outside of our solar system and new observations have now provided us with a first look at its atmosphere.Temperaturepressure profiles of Jupiter, WISE 0855, and what was previously the coldest extrasolar object with a 5-m spectrum, Gl 570D. Thicker lines show the location of each objects 5-m photospheres. WISE 0855s and Jupiters photospheres are near the point where water starts to condense out into clouds (dashed line). [Skemer et al. 2016]Challenging ObservationsWith a chilly temperature of 250 K, the brown dwarf WISE 0855 is the closest thing weve been able to observe to a body resembling Jupiters ~130 K. WISE 0855 therefore presents an intriguing opportunity to directly study the atmosphere of an object whose physical characteristics are similar to our own gas giants.But studying the atmospheric characteristics of such a body is tricky. WISE 0855 is too cold and faint to be able to obtain traditional optical or near-infrared ( 2.5 m) spectroscopy of it. Luckily, like Jupiter, the opacity of its gas allows thermal emission from its deep atmosphere to escape through an atmospheric window around ~5 m.A team of scientists led by Andrew Skemer (UC Santa Cruz) set out to observe WISE 0855 in this window with the Gemini-North telescope and the Gemini Near-Infrared Spectrograph. Though WISE 0855 is five times fainter than the faintest object previously detected with ground-based 5-m spectroscopy, the dry air of Mauna Kea (and a lot of patience!) allowed the team to obtain unprecedented spectra of this object.WISE 0855s spectrum shows absorption features consistent with water vapor, and its best fit by a cloudy brown-dwarf model. [Skemer et al. 2016]Water Clouds FoundExoplanets and brown dwarfs cooler than ~350 K are expected to form water ice clouds in upper atmosphere

  3. Self-consistent evolution of accreting low-mass stars and brown dwarfs

    CERN Document Server

    Baraffe, I; Vorobyov, E I; Chabrier, G

    2016-01-01

    We present self-consistent calculations coupling numerical hydrodynamics simulations of collapsing pre-stellar cores and stellar evolution models of accreting objects. We analyse the main impact of consistent accretion history on the evolution and lithium depletion of young low-mass stars and brown dwarfs. These consistent models confirm the generation of a luminosity spread in Herzsprung-Russell diagrams at ages $\\sim$ 1-10 Myr. They also confirm that early accretion can produce objects with abnormal Li depletion, as found in a previous study that was based on arbitrary accretion rates. The results strengthen that objects with anomalously high level of Li depletion in young clusters should be extremely rare. We also find that early phases of burst accretion can produce coeval models of similar mass with a range of different Li surface abundances, and in particular with Li-excess compared to the predictions of non-accreting counterparts. This result is due to a subtle competition between the effect of burst a...

  4. BANYAN. VIII. New Low-Mass Stars and Brown Dwarfs with Candidate Circumstellar Disks

    CERN Document Server

    Boucher, Anne; Gagné, Jonathan; Malo, Lison; Faherty, Jacqueline K; Doyon, René; Chen, Christine H

    2016-01-01

    We present the results of a search for new circumstellar disks around low-mass stars and brown dwarfs with spectral types >K5 that are confirmed or candidate members of nearby young moving groups. Our search input sample was drawn from the BANYAN surveys of Malo et al. and Gagn\\'e et al. Two-Micron All-Sky Survey and Wide-field Infrared Survey Explorer data were used to detect near- to mid-infrared excesses that would reveal the presence of circumstellar disks. A total of 13 targets with convincing excesses were identified: four are new and nine were already known in the literature. The new candidates are 2MASS J05010082$-$4337102 (M4.5), J08561384$-$1342242 (M8$\\,\\gamma$), J12474428$-$3816464 (M9$\\,\\gamma$) and J02265658$-$5327032 (L0$\\,\\delta$), and are candidate members of the TW Hya ($\\sim10\\pm 3\\,$Myr), Columba ($\\sim 42^{+6}_{-4}\\,$Myr) and Tucana-Horologium ($\\sim 45\\pm 4\\,$Myr) associations, with masses of $120$ and $13-18\\,M_{\\mathrm{Jup}}$. The M8$-$L0 objects in Columba and Tucana-Horologium are po...

  5. Not Alone: Tracing the Origins of Very Low Mass Stars and Brown Dwarfs Through Multiplicity Studies

    CERN Document Server

    Burgasser, A J; Siegler, N; Close, L; Allen, P; Lowrance, P J; Gizis, J; Burgasser, Adam J.; Siegler, Nick; Close, Laird; Allen, Peter; Lowrance, Patrick; Gizis, John

    2006-01-01

    The properties of multiple stellar systems have long provided important empirical constraints for star formation theories, enabling (along with several other lines of evidence) a concrete, qualitative picture of the birth and early evolution of normal stars. At very low masses (VLM; M = 0.8) occurring infrequently (perhaps 10-30%). Both the frequency and maximum separation of stellar and brown dwarf binaries steadily decrease for lower system masses, suggesting that VLM binary formation and/or evolution may be a mass-dependent process. There is evidence for a fairly rapid decline in the number of loosely-bound systems below ~0.3 M_sun, corresponding to a factor of 10-20 increase in the minimum binding energy of VLM binaries as compared to more massive stellar binaries. This wide-separation ``desert'' is present among both field (~1-5 Gyr) and older (> 100 Myr) cluster systems, while the youngest (<~10 Myr) VLM binaries, particularly those in nearby, low-density star forming regions, appear to have somewhat...

  6. On the survival of brown dwarfs and planets engulfed by their giant host star

    CERN Document Server

    Passy, Jean-Claude; De Marco, Orsola

    2012-01-01

    The recent discovery of two Earth-mass planets in close orbits around an evolved star has raised questions as to whether substellar companions can survive encounters with their host stars. We consider whether these companions could have been stripped of significant amounts of mass during the phase when they orbited through the dense inner envelopes of the giant. We apply the criterion derived by Murray et al. for disruption of gravitationally bound objects by ram pressure, to determine whether mass loss may have played a role in the histories of these and other recently discovered low-mass companions to evolved stars. We find that the brown dwarf and Jovian mass objects circling WD 0137-349, SDSS J08205+0008, and HIP 13044 are most unlikely to have lost significant mass during the common envelope phase. However, the Earth-mass planets found around KIC 05807616 could well be the remnant of one or two Jovian mass planets that lost extensive mass during the common envelope phase.

  7. Extended transiting discs and rings around planets and brown dwarfs: theoretical constraints

    Science.gov (United States)

    Zanazzi, J. J.; Lai, Dong

    2017-02-01

    Newly formed planets (or brown dwarfs) may possess discs or rings which occupy an appreciable fraction of the planet's Hill sphere and extend beyond the Laplace radius, where the tidal torque from the host star dominates over the torque from the oblate planet. Such a disc/ring can exhibit unique, detectable transit signatures, provided that the disc/ring is significantly misaligned with the orbital plane of the planet. There exists tentative evidence for an extended ring system around the young K5 star 1 SWASP J140747-354542. We present a general theoretical study of the inclination (warp) profile of circumplanetary discs under the combined influences of the tidal torque from the central star, the torque from the oblate planet, and the self-gravity of the disc. We calculate the equilibrium warp profile (`generalized Laplace surface') and investigate the condition for coherent precession of the disc. We find that to maintain a non-negligible misalignment between the extended outer disc and the planet's orbital plane, and to ensure coherent disc precession, the disc surface density must be sufficiently large so that the self-gravity torque overcomes the tidal torque from the central star. Our analysis and quantitative results can be used to constrain the parameters of transiting circumplanetary discs which may be detected in the future.

  8. The SOPHIE search for northern extrasolar planets. IV. Massive companions in the planet-brown dwarf boundary

    Science.gov (United States)

    Díaz, R. F.; Santerne, A.; Sahlmann, J.; Hébrard, G.; Eggenberger, A.; Santos, N. C.; Moutou, C.; Arnold, L.; Boisse, I.; Bonfils, X.; Bouchy, F.; Delfosse, X.; Desort, M.; Ehrenreich, D.; Forveille, T.; Lagrange, A.-M.; Lovis, C.; Pepe, F.; Perrier, C.; Queloz, D.; Ségransan, D.; Udry, S.; Vidal-Madjar, A.

    2012-02-01

    Context. The mass domain where massive extrasolar planets and brown dwarfs lie is still poorly understood. Indeed, not even a clear dividing line between massive planets and brown dwarfs has been established yet. This is partly because these objects are very scarce in close orbits around solar-type stars, the so-called brown dwarf desert. Owing to this, it has proven difficult to set up a strong observational base with which to compare models and theories of formation and evolution. Aims: We search to increase the current sample of massive sub-stellar objects with precise orbital parameters, and to constrain the true mass of detected sub-stellar candidates. Methods: The initial identification of sub-stellar candidates was made using precise radial velocity measurements obtained with the SOPHIE spectrograph at the 1.93-m telescope of the Haute-Provence Observatory. Subsequent characterisation of these candidates, with the principal aim of identifying stellar companions in low-inclination orbits, was made by means of different spectroscopic diagnostics such as the measurement of the bisector velocity span and the study of the correlation mask effect. With this objective, we also employed astrometric data from the Hipparcos mission, and a novel method of simulating stellar cross-correlation functions. Results: Seven new objects with minimum masses between ~10 MJup and ~90 MJup are detected. Out of these, two are identified as low-mass stars in low-inclination orbits, and two others have masses below the theoretical deuterium-burning limit, and are therefore planetary candidates. The remaining three are brown dwarf candidates; the current upper limits for their the masses do not allow us to conclude on their nature. Additionally, we have improved the parameters of an already-known brown dwarf (HD 137510b), confirmed by astrometry. Based on observations collected with the SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS), France, by

  9. Recent Variability Observations of Solar System Giant Planets: Fresh Context for Understanding Exoplanet and Brown Dwarf Weather

    Science.gov (United States)

    Marley, Mark S.; Kepler Giant Planet Variability Team, Spitzer Ice Giant Variability Team

    2016-10-01

    Over the past several years a number of of high cadence photometric observations of solar system giant planets have been acquired by various platforms. Such observations are of interest as they provide points of comparison to the already expansive set of brown dwarf variability observations and the small, but growing, set of exoplanet variability observations. By measuring how rapidly the integrated light from solar system giant planets can evolve, variability observations of substellar objects that are unlikely to ever be resolved can be placed in a fuller context. Examples of brown dwarf variability observations include extensive work from the ground (e.g., Radigan et al. 2014), Spitzer (e.g., Metchev et al. 2015), Kepler (Gizis et al. 2015), and HST (Yang et al. 2015). Variability has been measured on the planetary mass companion to the brown dwarf 2MASS 1207b (Zhou et al. 2016) and further searches are planned in thermal emission for the known directly imaged planets with ground based telescopes (Apai et al. 2016) and in reflected light with future space based telescopes. Recent solar system variability observations include Kepler monitoring of Neptune (Simon et al. 2016) and Uranus, Spitzer observations of Neptune (Stauffer et al. 2016), and Cassini observations of Jupiter (West et al. in prep). The Cassini observations are of particular interest as they measured the variability of Jupiter at a phase angle of ˜60○, comparable to the viewing geometry expected for space based direct imaging of cool extrasolar Jupiters in reflected light. These solar system analog observations capture many of the characteristics seen in brown dwarf variability, including large amplitudes and rapid light curve evolution on timescales as short as a few rotation periods. Simon et al. (2016) attribute such variations at Neptune to a combination of large scale, stable cloud structures along with smaller, more rapidly varying, cloud patches. The observed brown dwarf and exoplanet

  10. Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G 196-3 B

    Science.gov (United States)

    Zakhozhay, Olga V.; Zapatero Osorio, María Rosa; Béjar, Víctor J. S.; Boehler, Yann

    2017-01-01

    The origin of the very red optical and infrared colours of intermediate-age (˜10-500 Myr) L-type dwarfs remains unknown. It has been suggested that low-gravity atmospheres containing large amounts of dust may account for the observed reddish nature. We explored an alternative scenario by simulating debris disc around G 196-3 B, which is an L3 young brown dwarf with a mass of ˜15 MJup and an age in the interval 20-300 Myr. The best-fit solution to G 196-3 B's photometric spectral energy distribution from optical wavelengths through 24 μm corresponds to the combination of an unreddened L3 atmosphere (Teff ≈ 1870 K) and a warm (≈1280 K), narrow (≈0.07-0.11 R⊙) debris disc located at very close distances (≈0.12-0.20 R⊙) from the central brown dwarf. This putative, optically thick, dusty belt, whose presence is compatible with the relatively young system age, would have a mass ≥7 × 10-10 M⊕ comprised of submicron/micron characteristic dusty particles with temperatures close to the sublimation threshold of silicates. Considering the derived global properties of the belt and the disc-to-brown dwarf mass ratio, the dusty ring around G 196-3 B may resemble the rings of Neptune and Jupiter, except for its high temperature and thick vertical height (≈6 × 103 km). Our inferred debris disc model is able to reproduce G 196-3 B's spectral energy distribution to a satisfactory level of achievement.

  11. Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G 196-3 B

    Science.gov (United States)

    Zakhozhay, Olga V.; Zapatero Osorio, María Rosa; Béjar, Víctor J. S.; Boehler, Yann

    2016-09-01

    The origin of the very red optical and infrared colours of intermediate-age (˜10-500 Myr) L-type dwarfs remains unknown. It has been suggested that low-gravity atmospheres containing large amounts of dust may account for the observed reddish nature. We explored an alternative scenario by simulating protoplanetary and debris discs around G 196-3 B, which is an L3 young brown dwarf with a mass of ˜15 MJup and an age in the interval 20-300 Myr. The best-fit solution to G 196-3 B's photometric spectral energy distribution from optical wavelengths through 24 μm corresponds to the combination of an unreddened L3 atmosphere (Teff ≈ 1870 K) and a warm (≈ 1280 K), narrow (≈ 0.07-0.11 R⊙) debris disc located at very close distances (≈ 0.12-0.20 R⊙) from the central brown dwarf. This putative, optically thick, dusty belt, whose presence is compatible with the relatively young system age, would have a mass ≥7 × 10-10 M⊕ comprised of sub-micron/micron characteristic dusty particles with temperatures close to the sublimation threshold of silicates. Considering the derived global properties of the belt and the disc-to-brown dwarf mass ratio, the dusty ring around G 196-3 B may resemble the rings of Neptune and Jupiter, except for its high temperature and thick vertical height (≈6 × 103 km). Our inferred debris disc model is able to reproduce G 196-3 B's spectral energy distribution to a satisfactory level of achievement.

  12. WISEP J004701.06+680352.1: AN INTERMEDIATE SURFACE GRAVITY, DUSTY BROWN DWARF IN THE AB DOR MOVING GROUP

    Energy Technology Data Exchange (ETDEWEB)

    Gizis, John E. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Allers, Katelyn N. [Department of Physics and Astronomy, Bucknell University, Lewisburg, PA 17837 (United States); Liu, Michael C. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu HI 96822 (United States); Harris, Hugh C. [US Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001 (United States); Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road NW, Washington, DC 20015 (United States); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Kirkpatrick, J. Davy [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States)

    2015-02-01

    We present spectroscopy, astrometry, and photometry of the brown dwarf WISEP J004701.06+680352.1 (W0047+68), an unusually red field L dwarf at a distance of 12.2 ± 0.4 pc. The three-dimensional space motion identifies it as a member of the AB Dor Moving Group, an identification supported by our classification of W0047+68 as intermediate surface gravity (INT-G) using the Allers and Liu near-infrared classification system. This moving group membership implies near-solar metallicity, age ∼100-125 Myr, M ≈ 0.018 M {sub ☉}, and log g ≈ 4.5; the thick condensate clouds needed to explain the infrared spectrum are, therefore, a result of surface gravity that is lower than that of ordinary field brown dwarfs. From the observed luminosity and evolutionary model radius, we find T {sub eff} ≈ 1300 K, a temperature normally associated with early T dwarfs. Thick clouds are also used to explain the spectral properties of directly imaged giant planets, and we discuss the successes and challenges for such substellar models in matching the observed optical and infrared spectra. W0047+68 shows that cloud thickness is more sensitive to intermediate surface gravity than in most models. We also present a trigonometric parallax of the dusty L6 dwarf 2MASS J21481628+4003593. It lies at 8.060 ± 0.036 parsecs; its astrometry is consistent with the view that it is older and metal-rich.

  13. DEEP NEAR-IR OBSERVATIONS OF THE GLOBULAR CLUSTER M4: HUNTING FOR BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Dieball, A. [Argelander Institut für Astronomie, Helmholtz Institut für Strahlen- und Kernphysik, University of Bonn (Germany); Bedin, L. R. [INAF-Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy); Knigge, C. [Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom); Rich, R. M. [Department of Physics and Astronomy, University of California at Los Angeles, Los Angeles, CA 90095-1562 (United States); Allard, F. [Centre de Recherche Astrophysique de Lyon, UMR 5574: CNRS, Université de Lyon, École Normale Supérieure de Lyon, 46 allée d’Italie, F-69364 Lyon Cedex 07 (France); Dotter, A. [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT (Australia); Richer, H. [Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, V6T 1Z1 (Canada); Zurek, D., E-mail: adieball@astro.uni-bonn.de [Department of Astrophysics, American Museum of Natural History, New York, NY 10024 (United States)

    2016-01-20

    We present an analysis of deep Hubble Space Telescope (HST)/Wide Field Camera 3 near-IR (NIR) imaging data of the globular cluster (GC) M4. The best-photometry NIR color–magnitude diagram (CMD) clearly shows the main sequence extending toward the expected end of the hydrogen-burning limit and going beyond this point toward fainter sources. The white dwarf (WD) sequence can be identified. As such, this is the deepest NIR CMD of a GC to date. Archival HST optical data were used for proper-motion cleaning of the CMD and for distinguishing the WDs from brown dwarf (BD) candidates. Detection limits in the NIR are around F110W ≈ 26.5 mag and F160W ≈ 27 mag, and in the optical around F775W ≈ 28 mag. Comparing our observed CMDs with theoretical models, we conclude that we have reached beyond the H-burning limit in our NIR CMD and are probably just above or around this limit in our optical–NIR CMDs. Thus, any faint NIR sources that have no optical counterpart are potential BD candidates, since the optical data are not deep enough to detect them. We visually inspected the positions of NIR sources that are fainter than the H-burning limit in F110W and for which the optical photometry did not return a counterpart. We found in total five sources for which we did not get an optical measurement. For four of these five sources, a faint optical counterpart could be visually identified, and an upper optical magnitude was estimated. Based on these upper optical magnitude limits, we conclude that one source is likely a WD, one source could be either a WD or BD candidate, and the remaining two sources agree with being BD candidates. No optical counterpart could be detected for just one source, which makes this source a good BD candidate. We conclude that we found in total four good BD candidates.

  14. Diagnostics of models and observations in the contexts of exoplanets, brown dwarfs, and very low-mass stars.

    Science.gov (United States)

    Kopytova, Taisiya

    2016-01-01

    When studying isolated brown dwarfs and directly imaged exoplanets with insignificant orbital motion,we have to rely on theoretical models to determine basic parameters such as mass, age, effective temperature, and surface gravity.While stellar and atmospheric models are rapidly evolving, we need a powerful tool to test and calibrate them.In my thesis, I focussed on comparing interior and atmospheric models with observational data, in the effort of taking into account various systematic effects that can significantly influence the data analysis.As a first step, about 460 candidate member os the Hyades were screened for companions using diffraction limited imaging observation (both our own data and archival data). As a result I could establish the single star sequence for the Hyades comprising about 250 stars (Kopytova et al. 2015, accepted to A&A). Open clusters contain many coeval objects of the same chemical composition and age, and spanning a range of masses. We compare the obtained sequence with a set of theoretical isochrones identifying systematic offsets and revealing probable issues in the models.However, there are many cases when it is impossible to test models before comparing them with observations.As a second step, we apply atmospheric models for constraining parameters of WISE 0855-07, the coolest known Y dwarf(Kopytova et al. 2014, ApJ 797, 3). We demonstrate the limits of constraining effective temperature and the presence/absence of water clouds.As a third step, we introduce a novel method to take into account the above-mentioned systematics. We construct a "systematics vector" that allows us to reveal problematic wavelength ranges when fitting atmospheric models to observed near-infrared spectraof brown dwarfs and exoplanets (Kopytova et al., in prep.). This approach plays a crucial role when retrieving abundances for these objects, in particularly, a C/O ratio. The latter parameter is an important key to formation scenarios of brown dwarf and

  15. A Sample of Very Young Field L Dwarfs and Implications for the Brown Dwarf "Lithium Test" at Early Ages

    CERN Document Server

    Kirkpatrick, J Davy; Barman, Travis S; Burgasser, Adam J; Looper, Dagny L; Tinney, C G; Gelino, Christopher R; Lowrance, Patrick J; Liebert, James; Carpenter, John M; Hillenbrand, Lynne A; Stauffer, John R

    2008-01-01

    Using a large sample of optical spectra of late-type dwarfs, we identify a subset of late-M through L field dwarfs that, because of the presence of low-gravity features in their spectra, are believed to be unusually young. From a combined sample of 303 field L dwarfs, we find observationally that 7.6+/-1.6% are younger than 100 Myr. This percentage is in agreement with theoretical predictions once observing biases are taken into account. We find that these young L dwarfs tend to fall in the southern hemisphere (Dec < 0 deg) and may be previously unrecognized, low-mass members of nearby, young associations like Tucana-Horologium, TW Hydrae, beta Pictoris, and AB Doradus. We use a homogeneously observed sample of roughly one hundred and fifty 6300-10000 Angstrom spectra of L and T dwarfs taken with the Low-Resolution Imaging Spectrometer at the W. M. Keck Observatory to examine the strength of the 6708-A Li I line as a function of spectral type and further corroborate the trends noted by Kirkpatrick et al. (...

  16. Spectral energy distribution simulations of a possible ring structure around the young, red brown dwarf G196-3B

    CERN Document Server

    Zakhozhay, Olga V; Béjar, Víctor J S; Boehler, Yann

    2016-01-01

    The origin of the very red optical and infrared colours of intermediate-age ($\\sim$10 - 500 Myr) L-type dwarfs remains unknown. It has been suggested that low-gravity atmospheres containing large amounts of dust may account for the observed reddish nature. We explored an alternative scenario by simulating protoplanetary and debris discs around G196-3B, which is an L3 young brown dwarf with a mass of $\\sim 15$ $M_{\\rm Jup}$ and an age in the interval 20 - 300 Myr. The best-fit solution to G196-3B's photometric spectral energy distribution from optical wavelengths through 24 $\\mu$m corresponds to the combination of an unreddened L3 atmosphere ($T_{\\rm eff} \\approx 1870$~K) and a warm ($\\approx$ 1280 K), narrow ($\\approx$ 0.07 - 0.11 R$_{\\odot}$) debris disc located at very close distances ($\\approx$ 0.12 - 0.20 R$_{\\odot}$) from the central brown dwarf. This putative, optically thick, dusty belt, whose presence is compatible with the relatively young system age, would have a mass $\\ge 7\\times 10^{-10}$ M$_{\\opl...

  17. CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System

    CERN Document Server

    Liu, Michael C; Dupuy, Trent J; Bowler, Brendan P; Albert, Loic; Artigau, Etienne; Reyle, Celine; Forveille, Thierry; Delfosse, Xavier

    2011-01-01

    (Abridged) We have identified CFBDSIR J1458+10 as a 0.11" binary using Keck laser guide star AO imaging. We measure a parallactic distance of 23.1+/-2.4 pc to the system based on CFHT near-IR astrometry. We assign a spectral type of T9.5 to the integrated-light near-IR spectrum, and model atmospheres suggest a slightly higher temperature and surface gravity than the T10 dwarf UGPS J0722-05. Thus, CFBDSIR J1458+10AB is the coolest brown dwarf binary to date. Its secondary component has an absolute H-band magnitude that is 1.9+/-0.3 mag fainter than UGPS J0722-05, giving an inferred spectral type of >T10. The secondary's bolometric luminosity of ~2 x 10^{-7} L_sun makes it the least luminous known brown dwarf by a factor of 4-5. By comparing to models and known T9-T10 objects, we estimate a temperature of 370+/-40 K and a mass of 6-15 Mjup for CFBDSIR J1458+10B. At such extremes, atmospheric models predict the onset of novel photospheric processes, namely the appearance of water clouds and the removal of strong...

  18. The Initial Mass Function of Low-Mass Stars and Brown Dwarfs in Young Clusters

    Science.gov (United States)

    Luhman, K. L.; Rieke, G. H.; Young, Erick T.; Cotera, Angela S.; Chen, H.; Rieke, Marcia J.; Schneider, Glenn; Thompson, Rodger I.

    2000-09-01

    We have obtained images of the Trapezium Cluster (140''×140'' 0.3 pc×0.3 pc) with the Hubble Space Telescope Near-Infrared Camera and Multi-Object Spectrometer (NICMOS). Combining these data with new ground-based K-band spectra (R=800) and existing spectral types and photometry, we have constructed an H-R diagram and used it and other arguments to infer masses and ages. To allow comparison with the results of our previous studies of IC 348 and ρ Oph, we first use the models of D'Antona & Mazzitelli. With these models, the distributions of ages of comparable samples of stars in the Trapezium, ρ Oph, and IC 348 indicate median ages of ~0.4 Myr for the first two regions and ~1-2 Myr for the latter. The low-mass initial mass functions (IMFs) in these sites of clustered star formation are similar over a wide range of stellar densities (ρ Oph, n=0.2-1×103 pc-3 IC 348, n=1×103 pc-3 Trapezium, n=1-5×104 pc-3) and other environmental conditions (e.g., presence or absence of OB stars). With current data, we cannot rule out modest variations in the substellar mass functions among these clusters. We then make the best estimate of the true form of the IMF in the Trapezium by using the evolutionary models of Baraffe et al. and an empirically adjusted temperature scale and compare this mass function to recent results for the Pleiades and the field. All of these data are consistent with an IMF that is flat or rises slowly from the substellar regime to about 0.6 Msolar and then rolls over into a power law that continues from about 1 Msolar to higher masses with a slope similar to or somewhat larger than the Salpeter value of 1.35. For the Trapezium, this behavior holds from our completeness limit of ~0.02 Msolar and probably, after a modest completeness correction, even from 0.01-0.02 Msolar. These data include ~50 likely brown dwarfs. We test the predictions of theories of the IMF against (1) the shape of the IMF, which is not log-normal, in clusters and the field, (2) the

  19. FURTHER DEFINING SPECTRAL TYPE 'Y' AND EXPLORING THE LOW-MASS END OF THE FIELD BROWN DWARF MASS FUNCTION

    Energy Technology Data Exchange (ETDEWEB)

    Davy Kirkpatrick, J.; Gelino, Christopher R.; Griffith, Roger L.; Marsh, Kenneth A. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C. [Department of Physics and Astronomy, MS 111, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606-3328 (United States); Mace, Gregory N.; Wright, Edward L.; McLean, Ian S. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Skrutskie, Michael F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Eisenhardt, Peter R.; Mainzer, Amanda K. [NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Burgasser, Adam J. [Department of Physics, University of California, San Diego, CA 92093 (United States); Tinney, C. G.; Parker, Stephen; Salter, Graeme, E-mail: davy@ipac.caltech.edu [Department of Astrophysics, School of Physics, University of New South Wales, NSW 2052 (Australia)

    2012-07-10

    We present the discovery of another seven Y dwarfs from the Wide-field Infrared Survey Explorer (WISE). Using these objects, as well as the first six WISE Y dwarf discoveries from Cushing et al., we further explore the transition between spectral types T and Y. We find that the T/Y boundary roughly coincides with the spot where the J - H colors of brown dwarfs, as predicted by models, turn back to the red. Moreover, we use preliminary trigonometric parallax measurements to show that the T/Y boundary may also correspond to the point at which the absolute H (1.6 {mu}m) and W2 (4.6 {mu}m) magnitudes plummet. We use these discoveries and their preliminary distances to place them in the larger context of the solar neighborhood. We present a table that updates the entire stellar and substellar constituency within 8 pc of the Sun, and we show that the current census has hydrogen-burning stars outnumbering brown dwarfs by roughly a factor of six. This factor will decrease with time as more brown dwarfs are identified within this volume, but unless there is a vast reservoir of cold brown dwarfs invisible to WISE, the final space density of brown dwarfs is still expected to fall well below that of stars. We also use these new Y dwarf discoveries, along with newly discovered T dwarfs from WISE, to investigate the field substellar mass function. We find that the overall space density of late-T and early-Y dwarfs matches that from simulations describing the mass function as a power law with slope -0.5 < {alpha} < 0.0; however, a power law may provide a poor fit to the observed object counts as a function of spectral type because there are tantalizing hints that the number of brown dwarfs continues to rise from late-T to early-Y. More detailed monitoring and characterization of these Y dwarfs, along with dedicated searches aimed at identifying more examples, are certainly required.

  20. An overlooked brown dwarf neighbour (T7.5 at d~5pc) of the Sun and two further T dwarfs at about 10pc

    CERN Document Server

    Bihain, Gabriel; Storm, Jesper; Schnurr, Olivier

    2013-01-01

    Although many new brown dwarf (BD) neighbours have been recently discovered thanks to new sky surveys in the mid- and near-infrared (MIR, NIR), their numbers are still more than five times lower than those of stars in the same volume. We aim at detecting and classifying new BDs to eventually complete their census in the immediate Solar neighbourhood. We combine multi-epoch data from sky surveys at different wavelengths to detect BD neighbours of the Sun by their high proper motion (HPM). We concentrate at relatively bright MIR (w2<13.5) BD candidates from WISE expected to be so close to the Sun that they may also be seen in older NIR (2MASS, DENIS) or even red optical (SDSS i- and z-band, SSS I-band) surveys. With low-resolution NIR spectroscopy we classify the new BDs and estimate their distances and velocities. We have discovered the HPM (pm~470mas/yr) T7.5 dwarf WISE J0521+1025 at d=5.0+-1.3pc from the Sun, and two early-T dwarfs WISE J0457-0207 (T2) and WISE J2030+0749 (T1.5) with proper motions of ~12...

  1. FIRST DETECTION OF THERMAL RADIOJETS IN A SAMPLE OF PROTO-BROWN DWARF CANDIDATES

    Energy Technology Data Exchange (ETDEWEB)

    Morata, Oscar [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 106, Taiwan (China); Palau, Aina; González, Ricardo F. [Centro de Radioastronomía y Astrofísica, Universidad Nacional Autónoma de México, P.O. Box 3-72, 58090 Morelia, Michoacán, México (Mexico); Gregorio-Monsalvo, Itziar de [Joint ALMA Observatory (JAO), Alonso de Córdova 3107, Vitacura, Santiago (Chile); Ribas, Álvaro [European Space Astronomy Centre (ESA), P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Perger, Manuel [Institut de Ciències de l’Espai (CSIC-IEEC), Campus UAB—Facultat de Ciències, Torre C5—parell 2, E-08193 Bellaterra, Catalunya (Spain); Bouy, Hervé; Barrado, David; Huélamo, Nuria; Morales-Calderón, María [Centro de Astrobiología, INTA-CSIC, Dpto.Astrofísica, ESAC Campus, P.O. Box 78, E-28691 Villanueva de la Cañada, Madrid (Spain); Eiroa, Carlos [Departamento de Física Teórica, Facultad de Ciencias, Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Bayo, Amelia, E-mail: omorata@asiaa.sinica.edu.tw [Max Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); and others

    2015-07-01

    We observed with the Jansky Very Large Array at 3.6 and 1.3 cm a sample of 11 proto-brown dwarf (BD) candidates in Taurus in a search for thermal radio jets driven by the most embedded BDs. We detected for the first time four thermal radio jets in proto-BD candidates. We compiled data from UKIDSS, 2MASS, Spitzer, WISE, and Herschel to build the spectral energy distribution (SED) of the objects in our sample, which are similar to typical Class I SEDs of young stellar objects (YSOs). The four proto-BD candidates driving thermal radio jets also roughly follow the well-known trend of centimeter luminosity against bolometric luminosity determined for YSOs, assuming they belong to Taurus, although they present some excess of radio emission compared to the known relation for YSOs. Nonetheless, we are able to reproduce the flux densities of the radio jets modeling the centimeter emission of the thermal radio jets using the same type of models applied to YSOs, but with corresponding smaller stellar wind velocities and mass-loss rates, and exploring different possible geometries of the wind or outflow from the star. Moreover, we also find that the modeled mass outflow rates for the bolometric luminosities of our objects agree reasonably well with the trends found between the mass outflow rates and bolometric luminosities of YSOs, which indicates that, despite the “excess” centimeter emission, the intrinsic properties of proto-BDs are consistent with a continuation of those of very low-mass stars to a lower mass range. Overall, our study favors the formation of BDs as a scaled-down version of low-mass stars.

  2. Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample

    Science.gov (United States)

    Borgniet, S.; Lagrange, A.-M.; Meunier, N.; Galland, F.

    2017-03-01

    Context. Massive, main-sequence (MS) AF-type stars have so far remained unexplored in past radial velocities (RV) surveys due to their small number of spectral lines and high rotational velocities that prevent the classic RV computation method. Aims: Our aim is to search for giant planets (GPs) around AF MS stars, to get primary statistical information on their occurrence rate and to compare the results with evolved stars and lower-mass MS stars. Methods: We used the HARPS spectrograph located on the 3.6 m telescope at ESO La Silla Observatory to observe 108 AF MS stars with B-V in the range -0.04 to 0.58 and masses in the range 1.1 to 3.6 M⊙. We used our SAFIR software developed to compute the RV and other spectroscopic observables of these early-type stars. We characterized the detected companions as well as the intrinsic stellar variability. We computed the detection limits and used them as well as the detected companions to derive the first estimates of the close-in brown dwarf (BD) and GP frequencies around AF stars. Results: We report the detection of a mpsini = 4.51MJup planetary companion with an 826-day period to the F6V dwarf HD 111998. We also present new data on the two-planet system around the F6IV-V dwarf HD 60532. We also report the detections of 14 binaries with long-term RV trends and/or high-amplitude RV variations combined to a flat RV-bisector span diagram. We constrain the minimal masses and semi-major axes of these companions and check that these constraints are compatible with the stellar companions previously detected by direct imaging or astrometry for six of these targets. We get detection limits deep into the planetary domain with 70% of our targets showing detection limits between 0.1 and 10 MJup at all orbital periods in the 1- to 103-day range. We derive BD (13 ≤mpsini ≤ 80 MJup) occurrence rates in the 1- to 103-day period range of 2-2+5% and 2.6-2.6+6.7% for stars with M⋆ in the ranges 1.1 to 1.5 and 1.5 to 3 M

  3. WISEP J060738.65+242953.4: A Nearby. Pole-On L8 Brown Dwarf with Radio Emission

    CERN Document Server

    Gizis, John E; Burgasser, Adam J; Libralato, Mattia; Nardiello, Domenico; Piotto, Giampaolo; Bedin, Luigi R; Berger, Edo; Paudel, Rishi

    2016-01-01

    We present a simultaneous, multi-wavelength campaign targeting the nearby (7.2 pc) L8/L9 (optical/near-infrared) dwarf WISEP J060738.65+242953.4 in the mid-infrared, radio, and optical. Spitzer Space Telescope observations show no variability at the 0.2% level over 10 hours each in the 3.6 and 4.5 micron bands. Kepler K2 monitoring over 36 days in Campaign 0 rules out stable periodic signals in the optical with amplitudes great than 1.5% and periods between 1.5 hours and 2 days. Non-simultaneous Gemini optical spectroscopy detects lithium, constraining this L dwarf to be less than ~2 Gyr old, but no Balmer emission is observed. The low measured projected rotation velocity (v sin i < 6 km/s) and lack of variability are very unusual compared to other brown dwarfs, and we argue that this substellar object is likely viewed pole-on. We detect quiescent (non-bursting) radio emission with the VLA. Amongst radio detected L and T dwarfs, it has the lowest observed L_nu and the lowest v sin i. We discuss the implica...

  4. A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself to be a Very Long Period, Highly Eccentric Spectroscopic Stellar Binary

    Science.gov (United States)

    Mack, Claude E., III; Ge, Jian; Deshpande, Rohit; Wisniewski, John P.; Stassun, Keivan G.; Gaudi, B. Scott; Fleming, Scott W.; Mahadevan, Suvrath; De Lee, Nathan; Eastman, Jason; Ghezzi, Luan; González Hernández, Jonay I.; Femenía, Bruno; Ferreira, Letícia; Porto de Mello, Gustavo; Crepp, Justin R.; Mata Sánchez, Daniel; Agol, Eric; Beatty, Thomas G.; Bizyaev, Dmitry; Brewington, Howard; Cargile, Phillip A.; da Costa, Luiz N.; Esposito, Massimiliano; Ebelke, Garret; Hebb, Leslie; Jiang, Peng; Kane, Stephen R.; Lee, Brian; Maia, Marcio A. G.; Malanushenko, Elena; Malanushenko, Victor; Oravetz, Daniel; Paegert, Martin; Pan, Kaike; Allende Prieto, Carlos; Pepper, Joshua; Rebolo, Rafael; Roy, Arpita; Santiago, Basílio X.; Schneider, Donald P.; Simmons, Audrey; Siverd, Robert J.; Snedden, Stephanie; Tofflemire, Benjamin M.

    2013-05-01

    We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R <~ 30, 000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin i ~ 50 M Jup) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e ~ 0.8), its relatively long period (P ~ 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (ω ~ 189°). As a result of these properties, for ~95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e ~ 0.3). Only during the ~5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of ~15 km s-1 reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.

  5. Multiple scattering polarization – Application of Chandrasekhar’s formalisms to the atmosphere of brown dwarfs and extrasolar planets

    Indian Academy of Sciences (India)

    Sujan Sengupta; Mark S Marley

    2011-07-01

    Chandrasekhar’s formalisms for the transfer of polarized radiation are used to explain the observed dust scattering polarization of brown dwarfs in the optical band. Model polarization profiles for hot and young directly imaged extrasolar planets are presented with specific prediction of the degree of polarization in the infrared. The model invokes Chandrasekhar’s formalism for the rotation-induced oblateness of the objects that gives rise to the necessary asymmetry for yielding net non-zero disk integrated linear polarization. The observed optical polarization constrains the surface gravity and could be a tool to estimate the mass of extrasolar planets.

  6. WISE Brown Dwarf Binaries: The Discovery of a T5+T5 and a T8.5+T9 System

    CERN Document Server

    Gelino, Christopher R; Cushing, Michael C; Eisenhardt, Peter R; Griffith, Roger L; Mainzer, Amanda K; Marsh, Kenneth A; Skrutskie, Michael F; Wright, Edward L

    2011-01-01

    The multiplicity properties of brown dwarfs are critical empirical constraints for formation theories, while multiples themselves provide unique opportunities to test evolutionary and atmospheric models and examine empirical trends. Studies using high-resolution imaging can not only uncover faint companions, but they can also be used to determine dynamical masses through long-term monitoring of binary systems. We have begun a search for the coolest brown dwarfs using preliminary processing of data from the Wide-field Infrared Survey Explorer (WISE) and have confirmed many of the candidates as late-type T dwarfs. In order to search for companions to these objects, we are conducting observations using the Laser Guide Star Adaptive Optics system on Keck II. Here we present the first results of that search, including a T5 binary with nearly equal mass components and a faint companion to a T8.5 dwarf with an estimated spectral type of T9.

  7. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations in a Young, Extremely Red L-type Brown Dwarf

    Science.gov (United States)

    Lew, Ben W. P.; Apai, Daniel; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J.; Karalidi, Theodora; Yang, Hao; Marley, Mark S.; Cowan, Nicolas B.; Bedin, Luigi R.; Metchev, Stanimir A.; Radigan, Jacqueline; Lowrance, Patrick J.

    2016-10-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs, but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here, we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-K s = 2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy, we find a best-fit rotational period (13.20 ± 0.14 hr) with a larger amplitude at 1.1 μm than at 1.7 μm. This is the third-largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentative trend between the wavelength dependence of relative amplitude, possibly proxy for small dust grains lofted in the upper atmosphere, and the likelihood of large-amplitude variability. By assuming forsterite as a haze particle, we successfully explain the wavelength-dependent amplitude with submicron-sized haze particle sizes of around 0.4 μm. W0047 links the earlier spectral and later spectral type brown dwarfs in which rotational modulations have been observed; the large amplitude variations in this object make this a benchmark brown dwarf for the study of cloud properties close to the L/T transition.

  8. Kelu-1 is a Binary L Dwarf: First Brown Dwarf Science from Laser Guide Star Adaptive Optics

    CERN Document Server

    Liu, M C; Liu, Michael C.; Leggett, Sandy K.

    2005-01-01

    (Abridged) We present near-IR imaging of the nearby L dwarf Kelu-1 obtained with the Keck sodium laser guide star adaptive optics (LGS AO) system as part of a high angular resolution survey for substellar binaries. Kelu-1 was one of the first free-floating L dwarfs identified, and the origin of its overluminosity compared to other similar objects has been a long-standing question. Our images clearly resolve Kelu-1 into a 0.29'' (5.4 AU) binary, and a previous non-detection by HST demonstrates that the system is a true physical pair. Binarity explains the properties of Kelu-1 that were previously noted to be anomalous compared to other early-L dwarfs. We estimate spectral types of L1.5-L3 and L3-L4.5 for the two components, giving model-derived masses of 0.05-0.07 Msun and 0.045-0.065 Msun for an estimated age of 0.3-0.8 Gyr. More distant companions are not detected to a limit of 5-9 Mjup. The presence of lithium absorption indicates that both components are substellar, but the weakness of this feature relativ...

  9. Classical T Tauri-like Outflow Activity in the Brown Dwarf Mass Regime

    Science.gov (United States)

    Whelan, E. T.; Ray, T. P.; Podio, L.; Bacciotti, F.; Randich, S.

    2009-12-01

    Over the last number of years, spectroscopic studies have strongly supported the assertion that protostellar accretion and outflow activity persist to the lowest masses. Indeed, previous to this work, the existence of three brown dwarf (BD) outflows had been confirmed by us. In this paper, we present the results of our latest investigation of BD outflow activity and report on the discovery of two new outflows. Observations to date have concentrated on studying the forbidden emission line (FEL) regions of young BDs and in all cases data have been collected using the UV-Visual Echelle Spectrometer (UVES) on the ESO Very Large Telescope. Offsets in the FEL regions are recovered using spectro-astrometry. Here, ISO-Oph 32 is shown to drive a blueshifted outflow with a radial velocity of 10-20 km s-1 and spectro-astrometric analysis constrains the position angle of this outflow to 240° ± 7°. The BD candidate, ISO-ChaI 217 is found to have a bipolar outflow bright in several key forbidden lines (VRAD = -20 km s-1, +40 km s-1) and with a P.A. of 193°-209°. A striking feature of the ISO-ChaI 217 outflow is the strong asymmetry between the red- and blueshifted lobes. This asymmetry is revealed in the relative brightness of the two lobes (redshifted lobe is brighter), the factor of 2 difference in radial velocity (the redshifted lobe is faster) and the difference in the electron density (again higher in the red lobe). Such asymmetries are common in jets from low-mass protostars and the observation of a marked asymmetry at such a low mass (Bacciotti & Eislöffel technique is used to study the ionization fraction, electron temperature, and total density. For LS-RCrA 1, ISO-ChaI 217 and ISO-Oph 102 \\dot{M}_out are measured to be in the range 10-10 to 10-9 M ⊙ yr-1 using a method based on the luminosity of the [O I]λ6300 and [S II]λ6731 lines. Mass loss rates for our sample of BD outflows are found to be comparable to the mass accretion rates. Overall, as our results

  10. A search for companions to brown dwarfs in the Taurus and Chamaeleon star-forming regions

    Energy Technology Data Exchange (ETDEWEB)

    Todorov, K. O.; Luhman, K. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Konopacky, Q. M. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); McLeod, K. K. [Whitin Observatory, Wellesley College, Wellesley, MA 02481 (United States); Apai, D.; Pascucci, I. [Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Ghez, A. M. [Division of Astronomy and Astrophysics, University of California, Los Angeles, CA 90095 (United States); Robberto, M., E-mail: todorovk@phys.ethz.ch [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-06-10

    We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ∼ 0.01-0.1 M {sub ☉}). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ∼ 10 Myr), we measure binary fractions of 14/93 = 0.15{sub −0.03}{sup +0.05} for M4-M6 (M ∼ 0.1-0.3 M {sub ☉}) and 4/108 = 0.04{sub −0.01}{sup +0.03} for >M6 (M ≲ 0.1 M {sub ☉}) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.

  11. Herschel/PACS view of disks around low-mass stars and brown dwarfs in the TW Hya association

    CERN Document Server

    Liu, Yao; Gong, Munan; Allers, Katelyn N; Brown, Joanna M; Kraus, Adam L; Liu, Michael C; Shkolnik, Evgenya L; van Dishoeck, Ewine F

    2014-01-01

    We conducted Herschel/PACS observations of five very low-mass stars or brown dwarfs located in the TW Hya association with the goal of characterizing the properties of disks in the low stellar mass regime. We detected all five targets at $70\\,\\mu{\\rm{m}}$ and $100\\,\\mu{\\rm{m}}$ and three targets at $160\\,\\mu{\\rm{m}}$. Our observations, combined with previous photometry from 2MASS, WISE, and SCUBA-2, enabled us to construct SEDs with extended wavelength coverage. Using sophisticated radiative transfer models, we analyzed the observed SEDs of the five detected objects with a hybrid fitting strategy that combines the model grids and the simulated annealing algorithm and evaluated the constraints on the disk properties via the Bayesian inference method. The modelling suggests that disks around low-mass stars and brown dwarfs are generally flatter than their higher mass counterparts, but the range of disk mass extends to well below the value found in T Tauri stars, and the disk scale heights are comparable in both...

  12. A Cautionary Tale: MARVELS Brown Dwarf Candidate Reveals Itself To Be A Very Long Period, Highly Eccentric Spectroscopic Stellar Binary

    CERN Document Server

    Mack, Claude E; Deshpande, Rohit; Wisniewski, John P; Stassun, Keivan G; Gaudi, B Scott; Fleming, Scott W; Mahadevan, Suvrath; De Lee, Nathan; Eastman, Jason; Ghezzi, Luan; Hernandez, Jonay I Gonzalez; Femenia, Bruno; Ferreira, Leticia; de Mello, Gustavo Porto; Crepp, Justin R; Sanchez, Daniel Mata; Agol, Eric; Beatty, Thomas G; Bizyaev, Dmitry; Brewington, Howard; Cargile, Phillip A; da Costa, Luiz N; Esposito, Massimiliano; Ebelke, Garret; Hebb, Leslie; Jiang, Peng; Kane, Stephen R; Lee, Brian; Maia, Marcio A G; Malanushenko, Elena; Malanushenko, Victor; Oravetz, Daniel; Paegert, Martin; Pan, Kaike; Prieto, Carlos Allende; Peper, Joshua; Rebolo, Rafael; Roy, Arpita; Santiago, Basilio X; Schneider, Donald P; Simmons, Audrey; Siverd, Robert J; Snedden, Stephanie; Tofflemire, Benjamin M

    2013-01-01

    We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R ~ <30,000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin(i)~50 M_Jup) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very low-mass companion: its large eccentricity (e~0.8), its relatively long period (P~238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight (omega~189 degrees). As a result of these properties, for ~95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding ...

  13. MARVELS-1b: A Short-Period, Brown Dwarf Desert Candidate from the SDSS-III MARVELS Planet Search

    CERN Document Server

    Lee, Brian L; Fleming, Scott W; Stassun, Keivan G; Gaudi, B Scott; Barnes, Rory; Mahadevan, Suvrath; Eastman, Jason D; Wright, Jason; Siverd, Robert J; Gary, Bruce; Ghezzi, Luan; Laws, Chris; Wisniewski, John P; de Mello, G F Porto; Ogando, Ricardo L C; Maia, Marcio A G; da Costa, Luiz Nicolaci; Sivarani, Thirupathi; Pepper, Joshua; Nguyen, Duy Cuong; Hebb, Leslie; De Lee, Nathan; Wang, Ji; Wan, Xiaoke; Zhao, Bo; Chang, Liang; Groot, John; Varosi, Frank; Hearty, Fred; Hanna, Kevin; van Eyken, J C; Kane, Stephen R; Agol, Eric; Bizyaev, Dmitry; Bochanski, John J; Brewington, Howard; Chen, Zhiping; Costello, Erin; Dou, Liming; Eisenstein, Daniel J; Fletcher, Adam; Ford, Eric B; Guo, Pengcheng; Holtzman, Jon A; Jiang, Peng; Leger, R French; Liu, Jian; Long, Daniel C; Malanushenko, Elena; Malanushenko, Viktor; Malik, Mohit; Oravetz, Daniel; Pan, Kaike; Rohan, Pais; Schneider, Donald P; Shelden, Alaina; Snedden, Stephanie A; Simmons, Audrey; Weaver, B A; Weinberg, David H; Xie, Ji-Wei

    2010-01-01

    We present a new short-period brown dwarf candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the third phase of the Sloan Digital Sky Survey (SDSS-III), and we designate the brown dwarf as MARVELS-1b. MARVELS uses the technique of dispersed fixed-delay interferometery to simultaneously obtain radial velocity measurements for 60 objects per field using a single, custom-built instrument that is fiber fed from the SDSS 2.5-m telescope. From our 20 radial velocity measurements spread over a ~370 d time baseline, we derive a Keplerian orbital fit with semi-amplitude K=2.533+/-0.025 km/s, period P=5.8953+/-0.0004 d, and eccentricity consistent with circular. Independent follow-up radial velocity data confirm the orbit. Adopting a mass of 1.37+/-0.11 M_Sun for the slightly evolved F9 host star, we infer that the companion has a minimum mass of 28.0+/-1.5 M_Jup, a semimajor axis 0....

  14. Young brown dwarfs at high cadence: Warm Spitzer time series monitoring of very low mass Sigma Orionis cluster members

    CERN Document Server

    Cody, Ann Marie

    2011-01-01

    The continuous temporal coverage and high photometric precision afforded by space observatories has opened up new opportunities for the study of variability processes in young stellar cluster members. Of particular interest is the phenomenon of deuterium-burning pulsation in brown dwarfs and very-low-mass stars, whose existence on 1-4 hours timescales has been proposed but not yet borne out by observations. To investigate short-timescale variability in young, low-mass objects, we carried out high-precision, high-cadence time series monitoring with the Warm Spitzer mission on 14 low mass stars and brown dwarfs in the ~3 Myr Sigma Orionis cluster. The flux in many of our raw light curves is strongly correlated with sub-pixel position and can vary systematically as much as 10%. We present a new approach to disentangle true stellar variability from this "pixel-phase effect," which is more pronounced in Warm Spitzer observations as compared to the cryogenic mission. The light curves after correction reveal that mo...

  15. $Extrasolar~Storms$: Pressure-dependent Changes In Light Curve Phase In Brown Dwarfs From Simultaneous $Hubble$ and $Spitzer$ Observations

    CERN Document Server

    Yang, Hao; Marley, Mark S; Karalidi, Theodora; Flateau, Davin; Showman, Adam P; Metchev, Stanimir; Buenzli, Esther; Radigan, Jacqueline; Artigau, Étienne; Lowrance, Patrick J; Burgasser, Adam J

    2016-01-01

    We present $Spitzer$/IRAC Ch1 and Ch2 monitoring of six brown dwarfs during 8 different epochs over the course of 20 months. For four brown dwarfs, we also obtained simulataneous $HST$/WFC3 G141 Grism spectra during two epochs and derived light curves in five narrow-band filters. Probing different pressure levels in the atmospheres, the multi-wavelength light curves of our six targets all exhibit variations, and the shape of the light curves evolves over the timescale of a rotation period, ranging from 1.4 h to 13 h. We compare the shapes of the light curves and estimate the phase shifts between the light curves observed at different wavelengths by comparing the phase of the primary Fourier components. We use state-of-the-art atmosphere models to determine the flux contribution of different pressure layers to the observed flux in each filter. We find that the light curves that probe higher pressures are similar and in phase, but are offset and often different from the light curves that probe lower pressures. ...

  16. Multi-Object and Long-Slit Spectroscopy of Very Low Mass Brown Dwarfs in Orion Nebular Cluster

    CERN Document Server

    Suenaga, Takuya; Kuzuhara, Masayuki; Yanagisawa, Kenshi; Ishii, Miki; Lucas, Philip W

    2013-01-01

    We present the results of a H- and K-band multi-object and long-slit spectroscopic survey of substellar mass candidates in the outer regions of the Orion Nebula Cluster. The spectra were obtained using MOIRCS on the 8.2-m Subaru telescope and ISLE on the 1.88-m telescope of Okayama Astronomical Observatory. Eight out of twelve spectra show strong water absorptions and we confirm that their effective temperatures are M6) from a chi-square fit to synthetic spectra. We plot our sources on an HR diagram overlaid with theoretical isochrones of low-mass objects and identify three new young brown dwarf candidates. One of the three new candidates is a cool object near the brown dwarf and planetary mass boundary. Based on our observations and those of previous studies, we determine the stellar (0.08 < M/Msun < 1) to substellar (0.03 < M/Msun < 0.08) mass number ratio in the outer regions of the Orion nebular cluster to be 3.5 +/- 0.8. In combination with the number ratio reported for the central region (3...

  17. Variable and polarized radio emission from the T6 brown dwarf WISEP J112254.73+255021.5

    CERN Document Server

    Williams, P K G; Berger, E

    2016-01-01

    Route & Wolszczan (2016) recently detected five radio bursts from the T6 dwarf WISEP J112254.73+255021.5 and used the timing of these events to propose that this object rotates with an ultra-short period of ~17.3 minutes. We conducted follow-up observations with the Very Large Array and Gemini-North but found no evidence for this periodicity. We do, however, observe variable, highly circularly polarized radio emission possibly with a period of 116 minutes, although our observation lasted only 162 minutes and so more data are needed to confirm it. Our proposed periodicity is typical of other radio-active ultracool dwarfs. The handedness of the circular polarization alternates with time and there is no evidence for any unpolarized emission component, the first time such a phenomenology has been observed in radio studies of very low-mass stars and brown dwarfs. We suggest that the object's magnetic dipole axis may be highly misaligned relative to its rotation axis.

  18. Kinematic Constraints on Evolutionary Scenarios for Blue Compact Dwarf Galaxies I. Neutral Gas Dynamics

    CERN Document Server

    Van Zee, L; Skillman, E D; Zee, Liese van; Salzer, John J.; Skillman, Evan D.

    2001-01-01

    We present the results of high spatial resolution HI synthesis observations of six blue compact dwarf (BCD) galaxies. Optically, the selected galaxies have smooth, symmetric isophotes, and thus are the most likely of the BCD class to fade into an object morphologically similar to a dwarf elliptical when the current starburst ends. The neutral gas in all six galaxies appears to be rotationally supported, however, indicating that true morphological transformation from a BCD to a dE will require significant loss of angular momentum. Based on the observed neutral gas dynamics of these and other BCDs, it is unlikely that present-day BCDs will evolve directly into dwarf ellipticals after a starburst phase. We discuss alternative evolutionary scenarios for BCDs and place them within the larger context of galaxy formation and evolution models.

  19. Cloud Atlas: Discovery of Patchy Clouds and High-amplitude Rotational Modulations In a Young, Extremely Red L-type Brown Dwarf

    CERN Document Server

    Lew, Ben W P; Zhou, Yifan; Schneider, Glenn; Burgasser, Adam J; Karalidi, Theodora; Yang, Hao; Marley, Mark S; Cowan, N B; Bedin,; R., L; Metchev, Stanimir A; Radigan, Jacqueline; Lowrance, Patrick J

    2016-01-01

    Condensate clouds fundamentally impact the atmospheric structure and spectra of exoplanets and brown dwarfs but the connections between surface gravity, cloud structure, dust in the upper atmosphere, and the red colors of some brown dwarfs remain poorly understood. Rotational modulations enable the study of different clouds in the same atmosphere, thereby providing a method to isolate the effects of clouds. Here we present the discovery of high peak-to-peak amplitude (8%) rotational modulations in a low-gravity, extremely red (J-Ks=2.55) L6 dwarf WISEP J004701.06+680352.1 (W0047). Using the Hubble Space Telescope (HST) time-resolved grism spectroscopy we find a best-fit rotational period (13.20$\\pm$0.14 hours) with a larger amplitude at 1.1 micron than at 1.7 micron. This is the third largest near-infrared variability amplitude measured in a brown dwarf, demonstrating that large-amplitude variations are not limited to the L/T transition but are present in some extremely red L-type dwarfs. We report a tentativ...

  20. The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

    CERN Document Server

    Bouchy, F; Díaz, R F; Forveille, T; Boisse, I; Arnold, L; Astudillo-Defru, N; Beuzit, J -L; Bonfils, X; Borgniet, S; Bourrier, V; Courcol, B; Delfosse, X; Demangeon, O; Delorme, P; Ehrenreich, D; Hébrard, G; Lagrange, A -M; Mayor, M; Montagnier, G; Moutou, C; Naef, D; Pepe, F; Perrier, C; Queloz, D; Rey, J; Sahlmann, J; Santerne, A; Santos, N C; Sivan, J -P; Udry, S; Wilson, P A

    2015-01-01

    Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-year radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of s...

  1. A CAUTIONARY TALE: MARVELS BROWN DWARF CANDIDATE REVEALS ITSELF TO BE A VERY LONG PERIOD, HIGHLY ECCENTRIC SPECTROSCOPIC STELLAR BINARY

    Energy Technology Data Exchange (ETDEWEB)

    Mack, Claude E. III; Stassun, Keivan G.; De Lee, Nathan [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Ge, Jian; Fleming, Scott W. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL, 32611-2055 (United States); Deshpande, Rohit; Mahadevan, Suvrath [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802 (United States); Wisniewski, John P. [Homer L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St, Norman, OK 73019 (United States); Gaudi, B. Scott; Eastman, Jason; Beatty, Thomas G. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Ghezzi, Luan [Observatorio Nacional, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Gonzalez Hernandez, Jonay I.; Femenia, Bruno; Mata Sanchez, Daniel [Instituto de Astrofisica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Ferreira, Leticia; Porto de Mello, Gustavo [Laboratorio Interinstitucional de e-Astronomia-LIneA, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Agol, Eric [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195 (United States); Bizyaev, Dmitry, E-mail: claude.e.mack@vanderbilt.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); and others

    2013-05-15

    We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R {approx}< 30, 000), this particular stellar binary mimics a single-lined binary with an RV signal that would be induced by a brown dwarf companion (Msin i {approx} 50 M{sub Jup}) to a solar-type primary. At least three properties of this system allow it to masquerade as a single star with a very-low-mass companion: its large eccentricity (e {approx} 0.8), its relatively long period (P {approx} 238 days), and the approximately perpendicular orientation of the semi-major axis with respect to the line of sight ({omega} {approx} 189 Degree-Sign ). As a result of these properties, for {approx}95% of the orbit the two sets of stellar spectral lines are completely blended, and the RV measurements based on centroiding on the apparently single-lined spectrum is very well fit by an orbit solution indicative of a brown dwarf companion on a more circular orbit (e {approx} 0.3). Only during the {approx}5% of the orbit near periastron passage does the true, double-lined nature and large RV amplitude of {approx}15 km s{sup -1} reveal itself. The discovery of this binary system is an important lesson for RV surveys searching for substellar companions; at a given resolution and observing cadence, a survey will be susceptible to these kinds of astrophysical false positives for a range of orbital parameters. Finally, for surveys like MARVELS that lack the resolution for a useful line bisector analysis, it is imperative to monitor the peak of the cross-correlation function for suspicious changes in width or shape, so that such false positives can be flagged during the candidate vetting process.

  2. A Pan-STARRS1 Proper-Motion Survey for Young Brown Dwarfs in the Taurus and the Upper Scorpius Star-Forming Regions

    Science.gov (United States)

    Zhang, Zhoujian; Liu, Michael C.; Best, William M. J.; Magnier, Eugene A.; Aller, Kimberly Mei

    2017-01-01

    Young brown dwarfs are of prime importance to investigate the universality of the initial mass function (IMF) and to understand the physical connections between substellar and planetary-mass objects. Pan-STARRS1 (PS1) 3π survey (δ ≥ -30○) is finished and has obtained stacked images reaching down to the planetary regime (≤ 13 MJup) in nearby star-forming regions, thus providing an innovative tool to search for brown dwarfs. Using photometry and astrometry from PS1, WISE, 2MASS and UKIDSS, we are performing the widest and deepest brown dwarf survey in Taurus (≈370 deg2, ˜1 Myr) and Upper Scorpius (USco, ≈450 deg2, ˜10 Myr), which are among the closest star-forming regions. Our work is the first to measure proper motions, a robust proxy of membership, for Taurus and USco brown dwarf candidates over such large area and long time baseline (˜13 yr by combining PS1 and 2MASS). Our spectroscopic follow-up has found the lowest-mass objects in both regions (Taurus: ≈ 6 MJup USco: ≈ 14 MJup), and has yielded a success rates of ≈ 80% and ≈ 90% in Taurus and USco, respectively, far better than any previous searches (≤ 50%). Our newly confirmed members have already added ≈ 60% more brown dwarfs in USco and more than doubled the number of L-type members (≤ 20 MJup) in both regions. Upon completion, our discoveries will be a significant addition to the substellar regimes of the Taurus and the USco IMF and will provide more benchmarks to investigate the compositions of substellar and planetary atmospheres.

  3. Chemical Abundances and Kinematics in Globular Clusters and Local Group Dwarf Galaxies and Their Implications for Formation Theories of the Galactic Halo

    CERN Document Server

    Geisler, Doug; Smith, Verne V; Casetti-Dinescu, Dana I

    2007-01-01

    We review Galactic halo formation theories and supporting evidence, in particular kinematics and detailed chemical abundances of stars in some relevant globular clusters as well as Local Group dwarf galaxies. Outer halo red HB clusters tend to have large eccentricities and inhabit the area populated by dwarf spheroidal stars, favoring an extraGalactic origin. Old globulars show the full range of eccentricities, while younger ones seem to have preferentially high eccentricities, again hinting at their extraGalactic origin. We compare detailed abundances of a variety of elements between the halo and all dwarf galaxies studied to date, including both dwarf spheroidals and irregulars. The salient feature is that halo abundances are essentially unique. In particular, the general alpha vs. [Fe/H] pattern of 12 of the 13 galaxies studied are similar to each other and very different from the Milky Way. Sagittarius appears to be the only possible exception. It appears very unlikely that a significant fraction of the m...

  4. Modeling the Cloudy Atmospheres of Cool Stars, Brown Dwarfs and Hot Exoplanets

    DEFF Research Database (Denmark)

    Juncher, Diana

    M-dwarfs are very attractive targets when searching for new exoplanets. Unfortunately, they are also very difficult to model since their temperatures are low enough for dust clouds to form in their atmospheres. Because the properties of an exoplanet cannot be determined without knowing...... of their clouds and found that their synthetic spectra fit the observed spectra of mid to late type M-dwarfs and early type L-dwarfs well. With additional development into even cooler regimes, they could be used to characterize the atmospheres of exoplanets and aid us in our search for the kind of chemical...... imbalances that suggest the presence of life. I have also directly performed spectroscopic and photometric observations of exoplanets to discover and/or improve our knowledge of their properties and to participate in the development of the techniques that is being used to discover and characterize exoplanets."...

  5. Ionisation in atmospheres of brown dwarfs and extrasolar planets VI: Properties of large-scale discharge events

    CERN Document Server

    Bailey, R L; Hodos, G; Bilger, C; Stark, C R

    2013-01-01

    Mineral clouds in substellar atmospheres play a special role as a catalyst for a variety of charge processes. If clouds are charged, the surrounding environment becomes electrically activated, and ensembles of charged grains are electrically discharging (e.g. by lightning), which significantly infuences the local chemistry creating conditions similar to those thought responsible for life in early planetary atmospheres. We note that such lightning discharges contribute also to the ionisation state of the atmosphere. We apply scaling laws for electrical discharge processes from laboratory measurements and numerical experiments to Drift-Phoenix model atmosphere results to model the discharge's propagation downwards (as lightning) and upwards (as sprites) through the atmospheric clouds. We evaluate the spatial extent and energetics of lightning discharges. The atmospheric volume affected (e.g. by increase of temperature or electron number) is larger in a brown dwarf atmosphere ($10^8 -~10^{10}$m$^3$) than in a gi...

  6. Tidal evolution of CoRoT massive planets and brown dwarfs and of their host stars

    CERN Document Server

    Ferraz-Mello, Sylvio

    2016-01-01

    Aims: Revisit and improvement of the main results obtained in the study of the tidal evolution of several massive CoRoT planets and brown dwarfs and of the rotation of their host stars. Methods: Simulations of the past and future evolution of the orbital and rotational elements of the systems under the joint action of the tidal torques and the braking due to the stellar wind. Results: Presentation of several paradigms and significant examples of tidal evolution in extrasolar planetary systems. It is shown that the high quality of the photometric and spectrographic observations of the CoRoT objects allow for a precise study of their past and future evolution and to estimate the tidal parameters ruling the dissipation in the systems.

  7. Emission line diagnostics for accretion and outflows in young very low-mass stars and brown dwarfs

    Directory of Open Access Journals (Sweden)

    Stelzer B.

    2014-01-01

    Full Text Available We discuss accretion and outflow properties of three very low-mass young stellar objects based on broad-band mid-resolution X-Shooter/VLT spectra. Our targets (FU Tau A, 2M1207-39, and Par-Lup3-4 have spectral types between M5 and M8, ages between 1Myr and ~ 10Myr, and are known to be accreting from previous studies. The final objective of our project is the determination of mass outflow to accretion rate for objects near or within the substellar regime as a probe for the T Tauri phase of brown dwarfs and the investigation of variability in the accretion and outflow processes.

  8. FIRST OPTICAL AND NEAR-INFRARED POLARIMETRY OF A MOLECULAR CLOUD FORMING A PROTO-BROWN DWARF CANDIDATE

    Energy Technology Data Exchange (ETDEWEB)

    Soam, A.; Maheswar, G. [Aryabhatta Research Institute of Observational Sciences (ARIES), Manora Peak, Nainital-263 002 (India); Kwon, Jugmi; Tamura, Motohide [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Lee, Chang Won, E-mail: archana@aries.res.in [Korea Astronomy and Space Science Institute (KASI), 776 Daedeokdae-ro, Yuseong-gu, Daejeon 305-348 (Korea, Republic of)

    2015-04-20

    LDN 328 is cited as an example of a fairly isolated clump contracting to form multiple sub-cores, possibly through gravitational fragmentation. In one of these sub-cores, a proto-brown dwarf (L328-IRS) candidate is in the process of formation through the self-gravitating contraction, similar to the formation scenario of a low-mass star. We present results of our optical and near-infrared polarization observations of regions toward LDN 328. This is the first observational attempt to map the magnetic field geometry of a cloud harboring a proto-brown dwarf candidate associated with a sub-parsec-scale molecular outflow. On a parsec scale, the magnetic field is found to follow the curved structure of the cloud showing a head–tail morphology. The magnetic field is found to be well ordered over a 0.02–0.2 pc scale around L328-IRS. Taking into account the uncertainties in the determination of position angles, the projected angular offset between the magnetic field direction and the outflow axis is found to be in the range of 0°–70°. Considering outflow to be the proxy for the rotation axis, the result obtained in this study implies that the rotation axis in L328 is preferably parallel to the local magnetic field. The magnetic field strength estimated in the close vicinity of L328-IRS is ∼20 μG. Results from the present study suggest that the magnetic field may be playing a vital role even in the cores that are forming sub-stellar sources.

  9. A Gemini/GMOS study of the physical conditions and kinematics of the blue compact dwarf galaxy Mrk 996

    CERN Document Server

    Telles, Eduardo; Izotov, Yuri I; Carrasco, Eleazar Rodrigo

    2013-01-01

    We present an integral field spectroscopic study with the Gemini Multi-Object Spectrograph (GMOS) of the unusual blue compact dwarf (BCD) galaxy Mrk 996. We show through velocity and dispersion maps, emission-line intensity and ratio maps, and by a new technique of electron density limit imaging that the ionization properties of different regions in Mrk 996 are correlated with their kinematic properties. From the maps, we can spatially distinguish a very dense high-ionization zone with broad lines in the nuclear region, and a less dense low-ionization zone with narrow lines in the circumnuclear region. Four kinematically distinct systems of lines are identified in the integrated spectrum of Mrk 996, suggesting stellar wind outflows from a population of Wolf-Rayet (WR) stars in the nuclear region, superposed on an underlying rotation pattern. From the intensities of the blue and red bumps, we derive a population of $\\sim$473 late nitrogen (WNL) stars and $\\sim$98 early carbon (WCE) stars in the nucleus of Mrk ...

  10. New Evidence for a Substellar Luminosity Problem: Dynamical Mass for the Brown Dwarf Binary Gl 417BC

    CERN Document Server

    Dupuy, Trent J; Ireland, Michael J

    2014-01-01

    We present new evidence for a problem with cooling rates predicted by substellar evolutionary models that implies model-derived masses in the literature for brown dwarfs and directly imaged planets may be too high. Based on our dynamical mass for Gl 417BC (L4.5+L6) and a gyrochronology system age from its young, solar-type host star, commonly used models predict luminosities 0.2$-$0.4 dex lower than we observe. This corroborates a similar luminosity$-$age discrepancy identified in our previous work on the L4+L4 binary HD 130948BC, which coincidentally has nearly identical component masses ($\\approx$50$-$55 $M_{\\rm Jup}$) and age ($\\approx$800 Myr) as Gl 417BC. Such a luminosity offset would cause systematic errors of 15%$-$25% in model-derived masses at this age. After comparing different models, including cloudless models that should not be appropriate for mid-L dwarfs like Gl 417BC and HD 130948BC but actually match their luminosities better, we speculate the observed over-luminosity could be caused by opac...

  11. Adaptive Optics imaging of VHS 1256-1257: A Low Mass Companion to a Brown Dwarf Binary System

    CERN Document Server

    Stone, Jordan M; Kratter, Kaitlin M; Dupuy, Trent J; Close, Laird M; Eisner, Josh A; Fortney, Jonathan J; Hinz, Philip M; Males, Jared R; Morley, Caroline V; Morzinski, Katie M; Ward-Duong, Kimberly

    2016-01-01

    Recently, Gauza et al. (2015) reported the discovery of a companion to the late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute photometry suggests its mass and atmosphere are similar to the HR 8799 planets. However, as a wide companion to a late-type star, it is more accessible to spectroscopic characterization. We discovered that the primary of this system is an equal-magnitude binary. For an age $\\sim300$ Myr the A and B components each have a mass of $64.6^{+0.8}_{-2.0}~M_{\\mathrm{Jup}}$, and the b component has a mass of $11.2^{+9.7}_{-1.8}$, making VHS 1256-1257 only the third brown dwarf triple system. There exists some tension between the spectrophotometric distance of $17.2\\pm2.6$ pc and the parallax distance of $12.7\\pm1.0$ pc. At 12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are even faint outliers among M8 types. If the larger spectrophotmetric distance is more accurate than the parallax, then the mass of each component increases. In particul...

  12. Astrophysics of brown dwarfs; Proceedings of the Workshop, George Mason University, Fairfax, VA, Oct. 14, 15, 1985

    Science.gov (United States)

    Kafatos, Minas C. (Editor); Harrington, Robert S. (Editor); Maran, Stephen P. (Editor)

    1986-01-01

    Various reports on theoretical and observational studies of brown dwarfs (BDs) are presented. The topics considered include: astrometric detection of BDs, search for substellar companions to nearby stars using IR imaging, constraints on BD mass function from optical and IR searches, properties of stellar objects near the main sequence mass limit, search for low-mass stellar companions with the HF precision velocity technique, dynamical search for substellar objects, search for BDs in the IRAS data base, deep CCD survey for low mass stars in the disk and halo, the Berkeley search for a faint solar companion, the luminosity function for late M stars, astronomic search for IR dwarfs, and the role of the Space Telescope in the detection of BDs. Also addressed are: theoretical significance of BDs, evolution of super-Jupiters, compositional indicators in IR spectra of BDs, evolution of BDs and the evolutionary status of VB8B, the position of BDs on universal diagrams, theoretical determination of the minimum protostellar mass, Population II BDs and dark halos.

  13. The properties of brown dwarfs and low-mass hydrogen-burning stars formed by disc fragmentation

    CERN Document Server

    Stamatellos, Dimitris

    2008-01-01

    We suggest that a high proportion of brown dwarfs are formed by gravitational fragmentation of massive extended discs around Sun-like stars. Such discs should arise frequently, but should be observed infrequently, precisely because they fragment rapidly. By performing an ensemble of radiation-hydrodynamic simulations, we show that such discs fragment within a few thousand years, and produce mainlybrown dwarf (BDs) stars, but also planetary mass (PM) stars and very low-mass hydrogen-burning (HB) stars. Most of the the PM stars and BDs are ejected by mutual interactions. We analyse the statistical properties of these stars, and compare them with observations. After a few hundred thousand years the Sun-like primary is typically left with a close low-mass HB companion, and two much wider companions: a low-mass HB star and a BD star, or a BD-BD binary. There is a BD desert extending out to at least ~100 AU; this is because BDs tend to be formed further out than low-mass HB stars, and then they tend to be scattered...

  14. First simultaneous microlensing observations by two space telescopes: $Spitzer$ & $Swift$ reveal a brown dwarf in event OGLE-2015-BLG-1319

    CERN Document Server

    Shvartzvald, Y; Udalski, A; Gould, A; Sumi, T; Street, R A; Novati, S Calchi; Hundertmark, M; Bozza, V; Beichman, C; Bryden, G; Carey, S; Drummond, J; Fausnaugh, M; Gaudi, B S; Henderson, C B; Tan, T G; Wibking, B; Pogge, R W; Yee, J C; Zhu, W; Tsapras, Y; Bachelet, E; Dominik, M; Bramich, D M; Cassan, A; Jaimes, R Figuera; Horne, K; Ranc, C; Schmidt, R; Snodgrass, C; Wambsganss, J; Steele, I A; Menzies, J; Mao, S; Poleski, R; Pawlak, M; Szymański, M K; Skowron, J; Mróz, P; Kozłowski, S; Wyrzykowski, Ł; Pietrukowicz, P; Soszyński, I; Ulaczyk, K; Abe, F; Asakura, Y; Barry, R K; Bennett, D P; Bhattacharya, A; Bond, I A; Freeman, M; Hirao, Y; Itow, Y; Koshimoto, N; Li, M C A; Ling, C H; Masuda, K; Fukui, A; Matsubara, Y; Muraki, Y; Nagakane, M; Nishioka, T; Ohnishi, K; Oyokawa, H; Rattenbury, N J; Saito, To; Sharan, A; Sullivan, D J; Suzuki, D; Tristram, P J; Yonehara, A; Jørgensen, U G; Burgdorf, M J; Ciceri, S; D'Ago, G; Evans, D F; Hinse, T C; Kains, N; Kerins, E; Korhonen, H; Mancini, L; Popovas, A; Rabus, M; Rahvar, S; Scarpetta, G; Skottfelt, J; Southworth, J; Peixinho, N; Verma, P; Sbarufatti, B; Kennea, J A; Gehrels, N

    2016-01-01

    Simultaneous observations of microlensing events from multiple locations allow for the breaking of degeneracies between the physical properties of the lensing system, specifically by exploring different regions of the lens plane and by directly measuring the "microlens parallax". We report the discovery of a 30-55$M_J$ brown dwarf orbiting a K dwarf in microlensing event OGLE-2015-BLG-1319. The system is located at a distance of $\\sim$5 kpc toward the Galactic bulge. The event was observed by several ground-based groups as well as by $Spitzer$ and $Swift$, allowing the measurement of the physical properties. However, the event is still subject to an 8-fold degeneracy, in particular the well-known close-wide degeneracy, and thus the projected separation between the two lens components is either $\\sim$0.25 AU or $\\sim$45 AU. This is the first microlensing event observed by $Swift$, with the UVOT camera. We study the region of microlensing parameter space to which $Swift$ is sensitive, finding that while for thi...

  15. Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown Dwarfs

    Science.gov (United States)

    Kirby, Kate; Babb, J.; Yoshino, K.

    2004-01-01

    In L-dwarfs and T-dwarfs the resonance lines of sodium and potassium are so profoundly pressure-broadened that their wings extend several hundred nanometers from line center. With accurate knowledge of the line profiles as a function of temperature and pressure: such lines can prove to be valuable diagnostics of the atmospheres of such objects. We have initiated a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Although potassium and sodium are the alkali species of most interest in the atmospheres of cool brown dwarfs and extrasolar giant planets, some of our theoretical focus this year has involved the calculation of pressure-broadening of lithium resonance lines by He, as a test of a newly developed suite of computer codes. In addition, theoretical calculations have been carried out to determine the leading long range van der Waals coefficients for the interactions of ground and excited alkali metal atoms with helium atoms, to within a probable error of 2%. Such data is important in determining the behavior of the resonance line profiles in the far wings. Important progress has been made on the experimental aspects of the program since the arrival of a postdoctoral fellow in September. A new absorption cell has been designed, which incorporates a number of technical improvements over the previous cell, including a larger cell diameter to enhance the signal, and fittings which allow for easier cleaning, thereby significantly reducing the instrument down-time.

  16. The rotation and Galactic kinematics of mid M dwarfs in the Solar Neighborhood

    CERN Document Server

    Newton, Elisabeth R; Charbonneau, David; Berta-Thompson, Zachory K; Dittmann, Jason A; West, Andrew A

    2015-01-01

    Rotation is a directly-observable stellar property, and drives magnetic field generation and activity through a magnetic dynamo. Main sequence stars with masses below approximately 0.35Msun (mid-to-late M dwarfs) are fully-convective, and are expected to have a different type of dynamo mechanism than solar-type stars. Measurements of their rotation rates provide insights into these mechanisms, but few rotation periods are available for these stars at field ages. Using photometry from the MEarth transit survey, we measure rotation periods for 391 nearby, mid-to-late M dwarfs in the Northern hemisphere, finding periods from 0.1 to 150 days. The typical detected rotator has stable, sinusoidal photometric modulations at a semi-amplitude of 0.5 to 1%. We find no period-amplitude relation for stars below 0.25Msun and an anti-correlation between period and amplitude for higher-mass M dwarfs. We highlight the existence of older, slowly-rotating stars without H{\\alpha} emission that nevertheless have strong photometri...

  17. Seventy six T dwarfs from the UKIDSS LAS: benchmarks, kinematics and an updated space density

    CERN Document Server

    Burningham, Ben; Smith, L; Leggett, S K; Smart, R L; Mann, A W; Dhital, S; Lucas, P W; Tinney, C G; Pinfield, D J; Zhang, Z; Morley, C; Saumon, D; Aller, K; Littlefair, S P; Homeier, D; Lodieu, N; Deacon, N; Marley, M S; van Spaandonk, L; Baker, D; Allard, F; Andrei, A H; Canty, J; Clarke, J; Day-Jones, A C; Dupuy, T; Fortney, J J; Gomes, J; Ishii, M; Jones, H R A; Liu, M; Magazzu, A; Marocco, F; Murray, D N; Rojas-Ayala, B; Tamura, M

    2013-01-01

    We report the discovery of 76 new T dwarfs from the UKIDSS Large Area Survey (LAS). Near-infrared broad and narrow-band photometry and spectroscopy are presented for the new objects, along with WISE and warm-Spitzer photometry. Proper motions for 128 UKIDSS T dwarfs are presented from a new two epoch LAS proper motion catalogue. We use these motions to identify two new benchmark systems: LHS 6176AB, a T8+M4 pair and HD118865AB, a T5.5+F8 pair. Using age constraints from the primaries and evolutionary models to constrain the radii we have estimated their physical properties from their bolometric luminosity. We compare the colours and properties of known benchmark T dwarfs to the latest model atmospheres and draw two principal conclusions. Firstly, it appears that the H - [4.5] and J - W2 colours are more sensitive to metallicity than has previously been recognised, such that differences in metallicity may dominate over differences in Teff when considering relative properties of cool objects using these colours...

  18. THE NEXT GENERATION VIRGO CLUSTER SURVEY. VI. THE KINEMATICS OF ULTRA-COMPACT DWARFS AND GLOBULAR CLUSTERS IN M87

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hong-Xin; Peng, Eric W.; Li, Biao [Department of Astronomy, Peking University, Beijing 100871 (China); Côté, Patrick; Ferrarese, Laura; Gwyn, Stephen D. J.; Blakeslee, John P. [National Research Council of Canada, Herzberg Astronomy and Astrophysics Program, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada); Liu, Chengze [Center for Astronomy and Astrophysics, Department of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240 (China); Cuillandre, Jean-Charles [Canada-France-Hawaii Telescope Corporation, Kamuela, HI 96743 (United States); Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Jordán, Andrés; Muñoz, Roberto P.; Puzia, Thomas H. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, Av. Vicuña Mackenna 4860, 7820436 Macul, Santiago (Chile); Lançon, Ariane [Observatoire astronomique de Strasbourg, Université de Strasbourg, CNRS, UMR 7550, 11 rue de l' Universite, F-67000 Strasbourg (France); Bekki, Kenji [School of Physics, University of New South Wales, Sydney 2052, NSW (Australia); Boselli, Alessandro [Aix Marseille Université, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Drinkwater, Michael J. [School of Mathematics and Physics, University of Queensland, Brisbane, QLD 4072 (Australia); Duc, Pierre-Alain, E-mail: hongxin@pku.edu.cn, E-mail: peng@pku.edu.cn [Laboratoire AIM Paris-Saclay, CNRS/INSU, Université Paris Diderot, CEA/IRFU/SAp, F-91191 Gif-sur-Yvette Cedex (France); and others

    2015-03-20

    The origin of ultra-compact dwarfs (UCDs; r{sub h} ≳ 10 pc)—objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies—has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme star clusters, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs and 911 GCs associated with the central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M {sub *} ≳ 2× 10{sup 6} M {sub ☉} and 92% are as blue as the classic blue GCs, nearly triple the confirmed sample of Virgo UCDs, providing by far the best opportunity for studying global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of blue GCs in the inner ∼70 kpc and as steep as that of red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than GCs, and blue GCs seem to have a velocity field that is more consistent with that of the surrounding dwarf ellipticals than with that of UCDs; (3) UCDs have an orbital anisotropy profile that is tangentially biased at radii ≲40 kpc and radially biased farther out, whereas blue GCs become more tangentially biased at larger radii beyond ∼40 kpc; (4) GCs with M {sub *} ≳ 2 × 10{sup 6} M {sub ☉} have rotational properties indistinguishable from the less massive ones, suggesting that it is the size, instead of mass, that differentiates UCDs from GCs as kinematically distinct populations. We conclude that most UCDs in M87 are not consistent with being merely the most luminous and extended examples of otherwise normal GCs. The radially biased orbital structure of UCDs at large radii is in general agreement with the 'tidally threshed dwarf galaxy' scenario.

  19. OGLE‐2008‐BLG‐510: first automated real‐time detection of a weak microlensing anomaly – brown dwarf or stellar binary?★

    DEFF Research Database (Denmark)

    Bozza, V.; Dominik, M.; Rattenbury, N. J.

    2012-01-01

    The microlensing event OGLE‐2008‐BLG‐510 is characterized by an evident asymmetric shape of the peak, promptly detected by the Automated Robotic Terrestrial Exoplanet Microlensing Search (ARTEMiS) system in real time. The skewness of the light curve appears to be compatible both with binary......‐lens and binary‐source models, including the possibility that the lens system consists of an M dwarf orbited by a brown dwarf. The detection of this microlensing anomaly and our analysis demonstrate that: (1) automated real‐time detection of weak microlensing anomalies with immediate feedback is feasible...

  20. Stellar Kinematics and Metallicities in the Ultra-faint Dwarf Galaxy Reticulum II

    Science.gov (United States)

    Simon, J. D.; Drlica-Wagner, A.; Li, T. S.; Nord, B.; Geha, M.; Bechtol, K.; Balbinot, E.; Buckley-Geer, E.; Lin, H.; Marshall, J.; Santiago, B.; Strigari, L.; Wang, M.; Wechsler, R. H.; Yanny, B.; Abbott, T.; Bauer, A. H.; Bernstein, G. M.; Bertin, E.; Brooks, D.; Burke, D. L.; Capozzi, D.; Carnero Rosell, A.; Carrasco Kind, M.; D'Andrea, C. B.; da Costa, L. N.; DePoy, D. L.; Desai, S.; Diehl, H. T.; Dodelson, S.; Cunha, C. E.; Estrada, J.; Evrard, A. E.; Fausti Neto, A.; Fernandez, E.; Finley, D. A.; Flaugher, B.; Frieman, J.; Gaztanaga, E.; Gerdes, D.; Gruen, D.; Gruendl, R. A.; Honscheid, K.; James, D.; Kent, S.; Kuehn, K.; Kuropatkin, N.; Lahav, O.; Maia, M. A. G.; March, M.; Martini, P.; Miller, C. J.; Miquel, R.; Ogando, R.; Romer, A. K.; Roodman, A.; Rykoff, E. S.; Sako, M.; Sanchez, E.; Schubnell, M.; Sevilla, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Swanson, M. E. C.; Tarle, G.; Thaler, J.; Tucker, D.; Vikram, V.; Walker, A. R.; Wester, W.; DES Collaboration

    2015-07-01

    We present Magellan/M2FS, Very Large Telescope/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8+/- 0.5 {km} {{{s}}}-1 and a velocity dispersion of 3.3+/- 0.7 {km} {{{s}}}-1. The mass-to-light ratio of Ret II within its half-light radius is 470+/- 210 {M}⊙ /{L}⊙ , demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 {km} {{{s}}}-1, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 ± 0.09 dex, and we identify several extremely metal-poor stars with {{[Fe/H]}}\\lt -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a mean metallicity of {{[Fe/H]}}=-2.65+/- 0.07, Ret II matches Segue 1 as the most metal-poor galaxy known. Although Ret II is the third-closest dwarf galaxy to the Milky Way, the line-of-sight integral of the dark matter density squared is {{log}}10(J)=18.8+/- 0.6 {GeV}{ }2 {{cm}}-5 within 0.°2, indicating that the predicted gamma-ray flux from dark matter annihilation in Ret II is lower than that of several other dwarf galaxies. Based on data obtained from the ESO Science Archive Facility under request number 157689.

  1. The Stellar and Gas Kinematics of the LITTLE THINGS Dwarf Irregular Galaxy NGC 1569

    CERN Document Server

    Johnson, Megan; Oh, Se-Heon; Zhang, Hong-Xin; Elmegreen, Bruce; Brinks, Elias; Tollerud, Erik; Herrmann, Kimberly

    2012-01-01

    In order to understand the formation and evolution of dIm galaxies, one needs to understand their three-dimensional structure. We present measurements of the stellar velocity dispersion in NGC 1569, a nearby post-starburst dIm galaxy. The stellar vertical velocity dispersion, $\\sigma_{\\rm z}$, coupled with the maximum rotational velocity derived from \\ion{H}{1} observations, $V_{\\rm max}$, gives a measure of how kinematically hot the galaxy is, and, therefore, indicates its structure. We conclude that the stars in NGC 1569 are in a thick disk with a $V_{\\rm max} / \\sigma_{\\rm z}$ = 2.4 $\\pm$ 0.7. In addition to the structure, we analyze the ionized gas kinematics from \\ion{O}{3} observations along the morphological major axis. These data show evidence for outflow from the inner starburst region and a potential expanding shell near supermassive star cluster (SSC) A. When compared to the stellar kinematics, the velocity dispersion of the stars increase in the region of SSC A supporting the hypothesis of an expa...

  2. Virgo Cluster and field dwarf ellipticals in 3D: I. On the variety of stellar kinematic and line-strength properties

    CERN Document Server

    Ryś, Agnieszka; van de Ven, Glenn

    2012-01-01

    We present the first large-scale stellar kinematic and line-strength maps for dwarf elliptical galaxies (9 in the Virgo Cluster and 3 in the field environment) obtained with the SAURON integral-field unit. No two galaxies in our sample are alike: we see that the level of rotation is not tied to flattening (we have, e.g. round rotators and flattened nonrotators); we observe kinematic twists in 1 Virgo and 1 field object; we discover large-scale kinematically-decoupled components in 2 field galaxies; we see varying gradients in line-strength maps, from nearly flat to strongly peaked in the center. The great variety of morphological, kinematic, and stellar population parameters seen in our data points to a formation scenario in which properties are shaped stochastically. A combined effect of ram-pressure stripping and galaxy harassment is the most probable explanation. We show the need for a comprehensive analysis of kinematic, dynamical, and stellar population properties which will enable us to place dwarf elli...

  3. Kinematic Properties and Dark Matter Fraction of Virgo Dwarf Early-Type Galaxies

    CERN Document Server

    Toloba, E; Peletier, R; Gorgas, J

    2012-01-01

    What happens to dwarf galaxies as they enter the cluster potential well is one of the main unknowns in studies of galaxy evolution. Several evidence suggests that late-type galaxies enter the cluster and are transformed to dwarf early-type galaxies (dEs). We study the Virgo cluster to understand which mechanisms are involved in this transformation. We find that the dEs in the outer parts of Virgo have rotation curves with shapes and amplitudes similar to late-type galaxies of the same luminosity. These dEs are rotationally supported, have disky isophotes, and younger ages than those dEs in the center of Virgo, which are pressure supported, often have boxy isophotes and are older. Ram pressure stripping, thus, explains the properties of the dEs located in the outskirts of Virgo. However, the dEs in the central cluster regions, which have lost their angular momentum, must have suffered a more violent transformation. A combination of ram pressure stripping and harassment is not enough to remove the rotation and ...

  4. Life at the Periphery of the Local Group: the kinematics of the Tucana Dwarf Galaxy

    CERN Document Server

    Fraternali, F; Irwin, M; Cole, A

    2009-01-01

    Dwarf spheroidal galaxies in the Local Group are usually located close to the Milky Way or M31. Currently, there are two clear exceptions to this rule, and the Tucana dwarf galaxy is the most distant at almost 1 Mpc from the Milky Way. Using the VLT/FORS2 spectrograph in multi-object mode we were able to measure the velocities of 23 individual Red Giant Branch stars in and around Tucana using the Ca triplet absorption lines. From this sample 17 reliable members have been identified. We measured the systemic velocity and dispersion of Tucana to be v_hel = +194.0+-4.3 km/s and sigma_l.o.s. = 15.8+4.1-3.1 km/s respectively. These measures are derived after removing the signature of rotation using a linear gradient of 6.5 x R/R_core+-2.9 km/s, which corresponds to a rotation of 16 km/s at the reliable limit of our data. Our systemic velocity corresponds to a receding velocity from the barycentre of the Local Group of v_LG = +73.3 km/s. We also determined the mean metallicity of Tucana to be [Fe/H] = -1.95+-0.15 w...

  5. Three new massive companions in the planet-brown dwarf boundary detected with SOPHIE

    Directory of Open Access Journals (Sweden)

    Santerne A.

    2011-02-01

    Full Text Available We report the detection of three new massive companions to mainsequence stars based on precise radial velocities obtained with the SOPHIE spectrograph, as part of an ongoing programme to search for extrasolar planets. The minimum masses of the detected companions range from around 16 Mjup to around 60 Mjup, and therefore lie at both sides of the boundary between massive extrasolar planets and brown dwarves.

  6. Willman 1 - a probable dwarf galaxy with an irregular kinematic distribution

    CERN Document Server

    Willman, Beth; Strader, Jay; Strigari, Louis E; Simon, Joshua D; Kirby, Evan; Warres, Alex

    2010-01-01

    We investigate the kinematic properties and stellar population of the Galactic satellite Willman 1 (Wil 1) by combining Keck/DEIMOS spectroscopy with KPNO mosaic camera imaging. Wil 1 is a nearby, ultra-low luminosity Milky Way companion. This object lies in a region of size-luminosity space (M_V ~ -2 mag, d ~ 38 kpc, r_half ~ 20 pc) also occupied by the Galactic satellites Bo\\"otes II and Segue 1 and 2, but no other known old stellar system. We use kinematic and color-magnitude criteria to identify 45 stars as possible members of Wil 1. With a systemic velocity of -12.8 +\\- 1.0 km/s, Wil 1 stars have velocities similar to those of foreground Milky Way stars. Informed by Monte-Carlo simulations, we identify 5 of the 45 candidate member stars as likely foreground contaminants, with a small number possibly remaining at faint apparent magnitudes. These contaminants could have mimicked a large velocity dispersion and an abundance spread in previous work. The significant spread in the [Fe/H] of the two brightest W...

  7. Extrasolar planets and brown dwarfs around AF-type stars. IX. The HARPS southern sample

    CERN Document Server

    Borgniet, Simon; Meunier, Nadège; Galland, Franck

    2016-01-01

    Massive, Main-Sequence AF-type stars have so far remained unexplored in past radial velocity surveys, due to their small number of spectral lines and their high rotational velocities that prevent the classic RV computation method. Our aim was to search for giant planets around AF MS stars, to get first statistical information on their occurrence rate and to compare the results with evolved stars and lower-mass MS stars. We used the HARPS spectrograph located on the 3.6m telescope at ESO La Silla Observatory to observe 108 AF MS stars with B-V in the -0.04 to 0.58 range and masses in the range 1.1-3.6 Msun. We used our SAFIR software specifically developed to compute the radial velocities of these early-type stars. We report the new detection of a mpsini = 4.51 Mjup companion with a ~826-day period to the F6V dwarf HD111998. We present new data on the 2-planet system around the F6IV-V dwarf HD60532. We also report the detection of 14 binaries with long-term RV trends. 70% of our targets show detection limits b...

  8. VERTICAL ATMOSPHERIC STRUCTURE IN A VARIABLE BROWN DWARF: PRESSURE-DEPENDENT PHASE SHIFTS IN SIMULTANEOUS HUBBLE SPACE TELESCOPE-SPITZER LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Buenzli, Esther; Apai, Daniel; Flateau, Davin [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Morley, Caroline V. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, Santa Cruz, CA 95060 (United States); Showman, Adam P.; Lewis, Nikole K. [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States); Burrows, Adam [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Marley, Mark S. [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Reid, I. Neill, E-mail: ebuenzli@email.arizona.edu [Space Telescope Science Institute, Baltimore, MD 21218 (United States)

    2012-12-01

    Heterogeneous clouds or temperature perturbations in rotating brown dwarfs produce variability in the observed flux. We report time-resolved simultaneous observations of the variable T6.5 brown dwarf 2MASS J22282889-431026 over the wavelength ranges 1.1-1.7 {mu}m and broadband 4.5 {mu}m. Spectroscopic observations were taken with Wide Field Camera 3 on board the Hubble Space Telescope and photometry with the Spitzer Space Telescope. The object shows sinusoidal infrared variability with a period of 1.4 hr at most wavelengths with peak-to-peak amplitudes between 1.45% and 5.3% of the mean flux. While the light curve shapes are similar at all wavelengths, their phases differ from wavelength to wavelength with a maximum difference of more than half of a rotational period. We compare the spectra with atmospheric models of different cloud prescriptions, from which we determine the pressure levels probed at different wavelengths. We find that the phase lag increases with decreasing pressure level, or higher altitude. We discuss a number of plausible scenarios that could cause this trend of light curve phase with probed pressure level. These observations are the first to probe heterogeneity in an ultracool atmosphere in both horizontal and vertical directions, and thus are an ideal test case for realistic three-dimensional simulations of the atmospheric structure with clouds in brown dwarfs and extrasolar planets.

  9. CLOUD STRUCTURE OF THE NEAREST BROWN DWARFS: SPECTROSCOPIC VARIABILITY OF LUHMAN 16AB FROM THE HUBBLE SPACE TELESCOPE

    Energy Technology Data Exchange (ETDEWEB)

    Buenzli, Esther [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Saumon, Didier [Los Alamos National Laboratory, Mail Stop F663, Los Alamos, NM 87545 (United States); Marley, Mark S. [NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States); Apai, Dániel [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Radigan, Jacqueline; Reid, I. Neill [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bedin, Luigi R. [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Morley, Caroline V., E-mail: buenzli@mpia.de [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2015-01-10

    The binary brown dwarf WISE J104915.57–531906.1 (also Luhman 16AB), composed of a late-L and early-T dwarf, is a prototypical L/T transition flux reversal binary located at a distance of only 2 pc. Luhman 16B is a known variable whose light curves evolve rapidly. We present a spatially resolved spectroscopic time-series of Luhman 16A and B covering 6.5 hr using the Hubble Space Telescope/WFC3 at 1.1-1.66 μm. The small, count-dependent variability of Luhman 16A at the beginning of the observations likely stems from instrumental systematics; Luhman 16A appears non-variable above ≈0.4%. Its spectrum is well fit by a single cloud layer with intermediate cloud thickness (f {sub sed} = 2, T {sub eff} = 1200 K). Luhman 16B varies at all wavelengths with peak-to-valley amplitudes of 7%-11%. The amplitude and light curve shape changes over only one rotation period. The lowest relative amplitude is found in the deep water absorption band at 1.4 μm, otherwise it mostly decreases gradually from the blue to the red edge of the spectrum. This is very similar to the other two known highly variable early-T dwarfs. A two-component cloud model accounts for most of the variability, although small deviations are seen in the water absorption band. We fit the mean spectrum and relative amplitudes with a linear combination of two models of a warm, thinner cloud (T {sub eff} = 1300 K, f {sub sed} = 3) and a cooler, thicker cloud (T {sub eff} = 1000-1100 K, f {sub sed} = 1), assuming out-of-equilibrium atmospheric chemistry. A model with parameters as for Luhman 16A except for the addition of cloud holes cannot reproduce the variability of Luhman 16B, indicating more complex cloud evolution through the L/T transition. The projected separation of the binary has decreased by ≈0.''3 in eight months.

  10. The spectroscopic study of M8.5-M9.5 stars and brown dwarfs

    Directory of Open Access Journals (Sweden)

    Pavlenko Y.V.

    2013-04-01

    Full Text Available We present high-resolution spectra analysis of the three late-M dwarfs LP944-20, SIPS J2045-6332 and DENIS-P J0021.0-4244. The stellar spectra were observed with Very Large Telescope/Ultraviolet–Visual Echelle Spectrograph (VLT/UVES in optical and near-infrared regions. The effective temperatures Teff and log g was defined by comparing observed and theoretical energy distributions for the investigated objects. Synthetic spectra were calculated for PHOENIX atmosphere models – COND and DUSTY, as well as for Semi-empirical atmosphere model. We discuss the influence of the effects associated with dust in stellar atmosphere on the energy distribution in the stellar spectra.

  11. Stellar Kinematics and Metallicities in the Ultra-Faint Dwarf Galaxy Reticulum II

    CERN Document Server

    Simon, J D; Li, T S; Nord, B; Geha, M; Bechtol, K; Balbinot, E; Buckley-Geer, E; Lin, H; Marshall, J; Santiago, B; Strigari, L; Wang, M; Wechsler, R H; Yanny, B; Abbott, T; Bauer, A H; Bernstein, G M; Bertin, E; Brooks, D; Burke, D L; Capozzi, D; Rosell, A Carnero; Kind, M Carrasco; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Dodelson, S; Cunha, C E; Estrada, J; Evrard, A E; Neto, A Fausti; Fernandez, E; Finley, D A; Flaugher, B; Frieman, J; Gaztanaga, E; Gerdes, D; Gruen, D; Gruendl, R A; Honscheid, K; James, D; Kuehn, K; Kuropatkin, N; Lahav, O; Maia, M A G; March, M; Martini, P; Miller, C J; Miquel, R; Ogando, R; Romer, A K; Roodman, A; Rykoff, E S; Sako, M; Sanchez, E; Schubnell, M; Sevilla, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thaler, J; Tucker, D; Vikram, V; Walker, A R; Wester, W

    2015-01-01

    We present Magellan/M2FS, VLT/GIRAFFE, and Gemini South/GMOS spectroscopy of the newly discovered Milky Way satellite Reticulum II. Based on the spectra of 25 Ret II member stars selected from Dark Energy Survey imaging, we measure a mean heliocentric velocity of 62.8 +/- 0.5 km/s and a velocity dispersion of 3.3 +/- 0.7 km/s. The mass-to-light ratio of Ret II within its half-light radius is 470 +/- 210 Msun/Lsun, demonstrating that it is a strongly dark matter-dominated system. Despite its spatial proximity to the Magellanic Clouds, the radial velocity of Ret II differs from that of the LMC and SMC by 199 and 83 km/s, respectively, suggesting that it is not gravitationally bound to the Magellanic system. The likely member stars of Ret II span 1.3 dex in metallicity, with a dispersion of 0.28 +/- 0.09 dex, and we identify several extremely metal-poor stars with [Fe/H] < -3. In combination with its luminosity, size, and ellipticity, these results confirm that Ret II is an ultra-faint dwarf galaxy. With a me...

  12. Spatially Resolved Observations of the Bipolar Optical Outflow from the Brown Dwarf 2MASSJ12073347-3932540

    CERN Document Server

    Whelan, Emma; Comeron, Fernando; Bacciotti, Francesca; Kavanagh, Patrick

    2012-01-01

    Studies of brown dwarf (BD) outflows provide information pertinent to questions on BD formation, as well as allowing outflow mechanisms to be investigated at the lowest masses. Here new observations of the bipolar outflow from the 24 M$_{JUP}$ BD, 2MASSJ12073347-3932540 are presented. The outflow was originally identified through the spectro-astrometric analysis of the [OI]$\\lambda$6300 emission line. Follow-up observations consisting of spectra and [SII], R-band and I-band images were obtained. The new spectra confirm the original results and are used to constrain the outflow PA at $\\sim$ 65$^{\\circ}$. The [OI]$\\lambda$6300 emission line region is spatially resolved and the outflow is detected in the [SII] images. The detection is firstly in the form of an elongation of the point spread function along the direction of the outflow PA. Four faint knot-like features (labelled {\\it A-D}) are also observed to the south-west of 2MASSJ12073347-3932540 along the same PA suggested by the spectra and the elongation in...

  13. Discovery of seven T Tauri stars and a brown dwarf candidate in the nearby TW Hydrae Association

    CERN Document Server

    Webb, R A; Platais, I; Patience, J; White, R J; Schwartz, M J; McCarthy, C

    1999-01-01

    We report the discovery of five T Tauri star systems, two of which are resolved binaries, in the vicinity of the nearest known region of recent star formation, the TW Hydrae Association. The newly discovered systems display the same signatures of youth (namely high X-ray flux, large Li abundance and strong chromospheric activity) and the same proper motion as the original five members. These similarities firmly establish the group as a bona fide T Tauri association, unique in its proximity to Earth and its complete isolation from any known molecular clouds. At an age of ~10 Myr and a distance of ~50 pc, the association members are excellent candidates for future studies of circumstellar disk dissipation and the formation of brown dwarfs and planets. Indeed, as an example, our speckle imaging revealed a faint, very likely companion 2" north of CoD-33 7795 (TWA 5). Its color and brightness suggest a spectral type ~M8.5 which, at an age of ~10^7 years, implies a mass ~20 M(Jupiter).

  14. NEPTUNE’S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES

    Science.gov (United States)

    Rowe, Jason F.; Gaulme, Patrick; Hammel, Heidi B.; Casewell, Sarah L.; Fortney, Jonathan J.; Gizis, John E.; Lissauer, Jack J.; Morales-Juberias, Raul; Orton, Glenn S.; Wong, Michael H.; Marley, Mark S.

    2017-01-01

    Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired nine months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune’s zonal wind profile, and confirms observed cloud feature variability. Although Neptune’s clouds vary in location and intensity on short and long timescales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extrasolar planet variability measurements. In particular we suggest that the balance between large, relatively stable, atmospheric features and smaller, more transient, clouds controls the character of substellar atmospheric variability. Atmospheres dominated by a few large spots may show inherently greater light curve stability than those which exhibit a greater number of smaller features. PMID:28127087

  15. Investigating the rotational evolution of very low-mass stars and brown dwarfs in young clusters using Monte Carlo simulations

    CERN Document Server

    Vasconcelos, M J

    2016-01-01

    Context. Very low-mass (VLM) stars and brown dwarfs (BDs) present a different rotational behaviour from their solar mass counter-parts. Aims. We investigate the rotational evolution of young VLM stars and BDs using Monte Carlo simulations under the hypothesis of disk locking and stellar angular momentum conservation. Methods. We built a set of objects with masses ranging from 0.01 Mo to 0.4 Mo and considered models with single- and double- peaked initial period distributions with and without disk locking. An object is considered to be diskless when its mass accretion rate is below a given threshold. Results. Models with initial single-peaked period distributions reproduce the observations well given that BDs rotate faster than VLM stars. We observe a correlation between rotational period and mass when we relax the disk locking hypothesis, but with a shallower slope compared to some observational results. The angular momentum evolution of diskless stars is flatter than it is for stars with a disk which occurs ...

  16. The number fraction of discs around brown dwarfs in Orion OB1a and the 25 Orionis group

    CERN Document Server

    Downes, Juan José; Ballesteros-Paredes, Javier; Mateu, Cecilia; Briceño, César; Hernández, Jesús; Petr-Gotzens, Monika G; Calvet, Nuria; Hartmann, Lee; Mauco, Karina

    2015-01-01

    We present a study of 15 new brown dwarfs belonging to the $\\sim7$ Myr old 25 Orionis group and Orion OB1a sub-association with spectral types between M6 and M9 and estimated masses between $\\sim0.07$M$_\\odot$ and $\\sim0.01$ M$_\\odot$. By comparing them through a Bayesian method with low mass stars ($0.8\\lesssim$ M/M$_\\odot\\lesssim0.1$) from previous works in the 25 Orionis group, we found statistically significant differences in the number fraction of classical T Tauri stars, weak T Tauri stars, class II, evolved discs and purely photospheric emitters at both sides of the sub-stellar mass limit. Particularly we found a fraction of $3.9^{+2.4}_{-1.6}~\\%$ low mass stars classified as CTTS and class II or evolved discs, against a fraction of $33.3^{+10.8}_{-9.8}~\\%$ in the sub-stellar mass domain. Our results support the suggested scenario in which the dissipation of discs is less efficient for decreasing mass of the central object.

  17. Search for very low-mass brown dwarfs and free-floating planetary-mass objects in Taurus

    CERN Document Server

    Quanz, Sascha P; Henning, Thomas; Brandner, Wolfgang; Burrows, Adam; Hofstetter, Lorne W

    2009-01-01

    The number of low-mass brown dwarfs and even free floating planetary mass objects in young nearby star-forming regions and associations is continuously increasing, offering the possibility to study the low-mass end of the IMF in greater detail. In this paper, we present six new candidates for (very) low-mass objects in the Taurus star-forming region one of which was recently discovered in parallel by Luhman et al. (2009). The underlying data we use is part of a new database from a deep near-infrared survey at the Calar Alto observatory. The survey is more than four magnitudes deeper than the 2MASS survey and covers currently ~1.5 square degree. Complementary optical photometry from SDSS were available for roughly 1.0 square degree. After selection of the candidates using different color indices, additional photometry from Spitzer/IRAC was included in the analysis. In greater detail we focus on two very faint objects for which we obtained J-band spectra. Based on comparison with reference spectra we derive a s...

  18. VizieR Online Data Catalog: The ELM survey. VII. 15 new ELM white dwarf cand. (Brown+, 2016)

    Science.gov (United States)

    Brown, W. R.; Gianninas, A.; Kilic, M.; Kenyon, S. J.; Allende Prieto, C.

    2016-05-01

    We present observations of 15 new extremely low-mass white dwarf (ELM WD) candidates. Ten objects are selected by color for our targeted spectroscopic ELM Survey program as described in Brown et al. (2012ApJ...744..142B). Five objects come from follow-up spectroscopy of the completed Hypervelocity Star survey. We acquire spectra for the 15 ELM WD candidates using the Blue Channel spectrograph on the 6.5m MMT telescope. We configured the Blue Channel spectrograph to obtain 3650-4500Å spectral coverage with 1.0Å spectral resolution. We acquire additional spectra for 5 objects using the KOSMOS spectrograph on the Kitt Peak National Observatory 4m Mayall telescope on program numbers 2014B-0119 and 2015A-0082. We configured the KOSMOS spectrograph to obtain 3500-6200Å spectral coverage with 2.0Å spectral resolution. We also acquire spectra for objects with g<17mag using the FAST spectrograph on the Fred Lawrence Whipple Observatory 1.5m Tillinghast telescope. We configured the FAST spectrograph to obtain 3500-5500Å spectral coverage with 1.7Å spectral resolution. (3 data files).

  19. IRAS 16253-2429: the First Proto-Brown Dwarf Binary Candidate Identified through Dynamics of Jets

    CERN Document Server

    Hsieh, Tien-Hao; Belloche, Arnaud; Wyrowski, Friedrich

    2016-01-01

    The formation mechanism of brown dwarfs (BDs) is one of the long-standing problems in star formation because the typical Jeans mass in molecular clouds is too large to form these substellar objects. To answer this question, it is crucial to study a BD at the embedded phase. IRAS 16253-2429 is classified as a very low luminosity object (VeLLO) with internal luminosity 0.1 Lsun. VeLLOs are believed to be very low-mass protostars or even proto-BDs. We observed the jet/outflow driven by IRAS 16253-2429 in CO (2-1), (6-5), and (7-6) using the IRAM 30 m and APEX telescopes and the SMA in order to study its dynamical features and physical properties. Our SMA map reveals two protostellar jets, indicating the existence of a proto-binary system as implied by the precessing jet detected in H2 emission. We detect a wiggling pattern in the position-velocity diagrams along the jet axes, which is likely due to the binary orbital motion. Based on this, we derive the current mass of the binary as ~0.032 Msun. Given the low en...

  20. Microlensing discovery of a tight, low-mass-ratio planetary-mass object around an old field brown dwarf

    Energy Technology Data Exchange (ETDEWEB)

    Han, C.; Jung, Y. K. [Department of Physics, Chungbuk National University, Cheongju 371-763 (Korea, Republic of); Udalski, A.; Szymański, M. K.; Kubiak, M.; Pietrzyński, G.; Soszyński, I.; Skowron, J.; Kozłowski, S.; Poleski, R.; Ulaczyk, K.; Wyrzykowski, Ł.; Pietrukowicz, P. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Sumi, T. [Department of Earth and Space Science, Osaka University, Osaka 560-0043 (Japan); Gaudi, B. S.; Gould, A. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Bennett, D. P. [University of Notre Dame, Department of Physics, 225 Nieuwland Science Hall, Notre Dame, IN 46556-5670 (United States); Tsapras, Y. [Las Cumbres Observatory Global Telescope Network, 6740B Cortona Dr, Goleta, CA 93117 (United States); Abe, F. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Bond, I. A. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Collaboration: OGLE Collaboration; MOA Collaboration; μFUN Collaboration; RoboNet Collaboration; and others

    2013-11-20

    Observations of accretion disks around young brown dwarfs (BDs) have led to the speculation that they may form planetary systems similar to normal stars. While there have been several detections of planetary-mass objects around BDs (2MASS 1207-3932 and 2MASS 0441-2301), these companions have relatively large mass ratios and projected separations, suggesting that they formed in a manner analogous to stellar binaries. We present the discovery of a planetary-mass object orbiting a field BD via gravitational microlensing, OGLE-2012-BLG-0358Lb. The system is a low secondary/primary mass ratio (0.080 ± 0.001), relatively tightly separated (∼0.87 AU) binary composed of a planetary-mass object with 1.9 ± 0.2 Jupiter masses orbiting a BD with a mass 0.022 M {sub ☉}. The relatively small mass ratio and separation suggest that the companion may have formed in a protoplanetary disk around the BD host in a manner analogous to planets.

  1. Brown dwarfs and very low mass stars in the Praesepe open cluster: a dynamically unevolved mass function?

    CERN Document Server

    Boudreault, S; Goldman, B; Henning, T; Caballero, J A

    2009-01-01

    [Abridged] In this paper, we present the results of a photometric survey to identify low mass and brown dwarf members of the old open cluster Praesepe (age of 590[+150][-120]Myr and distance of 190[+6.0][-5.8]pc) and use this to infer its mass function which we compare with that of other clusters. We have performed an optical (Ic-band) and near-infrared (J and Ks-band) photometric survey of Praesepe with a spatial coverage of 3.1deg^2. With 5sigma detection limits of Ic=23.4 and J=20.0, our survey is sensitive to objects with masses from about 0.6 to 0.05Msol. The mass function of Praesepe rises from 0.6Msol down to 0.1Msol and then turns-over at ~0.1Msol. The rise observed is in agreement with the mass function derived by previous studies, including a survey based on proper motion and photometry. Comparing our mass function with that for another open cluster with a similar age, the Hyades (age ~ 600Myr), we see a significant difference. Possible reasons are that dynamical evaporation has not influenced the H...

  2. Treatment of overlapping gaseous absorption with the correlated-k method in hot Jupiter and brown dwarf atmosphere models

    CERN Document Server

    Amundsen, David S; Manners, James; Baraffe, Isabelle; Mayne, Nathan J

    2016-01-01

    The correlated-k method is frequently used to speed up radiation calculations in both one-dimensional and three-dimensional atmosphere models. An inherent difficulty with this method is how to treat overlapping absorption, i.e. absorption by more than one gas in a given spectral region. We have evaluated the applicability of three different methods in hot Jupiter and brown dwarf atmosphere models, all of which have been previously applied within models in the literature: (i) Random overlap, both with and without resorting and rebinning, (ii) equivalent extinction and (iii) pre-mixing of opacities, where (i) and (ii) combine k-coefficients for different gases to obtain k-coefficients for a mixture of gases, while (iii) calculates k-coefficients for a given mixture from the corresponding mixed line-by-line opacities. We find that the random overlap method is the most accurate and flexible of these treatments, and is fast enough to be used in one-dimensional models with resorting and rebinning. In three-dimensio...

  3. The theory of globulettes: candidate precursors of brown dwarfs and free floating planets in H II regions

    CERN Document Server

    Haworth, Thomas J; Clarke, Cathie J

    2014-01-01

    Large numbers of small opaque dust clouds - termed 'globulettes' by Gahm et al - have been observed in the H II regions surrounding young stellar clusters. With masses typically in the planetary (or low mass brown dwarf) regime, these objects are so numerous in some regions (e.g. the Rosette) that, if only a small fraction of them could ultimately collapse, then they would be a very significant source of free floating planets. Here we review the properties of globulettes and present a theoretical framework for their structure and evolution. We demonstrate that their interior structure is well described by a pressure confined isothermal Bonnor-Ebert sphere and that the observed mass-radius relation (mass approximately proportional to the radius squared) is a systematic consequence of a column density threshold below which components of the globulette are not identified. We also find that globulettes with this interior structure are very stable against collapse within H II regions. We follow Gahm et al in assum...

  4. Microlens Terrestrial Parallax Mass Measurements: A Rare Probe of Isolated Brown Dwarfs and Free-Floating Planets

    CERN Document Server

    Gould, Andrew

    2012-01-01

    Terrestrial microlens parallax is one of the very few methods that can measure the mass and number density of isolated dark low-mass objects, such as old free-floating planets and brown dwarfs. Terrestrial microlens parallax can be measured whenever a microlensing event differs substantially as observed from two or more well-separated sites. If the lens also transits the source during the event, then its mass can be measured. We derive an analytic expression for the expected rate of such events and then use this to derive two important conclusions. First the rate is directly proportional to the number density of a given population, greatly favoring low-mass populations relative to their contribution to the general microlensing rate, which further scales as sqrt{M} where M is the lens mass. Second, the rate rises sharply as one probes smaller source stars, despite the fact that the probability of transit falls directly with source size. We propose modifications to current observing strategies that could yield ...

  5. The large-scale disk fraction of brown dwarfs in the Taurus cloud as measured with Spitzer

    CERN Document Server

    Monin, J -L; Pinte, C; Rebull, L; Goldsmith, P; Fukagawa, M; Ménard, F; Padgett, D; Stappelfeld, K; McCabe, C; Carey, S; Noriega-Crespo, A; Brooke, T; Huard, T; Terebey, S; Hillenbrand, L; Guedel, M

    2010-01-01

    Aims. The brown dwarf (BD) formation process has not yet been completely understood. To shed more light on the differences and similarities between star and BD formation processes, we study and compare the disk fraction among both kinds of objects over a large angular region in the Taurus cloud. In addition, we examine the spatial distribution of stars and BD relative to the underlying molecular gas Methods. In this paper, we present new and updated photometry data from the Infrared Array Camera (IRAC) aboard the Spitzer Space Telescope on 43 BDs in the Taurus cloud, and recalculate of the BD disk fraction in this region. We also useed recently available CO mm data to study the spatial distribution of stars and BDs relative to the cloud's molecular gas. Results. We find that the disk fraction among BDs in the Taurus cloud is 41 \\pm 12%, a value statistically consistent with the one among TTS (58 \\pm 9%). We find that BDs in transition from a state where they have a disk to a diskless state are rare, and we st...

  6. Deuterium Burning in Massive Giant Planets and Low-Mass Brown Dwarfs formed by Core-Nucleated Accretion

    CERN Document Server

    Bodenheimer, Peter; Lissauer, Jack J; Fortney, Jonathan J; Saumon, Didier

    2013-01-01

    Formation of bodies near the deuterium-burning limit is considered by detailed numerical simulations according to the core-nucleated giant planet accretion scenario. The objects, with heavy-element cores in the range 5-30 Mearth, are assumed to accrete gas up to final masses of 10-15 Jupiter masses (Mjup). After the formation process, which lasts 1-5 Myr and which ends with a 'cold-start', low-entropy configuration, the bodies evolve at constant mass up to an age of several Gyr. Deuterium burning via proton capture is included in the calculation, and we determined the mass, M50, above which more than 50% of the initial deuterium is burned. This often-quoted borderline between giant planets and brown dwarfs is found to depend only slightly on parameters, such as core mass, stellar mass, formation location, solid surface density in the protoplanetary disk, disk viscosity, and dust opacity. The values for M50 fall in the range 11.6-13.6 Mjup, in agreement with previous determinations that do not take the formati...

  7. Astrometric follow-up observations of directly imaged sub-stellar companions to young stars and brown dwarfs

    CERN Document Server

    Ginski, C; Mugrauer, M; Neuhäuser, R; Vogt, N; Errmann, R; Berndt, A

    2014-01-01

    The formation of massive planetary or brown dwarf companions at large projected separations from their host star is not yet well understood. In order to put constraints on formation scenarios we search for signatures in the orbit dynamics of the systems. We are specifically interested in the eccentricities and inclinations since those parameters might tell us about the dynamic history of the systems and where to look for additional low-mass sub-stellar companions. For this purpose we utilized VLT/NACO to take several well calibrated high resolution images of 6 target systems and analyze them together with available literature data points of those systems as well as Hubble Space Telescope archival data. We used a statistical Least-Squares Monte-Carlo approach to constrain the orbit elements of all systems that showed significant differential motion of the primary star and companion. We show for the first time that the GQ Lup system shows significant change in both separation and position angle. Our analysis yi...

  8. Physical Properties of Young Brown Dwarfs and Very Low-Mass Stars Inferred from High-Resolution Model Spectra

    CERN Document Server

    Rice, Emily L; McLean, Ian S; Prato, L; Kirkpatrick, J Davy

    2009-01-01

    By comparing near-infrared spectra with atmosphere models, we infer the effective temperature, surface gravity, projected rotational velocity, and radial velocity for 21 very-low-mass stars and brown dwarfs. The unique sample consists of two sequences in spectral type from M6-M9, one of 5-10 Myr objects and one of >1 Gyr field objects. A third sequence is comprised of only ~M6 objects with ages ranging from 1 Gyr. Spectra were obtained in the J band at medium (R~2,000) and high (R~20,000) resolutions with NIRSPEC on the Keck II telescope. Synthetic spectra were generated from atmospheric structures calculated with the PHOENIX model atmosphere code. Using multi-dimensional least-squares fitting and Monte Carlo routines we determine the best-fit model parameters for each observed spectrum and note which spectral regions provide consistent results. We identify successes in the reproduction of observed features by atmospheric models, including pressure-broadened KI lines, and investigate deficiencies in the model...

  9. HST ROTATIONAL SPECTRAL MAPPING OF TWO L-TYPE BROWN DWARFS: VARIABILITY IN AND OUT OF WATER BANDS INDICATES HIGH-ALTITUDE HAZE LAYERS

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Hao; Apai, Dániel; Karalidi, Theodora [Department of Astronomy, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Marley, Mark S. [NASA Ames Research Center, Naval Air Station, Moffett Field, Mountain View, CA 94035 (United States); Saumon, Didier [Los Alamos National Lab, Los Alamos, NM 87545 (United States); Morley, Caroline V. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Buenzli, Esther [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Artigau, Étienne [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada); Radigan, Jacqueline [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Metchev, Stanimir [Department of Physics and Astronomy, Western University, 1151 Richmond Street, London, ON N6A 3K7 (Canada); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Mohanty, Subhanjoy [Imperial College London, 1010 Blackett Lab, Prince Consort Road, London SW7 2AZ (United Kingdom); Lowrance, Patrick J. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Showman, Adam P.; Flateau, Davin [Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Heinze, Aren N., E-mail: haoyang@email.arizona.edu [Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794-3800 (United States)

    2015-01-01

    We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759–1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 μm and 1.7 μm. We find that the water absorption bands of the two L5 dwarfs at 1.15 μm and 1.4 μm vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 μm displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs. We utilize the models of Saumon and Marley and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altitude haze layers above the condensate clouds. Therefore, our observations show that the heterogeneity of haze layers—the driver of the variability—must be located at very low pressures, where even the water opacity is negligible. In the near future, the rotational spectral mapping technique could be utilized for other atomic and molecular species to probe different pressure levels in the atmospheres of brown dwarfs and exoplanets and uncover both horizontal and vertical cloud structures.

  10. Quenching of Carbon Monoxide and Methane in the Atmospheres of Cool Brown Dwarfs and Hot Jupiters

    CERN Document Server

    Visscher, Channon

    2011-01-01

    We explore CO-CH4 quench kinetics in the atmospheres of substellar objects using updated time-scale arguments, as suggested by a thermochemical kinetics and diffusion model that transitions from the thermochemical-equilibrium regime in the deep atmosphere to a quench-chemical regime at higher altitudes. More specifically, we examine CO quench chemistry on the T dwarf Gliese 229B and CH4 quench chemistry on the hot-Jupiter HD 189733b. We describe a method for correctly calculating reverse rate coefficients for chemical reactions, discuss the predominant pathways for CO-CH4 interconversion as indicated by the model, and demonstrate that a simple time-scale approach can be used to accurately describe the behavior of quenched species when updated reaction kinetics and mixing-length-scale assumptions are used. Proper treatment of quench kinetics has important implications for estimates of molecular abundances and/or vertical mixing rates in the atmospheres of substellar objects. Our model results indicate signific...

  11. Dancing in the Dark: New Brown Dwarf Binaries from Kernel Phase Interferometry

    CERN Document Server

    Pope, Benjamin; Tuthill, Peter

    2013-01-01

    This paper revisits a sample of ultracool dwarfs in the Solar neighborhood previously observed with the Hubble Space Telescope's NICMOS NIC1 instrument. We have applied a novel high angular resolution data analysis technique based on the extraction and fitting of kernel phases to archival data. This was found to deliver a dramatic improvement over earlier analysis methods, permitting a search for companions down to projected separations of $\\sim$1 AU on NIC1 snapshot images. We reveal five new close binary candidates and present revised astrometry on previously-known binaries, all of which were recovered with the technique. The new candidate binaries have sufficiently close separation to determine dynamical masses in a short-term observing campaign. We also present four marginal detections of objects which may be very close binaries or high contrast companions. Including only confident detections within 19 parsecs, we report a binary fraction of at least $\\epsilon_b = 17.2^{+5.7}_{-3.7}%$. The results reporte...

  12. The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits: II- Survey description, results and performances

    CERN Document Server

    Chauvin, G; Bonnefoy, M; Desidera, S; Bonavita, M; Mesa, D; Boccaletti, A; Buenzli, E; Carson, J; Delorme, P; Hagelberg, J; Montagnier, G; Mordasini, C; Quanz, S P; Segransan, D; Thalmann, C; Beuzit, J -L; Biller, B; Covino, E; Feldt, M; Girard, J; Gratton, R; Henning, T; Kasper, M; Lagrange, A -M; Messina, S; Meyer, M; Mouillet, D; Moutou, C; Reggianni, M; Schlieder, J E; Zurlo, A

    2014-01-01

    In anticipation of the VLT/SPHERE planet imager guaranteed time programs, we have conducted a preparatory survey of 86 stars between 2009 and 2013 in order to identify new faint comoving companions to ultimately carry out a comprehensive analysis of the occurence of giant planets and brown dwarf companions at wide (10-2000 AU) orbits around young, solar-type stars. We used NaCo at VLT to explore the occurrence rate of giant planets and brown dwarfs between typically 0.1 and 8''. Diffraction-limited observations in H-band combined with angular differential imaging enabled us to reach primary star-companion brightness ratios as small as 10-6 at 1.5''. 12 systems were resolved as new binaries, including the discovery of a new white dwarf companion to the star HD8049. Around 34 stars, at least one companion candidate was detected in the observed field of view. More than 400 faint sources were detected, 90% of them in 4 crowded fields. With the exception of HD8049B, we did not identify any new comoving companions....

  13. Extended Magnetospheres in Pre-main-sequence Evolution: From T Tauri Stars to the Brown Dwarf Limit

    Science.gov (United States)

    Gómez de Castro, Ana I.; Marcos-Arenal, Pablo

    2012-04-01

    extended and dense stellar magnetosphere directly driven by local collisional processes. The brown dwarf 2MASS J12073346-3332539 has been found to follow the same flux-flux relations of the TTSs. Thus, TTS-normalized flux scaling laws seem to be extendable to the brown dwarf limit and can be used for identification/diagnosis purposes. We report the discovery of an inverse correlation between the C IV-normalized flux and the magnetospheric radius derived for stars with known magnetic fields. The normalized C IV flux is found to be vpropexp (- αr mag), with α = 0.5-0.7.

  14. A search for pre- and proto-brown dwarfs in the dark cloud Barnard 30 with ALMA

    Science.gov (United States)

    Huélamo, N.; de Gregorio-Monsalvo, I.; Palau, A.; Barrado, D.; Bayo, A.; Ruiz, M. T.; Zapata, L.; Bouy, H.; Morata, O.; Morales-Calderón, M.; Eiroa, C.; Ménard, F.

    2017-01-01

    Context. The origin of brown dwarfs is still under debate. While some models predict a star-like formation scenario, others invoke a substellar mass embryo ejection, a stellar disk fragmentation, or the photo-evaporation of an external core due to the presence of massive stars. Aims: The aim of our work is to characterize the youngest and lowest mass population of the dark cloud Barnard 30, a region within the Lambda Orionis star-forming region. In particular, we aim to identify proto-brown dwarfs and study the mechanism of their formation. Methods: We obtained ALMA continuum observations at 880 μm of 30 sub-mm cores previously identified with APEX/LABOCA at 870 μm. We have complemented part of the ALMA data with sub-mm APEX/SABOCA observations at 350 μm, and with multi-wavelength ancillary observations from the optical to the far-infrared (e.g., Spitzer, CAHA/O2000, WISE, INT/WFC). Results: We report the detection of five (out of 30) spatially unresolved sources with ALMA, with estimated masses between 0.9 and 67 MJup. From these five sources, only two show gas emission. The analysis of multi-wavelength photometry from these two objects, namely B30-LB14 and B30-LB19, is consistent with one Class II- and one Class I low-mass stellar object, respectively. The gas emission is consistent with a rotating disk in the case of B30-LB14, and with an oblate rotating envelope with infall signatures in the case of LB19. The remaining three ALMA detections do not have infrared counterparts and can be classified as either deeply embedded objects or as starless cores if B30 members. In the former case, two of them (LB08 and LB31) show internal luminosity upper limits consistent with Very Low Luminosity objects, while we do not have enough information for LB10. In the starless core scenario, and taking into account the estimated masses from ALMA and the APEX/LABOCA cores, we estimate final masses for the central objects in the substellar domain, so they could be classified as

  15. SPATIALLY RESOLVED OBSERVATIONS OF THE BIPOLAR OPTICAL OUTFLOW FROM THE BROWN DWARF 2MASS J12073347-3932540

    Energy Technology Data Exchange (ETDEWEB)

    Whelan, E. T.; Ray, T. P. [Dublin Institute for Advanced Studies, School of Cosmic Physics, 31 Fitzwilliam Place, Dublin 2 (Ireland); Comeron, F. [ESO, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Bacciotti, F. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Kavanagh, P. J. [Institut fuer Astronomie und Astrophysik, Kepler Center for Astro and Particle Physics, Eberhard Karls Universitaet, D-72076 Tuebingen (Germany)

    2012-12-20

    Studies of brown dwarf (BD) outflows provide information pertinent to questions on BD formation, as well as allowing outflow mechanisms to be investigated at the lowest masses. Here new observations of the bipolar outflow from the 24 M{sub JUP} BD 2MASS J12073347-3932540 are presented. The outflow was originally identified through the spectro-astrometric analysis of the [O I]{lambda}6300 emission line. Follow-up observations consisting of spectra and [S II], R-band and I-band images were obtained. The new spectra confirm the original results and are used to constrain the outflow position angle (P.A.) at {approx}65 Degree-Sign . The [O I]{lambda}6300 emission line region is spatially resolved and the outflow is detected in the [S II] images. The detection is firstly in the form of an elongation of the point-spread function (PSF) along the direction of the outflow P.A. Four faint knot-like features (labeled A-D) are also observed to the southwest of 2MASS J12073347-3932540 along the same P.A. suggested by the spectra and the elongation in the PSF. Interestingly, D, the feature furthest from the source, is bow shaped with the apex pointing away from 2MASS J12073347-3932540. A color-color analysis allows us to conclude that at least feature D is part of the outflow under investigation while A is likely a star or galaxy. Follow-up observations are needed to confirm the origin of B and C. This is a first for a BD, as BD optical outflows have to date only been detected using spectro-astrometry. This result also demonstrates for the first time that BD outflows can be collimated and episodic.

  16. Ionization in atmospheres of brown dwarfs and extrasolar planets VI: Properties of large-scale discharge events

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, R. L.; Helling, Ch.; Hodosán, G.; Bilger, C.; Stark, C. R., E-mail: ch@leap2010.eu [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews KY16 9SS (United Kingdom)

    2014-03-20

    Mineral clouds in substellar atmospheres play a special role as a catalyst for a variety of charge processes. If clouds are charged, the surrounding environment becomes electrically activated, and ensembles of charged grains are electrically discharging (e.g., by lightning), which significantly influences the local chemistry creating conditions similar to those thought responsible for life in early planetary atmospheres. We note that such lightning discharges contribute also to the ionization state of the atmosphere. We apply scaling laws for electrical discharge processes from laboratory measurements and numerical experiments to DRIFT-PHOENIX model atmosphere results to model the discharge's propagation downward (as lightning) and upward (as sprites) through the atmospheric clouds. We evaluate the spatial extent and energetics of lightning discharges. The atmospheric volume affected (e.g., by increase of temperature or electron number) is larger in a brown dwarf atmosphere (10{sup 8}-10{sup 10} m{sup 3}) than in a giant gas planet (10{sup 4}-10{sup 6} m{sup 3}). Our results suggest that the total dissipated energy in one event is <10{sup 12} J for all models of initial solar metallicity. First attempts to show the influence of lightning on the local gas phase indicate an increase of small carbohydrate molecules like CH and CH{sub 2} at the expense of CO and CH{sub 4}. Dust-forming molecules are destroyed and the cloud particle properties are frozen in unless enough time is available for complete evaporation. We summarize instruments potentially suitable to observe lightning on extrasolar objects.

  17. Treatment of overlapping gaseous absorption with the correlated-k method in hot Jupiter and brown dwarf atmosphere models

    Science.gov (United States)

    Amundsen, David S.; Tremblin, Pascal; Manners, James; Baraffe, Isabelle; Mayne, Nathan J.

    2017-02-01

    The correlated-k method is frequently used to speed up radiation calculations in both one-dimensional and three-dimensional atmosphere models. An inherent difficulty with this method is how to treat overlapping absorption, i.e. absorption by more than one gas in a given spectral region. We have evaluated the applicability of three different methods in hot Jupiter and brown dwarf atmosphere models, all of which have been previously applied within models in the literature: (i) random overlap, both with and without resorting and rebinning, (ii) equivalent extinction and (iii) pre-mixing of opacities, where (i) and (ii) combine k-coefficients for different gases to obtain k-coefficients for a mixture of gases, while (iii) calculates k-coefficients for a given mixture from the corresponding mixed line-by-line opacities. We find that the random overlap method is the most accurate and flexible of these treatments, and is fast enough to be used in one-dimensional models with resorting and rebinning. In three-dimensional models such as global circulation models (GCMs) it is too slow, however, and equivalent extinction can provide a speed-up of at least a factor of three with only a minor loss of accuracy while at the same time retaining the flexibility gained by combining k-coefficients computed for each gas individually. Pre-mixed opacities are significantly less flexible, and we also find that particular care must be taken when using this method in order to to adequately resolve steep variations in composition at important chemical equilibrium boundaries. We use the random overlap method with resorting and rebinning in our one-dimensional atmosphere model and equivalent extinction in our GCM, which allows us to e.g. consistently treat the feedback of non-equilibrium chemistry on the total opacity and therefore the calculated P-T profiles in our models.

  18. MARVELS-1b: A Short-period, Brown Dwarf Desert Candidate from the SDSS-III Marvels Planet Search

    Science.gov (United States)

    Lee, Brian L.; Ge, Jian; Fleming, Scott W.; Stassun, Keivan G.; Gaudi, B. Scott; Barnes, Rory; Mahadevan, Suvrath; Eastman, Jason D.; Wright, Jason; Siverd, Robert J.; Gary, Bruce; Ghezzi, Luan; Laws, Chris; Wisniewski, John P.; Porto de Mello, G. F.; Ogando, Ricardo L. C.; Maia, Marcio A. G.; Nicolaci da Costa, Luiz; Sivarani, Thirupathi; Pepper, Joshua; Nguyen, Duy Cuong; Hebb, Leslie; De Lee, Nathan; Wang, Ji; Wan, Xiaoke; Zhao, Bo; Chang, Liang; Groot, John; Varosi, Frank; Hearty, Fred; Hanna, Kevin; van Eyken, J. C.; Kane, Stephen R.; Agol, Eric; Bizyaev, Dmitry; Bochanski, John J.; Brewington, Howard; Chen, Zhiping; Costello, Erin; Dou, Liming; Eisenstein, Daniel J.; Fletcher, Adam; Ford, Eric B.; Guo, Pengcheng; Holtzman, Jon A.; Jiang, Peng; French Leger, R.; Liu, Jian; Long, Daniel C.; Malanushenko, Elena; Malanushenko, Viktor; Malik, Mohit; Oravetz, Daniel; Pan, Kaike; Rohan, Pais; Schneider, Donald P.; Shelden, Alaina; Snedden, Stephanie A.; Simmons, Audrey; Weaver, B. A.; Weinberg, David H.; Xie, Ji-Wei

    2011-02-01

    We present a new short-period brown dwarf (BD) candidate around the star TYC 1240-00945-1. This candidate was discovered in the first year of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the Sloan Digital Sky Survey (SDSS) III, and we designate the BD as MARVELS-1b. MARVELS uses the technique of dispersed fixed-delay interferometery to simultaneously obtain radial velocity (RV) measurements for 60 objects per field using a single, custom-built instrument that is fiber fed from the SDSS 2.5 m telescope. From our 20 RV measurements spread over a ~370 day time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 2.533 ± 0.025 km s-1, period P = 5.8953 ± 0.0004 days, and eccentricity consistent with circular. Independent follow-up RV data confirm the orbit. Adopting a mass of 1.37 ± 0.11 M sun for the slightly evolved F9 host star, we infer that the companion has a minimum mass of 28.0 ± 1.5 M Jup, a semimajor axis 0.071 ± 0.002 AU assuming an edge-on orbit, and is probably tidally synchronized. We find no evidence for coherent intrinsic variability of the host star at the period of the companion at levels greater than a few millimagnitudes. The companion has an a priori transit probability of ~14%. Although we find no evidence for transits, we cannot definitively rule them out for companion radii lsim1 R Jup.

  19. DEUTERIUM BURNING IN MASSIVE GIANT PLANETS AND LOW-MASS BROWN DWARFS FORMED BY CORE-NUCLEATED ACCRETION

    Energy Technology Data Exchange (ETDEWEB)

    Bodenheimer, Peter [UCO/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); D' Angelo, Gennaro; Lissauer, Jack J. [Space Science and Astrobiology Division, NASA-Ames Research Center, Moffett Field, CA 94035 (United States); Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Saumon, Didier, E-mail: peter@ucolick.org, E-mail: gennaro.dangelo@nasa.gov, E-mail: Jack.J.Lissauer@nasa.gov, E-mail: jfortney@ucolick.org, E-mail: dsaumon@lanl.gov [Los Alamos National Laboratory, P.O. Box 1663, Los Alamos, NM 87545 (United States)

    2013-06-20

    Using detailed numerical simulations, we study the formation of bodies near the deuterium-burning limit according to the core-nucleated giant planet accretion scenario. The objects, with heavy-element cores in the range 5-30 M{sub Circled-Plus }, are assumed to accrete gas up to final masses of 10-15 Jupiter masses (M{sub Jup}). After the formation process, which lasts 1-5 Myr and which ends with a ''cold-start'', low-entropy configuration, the bodies evolve at constant mass up to an age of several Gyr. Deuterium burning via proton capture is included in the calculation, and we determined the mass, M{sub 50}, above which more than 50% of the initial deuterium is burned. This often-quoted borderline between giant planets and brown dwarfs is found to depend only slightly on parameters, such as core mass, stellar mass, formation location, solid surface density in the protoplanetary disk, disk viscosity, and dust opacity. The values for M{sub 50} fall in the range 11.6-13.6 M{sub Jup}, in agreement with previous determinations that do not take the formation process into account. For a given opacity law during the formation process, objects with higher core masses form more quickly. The result is higher entropy in the envelope at the completion of accretion, yielding lower values of M{sub 50}. For masses above M{sub 50}, during the deuterium-burning phase, objects expand and increase in luminosity by one to three orders of magnitude. Evolutionary tracks in the luminosity versus time diagram are compared with the observed position of the companion to Beta Pictoris.

  20. New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main Sequence

    Science.gov (United States)

    Gizis, John E.; Monet, David G.; Reid, I. Neill; Kirkpatrick, J. Davy; Liebert, James; Williams, Rik J.

    2000-08-01

    We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with Ksmass function that is smooth across the stellar/substellar limit. We show the observed frequency of Hα emission peaks at ~100% for M7 dwarfs and then decreases for cooler dwarfs. In absolute terms, however, as measured by the ratio of Hα to bolometric luminosity, none of the ultracool M dwarfs can be considered very active compared to earlier M dwarfs, and we show that the decrease that begins at spectral type M6 continues to the latest L dwarfs. We find that flaring is common among the coolest M dwarfs and estimate the frequency of flares at 7% or higher. We show that the kinematics of relatively active (EW>6 Å) ultracool M dwarfs are consistent with an ordinary old disk stellar population, while the kinematics of inactive ultracool M dwarfs are more typical of a 0.5 Gyr old population. The early L dwarfs in the sample have kinematics consistent with old ages, suggesting that the hydrogen-burning limit is near spectral types L2-L4. We use the available data on M and L dwarfs to show that chromospheric activity drops with decreasing mass and temperature and that at a given (M8 or later) spectral type, the younger field (brown) dwarfs are less active than many of the older, more massive field stellar dwarfs. Thus, contrary to the well-known stellar age-activity relationship, low activity in field ultracool dwarfs can be an indication of comparative youth and substellar mass.

  1. SPLAT: Using Spectral Indices to Identify and Characterize Ultracool Stars, Brown Dwarfs and Exoplanets in Deep Surveys and as Companions to Nearby Stars

    Science.gov (United States)

    Aganze, Christian; Burgasser, Adam J.; Martin, Eduardo; Konopacky, Quinn; Masters, Daniel C.

    2016-06-01

    The majority of ultracool dwarf stars and brown dwarfs currently known were identified in wide-field red optical and infrared surveys, enabling measures of the local, typically isolated, population in a relatively shallow (quantitative methodologies to identify and robustly characterize sources for these specific populations, based on templates and tools developed as part of the SpeX Prism Library Analysis Toolkit. In particular, we define and characterize specifically-tuned sets spectral indices that optimize selection of cool dwarfs and distinguish rare populations (subdwarfs, young planetary-mass objects) based on low-resolution, limited-wavelength-coverage spectral data; and present a template-matching classification method for these instruments. We apply these techniques to HST/WFC3 parallel fields data in the WISPS and HST-3D programs, where our spectral index set allows high completeness and low contamination for searches of late M, L and T dwarfs to distances out to ~3 kpc.The material presented here is based on work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G.

  2. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    OpenAIRE

    Kuzmychov, O.; Berdyugina, S. V.

    2013-01-01

    We investigated the Paschen-Back effect in the (0,0) band of the A6{\\Sigma}+-X6{\\Sigma}+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field pertur...

  3. SIMP J2154–1055: A NEW LOW-GRAVITY L4β BROWN DWARF CANDIDATE MEMBER OF THE ARGUS ASSOCIATION

    Energy Technology Data Exchange (ETDEWEB)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Artigau, Étienne; Malo, Lison; Robert, Jasmin; Nadeau, Daniel [Département de Physique, Université de Montréal, C.P. 6128 Succ. Centre-ville, Montréal, QC H3C 3J7 (Canada)

    2014-09-01

    We present SIMP J21543454–1055308, a new L4β brown dwarf identified in the SIMP survey that displays signs of low gravity in its near-infrared spectrum. Using BANYAN II, we show that it is a candidate member of the Argus association, albeit with a 21% probability that it is a contaminant from the field. Measurements of radial velocity and parallax will be needed to verify its membership. If it is a member of Argus (age 30-50 Myr), then this object would have a planetary mass of 10 ± 0.5 M {sub Jup}.

  4. SIMP J2154-1055: A New Low-Gravity L4$\\beta$ Brown Dwarf Candidate Member of the Argus Association

    OpenAIRE

    2014-01-01

    We present SIMP J21543454-1055308, a new L4$\\beta$ brown dwarf identified in the Sondage Infrarouge de Mouvement Propre (SIMP) survey that displays signs of low gravity in its near-infrared spectrum. Using the Bayesian Analysis for Nearby Young AssociatioNs II (BANYAN II), we show that it is a candidate member of the Argus association, albeit with a 21% probability that it is a contaminant from the field. Measurements of radial velocity and parallax will be needed to verify its membership. If...

  5. SIMP J2154-1055: A New Low-gravity L4β Brown Dwarf Candidate Member of the Argus Association

    Science.gov (United States)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Artigau, Étienne; Malo, Lison; Robert, Jasmin; Nadeau, Daniel

    2014-09-01

    We present SIMP J21543454-1055308, a new L4β brown dwarf identified in the SIMP survey that displays signs of low gravity in its near-infrared spectrum. Using BANYAN II, we show that it is a candidate member of the Argus association, albeit with a 21% probability that it is a contaminant from the field. Measurements of radial velocity and parallax will be needed to verify its membership. If it is a member of Argus (age 30-50 Myr), then this object would have a planetary mass of 10 ± 0.5 M Jup.

  6. Contamination of stellar-kinematic samples and uncertainty about dark matter annihilation profiles in ultrafaint dwarf galaxies: the example of Segue I

    Science.gov (United States)

    Bonnivard, V.; Maurin, D.; Walker, M. G.

    2016-10-01

    The expected gamma-ray flux coming from dark matter annihilation in dwarf spheroidal (dSph) galaxies depends on the so-called J-factor, the integral of the squared dark matter density along the line of sight. We examine the degree to which estimates of J are sensitive to contamination (by foreground Milky Way stars and stellar streams) of the stellar-kinematic samples that are used to infer dark matter densities in `ultrafaint' dSphs. Applying standard kinematic analyses to hundreds of mock data sets that include varying levels of contamination, we find that misclassified contaminants can cause J-factors to be overestimated by orders of magnitude. Stellar-kinematic data sets for which we obtain such biased estimates tend (1) to include relatively large fractions of stars with ambiguous membership status, and (2) to give estimates for J that are sensitive to specific choices about how to weight and/or to exclude stars with ambiguous status. Comparing publicly available stellar-kinematic samples for the nearby dSphs Reticulum II and Segue I, we find that only the latter displays both of these characteristics. Estimates of Segue I's J-factor should therefore be regarded with a larger degree of caution when planning and interpreting gamma-ray observations. Moreover, robust interpretations regarding dark matter annihilation in dSph galaxies in general will require explicit examination of how interlopers might affect the inferred dark matter density profiles.

  7. AEOLUS: A MARKOV CHAIN MONTE CARLO CODE FOR MAPPING ULTRACOOL ATMOSPHERES. AN APPLICATION ON JUPITER AND BROWN DWARF HST LIGHT CURVES

    Energy Technology Data Exchange (ETDEWEB)

    Karalidi, Theodora; Apai, Dániel; Schneider, Glenn; Hanson, Jake R. [Steward Observatory, Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Pasachoff, Jay M., E-mail: tkaralidi@email.arizona.edu [Hopkins Observatory, Williams College, 33 Lab Campus Drive, Williamstown, MA 01267 (United States)

    2015-11-20

    Deducing the cloud cover and its temporal evolution from the observed planetary spectra and phase curves can give us major insight into the atmospheric dynamics. In this paper, we present Aeolus, a Markov chain Monte Carlo code that maps the structure of brown dwarf and other ultracool atmospheres. We validated Aeolus on a set of unique Jupiter Hubble Space Telescope (HST) light curves. Aeolus accurately retrieves the properties of the major features of the Jovian atmosphere, such as the Great Red Spot and a major 5 μm hot spot. Aeolus is the first mapping code validated on actual observations of a giant planet over a full rotational period. For this study, we applied Aeolus to J- and H-band HST light curves of 2MASS J21392676+0220226 and 2MASS J0136565+093347. Aeolus retrieves three spots at the top of the atmosphere (per observational wavelength) of these two brown dwarfs, with a surface coverage of 21% ± 3% and 20.3% ± 1.5%, respectively. The Jupiter HST light curves will be publicly available via ADS/VIZIR.

  8. Dust masses of disks around 8 Brown Dwarfs and Very Low-Mass Stars in Upper Sco OB1 and Ophiuchus

    CERN Document Server

    van der Plas, G; Ward-Duong, K; Bulger, J; Harvey, P M; Pinte, C; Patience, J; Hales, A; Casassus, S

    2016-01-01

    We present the results of ALMA band 7 observations of dust and CO gas in the disks around 7 objects with spectral types ranging between M5.5 and M7.5 in Upper Scorpius OB1, and one M3 star in Ophiuchus. We detect unresolved continuum emission in all but one source, and the $^{12}$CO J=3-2 line in two sources. We constrain the dust and gas content of these systems using a grid of models calculated with the radiative transfer code MCFOST, and find disk dust masses between 0.1 and 1 M$_\\oplus$, suggesting that the stellar mass / disk mass correlation can be extrapolated for brown dwarfs with masses as low as 0.05 M$_\\odot$. The one disk in Upper Sco in which we detect CO emission, 2MASS J15555600, is also the disk with warmest inner disk as traced by its H - [4.5] photometric color. Using our radiative transfer grid, we extend the correlation between stellar luminosity and mass-averaged disk dust temperature originally derived for stellar mass objects to the brown dwarf regime to $\\langle T_{dust} \\rangle \\appro...

  9. The Cornell High-order Adaptive Optics Survey for Brown Dwarfs in Stellar Systems-I: Observations, Data Reduction, and Detection Analysis

    CERN Document Server

    Carson, J C; Brandl, B R; Wilson, J C; Hayward, T L

    2005-01-01

    In this first of a two-paper sequence, we report techniques and results of the Cornell High-order Adaptive Optics Survey for brown dwarf companions (CHAOS). At the time of this writing, this study represents the most sensitive published population survey of brown dwarf companions to main sequence stars, for separation akin to our own outer solar system. The survey, conducted using the Palomar 200-inch Hale Telescope, consists of K-short coronagraphic observations of 80 main sequence stars out to 22 parsecs. At 1 arcsecond separations from a typical target system, the survey achieves median sensitivities 10 magnitudes fainter than the parent star. In terms of companion mass, the survey achieves typical sensitivities of 25 Jupiter masses (1 Gyr), 50 Jupiter masses (solar age), and 60 Jupiter masses (10 Gyr), using evolutionary models of Baraffe et al. (2003). Using common proper motion to distinguish companions from field stars, we find that no systems show positive evidence of a substellar companion (searchabl...

  10. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    Science.gov (United States)

    Kuzmychov, O.; Berdyugina, S. V.

    2013-10-01

    Aims: We investigated the Paschen-Back effect in the (0,0) band of the A6Σ+ - X6Σ+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. Methods: We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field perturbation (the Paschen-Back effect) was consistently taken into account. Then, we calculated frequencies and strengths of transitions between magnetic sublevels. Employing these results and solving numerically a set of the radiative transfer equations for polarized radiation, we calculated Stokes parameters for both the individual lines and the (0,0) band depending on the strength and orientation of the magnetic field. Results: We demonstrate that magnetic splitting of the individual CrH lines shows a significant asymmetry due to the Paschen-Back effect already at 1 G field. This leads to a considerable signal in both circular and linear polarization, up to 30% at the magnetic field strength of ≥3 kG in early L dwarfs. The polarization does not cancel out completely even at very low spectral resolution and is seen as broad-band polarization of a few percent. Since the line asymmetry depends only on the magnetic field strength and not on the filling factor, CrH lines provide a very sensitive tool for direct measurement of the stellar magnetic fields on faint cool objects, such as brown dwarfs and hot Jupiters, observed with low spectral resolution.

  11. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. III. ANGULAR MOMENTUM AND CONSTRAINTS ON FORMATION SCENARIOS

    Energy Technology Data Exchange (ETDEWEB)

    Toloba, E.; Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Boselli, A.; Boissier, S. [Aix Marseille Universit, CNRS, LAM (Laboratoire d' Astrophysique de Marseille) UMR 7326, F-13388 Marseille (France); Peletier, R. F. [Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen (Netherlands); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Lisker, T. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Van de Ven, G. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Simon, J. D.; Adams, J. J.; Benson, A. J. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Falcón-Barroso, J.; Ryś, A. [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38200 La Laguna, Tenerife (Spain); Den Brok, M. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Gorgas, J. [Departamento de Astrofísica y Ciencias de la Atmósfera, Universidad Complutense de Madrid, E-28040 Madrid (Spain); Hensler, G. [Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, A-1180 Vienna (Austria); Janz, J. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Laurikainen, E.; Salo, H. [Division of Astronomy, Department of Physics, University of Oulu, P.O. Box 3000, FI-90014 Oulu (Finland); Paudel, S., E-mail: toloba@ucolick.org [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2015-02-01

    We analyze the stellar kinematics of 39 dwarf early-type galaxies (dEs) in the Virgo Cluster. Based on the specific stellar angular momentum λ{sub Re} and the ellipticity, we find 11 slow rotators and 28 fast rotators. The fast rotators in the outer parts of the Virgo Cluster rotate significantly faster than fast rotators in the inner parts of the cluster. Moreover, 10 out of the 11 slow rotators are located in the inner 3° (D < 1 Mpc) of the cluster. The fast rotators contain subtle disk-like structures that are visible in high-pass filtered optical images, while the slow rotators do not exhibit these structures. In addition, two of the dEs have kinematically decoupled cores and four more have emission partially filling in the Balmer absorption lines. These properties suggest that Virgo Cluster dEs may have originated from late-type star-forming galaxies that were transformed by the environment after their infall into the cluster. The correlation between λ{sub Re} and the clustercentric distance can be explained by a scenario where low luminosity star-forming galaxies fall into the cluster, their gas is rapidly removed by ram-pressure stripping, although some of it can be retained in their core, their star formation is quenched but their stellar kinematics are preserved. After a long time in the cluster and several passes through its center, the galaxies are heated up and transformed into slow rotating dEs.

  12. An Activity-Rotation Relationship and Kinematic Analysis of Nearby Mid-to-Late-type M Dwarfs

    CERN Document Server

    West, Andrew A; Irwin, Jonathan; Berta-Thompson, Zachory K; Charbonneau, David; Dittmann, Jason; Pineda, J Sebastian

    2015-01-01

    Using spectroscopic observations and photometric light curves of 238 nearby M dwarfs from the MEarth exoplanet transit survey, we examine the relationships between magnetic activity (quantified by H-alpha emission), rotation period, and stellar age. Previous attempts to investigate the relationship between magnetic activity and rotation in these stars were hampered by the limited number of M dwarfs with measured rotation periods (and the fact that vsini measurements probe only rapid rotation). However, the photometric data from MEarth allows us to probe a wide range of rotation periods for hundreds of M dwarf stars (from shorter than than one to longer than 100 days). Over all M spectral types that we probe, we find that the presence of magnetic activity is tied to rotation, including for late-type, fully convective M dwarfs. We also find evidence that the fraction of late-type M dwarfs that are active may be higher at longer rotation periods compared to their early-type counterparts, with several active, lat...

  13. Transiting exoplanets from the CoRoT space mission XXVIII. CoRoT-33b, an object in the brown dwarf desert with 2:3 commensurability with its host star

    CERN Document Server

    Csizmadia, Sz; Gandolfi, G; Deleuil, M; Bouchy, M; Fridlund, M; Szabados, L; Parviainen, H; Cabrera, J; Aigrain, S; Alonso, R; Almenara, J M; Baglin, A; Bordé, P; Bonomo, A S; Deeg, H J; Dıaz, R F; Erikson, A; Ferraz-Mello, S; Santos, M Tadeu dos; Guenther, E W; Guillot, T; Grziwa, S; Hébrard, G; Klagyivik, P; Ollivier, M; Pätzold, M; Rauer, H; Rouan, D; Santerne, A; Schneider, J; Mazeh, T; Wuchterl, G; Carpano, S; Ofir, A

    2015-01-01

    We report the detection of a rare transiting brown dwarf with a mass of 59 M_Jup and radius of 1.1 R_Jup around the metal-rich, [Fe/H] = +0.44, G9V star CoRoT-33. The orbit is eccentric (e = 0.07) with a period of 5.82 d. The companion, CoRoT-33b, is thus a new member in the so-called brown dwarf desert. The orbital period is within 3% to a 3:2 resonance with the rotational period of the star. CoRoT-33b may be an important test case for tidal evolution studies. The true frequency of brown dwarfs close to their host stars (P < 10 d) is estimated to be approximately 0.2% which is about six times smaller than the frequency of hot Jupiters in the same period range. We suspect that the frequency of brown dwarfs declines faster with decreasing period than that of giant planets.

  14. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cancri

    Science.gov (United States)

    Shara, Michael M.; Drissen, Laurent; Martin, Thomas; Alarie, Alexandre; Stephenson, F. Richard

    2017-02-01

    The Z Cam-type dwarf nova AT Cancri (AT Cnc) displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a time-scale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, Canada-France-Hawaii Telescope's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km s-1. Coupled with the known distance to AT Cnc of 460 pc, the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred 330_{-90}^{+135} yr ago. This is the most rapid transition from a high mass-transfer rate, nova-like variable to a low mass-transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in the deduced outburst date (within a century of 1686 CE) of AT Cnc to a `guest star' reported in the constellation Cancer by Korean observers in 1645 CE.

  15. When does an old nova become a dwarf nova? Kinematics and age of the nova shell of the dwarf nova AT Cnc

    CERN Document Server

    Shara, Michael M; Martin, Thomas; Alarie, Alexandre

    2016-01-01

    The Z Cam-type dwarf nova AT Cnc displays a classical nova (CN) shell, demonstrating that mass transfer in cataclysmic binaries decreases substantially after a CN eruption. The hibernation scenario of cataclysmic binaries predicts such a decrease, on a timescale of a few centuries. In order to measure the time since AT Cnc's last CN eruption, we have measured the radial velocities of a hundred clumps in its ejecta with SITELLE, CFHT's recently commissioned imaging Fourier transform spectrometer. These range from -455 to +490 km/s. Coupled with the known distance to AT Cnc of 460 pc (Shara 2012), the size of AT Cnc's shell, and a simple model of nova ejecta deceleration, we determine that the last CN eruption of this system occurred $330_{-90}^{+135}$ years ago. This is the most rapid transition from a high mass transfer rate, novalike variable to a low mass transfer rate, dwarf nova yet measured, and in accord with the hibernation scenario of cataclysmic binaries. We conclude by noting the similarity in deduc...

  16. Stellar Kinematics and Metallicities in the Draco and Ursa Minor Dwarf Spheroidal Galaxies from WHT/AF2-WYFFOS

    NARCIS (Netherlands)

    Jin, S.; Irwin, M.; Tolstoy, E.; Lewis, J.; Hartke, J.; Skillen, I.; Barcells, M.; Trager, S.

    2016-01-01

    We present preliminary results from our chemo-dynamical survey of two Milky Way dwarf spheroidal (dSph) galaxies, Draco and Ursa Minor. The two galaxies have similar radial velocities and reside in close proximity in the outskirts of the Milky Way halo, yet exhibit noteworthy differences in their mo

  17. The VLT/NaCo Large program to probe the occurrence of exoplanets and brown dwarfs in wide orbits: I- Sample definition and characterization

    CERN Document Server

    Desidera, S; Messina, S; Carson, J; Hagelberg, J; Schlieder, J E; Biazzo, K; Alcala, J M; Chauvin, G; Vigan, A; Beuzit, J L; Bonavita, M; Bonnefoy, M; Delorme, P; D'Orazi, V; Esposito, M; Feldt, M; Girardi, L; Gratton, R; Henning, T; Lagrange, A M; Lanzafame, A C; Launhardt, R; Marmier, M; Melo, C; Meyer, M; Mouillet, D; Moutou, C; Segransan, D; Udry, S; Zaidi, C M

    2014-01-01

    Young, nearby stars are ideal targets to search for planets using the direct imaging technique. The determination of stellar parameters is crucial for the interpretation of imaging survey results particularly since the luminosity of substellar objects has a strong dependence on system age. We have conducted a large program with NaCo at the VLT in order to search for planets and brown dwarfs in wide orbits around 86 stars. A large fraction of the targets observed with NaCo were poorly investigated in the literature. We performed a study to characterize the fundamental properties (age, distance, mass) of the stars in our sample. To improve target age determinations, we compiled and analyzed a complete set of age diagnostics. We measured spectroscopic parameters and age diagnostics using dedicated observations acquired with FEROS and CORALIE spectrographs at La Silla Observatory. We also made extensive use of archival spectroscopic data and results available in the literature. Additionally, we exploited photomet...

  18. SIMP J2154-1055: A New Low-Gravity L4$\\beta$ Brown Dwarf Candidate Member of the Argus Association

    CERN Document Server

    Gagné, Jonathan; Doyon, René; Artigau, Étienne; Malo, Lison; Robert, Jasmin; Nadeau, Daniel

    2014-01-01

    We present SIMP J21543454-1055308, a new L4$\\beta$ brown dwarf identified in the Sondage Infrarouge de Mouvement Propre (SIMP) survey that display signs of low gravity in its near-infrared spectrum. Using the Bayesian Analysis for Nearby Young AssociatioNs II (BANYAN II), we show that it is a candidate member of the Argus association, albeit with a 21% probability that it is a contaminant from the field. Measurements of radial velocity and parallax will be needed to verify its membership. If it is a member of Argus (age 30-50 Myr), then this object would have a planetary mass of 10 $\\pm$ 0.5 $M_{\\mathrm{Jup}}$.

  19. The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5

    CERN Document Server

    Schneider, Adam C; Kirkpatrick, J Davy; Gelino, Chris R

    2016-01-01

    We present Hubble Space Telescope (HST) near-infrared photometry of the coldest known brown dwarf, WISE J085510.83$-$071442.5 (WISE 0855$-$0714). WISE 0855$-$0714 was observed with the Wide Field Camera 3 (WFC3) aboard HST using the F105W, F125W, and F160W filters, which approximate the $Y$, $J$, and $H$ near-infrared bands. WISE 0855$-$0714 is undetected at F105W with a corresponding 2$\\sigma$ magnitude limit of $\\sim$26.9. We marginally detect WISE 0855$-$0714 in the F125W images (S/N $\\sim$4), with a measured magnitude of 26.41 $\\pm$ 0.27, more than a magnitude fainter than the $J-$band magnitude reported by Faherty and coworkers. WISE J0855$-$0714 is clearly detected in the F160W band, with a magnitude of 23.90 $\\pm$ 0.02, the first secure detection of WISE 0855$-$0714 in the near-infrared. Based on these data, we find that WISE 0855$-$0714 has extremely red F105W$-$F125W and F125W$-$F160W colors relative to other known Y dwarfs. We find that when compared to the models of Saumon et al. and Morley et al.,...

  20. Observed Variability at 1um and 4um in the Y0 Brown Dwarf WISEP J173835.52+273258.9

    CERN Document Server

    Leggett, S K; Hardegree-Ullman, Kevin K; Trucks, Jesica L; Marley, M S; Morley, Caroline V; Saumon, D; Carey, S J; Fortney, J J; Gelino, C R; Gizis, J E; Kirkpatrick, J D; Mace, G N

    2016-01-01

    We have monitored photometrically the Y0 brown dwarf WISEP J173835.52+273258.9 (W1738) at both near- and mid-infrared wavelengths. This ~1 Gyr-old 400K dwarf is at a distance of 8pc and has a mass around 5 M_Jupiter. We observed W1738 using two near-infrared filters at lambda~1um, Y and J, on Gemini observatory, and two mid-infrared filters at lambda~4um, [3.6] and [4.5], on the Spitzer observatory. Twenty-four hours were spent on the source by Spitzer on each of June 30 and October 30 2013 UT. Between these observations, around 5 hours were spent on the source by Gemini on each of July 17 and August 23 2013 UT. The mid-infrared light curves show significant evolution between the two observations separated by four months. We find that a double sinusoid can be fit to the [4.5] data, where one sinusoid has a period of 6.0 +/- 0.1 hours and the other a period of 3.0 +/- 0.1 hours. The near-infrared observations suggest variability with a ~3.0 hour period, although only at a <~2 sigma confidence level. We inte...

  1. New Neighbors from 2MASS Activity and Kinematics at the Bottom of the Main Sequence

    CERN Document Server

    Gizis, J E; Reid, I N; Kirkpatrick, J D; Liebert, J; Williams, R J; Gizis, John E.; Monet, David G.; Liebert, James; Williams, Rik J.

    2000-01-01

    We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with K_s6 Angstroms) ultracool M dwarfs are consistent with an ordinary old disk stellar population, while the kinematics of inactive ultracool M dwarfs are more typical of a 0.5 Gyr old population. The early L dwarfs in the sample have kinematics consistent with old ages, suggesting that the hydrogen burning limit is near spectral types L2-L4. We use the available data on M and L dwarfs to show that chromospheric activity drops with decreasing mass and temperature, and that at a given (M8 or later) spectral type, the younger field (brown) dwarfs are less active than many of the older, more massive field stellar dwarfs. Thus, contrary to the well-known stellar age-activity relationship, low activity in field ultracool dwarfs can be an indication of comparative youth and substellar mass.

  2. Chemistry and Kinematics of the Late-Forming Dwarf Irregular Galaxies Leo A, Aquarius, and Sagittarius DIG

    CERN Document Server

    Kirby, Evan N; Held, Enrico V; Cohen, Judith G; Cole, Andrew A; Manning, Ellen M; Skillman, Evan D; Weisz, Daniel R

    2016-01-01

    We present Keck/DEIMOS spectroscopy of individual stars in the relatively isolated Local Group dwarf galaxies Leo A, Aquarius, and the Sagittarius dwarf irregular galaxy. The three galaxies--but especially Leo A and Aquarius--share in common delayed star formation histories relative to many other isolated dwarf galaxies. The stars in all three galaxies are supported by dispersion. We found no evidence of stellar velocity structure, even for Aquarius, which has rotating HI gas. The velocity dispersions indicate that all three galaxies are dark matter-dominated, with dark-to-baryonic mass ratios ranging from $4.4^{+1.1}_{-0.8}$ (SagDIG) to $9.6^{+2.5}_{-1.8}$ (Aquarius). Leo A and SagDIG have lower stellar metallicities than Aquarius, and they also have higher gas fractions, both of which would be expected if Aquarius were farther along in its chemical evolution. The metallicity distribution of Leo A is inconsistent with a Closed or Leaky Box model of chemical evolution, suggesting that the galaxy was pre-enric...

  3. STELLAR KINEMATICS AND STRUCTURAL PROPERTIES OF VIRGO CLUSTER DWARF EARLY-TYPE GALAXIES FROM THE SMAKCED PROJECT. II. THE SURVEY AND A SYSTEMATIC ANALYSIS OF KINEMATIC ANOMALIES AND ASYMMETRIES

    Energy Technology Data Exchange (ETDEWEB)

    Toloba, E.; Guhathakurta, P. [UCO/Lick Observatory, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Peletier, R. F. [Kapteyn Astronomical Institute, Postbus 800, 9700 AV Groningen (Netherlands); Boselli, A. [Laboratoire d' Astrophysique de Marseille-LAM, Université d' Aix-Marseille and CNRS, UMR 7326, 38 rue F. Joliot-Curie, 13388 Marseille Cedex 13 (France); Lisker, T. [Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstraße 12-14, D-69120 Heidelberg (Germany); Falcón-Barroso, J.; Ryś, A. [Instituto de Astrofísica de Canarias, Vía Láctea s/n, La Laguna, Tenerife (Spain); Simon, J. D. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Van de Ven, G. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Paudel, S. [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching (Germany); Janz, J. [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Den Brok, M. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Gorgas, J. [Departamento de Astrofísica y Física de la Atmósfera, Universidad Complutense de Madrid, E-28040, Madrid (Spain); Hensler, G. [Department of Astrophysics, University of Vienna, Türkenschanzstraße 17, 1180 Vienna (Austria); Laurikainen, E.; Salo, H. [Division of Astronomy, Department of Physics, PO Box 3000, FI-90014 University of Oulu (Finland); Niemi, S.-M., E-mail: toloba@ucolick.org [Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT (United Kingdom)

    2015-01-01

    We present spatially resolved kinematics and global stellar populations and mass-to-light ratios for a sample of 39 dwarf early-type (dE) galaxies in the Virgo cluster studied as part of the SMAKCED stellar absorption-line spectroscopy and imaging survey. This sample is representative of the early-type population in the Virgo cluster in the absolute magnitude range –19.0 < M{sub r} < –16.0 and of all morphological subclasses found in this galaxy population. For each dE, we measure the rotation curve and velocity dispersion profile and fit an analytic function to the rotation curve. We study the significance of the departure of the rotation curve from the best-fit analytic function (poorly fit) and of the difference between the approaching and receding sides of the rotation curve (asymmetry). Our sample includes two dEs with kinematically decoupled cores that have been previously reported. We find that 62 ± 8% (23 out of the 39) of the dEs have a significant anomaly in their rotation curve. Analysis of the images reveals photometric anomalies for most galaxies. However, there is no clear correlation between the significance of the photometric and kinematic anomalies. We measure age-sensitive (H{sub β} and H{sub γA}) and metallicity sensitive (Fe4668 and Mgb) Lick spectral indices in the LIS-5 Å system. This population of galaxies exhibits a wide range of ages and metallicities; we also find that 4 dEs show clear evidence of emission partially filling in the Balmer absorption lines. Finally, we estimate the total masses and dark matter fractions of the dEs and plot them in the mass-size, the mass-velocity dispersion, and the fundamental plane scaling relations. The dEs seem to be the bridge between massive early-type galaxies and dSphs, and have a median total mass within the R{sub e} of log M{sub e} = 9.1 ± 0.2 and a median dark matter fraction within the R{sub e} of f {sub DM} = 46 ± 18%. Any formation model for the dE galaxy class must account for this

  4. Formation and evolution of dwarf early-type galaxies in the Virgo cluster II. Kinematic Scaling Relations

    CERN Document Server

    Toloba, E; Peletier, R; Falcon-Barroso, J; van de Ven, G; Gorgas, J

    2012-01-01

    We place our sample of 18 Virgo dwarf early-type galaxies (dEs) on the V-K - velocity dispersion, Faber-Jackson, and Fundamental Plane (FP) scaling relations for massive early-type galaxies (Es). We use a generalized velocity dispersion, which includes rotation, to be able to compare the location of both rotationally and pressure supported dEs with those of early and late-type galaxies. We find that dEs seem to bend the Faber-Jackson relation of Es to lower velocity dispersions, being the link between Es and dwarf spheroidal galaxies (dSphs). Regarding the FP relation, we find that dEs are significantly offset with respect to massive hot stellar systems, and re-casting the FP into the so-called kappa-space suggests that this offset is related to dEs having a total mass-to-light ratio higher than Es but still significantly lower than dSph galaxies. Given a stellar mass-to-light ratio based on the measured line indices of dEs, the FP offset allows us to infer that the dark matter fraction within the half light ...

  5. ALFALFA Discovery of the Nearby Gas-rich Dwarf Galaxy Leo P. V. Neutral Gas Dynamics and Kinematics

    CERN Document Server

    Bernstein-Cooper, Elijah Z; Elson, Edward C; Warren, Steven R; Chengalur, Jayaram; Skillman, Evan D; Adams, Elizabeth A K; Bolatto, Alberto D; Giovanelli, Riccardo; Haynes, Martha P; McQuinn, Kristen B W; Pardy, Stephen A; Rhode, Katherine L; Salzer, John J

    2014-01-01

    We present new HI spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our HI images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The HI morphology is slightly elongated along the optical major-axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V_c = 15 +/- 5 km/s. Within the HI radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ~15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature ...

  6. The Next Generation Virgo Cluster Survey. VI. The Kinematics of Ultra-compact Dwarfs and Globular Clusters in M87

    CERN Document Server

    Zhang, Hong-Xin; Cote, Patrick; Liu, Chengze; Ferrarese, Laura; Cuillandre, Jean-Charles; Caldwell, Nelson; Gwyn, Stephen D J; Jordan, Andres; Lancon, Ariane; Li, Biao; Munoz, Roberto P; Puzia, Thomas H; Bekki, Kenji; Blakeslee, John; Boselli, Alessandro; Drinkwater, Michael J; Duc, Pierre-Alain; Durrell, Patrick; Emsellem, Eric; Firth, Peter; Sanchez-Janssen, Ruben

    2015-01-01

    The origin of ultra-compact dwarfs (UCDs)--objects larger and more massive than typical globular clusters (GCs), but more compact than typical dwarf galaxies--has been hotly debated in the 15 years since their discovery. Even whether UCDs should be considered galactic in origin, or simply the most extreme GCs, is not yet settled. We present the dynamical properties of 97 spectroscopically confirmed UCDs (rh >~10 pc) and 911 GCs associated with central cD galaxy of the Virgo cluster, M87. Our UCDs, of which 89% have M_star > ~2X10^6 M_sun and 92% are as blue as the classic blue GCs, nearly triple the sample of previous confirmed Virgo UCDs, providing by far the best opportunity for studying the global dynamics of a UCD system. We found that (1) UCDs have a surface number density profile that is shallower than that of the blue GCs in the inner ~ 70 kpc and as steep as that of the red GCs at larger radii; (2) UCDs exhibit a significantly stronger rotation than the GCs, and the blue GCs seem to have a velocity fi...

  7. CLOUD STRUCTURE OF THE NEAREST BROWN DWARFS. II. HIGH-AMPLITUDE VARIABILITY FOR LUHMAN 16 A AND B IN AND OUT OF THE 0.99 μm FeH FEATURE

    Energy Technology Data Exchange (ETDEWEB)

    Buenzli, Esther [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Marley, Mark S. [NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States); Apai, Dániel [Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Saumon, Didier [Los Alamos National Laboratory, Mail Stop F663, Los Alamos, NM 87545 (United States); Biller, Beth A. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Crossfield, Ian J. M. [Department of Planetary Sciences, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721 (United States); Radigan, Jacqueline, E-mail: buenzli@mpia.de [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2015-10-20

    The re-emergence of the 0.99 μm FeH feature in brown dwarfs of early- to mid-T spectral type has been suggested as evidence for cloud disruption where flux from deep, hot regions below the Fe cloud deck can emerge. The same mechanism could account for color changes at the L/T transition and photometric variability. We present the first observations of spectroscopic variability of brown dwarfs covering the 0.99 μm FeH feature. We observed the spatially resolved very nearby brown dwarf binary WISE J104915.57–531906.1 (Luhman 16AB), a late-L and early-T dwarf, with Hubble Space Telescope/WFC3 in the G102 grism at 0.8–1.15 μm. We find significant variability at all wavelengths for both brown dwarfs, with peak-to-valley amplitudes of 9.3% for Luhman 16B and 4.5% for Luhman 16A. This represents the first unambiguous detection of variability in Luhman 16A. We estimate a rotational period between 4.5 and 5.5 hr, very similar to Luhman 16B. Variability in both components complicates the interpretation of spatially unresolved observations. The probability for finding large amplitude variability in any two brown dwarfs is less than 10%. Our finding may suggest that a common but yet unknown feature of the binary is important for the occurrence of variability. For both objects, the amplitude is nearly constant at all wavelengths except in the deep K i feature below 0.84 μm. No variations are seen across the 0.99 μm FeH feature. The observations lend strong further support to cloud height variations rather than holes in the silicate clouds, but cannot fully rule out holes in the iron clouds. We re-evaluate the diagnostic potential of the FeH feature as a tracer of cloud patchiness.

  8. SCExAO and GPI Y JHBand Photometry and Integral Field Spectroscopy of the Young Brown Dwarf Companion to HD 1160

    Science.gov (United States)

    Garcia, E. Victor; Currie, Thayne; Guyon, Olivier; Stassun, Keivan G.; Jovanovic, Nemanja; Lozi, Julien; Kudo, Tomoyuki; Doughty, Danielle; Schlieder, Josh; Kwon, J.; Uyama, T.; Kuzuhara, M.; Carson, J. C.; Nakagawa, T.; Hashimoto, J.; Kusakabe, N.; Abe, L.; Brandner, W.; Brandt, T. D.; Feldt, M.; Goto, M.; Grady, C. A.; Hayano, Y.; Hayashi, M.; Hayashi, S. S.; Henning, T.; Hodapp, K. W.; Ishii, M.; Iye, M.; Janson, M.; Kandori, R.; Knapp, G. R.; Matsuo, T.; McElwain, M. W.; Miyama, S.; Morino, J.-I.; Moro-Martin, A.; Nishimura, T.; Pyo, T.-S.; Serabyn, E.; Suenaga, T.; Suto, H.; Suzuki, R.; Takahashi, Y. H.; Takami, H.; Takami, M.; Takato, N.; Terada, H.; Thalmann, C.; Turner, E. L.; Watanabe, M.; Wisniewski, J.; Yamada, T.; Usuda, T.; Tamura, M.

    2017-01-01

    We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957–1.120 μm) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5{}-0.5+1.0, where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000–3100 K, a surface gravity of log g = 4–4.5, a radius of 1.55 ± 0.10 R J, and a luminosity of log L/L ⊙ = ‑2.76 ± 0.05. Neither the primary’s Hertzspring–Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80–125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70–90 M J). If we consider HD 1160 A alone, younger ages (20–125 Myr) and a brown dwarf-like mass (35–90 M J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system’s age and how HD 1160 B fits within the context of (sub)stellar evolution.

  9. Clean Kinematic Samples in Dwarf Spheroidals: An Algorithm for Evaluating Membership and Estimating Distribution Parameters When Contamination is Present

    CERN Document Server

    Walker, Matthew G; Olszewski, Edward W; Sen, Bodhisattva; Woodroofe, Michael

    2008-01-01

    (abridged) We develop an algorithm for estimating parameters of a distribution sampled with contamination, employing a statistical technique known as ``expectation maximization'' (EM). Given models for both member and contaminant populations, the EM algorithm iteratively evaluates the membership probability of each discrete data point, then uses those probabilities to update parameter estimates for member and contaminant distributions. The EM approach has wide applicability to the analysis of astronomical data. Here we tailor an EM algorithm to operate on spectroscopic samples obtained with the Michigan-MIKE Fiber System (MMFS) as part of our Magellan survey of stellar radial velocities in nearby dwarf spheroidal (dSph) galaxies. These samples are presented in a companion paper and contain discrete measurements of line-of-sight velocity, projected position, and Mg index for ~1000 - 2500 stars per dSph, including some fraction of contamination by foreground Milky Way stars. The EM algorithm quantifies both dSp...

  10. The EBLM project. I. Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the brown dwarf limit

    Science.gov (United States)

    Triaud, A. H. M. J.; Hebb, L.; Anderson, D. R.; Cargile, P.; Collier Cameron, A.; Doyle, A. P.; Faedi, F.; Gillon, M.; Gomez Maqueo Chew, Y.; Hellier, C.; Jehin, E.; Maxted, P.; Naef, D.; Pepe, F.; Pollacco, D.; Queloz, D.; Ségransan, D.; Smalley, B.; Stassun, K.; Udry, S.; West, R. G.

    2013-01-01

    This paper introduces a series of papers aiming to study the dozens of low-mass eclipsing binaries (EBLM), with F, G, K primaries, that have been discovered in the course of the WASP survey. Our objects are mostly single-line binaries whose eclipses have been detected by WASP and were initially followed up as potential planetary transit candidates. These have bright primaries, which facilitates spectroscopic observations during transit and allows the study of the spin-orbit distribution of F, G, K+M eclipsing binaries through the Rossiter-McLaughlin effect. Here we report on the spin-orbit angle of WASP-30b, a transiting brown dwarf, and improve its orbital parameters. We also present the mass, radius, spin-orbit angle and orbital parameters of a new eclipsing binary, J1219-39b (1SWAPJ121921.03-395125.6, TYC 7760-484-1), which, with a mass of 95 ± 2 Mjup, is close to the limit between brown dwarfs and stars. We find that both objects have projected spin-orbit angles aligned with their primaries' rotation. Neither primaries are synchronous. J1219-39b has a modestly eccentric orbit and is in agreement with the theoretical mass-radius relationship, whereas WASP-30b lies above it. Using WASP-South photometric observations (Sutherland, South Africa) confirmed with radial velocity measurement from the CORALIE spectrograph, photometry from the EulerCam camera (both mounted on the Swiss 1.2 m Euler Telescope), radial velocities from the HARPS spectrograph on the ESO's 3.6 m Telescope (prog ID 085.C-0393), and photometry from the robotic 60 cm TRAPPIST telescope, all located at ESO, La Silla, Chile. The data is publicly available at the CDS Strasbourg and on demand to the main author.Tables A.1-A.3 are available in electronic form at http://www.aanda.orgPhotometry tables are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/549/A18

  11. Primeval very low-mass stars and brown dwarfs. I. Six new L subdwarfs, classification and atmospheric properties

    CERN Document Server

    Zhang, Z H; Galvez-Ortiz, M C; Burningham, B; Lodieu, N; Marocco, F; Burgasser, A J; Day-Jones, A C; Allard, F; Jones, H R A; Homeier, D; Gomes, J; Smart, R L

    2016-01-01

    We have conducted a search for L subdwarf candidates within the photometric catalogues of the UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey. Six of our candidates are confirmed as L subdwarfs spectroscopically at optical and/or near infrared wavelengths. We also present new optical spectra of three previously known L subdwarfs (WISEA J001450.17-083823.4, 2MASS J00412179+3547133, ULAS J124425.75+102439.3). We examined the spectral types and metallicity subclasses classification of known L subdwarfs. We summarised the spectroscopic properties of L subdwarfs with different spectral types and subclasses. We classify these new L subdwarfs by comparing their spectra to known L subdwarfs and L dwarf standards. We estimate temperatures and metallicities of 22 late type M and L subdwarfs by comparing their spectra to BT-Settl models. We find that L subdwarfs have temperatures between 1500 K and 2700 K, which are higher than similarly-typed L dwarfs by around 100-400 K depending on different subclasses an...

  12. Alfalfa discovery of the nearby gas-rich dwarf galaxy LEO P. V. Neutral gas dynamics and kinematics

    Energy Technology Data Exchange (ETDEWEB)

    Bernstein-Cooper, Elijah Z.; Pardy, Stephen A. [Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States); Cannon, John M., E-mail: ezbc@astro.wisc.edu, E-mail: spardy@astro.wisc.edu, E-mail: jcannon@macalester.edu [Department of Physics and Astronomy, Macalester College, 1600 Grand Avenue, Saint Paul, MN 55105 (United States); and others

    2014-08-01

    We present new H I spectral line imaging of the extremely metal-poor, star-forming dwarf irregular galaxy Leo P. Our H I images probe the global neutral gas properties and the local conditions of the interstellar medium (ISM). The H I morphology is slightly elongated along the optical major axis. We do not find obvious signatures of interaction or infalling gas at large spatial scales. The neutral gas disk shows obvious rotation, although the velocity dispersion is comparable to the rotation velocity. The rotation amplitude is estimated to be V {sub c} =15 ± 5 km s{sup –1}. Within the H I radius probed by these observations, the mass ratio of gas to stars is roughly 2:1, while the ratio of the total mass to the baryonic mass is ≳15:1. We use this information to place Leo P on the baryonic Tully-Fisher relation, testing the baryonic content of cosmic structures in a sparsely populated portion of parameter space that has hitherto been occupied primarily by dwarf spheroidal galaxies. We detect the signature of two temperature components in the neutral ISM of Leo P; the cold and warm components have characteristic velocity widths of 4.2 ± 0.9 km s{sup –1} and 10.1 ± 1.2 km s{sup –1}, corresponding to kinetic temperature upper limits of ∼1100 K and ∼6200 K, respectively. The cold H I component is unresolved at a physical resolution of 200 pc. The highest H I surface densities are observed in close physical proximity to the single H II region. A comparison of the neutral gas properties of Leo P with other extremely metal-deficient (XMD) galaxies reveals that Leo P has the lowest neutral gas mass of any known XMD, and that the dynamical mass of Leo P is more than two orders of magnitude smaller than any known XMD with comparable metallicity.

  13. Paschen-Back effect in the CrH molecule and its application for magnetic field measurements on stars, brown dwarfs, and hot exoplanets

    CERN Document Server

    Kuzmychov, O

    2013-01-01

    We investigated the Paschen-Back effect in the (0,0) band of the A6{\\Sigma}+-X6{\\Sigma}+ system of the CrH molecule, and we examined its potential for estimating magnetic fields on stars and substellar objects, such as brown dwarfs and hot exoplanets. We carried out quantum mechanical calculations to obtain the energy level structure of the electronic-vibrational-rotational states considered both in the absence and in the presence of a magnetic field. Level mixing due to magnetic field perturbation (the Paschen-Back effect) was consistently taken into account. Then, we calculated frequencies and strengths of transitions between magnetic sublevels. Employing these results and solving numerically a set of the radiative transfer equations for polarized radiation, we calculated Stokes parameters for both the individual lines and the (0,0) band depending on the strength and orientation of the magnetic field. We demonstrate that magnetic splitting of the individual CrH lines shows a significant asymmetry due to the...

  14. Atom Resonance Lines for Modeling Atmosphere: Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown Dwarfs

    Science.gov (United States)

    Hasan, Hashima (Technical Monitor); Kirby, K.; Babb, J.; Yoshino, K.

    2005-01-01

    We report on progress made in a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Accurate knowledge of the line profiles of Na and K as a function of temperature and pressure will allow such lines to serve as valuable diagnostics of the atmospheres of brown dwarfs and extra-solar giant planets. A new experimental apparatus has been designed, built and tested over the past year, and we are poised to begin collecting data on the first system of interest, the potassium resonance lines perturbed by collisions with helium. On the theoretical front, calculations of line-broadening due to sodium collisions with helium are nearly complete, using accurate molecular potential energy curves and transition moments just recently computed for this system. In addition we have completed calculations of the three relevant potential energy curves and associated transition moments for K - He, using the MOLPRO quantum chemistry codes. Currently, calculations of the potential surfaces describing K-H2 are in progress.

  15. The SOPHIE search for northern extrasolar planets . I. A companion around HD 16760 with mass close to the planet/brown-dwarf transition

    Science.gov (United States)

    Bouchy, F.; Hébrard, G.; Udry, S.; Delfosse, X.; Boisse, I.; Desort, M.; Bonfils, X.; Eggenberger, A.; Ehrenreich, D.; Forveille, T.; Lagrange, A. M.; Le Coroller, H.; Lovis, C.; Moutou, C.; Pepe, F.; Perrier, C.; Pont, F.; Queloz, D.; Santos, N. C.; Ségransan, D.; Vidal-Madjar, A.

    2009-10-01

    We report on the discovery of a substellar companion or a massive Jupiter orbiting the G5V star HD 16760 using the spectrograph SOPHIE installed on the OHP 1.93-m telescope. Characteristics and performances of the spectrograph are presented, as well as the SOPHIE exoplanet consortium program. With a minimum mass of 14.3 {M}_Jup, an orbital period of 465 days and an eccentricity of 0.067, HD 16760b seems to be located just at the end of the mass distribution of giant planets, close to the planet/brown-dwarf transition. Its quite circular orbit supports a formation in a gaseous protoplanetary disk. Based on observations made with SOPHIE spectrograph on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/OAMP), France (program 07A.PNP.CONS). Table 2 is also available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/505/853

  16. A Thermal Infrared Imaging Study of Very Low-Mass, Wide Separation Brown Dwarf Companions to Upper Scorpius Stars: Constraining Circumstellar Environments

    CERN Document Server

    Bailey, Vanessa; Currie, Thayne; Su, Kate Y L; Esposito, Simone; Hill, John M; Hoffmann, William F; Jones, Terry; Kim, Jihun; Leisenring, Jarron; Meyer, Michael; Murray-Clay, Ruth; Nelson, Matthew J; Pinna, Enrico; Puglisi, Alfio; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Skrutskie, Michael F; Vaitheeswaran, Vidhya; Wilson, John C

    2013-01-01

    We present a 3-5um LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low-masses/mass ratios (M_BD < 25M_Jup; M_BD / M_star ~ 1-2%), and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4um and 24um photometry to constrain the properties of the BDs and identify evidence for circumprimary/secondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24um excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4um excess, nor does its primary; however, the system as a whole has a modest 24um excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4um colors of HIP 7853...

  17. AB INITIO EQUATIONS OF STATE FOR HYDROGEN (H-REOS.3) AND HELIUM (He-REOS.3) AND THEIR IMPLICATIONS FOR THE INTERIOR OF BROWN DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Becker, Andreas; Lorenzen, Winfried; Schöttler, Manuel; Redmer, Ronald [Institut für Physik, Universität Rostock, D-18051 Rostock (Germany); Fortney, Jonathan J.; Nettelmann, Nadine [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2015-01-01

    We present new equations of state (EOSs) for hydrogen and helium covering a wide range of temperatures from 60 K to 10{sup 7} K and densities from 10{sup –10} g cm{sup –3} to 10{sup 3} g cm{sup –3}. They include an extended set of ab initio EOS data for the strongly correlated quantum regime with an accurate connection to data derived from other approaches for the neighboring regions. We compare linear mixing isotherms based on our EOS tables with available real mixture data. A first important astrophysical application of this new EOS data is the calculation of interior models for Jupiter and comparison with recent results. Second, mass-radius relations are calculated for Brown Dwarfs (BDs) which we compare with predictions derived from the widely used EOS of Saumon, Chabrier, and van Horn. Furthermore, we calculate interior models for typical BDs with different masses, namely, Corot-3b, Gliese-229b, and Corot-15b, and the giant planet KOI-889b. The predictions for the central pressures and densities differ by up to 10% dependent on the EOS used. Our EOS tables are made available in the supplemental material of this paper.

  18. A search for pre-substellar cores and proto-brown dwarf candidates in Taurus: multiwavelength analysis in the B213-L1495 clouds

    CERN Document Server

    Palau, Aina; Morata, Ò; Stamatellos, D; Huélamo, N; Eiroa, C; Bayo, A; Morales-Calderón, M; Bouy, H; Ribas, Á; Asmus, D; Barrado, D

    2012-01-01

    In an attempt to study whether the formation of brown dwarfs (BDs) takes place as a scaled-down version of low-mass stars, we conducted IRAM30m/MAMBO-II observations at 1.2 mm in a sample of 12 proto-BD candidates selected from Spitzer/IRAC data in the B213-L1495 clouds in Taurus. Subsequent observations with the CSO at 350 micron, VLA at 3.6 and 6 cm, and IRAM30m/EMIR in the 12CO(1-0), 13CO(1-0), and N2H+(1-0) transitions were carried out toward the two most promising Spitzer/IRAC source(s), J042118 and J041757. J042118 is associated with a compact (<10 arcsec or <1400 AU) and faint source at 350 micron, while J041757 is associated with a partially resolved (~16 arcsec or ~2000 AU) and stronger source emitting at centimetre wavelengths with a flat spectral index. The corresponding masses of the dust condensations are ~1 and ~5 Mjup for J042118 and J041757, respectively. In addition, about 40 arcsec to the northeast of J041757 we detect a strong and extended submillimetre source, J041757-NE, which is no...

  19. The dynamical evolution of low-mass hydrogen-burning stars, brown dwarfs and planetary-mass objects formed through disc fragmentation

    CERN Document Server

    Li, Yun; Stamatellos, D; Goodwin, S P

    2015-01-01

    Theory and simulations suggest that it is possible to form low-mass hydrogen-burning stars, brown dwarfs and planetary-mass objects via disc fragmentation. As disc fragmentation results in the formation of several bodies at comparable distances to the host star, their orbits are generally unstable. Here, we study the dynamical evolution of these objects. We set up the initial conditions based on the outcomes of the SPH simulations of Stamatellos & Whitworth, and for comparison we also study the evolution of systems resulting from lower-mass fragmenting discs. We refer to these two sets of simulations as set 1 and set 2. At 10 Myr, approximately half of the host stars have one companion left, and approximately 22% (set 1) to 9.8% (set 2) of the host stars are single. Systems with multiple secondaries in relatively stable configurations are common (about 30% and 44%, respectively). The majority of the companions are ejected within 1 Myr with velocities mostly below 5 km/s, with some runaway escapers with ve...

  20. Deep Near-Infrared Imaging of the rho Oph Cloud Core: Clues to the Origin of the Lowest-Mass Brown Dwarfs

    CERN Document Server

    Marsh, Kenneth A; Kirkpatrick, J Davy; Lowrance, Patrick J; Cutri, Roc M; Velusamy, Thangasamy

    2010-01-01

    A search for young substellar objects in the rho Oph cloud core region has been made using the deep-integration Combined Calibration Scan images of the 2MASS extended mission in J, H and Ks bands, and Spitzer IRAC images at 3.6, 4.5, 5.8 and 8.0 microns. The field of view of the combined observations was 1 deg x 9.3 arcmin, and the 5 sigma limiting magnitude at J was 20.5. Comparison of the observed SEDs with the predictions of the COND and DUSTY models, for an assumed age of 1 Myr, supports the identification of many of the sources with brown dwarfs, and enables the estimation of effective temperature, Teff. The cluster members are then readily distinguishable from background stars by their locations on a plot of flux density versus Teff. The range of estimated Teff extends down to ~ 750 K, suggesting the presence of objects of sub-Jupiter mass. The results also suggest that the mass function for the rho Oph cloud resembles that of the sigma Orionis cluster based on a recent study, with both rising towards l...

  1. Extrasolar planets and brown dwarfs around A-F type stars - VII. Theta Cygni radial velocity variations: planets or stellar phenomenon?

    CERN Document Server

    Desort, M; Galland, F; Udry, S; Montagnier, G; Beust, H; Boisse, I; Bonfils, X; Bouchy, F; Delfosse, X; Eggenberger, A; Ehrenreich, D; Forveille, T; Hébrard, G; Loeillet, B; Lovis, C; Mayor, M; Meunier, N; Moutou, C; Pepe, F; Perrier, C; Pont, F; Queloz, D; Santos, N C; Ségransan, D; Vidal-Madjar, A

    2009-01-01

    (abridged) In the frame of the search for extrasolar planets and brown dwarfs around early-type main-sequence stars, we present the results obtained on the early F-type star Theta Cygni. Elodie and Sophie at OHP were used to obtain the spectra. Our dedicated radial-velocity measurement method was used to monitor the star's radial velocities over five years. We also use complementary, high angular resolution and high-contrast images taken with PUEO at CFHT. We show that Theta Cygni radial velocities are quasi-periodically variable, with a ~150-day period. These variations are not due to the ~0.35-Msun stellar companion that we detected in imaging at more than 46 AU from the star. The absence of correlation between the bisector velocity span variations and the radial velocity variations for this 7 km/s vsini star, as well as other criteria indicate that the observed radial velocity variations are not due to stellar spots. The observed amplitude of the bisector velocity span variations also seems to rule out ste...

  2. Very Low Mass Stellar and Substellar Companions to Solar-like Stars From MARVELS IV: A Candidate Brown Dwarf or Low-Mass Stellar Companion to HIP 67526

    CERN Document Server

    Jiang, Peng; Cargile, Phillip; Crepp, Justin R; De Lee, Nathan; de Mello, Gustavo F Porto; Esposito, Massimiliano; Ferreira, Letícia D; Femenia, Bruno; Fleming, Scott W; Gaudi, B Scott; Ghezzi, Luan; Hernández, Jonay I González; Hebb, Leslie; Lee, Brian L; Ma, Bo; Stassun, Keivan G; Wang, Ji; Wisniewski, John P; Agol, Eric; Bizyaev, Dmitry; Brewington, Howard; Chang, Liang; da Costa, Luiz Nicolaci; Eastman, Jason D; Ebelke, Garrett; Gary, Bruce; Kane, Stephen R; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A G; Malanushenko, Viktor; Malanushenko, Elena; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L C; Oravetz, Audrey; Oravetz, Daniel; Pan, Kaike; Pepper, Joshua; Paegert, Martin; Prieto, Carlos Allende; Rebolo, Rafael; Santiago, Basilio X; Schneider, Donald P; Bradley, Alaina C Shelden; Sivarani, Thirupathi; Snedden, Stephanie; van Eyken, J C; Wan, Xiaoke; Weaver, Benjamin A; Zhao, Bo

    2013-01-01

    We report the discovery of a candidate brown dwarf or a very low mass stellar companion (MARVELS-5b) to the star HIP 67526 from the Multi-object APO Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 years. Our Keplerian fit using a Markov Chain Monte Carlo approach, reveals that the companion has an orbital period of $90.2695^{+0.0188}_{-0.0187}$ days, an eccentricity of $0.4375 \\pm 0.0040$ and a semi-amplitude of $2948.14^{+16.65}_{-16.55}$ m s$^{-1}$. Using additional high-resolution spectroscopy, we find the host star has an effective temperature $T_{\\rm{eff}}=6004 \\pm 34$ K, a surface gravity $\\log g$ [cgs] $=4.55 \\pm 0.17$ and a metallicity [Fe/H] $=+0.04 \\pm 0.06$. The stellar mass and radius determined through the empirical relationship of Torres et al. (2010), yields 1.10$\\pm$0.09 $M_{\\sun}$ and 0.92$\\pm$0.19 $R_{\\sun}$. The minimum mass of MARVELS-5b is $65.0 \\pm 2.9 M_{Jup}$, indicating that it is likely to be either a...

  3. Dust in brown dwarfs and extra-solar planets IV. Assessing TiO2 and SiO nucleation for cloud formation modeling

    CERN Document Server

    Lee, G; Giles, H; Bromley, S T

    2014-01-01

    Clouds form in atmospheres of brown dwarfs and planets. The cloud particle formation processes are similar to the dust formation process studied in circumstellar shells of AGB stars and in Supernovae. Cloud formation modelling in substellar objects requires gravitational settling and element replenishment in addition to element depletion. All processes depend on the local conditions, and a simultaneous treatment is required. We apply new material data in order to assess our cloud formation model results regarding the treatment of the formation of condensation seeds. We re-address the question of the primary nucleation species in view of new (TiO2)_N-cluster data and new SiO vapour pressure data. We apply the density functional theory using the computational chemistry package Gaussian 09 to derive updated thermodynamical data for (TiO2)_N-clusters as input for our TiO2 seed formation model. We test different nucleation treatments and their effect on the overall cloud structure by solving a system of dust momen...

  4. The Shape of LITTLE THINGS Dwarf Galaxies DDO 46 and DDO 168: Understanding the stellar and gas kinematics

    CERN Document Server

    Johnson, Megan C; Wood, Sarah; Oh, Se-Heon; Zhang, Hong-Xin; Herrmann, Kimberly A; Levine, Stephen E

    2015-01-01

    We present the stellar and gas kinematics of DDO 46 and DDO 168 from the LITTLE THINGS survey and determine their respective Vmax/sigma_z,0 values. We used the KPNO's 4-meter telescope with the Echelle spectrograph as a long-slit spectrograph. We acquired spectra of DDO 168 along four position angles by placing the slit over the morphological major and minor axes and two intermediate position angles. However, due to poor weather conditions during our observing run for DDO 46, we were able to extract only one useful data point from the morphological major axis. We determined a central stellar velocity dispersion perpendicular to the disk, sigma_z,0, of 13.5+/-8 km/s for DDO 46 and of 10.7+/-2.9 km/s for DDO 168. We then derived the maximum rotation speed in both galaxies using the LITTLE THINGS HI data. We separated bulk motions from non-circular motions using a double Gaussian decomposition technique and applied a tilted-ring model to the bulk velocity field. We corrected the observed HI rotation speeds for ...

  5. High-Contrast 3.8 Micron Imaging of the Brown Dwarf/Planet-Mass Companion to GJ 758

    Science.gov (United States)

    Currie, Thayne M.; Bailey, Vanessa; Fabrycky, Daniel; Murray-Clay, Ruth; Rodigas, Timothy; Hinz, Phil

    2011-01-01

    We present L' band (3.8 Micron) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. (2009) to have one - possibly two - faint comoving companions (GJ 7588 and "C", respectively). GJ 758B is detected in two distinct datasets. Additionally, we report a \\textit{possible} detection of the object identified by Thalmann et al as "GJ 758C" in our more sensitive dataset, though it is likely a residual speckle. However, if it is the same object as that reported by Thalmann et al. it cannot be a companion in a bound orbit. GJ 7588 has a H-L' color redder than nearly all known L-T8 dwarfs. 8ased on comparisons with the COND evolutionary models, GJ 7588 has Te approx. 560 K (+150 K, -90 K) and a mass ranging from approx.10-20 Mj if it is approx.1 Gyr old to approx. 25-40 Mj if it is 8.7 Gyr old. GJ 7588 is likely in a highly eccentric orbit, e approx. 0.73 (+0.12,-0.21), with a semimajor axis of approx. 44 AU (+32 AU, -14 AU). Though GJ 7588 is sometimes discussed within the context of exoplanet direct imaging, its mass is likely greater than the deuterium-burning limit and its formation may resemble that of binary stars rather than that of jovian-mass planets.

  6. Near-infrared integral-field spectra of the planet/brown dwarf companion AB Pic b

    CERN Document Server

    Bonnefoy, M; Rojo, P; Allard, F; Lagrange, A -M; Homeier, D; Dumas, C; Beuzit, J -L

    2010-01-01

    Chauvin et al. 2005 imaged a co-moving companion at ~260 AU from the young star AB Pic A. Evolutionary models predictions based on J H K photometry of AB Pic b suggested a mass of ~13 - 14 MJup, placing the object at the deuterium-burning boundary. We used the adaptive-optics-fed integral field spectrograph SINFONI to obtain high quality medium-resolution spectra of AB Pic b (R = 1500-2000) over the 1.1 - 2.5 microns range. Our analysis relies on the comparison of our spectra to young standard templates and to the latest libraries of synthetic spectra developed by the Lyon's Group. AB Pic b is confirmed to be a young early-L dwarf companion. We derive a spectral type L0-L1 and find several features indicative of intermediate gravity atmosphere. A comparison to synthetic spectra yields Teff = 2000+100-300 K and log(g) = 4 +- 0.5 dex. The determination of the derived atmospheric parameters of AB Pic b is limited by a non-perfect match of current atmosphere spectra with our near-infrared observations of AB Pic b...

  7. VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. IV. A CANDIDATE BROWN DWARF OR LOW-MASS STELLAR COMPANION TO HIP 67526

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Peng; Ge Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Ma Bo; Wang, Ji [Astronomy Department, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States); Cargile, Phillip; Hebb, Leslie; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Porto de Mello, Gustavo F.; Ferreira, Leticia D. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antonio, 43, CEP: 20080-090, Rio de Janeiro, RJ (Brazil); Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I. [Instituto de Astrofisica de Canarias, C/Via Lactea S/N, E-38200 La Laguna (Spain); Gaudi, B. Scott [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Ghezzi, Luan [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rio de Janeiro, RJ 20921-400 (Brazil); Wisniewski, John P. [Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Agol, Eric, E-mail: jpaty@mail.ustc.edu.cn [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); and others

    2013-09-15

    We report the discovery of a candidate brown dwarf (BD) or a very low mass stellar companion (MARVELS-5b) to the star HIP 67526 from the Multi-object Apache point observatory Radial Velocity Exoplanet Large-area Survey (MARVELS). The radial velocity curve for this object contains 31 epochs spread over 2.5 yr. Our Keplerian fit, using a Markov Chain Monte Carlo approach, reveals that the companion has an orbital period of 90.2695{sup +0.0188}{sub -0.0187} days, an eccentricity of 0.4375 {+-} 0.0040, and a semi-amplitude of 2948.14{sup +16.65}{sub -16.55} m s{sup -1}. Using additional high-resolution spectroscopy, we find the host star has an effective temperature T{sub eff} = 6004 {+-} 34 K, a surface gravity log g (cgs) =4.55 {+-} 0.17, and a metallicity [Fe/H] =+0.04 {+-} 0.06. The stellar mass and radius determined through the empirical relationship of Torres et al. yields 1.10 {+-} 0.09 M{sub Sun} and 0.92 {+-} 0.19 R{sub Sun }. The minimum mass of MARVELS-5b is 65.0 {+-} 2.9M{sub Jup}, indicating that it is likely to be either a BD or a very low mass star, thus occupying a relatively sparsely populated region of the mass function of companions to solar-type stars. The distance to this system is 101 {+-} 10 pc from the astrometric measurements of Hipparcos. No stellar tertiary is detected in the high-contrast images taken by either FastCam lucky imaging or Keck adaptive optics imaging, ruling out any star with mass greater than 0.2 M{sub Sun} at a separation larger than 40 AU.

  8. Testing Model Atmospheres for Young Very-low-mass Stars and Brown Dwarfs in the Infrared: Evidence for Significantly Underestimated Dust Opacities

    Science.gov (United States)

    Tottle, Jonathan; Mohanty, Subhanjoy

    2015-05-01

    We test state-of-the-art model atmospheres for young very-low-mass stars and brown dwarfs in the infrared, by comparing the predicted synthetic photometry over 1.2-24 μm to the observed photometry of M-type spectral templates in star-forming regions. We find that (1) in both early and late young M types, the model atmospheres imply effective temperatures ({{T}eff}) several hundred Kelvin lower than predicted by the standard pre-main sequence (PMS) spectral type-{{T}eff} conversion scale (based on theoretical evolutionary models). It is only in the mid-M types that the two temperature estimates agree. (2) The {{T}eff} discrepancy in the early M types (corresponding to stellar masses ≳ 0.4 {{M}⊙ } at ages of a few Myr) probably arises from remaining uncertainties in the treatment of atmospheric convection within the atmospheric models, whereas in the late M types it is likely due to an underestimation of dust opacity. (3) The empirical and model-atmosphere J-band bolometric corrections are both roughly flat, and similar to each other, over the M-type {{T}eff} range. Thus the model atmospheres yield reasonably accurate bolometric luminosities ({{L}bol}), but lead to underestimations of mass and age relative to evolutionary expectations (especially in the late M types) due to lower {{T}eff}. We demonstrate this for a large sample of young Cha I and Taurus sources. (4) The trends in the atmospheric model J-Ks colors, and their deviations from the data, are similar at PMS and main sequence ages, suggesting that the model dust opacity errors we postulate here for young ages also apply at field ages.

  9. A THERMAL INFRARED IMAGING STUDY OF VERY LOW MASS, WIDE-SEPARATION BROWN DWARF COMPANIONS TO UPPER SCORPIUS STARS: CONSTRAINING CIRCUMSTELLAR ENVIRONMENTS

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Vanessa; Hinz, Philip M.; Su, Kate Y. L.; Hoffmann, William F.; Rieke, George; Rodigas, Timothy; Skemer, Andrew; Vaitheeswaran, Vidhya [Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Currie, Thayne [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada); Esposito, Simone; Pinna, Enrico; Puglisi, Alfio [Osservatorio Astrofisico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Hill, John M. [Large Binocular Telescope Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Jones, Terry [School of Physics and Astronomy, University of Minnesota, 116 Church St. SE, Minneapolis, MN 55455 (United States); Kim, Jihun [College of Optical Sciences, University of Arizona, 1630 E. University Blvd., Tucson, AZ 85721 (United States); Leisenring, Jarron; Meyer, Michael [Institut fuer Angewandte Physik, Eidgenoessische Technische Hochschule-Zuerich, CH-8093 (Switzerland); Murray-Clay, Ruth; Skrutskie, Michael F. [Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden St., Cambridge, MA 02138 (United States); Nelson, Matthew J., E-mail: vbailey@as.arizona.edu [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); and others

    2013-04-10

    We present a 3-5 {mu}m LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (M{sub BD} <25 M{sub Jup}; M{sub BD}/M{sub *} Almost-Equal-To 1%-2%) and wide separations (300-700 AU): GSC 06214, 1RXS 1609, and HIP 78530. We combine these new thermal IR data with existing 1-4 {mu}m and 24 {mu}m photometry to constrain the properties of the BDs and identify evidence for circumprimary/circumsecondary disks in these unusual systems. We confirm that GSC 06214B is surrounded by a disk, further showing that this disk produces a broadband IR excess due to small dust near the dust sublimation radius. An unresolved 24 {mu}m excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4 {mu}m excess, nor does its primary; however, the system as a whole has a modest 24 {mu}m excess, which may come from warm dust around the primary and/or BD. Neither object in the HIP 78530 system exhibits near- to mid-IR excesses. We additionally find that the 1-4 {mu}m colors of HIP 78530B match a spectral type of M3 {+-} 2, inconsistent with the M8 spectral type assigned based on its near-IR spectrum, indicating that it may be a low-mass star rather than a BD. We present new upper limits on additional low-mass companions in the system (<5 M{sub Jup} beyond 175 AU). Finally, we examine the utility of circumsecondary disks as probes of the formation histories of wide BD companions, finding that the presence of a disk may disfavor BD formation near the primary with subsequent outward scattering.

  10. Planet Host Stars: Mass, Age and Kinematics

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    We determine the mass, age and kinematics of 51 extra-solar planet host stars. The results are then used to search for signs of connection of the data with metallicity and to investigate the population nature. We find that the increase in mean metallicity with stellar mass is similar to that in normal field stars, so it seems unsuitable to use this relation as a constraint on the theory of planet formation. The age and kinematic distributions seem to favour the metallicity of extra-solar planet host stars being initial. Although the kinematic data of these stars indicate their origin from two populations - the thin and the thick disks, kinematics may not help in the maintenance of the planet around the host. Stars with planets, brown dwarfs or stellar companions are sorted into three groups and re-investigated separately for their formation mechanism. The main results indicate that stars with M2 < 25MJ have [Fe/H] > -0.1 and a wide period range, but there are no other differences.Thus, there does not seem to be any physically distinguishable characteristics among the three star groups.

  11. THE DYNAMICAL EVOLUTION OF LOW-MASS HYDROGEN-BURNING STARS, BROWN DWARFS, AND PLANETARY-MASS OBJECTS FORMED THROUGH DISK FRAGMENTATION

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yun; Kouwenhoven, M. B. N. [Department of Astronomy, School of Physics, Peking University, Yiheyuan Lu 5, Haidian Qu, Beijing 100871 (China); Stamatellos, D. [Jeremiah Horrocks Institute for Mathematics, Physics and Astronomy, University of Central Lancashire, Preston, PR1 2HE (United Kingdom); Goodwin, S. P., E-mail: yunli@pku.edu.cn [Department of Physics and Astronomy, The University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom)

    2015-06-01

    Theory and simulations suggest that it is possible to form low-mass hydrogen-burning stars, brown dwarfs (BDs), and planetary-mass objects (PMOs) via disk fragmentation. As disk fragmentation results in the formation of several bodies at comparable distances to the host star, their orbits are generally unstable. Here, we study the dynamical evolution of these objects. We set up the initial conditions based on the outcomes of the smoothed-particle hydrodynamics simulations of Stamatellos and Whitworth, and for comparison we also study the evolution of systems resulting from lower-mass fragmenting disks. We refer to these two sets of simulations as set 1 and set 2, respectively. At 10 Myr, approximately half of the host stars have one companion left, and approximately 22% (set 1) to 9.8% (set 2) of the host stars are single. Systems with multiple secondaries in relatively stable configurations are common (about 30% and 44%, respectively). The majority of the companions are ejected within 1 Myr with velocities mostly below 5 km s{sup −1}, with some runaway escapers with velocities over 30 km s{sup −1}. Roughly 6% (set 1) and 2% (set 2) of the companions pair up into very low-mass binary systems, resulting in respective binary fractions of 3.2% and 1.2%. The majority of these pairs escape as very low-mass binaries, while others remain bound to the host star in hierarchical configurations (often with retrograde inner orbits). Physical collisions with the host star (0.43 and 0.18 events per host star for set 1 and set 2, respectively) and between companions (0.08 and 0.04 events per host star for set 1 and set 2, respectively) are relatively common and their frequency increases with increasing disk mass. Our study predicts observable properties of very low-mass binaries, low-mass hierarchical systems, the BD desert, and free-floating BDs and PMOs in and near young stellar groupings, which can be used to distinguish between different formation scenarios of very low

  12. K2 Discovery of Young Eclipsing Binaries in Upper Scorpius: Direct Mass and Radius Determinations for the Lowest Mass Stars and Initial Characterization of an Eclipsing Brown Dwarf Binary

    CERN Document Server

    David, Trevor J; Cody, Ann Marie; Carpenter, John M; Howard, Andrew W

    2015-01-01

    We report the discovery of three low-mass double-lined eclipsing binaries in the pre-main sequence Upper Scorpius association, revealed by $K2$ photometric monitoring of the region over $\\sim$ 78 days. The orbital periods of all three systems are $<$5 days. We use the $K2$ photometry plus multiple Keck/HIRES radial velocities and spectroscopic flux ratios to determine fundamental stellar parameters for both the primary and secondary components of each system, along with the orbital parameters. We present tentative evidence that EPIC 203868608 is a hierarchical triple system comprised of an eclipsing pair of $\\sim$25 $M_\\mathrm{Jup}$ brown dwarfs with a wide M-type companion. If confirmed, it would constitute only the second double-lined eclipsing brown dwarf binary system discovered to date. The double-lined system EPIC 203710387 is composed of nearly identical M4.5-M5 stars with fundamentally determined masses and radii measured to better than 3% precision ($M_1=0.1169\\pm0.0031 M_\\odot$, $M_2=0.1065\\pm0.0...

  13. The EBLM Project I-Physical and orbital parameters, including spin-orbit angles, of two low-mass eclipsing binaries on opposite sides of the Brown Dwarf limit

    CERN Document Server

    Triaud, Amaury H M J; Anderson, David R; Cargile, Phill; Cameron, Andrew Collier; Doyle, Amanda P; Faedi, Francesca; Gillon, Michaël; Chew, Yilen Gomez Maqueo; Hellier, Coel; Jehin, Emmanuel; Maxted, Pierre; Naef, Dominique; Pepe, Francesco; Pollacco, Don; Queloz, Didier; Ségransan, Damien; Smalley, Barry; Stassun, Keivan; Udry, Stéphane; West, Richard G

    2012-01-01

    This paper introduces a series of papers aiming to study the dozens of low mass eclipsing binaries (EBLM), with F, G, K primaries, that have been discovered in the course of the WASP survey. Our objects are mostly single-line binaries whose eclipses have been detected by WASP and were initially followed up as potential planetary transit candidates. These have bright primaries, which facilitates spectroscopic observations during transit and allows the study of the spin-orbit distribution of F, G, K+M eclipsing binaries through the Rossiter-McLaughlin effect. Here we report on the spin-orbit angle of WASP-30b, a transiting brown dwarf, and improve its orbital parameters. We also present the mass, radius, spin-orbit angle and orbital parameters of a new eclipsing binary, J1219-39b (1SWAPJ121921.03-395125.6, TYC 7760-484-1), which, with a mass of 95 +/- 2 Mjup, is close to the limit between brown dwarfs and stars. We find that both objects orbit in planes that appear aligned with their primaries' equatorial plane...

  14. Very Low-Mass Stellar and Substellar Companions to Solar-like Stars From MARVELS VI: A Giant Planet and a Brown Dwarf Candidate in a Close Binary System HD 87646

    CERN Document Server

    Ma, Bo; Wolszczan, Alex; Muterspaugh, Matthew W; Lee, Brian; Henry, Gregory W; Schneider, Donald P; Martin, Eduardo L; Niedzielski, Andrzej; Xie, Jiwei; Fleming, Scott W; Thomas, Neil; Williamson, Michael; Zhu, Zhaohuan; Agol, Eric; Bizyaev, Dmitry; da Costa, Luiz Nicolaci; Jiang, Peng; Fiorenzano, A F Martinez; Hernandez, Jonay I Gonzalez; Guo, Pengcheng; Grieves, Nolan; Li, Rui; Liu, Jane; Mahadevan, Suvrath; Mazeh, Tsevi; Nguyen, Duy Cuong; Paegert, Martin; Sithajan, Sirinrat; Stassun, Keivan; Thirupathi, Sivarani; van Eyken, Julian C; Wan, Xiaoke; Wang, Ji; Wisniewski, John P; Zhao, Bo; Zucker, Shay

    2016-01-01

    We report the detections of a giant planet (MARVELS-7b) and a brown dwarf candidate (MARVELS-7c) around the primary star in the close binary system, HD 87646. It is the first close binary system with more than one substellar circum-primary companion discovered to the best of our knowledge. The detection of this giant planet was accomplished using the first multi-object Doppler instrument (KeckET) at the Sloan Digital Sky Survey (SDSS) telescope. Subsequent radial velocity observations using ET at Kitt Peak National Observatory, HRS at HET, the "Classic" spectrograph at the Automatic Spectroscopic Telescope at Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period brown dwarf in this binary. HD 87646 is a close binary with a separation of $\\sim22$ AU between the two stars, estimated using the Hipparcos catalogue and our newly acquired AO image from PALAO on the 200-inch Hale Telescope at Palomar. The primary star in the binary, HD 87646...

  15. Runaway M Dwarf Candidates from the Sloan Digital Sky Survey

    CERN Document Server

    Favia, Andrej; Theissen, Christopher A

    2015-01-01

    We present a sample of 20 runaway M dwarf candidates (RdMs) within 1 kpc of the Sun whose Galactocentric velocities exceed 400 km s$^{-1}$. The candidates were selected from the SDSS DR7 M Dwarf Catalog of West et al. (2011). Our RdMs have SDSS+USNO-B proper motions that are consistent with those recorded in the PPMXL, LSPM, and combined WISE+SDSS+2MASS catalogs. Sixteen RdMs are classified as dwarfs, while the remaining four RdMs are subdwarfs. We model the Galactic potential using a bulge-disk-halo profile (Kenyon et al. 2008; Brown et al. 2014). Our fastest RdM, with Galactocentric velocity 658.5 $\\pm$ 236.9 km s$^{-1}$, is a possible hypervelocity candidate, as it is unbound in 77% of our simulations. About half of our RdMs have kinematics that are consistent with ejection from the Galactic center. Seven of our RdMs have kinematics consistent with an ejection scenario from M31 or M32 to within 2{\\sigma}, although our distance-limited survey makes such a realization unlikely. No more than four of our RdMs ...

  16. HST Rotational Spectral Mapping of Two L-Type Brown Dwarfs: Variability In and Out of Water Bands Indicates High-Altitude Haze Layers

    CERN Document Server

    Yang, Hao; Marley, Mark S; Saumon, Didier; Morley, Caroline V; Buenzli, Esther; Artigau, Etienne; Radigan, Jacqueline; Metchev, Stanimir; Burgasser, Adam J; Mohanty, Subhanjoy; Lowrance, Patrick L; Showman, Adam P; Karalidi, Theodora; Flateau, Davin; Heinze, Aren N

    2014-01-01

    We present time-resolved near-infrared spectroscopy of two L5 dwarfs, 2MASS J18212815+1414010 and 2MASS J15074759-1627386, observed with the Wide Field Camera 3 instrument on the Hubble Space Telescope (HST). We study the wavelength dependence of rotation-modulated flux variations between 1.1 $\\mu$m and 1.7 $\\mu$m. We find that the water absorption bands of the two L5 dwarfs at 1.15 $\\mu$m and 1.4 $\\mu$m vary at similar amplitudes as the adjacent continuum. This differs from the results of previous HST observations of L/T transition dwarfs, in which the water absorption at 1.4 $\\mu$m displays variations of about half of the amplitude at other wavelengths. We find that the relative amplitude of flux variability out of the water band with respect to that in the water band shows a increasing trend from the L5 dwarfs toward the early T dwarfs. We utilize the models of Saumon & Marley (2008) and find that the observed variability of the L5 dwarfs can be explained by the presence of spatially varying high-altit...

  17. Two Extraordinary Substellar Binaries at the T/Y Transition and the Y-Band Fluxes of the Coolest Brown Dwarfs

    CERN Document Server

    Liu, Michael C; Bowler, Brendan P; Leggett, S K; Best, William M J

    2012-01-01

    Using Keck laser guide star adaptive optics imaging, we have found that the T9 dwarf WISE J1217+1626 and T8 dwarf WISE J1711+3500 are exceptional binaries, with unusually wide separations (~0.8 arcsec, 8-15 AU), large near-IR flux ratios (~2-3 mags), and small mass ratios (~0.5). Keck/NIRSPEC H-band spectra give a spectral type of Y0 for WISE J1217+1626B, and photometric estimates suggest T9.5 for WISE J1711+3500B. The WISE J1217+1626AB system is very similar to the T9+Y0 binary CFBDSIR J1458+1013AB; these two systems are the coldest known substellar multiples, having secondary components of ~400 K and being planetary-mass binaries if their ages are <~1 Gyr. Both WISE J1217+1626B and CFBDSIR J1458+1013B have strikingly blue Y-J colors compared to previously known T dwarfs, including their T9 primaries. Combining all available data, we find that Y-J color drops precipitously between the very latest T dwarfs and the Y dwarfs. The fact that this is seen in (coeval, mono-metallicity) binaries demonstrates that...

  18. STELLAR METALLICITIES AND KINEMATICS IN A GAS-RICH DWARF GALAXY : FIRST CALCIUM TRIPLET SPECTROSCOPY OF RED GIANT BRANCH STARS IN WLM

    NARCIS (Netherlands)

    Leaman, Ryan; Cole, Andrew A.; Venn, Kim A.; Tolstoy, Eline; Irwin, Mike J.; Szeifert, Thomas; Skillman, Evan D.; McConnachie, Alan W.

    2009-01-01

    We present the first determination of the radial velocities and metallicities of 78 red giant stars in the isolated dwarf irregular galaxy WLM. Observations of the calcium II triplet in these stars were made with FORS2 at the VLT-UT2 in two separated fields of view in WLM, and the [Fe/H] values were

  19. Comparison of the potential rate of population increase of brown and green color morphs of Sitobion avenae (Homoptera: Aphididae) on barley infected and uninfected with Barley yellow dwarf virus.

    Science.gov (United States)

    Hu, Zu-Qing; Zhao, Hui-Yan; Thieme, Thomas

    2014-06-01

    Life tables of brown and green color morphs of the English grain aphid, Sitobion avenae (Fabricius) reared on barley under laboratory conditions at 20 ± 1°C, 65% ± 5% relative humidity and a photoperiod of 16 : 8 h (L : D) were compared. The plants were either: (i) infected with the Barley yellow dwarf virus (BYDV); (ii) not infected with virus but previously infested with aphids; or (iii) healthy barley plants, which were not previously infested with aphids. Generally, both color morphs of S. avenae performed significantly better when fed on BYDV-infected plants than on plants that were virus free but had either not been or had been previously infested with aphids. Furthermore, when fed on BYDV-infected plants, green S. avenae developed significantly faster and had a significantly shorter reproductive period than the brown color morph. There were no significant differences in this respect between the two color morphs of S. avenae when they were reared on virus-free plants that either had been or not been previously infested with aphids. These results indicate that barley infected with BYDV is a more favorable host plant than uninfected barley for both the color morphs of S. avenae tested, particularly the green color morph.

  20. LHS 2803B: A very wide mid-T dwarf companion to an old M dwarf identified from Pan-STARRS1

    CERN Document Server

    Deacon, Niall R; Magnier, Eugene A; Bowler, Brendan P; Mann, Andrew W; Redstone, Joshua A; Burgett, William S; Chambers, Ken C; Hodapp, Klaus W; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S; Price, Paul A; Tonry, John L; Wainscoat, Richard J

    2012-01-01

    We report the discovery of a wide (approximately 400 AU projected separation), common proper motion companion to the nearby M dwarf LHS 2803 (PSO J207.0300-13.7422). This object was discovered during our census of the local T dwarf population using Pan-STARRS1 and 2MASS data. Using IRTF/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawai`i 2.2m/SNIFS optical spectroscopy indicates the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable H_alpha emission. We use this lack of activity to set a lower age limit for the system of 3.5 Gyr. Using a comparison with chance alignments of brown dwarfs and nearby stars, we conclude that the two objects are unlikely to be a chance association. The primary's photometric distance of 21 pc and its proper motion implies thin disk kinematics. Based on these kinematics and its metallicity, we set an upper age limit for the system of 10 Gyr. Evolutionary model calculations suggest the sec...

  1. Binary frequency of planet-host stars at wide separations: A new brown dwarf companion to a planet-host star

    CERN Document Server

    Lodieu, N; Bejar, V J S; Gauza, B; Ruiz, M T; Rebolo, R; Pinfield, D J; Martin, E L

    2014-01-01

    The aim of the project is to improve our knowledge on the multiplicity of planet-host stars at wide physical separations. We cross-matched approximately 6200 square degree area of the Southern sky imaged by the Visible Infrared Survey Telescope for Astronomy (VISTA) Hemisphere Survey (VHS) with the Two Micron All Sky Survey (2MASS) to look for wide common proper motion companions to known planet-host stars. We complemented our astrometric search with photometric criteria. We confirmed spectroscopically the co-moving nature of seven sources out of 16 companion candidates and discarded eight, while the remaining one stays as a candidate. Among these new wide companions to planet-host stars, we discovered a T4.5 dwarf companion at 6.3 arcmin (~9000 au) from HIP70849, a K7V star which hosts a 9 Jupiter mass planet with an eccentric orbit. We also report two new stellar M dwarf companions to one G and one metal-rich K star. We infer stellar and substellar binary frequencies for our complete sample of 37 targets of...

  2. Identifying the Young Low-mass Stars within 25 pc. II. Distances, Kinematics, and Group Membership

    Science.gov (United States)

    Shkolnik, Evgenya L.; Anglada-Escudé, Guillem; Liu, Michael C.; Bowler, Brendan P.; Weinberger, Alycia J.; Boss, Alan P.; Reid, I. Neill; Tamura, Motohide

    2012-10-01

    We have conducted a kinematic study of 165 young M dwarfs with ages of lsim300 Myr. Our sample is composed of stars and brown dwarfs with spectral types ranging from K7 to L0, detected by ROSAT and with photometric distances of lsim25 pc assuming that the stars are single and on the main sequence. In order to find stars kinematically linked to known young moving groups (YMGs), we measured radial velocities for the complete sample with Keck and CFHT optical spectroscopy and trigonometric parallaxes for 75 of the M dwarfs with the CAPSCam instrument on the du Pont 2.5 m Telescope. Due to their youthful overluminosity and unresolved binarity, the original photometric distances for our sample underestimated the distances by 70% on average, excluding two extremely young (lsim3 Myr) objects found to have distances beyond a few hundred parsecs. We searched for kinematic matches to 14 reported YMGs and identified 10 new members of the AB Dor YMG and 2 of the Ursa Majoris group. Additional possible candidates include six Castor, four Ursa Majoris, two AB Dor members, and one member each of the Her-Lyr and β Pic groups. Our sample also contains 27 young low-mass stars and 4 brown dwarfs with ages lsim150 Myr that are not associated with any known YMG. We identified an additional 15 stars that are kinematic matches to one of the YMGs, but the ages from spectroscopic diagnostics and/or the positions on the sky do not match. These warn against grouping stars together based only on kinematics and that a confluence of evidence is required to claim that a group of stars originated from the same star-forming event. Based on observations collected at the W. M. Keck Observatory, the Canada-France-Hawaii Telescope, the du Pont Telescope at Las Campanas Observatory, and the Subaru Telescope. The Keck Observatory is operated as a scientific partnership between the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial

  3. The scatter about the "Universal" dwarf spheroidal mass profile: A kinematic study of the M31 satellites, And V and And VI

    CERN Document Server

    Collins, M L M; Rich, R M; Ibata, R A; Irwin, M J; Peñarrubia, J; Arimoto, N; Brooks, A M; Lewis, G F; McConnachie, A W; Venn, K

    2011-01-01

    While the satellites of the Milky Way (MW) have been shown to be largely consistent in terms of their mass contained within one half--light radius (M_{half}) with a "Universal" mass profile, a number of M31 satellites are found to be inconsistent with such relations, and seem kinematically colder in their central regions than their MW cousins. In this work, we present new kinematic and updated structural properties for two M31 dSphs, And V and And VI using data from the Keck Low Resolution Imaging Spectrograph (LRIS) and the DEep Imaging Multi-Object Spectrograph (DEIMOS) instruments and the Subaru Suprime-Cam imager. We measure systemic velocities of v_r=-393.1+/-4.2km/s and -344.8+/-2.5km/s, and dispersions of sigma_v=11.5{+5.3}{-4.4}km/s and sigma_v=9.4{+3.2}{-2.4}km/s for And V and And VI respectively, meaning these two objects are consistent with the trends in sigma_v and r_{half} set by their MW counterparts. We also investigate the nature of this scatter about the MW dSph mass profiles for the "Classic...

  4. A Search for Coronal Emission at the Bottom of the Main-Sequence: Stars and Brown Dwarf Candidates with Spectral Types Later than M7 and the Rotation-Activity Relation

    Science.gov (United States)

    Stringfellow, Guy

    2004-01-01

    This program intended to test whether the lowest mass stars at the bottom end of the main sequence and the lower mass brown dwarfs have coronae. If they have coronae, what are the coronal characteristics and what drives them? In the classical dynamo picture, the closed magnetic loop structure is generated near the boundary of the convective envelope and the radiative core. Stars with mass below 0.30 Msun however are fully convective, and the nature of the dynamo responsible for the generation of the coronae in this regime is poorly understood. Previous results from the ROSAT mission (e.g., Fleming et al. 1993, 1995; Schmitt et al. 1995) had confirmed three very important characteristics of M-star coronae: (1) a very high percentage of all M dwarfs have coronae (of order 85% in the local 7 pc sample), (2) those M dwarfs showing high chromospheric activity, such as having the Balmer series in emission or large/numerous optical flaring, indeed exhibit the highest coronal activity, and (3) that the maximum saturation boundary in X-ray luminosity, which amounts to 0.0001-0.001 for Lx/Lbol for the dMe stars, extends down to the current detection limit, through spectral types M7. It was likely that the incompleteness noted for result (1) above was simply a detection limit problem; for more distant sources, the X-ray fainter dM stars will drop below detection thresholds before the more X-ray luminous dMe stars. The latest stars for which direct detection of the corona had been successful were of spectral type dM7 (e.g., VB8, LHS 3003). This program proposed to obtain ROSAT HRI observations for a large number of the coolest known (at that time) stars at the bottom of the main-sequence, which had spectral types of M9 or later. Three stars were approved for observations with ROSAT-HRI totaling 180 ksec. The goal was to obtain X-ray detections or low upper limits for the three approved stars.

  5. Very Low Mass Stellar and Substellar Companions to Solar-Like Stars From MARVELS V: A Low Eccentricity Brown Dwarf from the Driest Part of the Desert, MARVELS-6b

    CERN Document Server

    De Lee, Nathan; Crepp, Justin R; Eastman, Jason; Esposito, Massimiliano; Femenía, Bruno; Fleming, Scott W; Gaudi, B Scott; Ghezzi, Luan; Hernández, Jonay I González; Lee, Brian L; Stassun, Keivan G; Wisniewski, John P; Wood-Vasey, W Michael; Agol, Eric; Prieto, Carlos Allende; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N; De Mello, G F Porto; Ferreira, Leticia D; Gary, Bruce; Hebb, Leslie; Holtzman, Jon; Liu, Jian; Ma, Bo; Mack, Claude E; Mahadevan, Suvrath; Maia, Marcio A G; Nguyen, Duy Cuong; Oravetz, Audrey; Oravetz, Daniel J; Paegert, Martin; Pan, Kaike; Pepper, Joshua; Malanushenko, Elena; Malanushenko, Viktor; Rebolo, Rafael; Santiago, Basilio X; Schneider, Donald P; Bradley, Alaina C Shelden; Wan, Xiaoke; Wang, Ji; Zhao, Bo

    2013-01-01

    We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 +/- 2.0 M_Jup to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M_Sun, and thus it is a high-confidence BD companion. It has a moderately long orbital period of 47.8929 +0.0063/-0.0062 days with a low eccentricty of 0.1442 +0.0078/-0.0073, and a semi-amplitude of 1644 +12/-13 m/s. Moderate resolution spectroscopy of the host star has determined the following parameters: T_eff = 5598 +/- 63, log g = 4.44 +/- 0.17, and [Fe/H] = +0.40 +/- 0.09. Based upon these measurements, GSC 03546-01452 has a probable mass and radius of M_star = 1.11 +/- 0.11 M_Sun and R_star = 1.06 +/- 0.23 R_Sun with an age consistent with less than ~6 Gyr at a distance of 219 +/- 21 pc from the Sun. Although MARVELS-6b is not observed to transit, we cannot definitively rule ...

  6. Very Low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels III: A Short-Period Brown Dwarf Candidate Around An Active G0Iv Subgiant

    CERN Document Server

    Ma, Bo; Barnes, Rory; Crepp, Justin R; De Lee, Nathan; Dutra-Ferreira, Leticia; Esposito, Massimiliano; Femenia, Bruno; Fleming, Scott W; Gaudi, B Scott; Ghezzi, Luan; Hebb, Leslie; Hernandez, Jonay I Gonzalez; Lee, Brian L; de Mello, G F Porto; Stassun, Keivan G; Wang, Ji; Wisniewski, John P; Agol, Eric; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; da Costa, Luiz Nicolaci; Eastman, Jason D; Gary, Bruce; Jiang, Peng; Kane, Stephen R; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A G; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L C; Oravetz, Daniel; Pepper, Joshua; Paegert, Martin; Prieto, Carlos Allende; Rebolo, Rafael; Santiago, Basilio X; Schneider, Donald P; Shelden, Alaina; Simmons, Audrey; Sivarani, Thirupathi; van Eyken, J C; Wan, Xiaoke; Weaver, Benjamin A; Zhao, Bo

    2012-01-01

    We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T_eff = 5903+/-42 K, surface gravity log (g) = 4.07+/-0.16 (cgs), and metallicity [Fe/H] = -0.23+/-0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey (MARVELS), which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K=3.571+/-0.041 km/s, period P=9.0090+/-0.0004 days, and eccentricity e=0.226+/-0.011. Adopting a mass of 1.16+/-0.11 Msun for the subgiant host star, we infer that the companion has a minimum mass of 40.0+/-2.5 M_Jup. Assuming an edge-on orbit, the semimajor axis is 0.090+/-0.003 AU. The host star is photometrically variable at the \\sim1% level with a period of \\sim13.16+/-0.01 days, indicating that the host sta...

  7. Planck cold clumps in the $\\lambda$ Orionis complex: I. Discovery of an extremely young Class 0 protostellar object and a proto-brown dwarf candidate in a bright rimmed clump PGCC G192.32-11.88

    CERN Document Server

    Liu, Tie; Kim, Kee-Tae; Wu, Yuefang; Lee, Chang Won; Lee, Jeong-Eun; Tatematsu, Kenichi; Choi, Minho; Juvela, Mika; Thompson, Mark; Goldsmith, Paul F; Liu, Sheng-yuan; Naomi, Hirano; Koch, Patrick; Henkel, Christian; Sanhueza, Patricio; He, JinHua; Rivera-Ingraham, Alana; Wang, Ke; Cunningham, Maria R; Tang, Ya-Wen; Lai, Shih-Ping; Yuan, Jinghua; Li, Di; Fuller, Gary; Kang, Miju; Luong, Quang Nguyen; Liu, Hauyu Baobab; Ristorcelli, Isabelle; Yang, Ji; Xu, Ye; Hirota, Tomoya; Mardones, Diego; Qin, Sheng-Li; Chen, Huei-Ru; Kwon, Woojin; Meng, FanYi; Zhang, Huawei; Kim, Mi-Ryang; Yi, Hee-Weon

    2015-01-01

    We are performing a series of observations with ground-based telescopes toward Planck Galactic cold clumps (PGCCs) in the $\\lambda$ Orionis complex in order to systematically investigate the effects of stellar feedback. In the particular case of PGCC G192.32-11.88, we discovered an extremely young Class 0 protostellar object (G192N) and a proto-brown dwarf candidate (G192S). G192N and G192S are located in a gravitationally bound bright-rimmed clump. The velocity and temperature gradients seen in line emission of CO isotopologues indicate that PGCC G192.32-11.88 is externally heated and compressed. G192N probably has the lowest bolometric luminosity ($\\sim0.8$ L$_{\\sun}$) and accretion rate (6.3$\\times10^{-7}$ M$_{\\sun}$~yr$^{-1}$) when compared with other young Class 0 sources (e.g. PACS Bright Red sources (PBRs)) in the Orion complex. It has slightly larger internal luminosity ($0.21\\pm0.01$ L$_{\\sun}$) and outflow velocity ($\\sim$14 km~s$^{-1}$) than the predictions of first hydrostatic cores (FHSCs). G192N...

  8. Large Amplitude Variations of an L/T Transition Brown Dwarf: Multi-Wavelength Observations of Patchy, High-Contrast Cloud Features

    CERN Document Server

    Radigan, Jacqueline; Lafrenière, David; Artigau, Etienne; Marley, Mark; Saumon, Didier

    2012-01-01

    We present multiple-epoch photometric monitoring in the $J$, $H$, and $K_s$ bands of the T1.5 dwarf 2MASS J21392676+0220226 (2M2139), revealing persistent, periodic ($P=7.72\\pm$0.05 hr) variability with a peak-to-peak amplitude as high as 26% in the $J$-band. The light curve shape varies on a timescale of days, suggesting that evolving atmospheric cloud features are responsible. Using interpolations between model atmospheres with differing cloud thicknesses to represent a heterogeneous surface, we find that the multi-wavelength variations and the near-infrared spectrum of 2M2139 can be reproduced by either (1)cool, thick cloud features sitting above a thinner cloud layer, or (2)warm regions of low condensate opacity in an otherwise cloudy atmosphere, possibly indicating the presence of holes or breaks in the cloud layer. We find that temperature contrasts between thick and thin cloud patches must be greater than 175 K and as high as 425 K. We also consider whether the observed variability could arise from an ...

  9. SCExAO and GPI $YJH$ Band Photometry and Integral Field Spectroscopy of the Young Brown Dwarf Companion to HD 1160

    CERN Document Server

    Garcia, Eugenio V; Guyon, Olivier; Stassun, Keivan; Jovanovic, Nemanja; Lozi, Julien; Kudo, Tomoyuki; Doughty, Danielle; Schlieder, Joshua; Kwon, J; Uyama, T; Kuzuhara, M; Carson, J; Nakagawa, T; Hashimoto, J; Kusakabe, N; Abe, L; Brander, W; Brandt, T D; Feldt, M; Goto, M; Grady, C; Hayano, Y; Hayashi, M; Hayashi, S; Henning, T; Hodapp, K; Ishii, M; Iye, M; Janson, M; Kandori, R; Knapp, G; Matsuo, T; McElwain, M; Miyama, S; Morino, J I; Moro-Martin, A; Nishimura, T; Pyo, T -S; Serabyn, E; Suenaga, T; Suto, H; Suzuki, R; Takahashi, Y H; Takami, H; Takato, N; Terada, H; Thalmann, C; Turner, E L; Watanabe, M; Wisniewski, J; Yamada, T; Usuda, T; Tamura, M

    2016-01-01

    We present high signal-to-noise ratio, precise $YJH$ photometry and $Y$ band (\\gpiwave~$\\mu$m) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign, using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5$^{+1.0}_{-0.5}$, where the blue edge of our $Y$ band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B having an effective temperature of 3000--3100 $K$, a surface gravity of log $g$ = 4--4.5, a radius of~\\bestfitradius~$R_{\\rm J}$, and a luminosity of log $L$/$L_{\\odot} = -2.76 \\pm 0.05$. Neither the primary's Hertzspring-Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a sub-solar metallicity. The interpretation of the HD 1160 B depends on which stellar system components are used to estimate an age. Considering HD 1160 A, B and C jointly, we derive an age of 80--1...

  10. White Dwarf Critical Tests for Modified Gravity

    CERN Document Server

    Jain, Rajeev Kumar; Nielsen, Niklas Grønlund

    2015-01-01

    Scalar-tensor theories of gravity can lead to modifications of the gravitational force inside astrophysical objects. We exhibit that compact stars such as white dwarfs provide a unique set-up to test such deviations from Newtonian gravitational physics inside the stars. We obtain stringent and independent constraints on the parameter $\\Upsilon$ characterizing the deviations from gravity using the mass-radius relation, the Chandrasekhar mass limit and the maximal rotational frequency of white dwarfs. We find that white dwarfs impose stronger constraints on $\\Upsilon$ than the red and brown dwarfs.

  11. VERY LOW MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. V. A LOW ECCENTRICITY BROWN DWARF FROM THE DRIEST PART OF THE DESERT, MARVELS-6b

    Energy Technology Data Exchange (ETDEWEB)

    De Lee, Nathan; Stassun, Keivan G.; Cargile, Phillip [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Ge, Jian; Fleming, Scott W.; Lee, Brian L.; Chang Liang [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Eastman, Jason; Gaudi, B. Scott [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I.; Allende Prieto, Carlos [Instituto de Astrofisica de Canarias (IAC), E-38205 La Laguna, Tenerife (Spain); Ghezzi, Luan [Observatorio Nacional, Rua Gal. Jose Cristino 77, Rio de Janeiro, RJ 20921-400 (Brazil); Wisniewski, John P. [H L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St Norman, OK 73019 (United States); Wood-Vasey, W. Michael [Pittsburgh Particle physics, Astrophysics, and Cosmology Center (PITT PACC), Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Agol, Eric; Barnes, Rory [Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195 (United States); Bizyaev, Dmitry, E-mail: nathan.delee@vanderbilt.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); and others

    2013-06-15

    We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 {+-} 2.0 M{sub Jup} to GSC 03546-01452 from the MARVELS radial velocity survey, which we designate as MARVELS-6b. For reasonable priors, our analysis gives a probability of 72% that MARVELS-6b has a mass below the hydrogen-burning limit of 0.072 M{sub Sun }, and thus it is a high-confidence BD companion. It has a moderately long orbital period of 47.8929{sup +0.0063}{sub -0.0062} days with a low eccentricity of 0.1442{sup +0.0078}{sub -0.0073}, and a semi-amplitude of 1644{sup +12}{sub -13} m s{sup -1}. Moderate resolution spectroscopy of the host star has determined the following parameters: T{sub eff} = 5598 {+-} 63, log g = 4.44 {+-} 0.17, and [Fe/H] = +0.40 {+-} 0.09. Based upon these measurements, GSC 03546-01452 has a probable mass and radius of M{sub *} = 1.11 {+-} 0.11 M{sub Sun} and R{sub *} = 1.06 {+-} 0.23 R{sub Sun} with an age consistent with less than {approx}6 Gyr at a distance of 219 {+-} 21 pc from the Sun. Although MARVELS-6b is not observed to transit, we cannot definitively rule out a transiting configuration based on our observations. There is a visual companion detected with Lucky Imaging at 7.''7 from the host star, but our analysis shows that it is not bound to this system. The minimum mass of MARVELS-6b exists at the minimum of the mass functions for both stars and planets, making this a rare object even compared to other BDs. It also exists in an underdense region in both period/eccentricity and metallicity/eccentricity space.

  12. Masses and Multiplicity of Nearby Free- floating Methane and L Dwarfs

    Science.gov (United States)

    Brandner, Wolfgang

    2000-07-01

    Brown dwarfs never stabilize themselves on the hydrogen main sequence, thus there is an ambiguity between the temperature or luminosity of a given object and its mass or age. In order to test the mass-luminosity relations of {still uncertain} evolutionary models, a direct dynamical determination of mass is required. As a first step towards a dynamical mass estimate for brown dwarfs, we have compiled a sample of 50 very-low-mass objects {Mmasses for brown dwarfs and to calibrate evolutionary tracks. Binary properties like multiplicity, distribution of binary separations and brightness ratios hold clues on the origin of free-floating brown dwarf binaries. Our program will be an important step towards a better understanding of the still elusive class of brown dwarfs.

  13. VERY-LOW-MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. III. A SHORT-PERIOD BROWN DWARF CANDIDATE AROUND AN ACTIVE G0IV SUBGIANT

    Energy Technology Data Exchange (ETDEWEB)

    Ma Bo; Ge Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Wang Ji [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Barnes, Rory; Agol, Eric [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Dutra-Ferreira, Leticia; Porto de Mello, G. F. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antonio, 43, CEP: 20080-090, Rio de Janeiro, RJ (Brazil); Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I. [Instituto de Astrofisica de Canarias, C/Via Lctea S/N, E-38200 La Laguna (Spain); Gaudi, B. Scott [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Ghezzi, Luan [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rio de Janeiro, RJ 20921-400 (Brazil); Hebb, Leslie; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Wisniewski, John P. [Homer L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St, Norman, OK 73019 (United States); Bizyaev, Dmitry, E-mail: boma@astro.ufl.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); and others

    2013-01-01

    We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T{sub eff} = 5903 {+-} 42 K, surface gravity log (g) = 4.07 {+-} 0.16 (cgs), and metallicity [Fe/H] = -0.23 {+-} 0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey, which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 3.571 {+-} 0.041 km s{sup -1}, period P = 9.0090 {+-} 0.0004 days, and eccentricity e = 0.226 {+-} 0.011. Adopting a mass of 1.16 {+-} 0.11 M{sub Sun} for the subgiant host star, we infer that the companion has a minimum mass of 40.0 {+-} 2.5 M{sub Jup}. Assuming an edge-on orbit, the semimajor axis is 0.090 {+-} 0.003 AU. The host star is photometrically variable at the {approx}1% level with a period of {approx}13.16 {+-} 0.01 days, indicating that the host star spin and companion orbit are not synchronized. Through adaptive optics imaging we also found a point source 643 {+-} 10 mas away from TYC 2087-00255-1, which would have a mass of 0.13 M{sub Sun} if it is physically associated with TYC 2087-00255-1 and has the same age. Future proper motion observation should be able to resolve if this tertiary object is physically associated with TYC 2087-00255-1 and make TYC 2087-00255-1 a triple body system. Core Ca II H and K line emission indicate that the host is chromospherically active, at a level that is consistent with the inferred spin period and measured v{sub rot}sin i, but unusual for a subgiant of this T{sub eff}. This activity could be explained by ongoing tidal spin-up of the host star by the companion.

  14. Very-low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels. III. A Short-period Brown Dwarf Candidate around an Active G0IV Subgiant

    Science.gov (United States)

    Ma, Bo; Ge, Jian; Barnes, Rory; Crepp, Justin R.; De Lee, Nathan; Dutra-Ferreira, Leticia; Esposito, Massimiliano; Femenia, Bruno; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; Hebb, Leslie; Gonzalez Hernandez, Jonay I.; Lee, Brian L.; Porto de Mello, G. F.; Stassun, Keivan G.; Wang, Ji; Wisniewski, John P.; Agol, Eric; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Nicolaci da Costa, Luiz; Eastman, Jason D.; Gary, Bruce; Jiang, Peng; Kane, Stephen R.; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A. G.; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Daniel; Pepper, Joshua; Paegert, Martin; Allende Prieto, Carlos; Rebolo, Rafael; Santiago, Basilio X.; Schneider, Donald P.; Shelden, Alaina; Simmons, Audrey; Sivarani, Thirupathi; van Eyken, J. C.; Wan, Xiaoke; Weaver, Benjamin A.; Zhao, Bo

    2013-01-01

    We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T eff = 5903 ± 42 K, surface gravity log (g) = 4.07 ± 0.16 (cgs), and metallicity [Fe/H] = -0.23 ± 0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey, which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 3.571 ± 0.041 km s-1, period P = 9.0090 ± 0.0004 days, and eccentricity e = 0.226 ± 0.011. Adopting a mass of 1.16 ± 0.11 M ⊙ for the subgiant host star, we infer that the companion has a minimum mass of 40.0 ± 2.5 M Jup. Assuming an edge-on orbit, the semimajor axis is 0.090 ± 0.003 AU. The host star is photometrically variable at the ~1% level with a period of ~13.16 ± 0.01 days, indicating that the host star spin and companion orbit are not synchronized. Through adaptive optics imaging we also found a point source 643 ± 10 mas away from TYC 2087-00255-1, which would have a mass of 0.13 M ⊙ if it is physically associated with TYC 2087-00255-1 and has the same age. Future proper motion observation should be able to resolve if this tertiary object is physically associated with TYC 2087-00255-1 and make TYC 2087-00255-1 a triple body system. Core Ca II H and K line emission indicate that the host is chromospherically active, at a level that is consistent with the inferred spin period and measured v rotsin i, but unusual for a subgiant of this T eff. This activity could be explained by ongoing tidal spin-up of the host star by the companion.

  15. Ultracool Dwarf Science from Widefield Multi-Epoch Surveys

    CERN Document Server

    Deacon, N R; Lucas, P W; Liu, Michael C; Bessell, M S; Burningham, B; Cushing, M C; Day-Jones, A C; Dhital, S; Law, N M; Mainzer, A K; Zhang, Z H

    2010-01-01

    Widefield surveys have always provided a rich hunting ground for the coolest stars and brown dwarfs. The single epoch surveys at the beginning of this century greatly expanded the parameter space for ultracool dwarfs. Here we outline the science possible from new multi-epoch surveys which add extra depth and open the time domain to study.

  16. A brown dwarf orbiting an M-dwarf

    DEFF Research Database (Denmark)

    Bachelet, E.; Fouqué, P.; Albrow, M.D.

    2012-01-01

    Context. Caustic crossing is the clearest signature of binary lenses in microlensing. In the present context, this signature is diluted by the large source star but a detailed analysis has allowed the companion signal to be extracted. Aims. MOA 2009-BLG-411 was detected on August 5, 2009 by the MOA-Collaboration....... Alerted as a high-magnification event, it was sensitive to planets. Suspected anomalies in the light curve were not confirmed by a real-time model, but further analysis revealed small deviations from a single lens extended source fit. Methods. Thanks to observations by all the collaborations, this event...

  17. Detection of lithium in nearby young late-M dwarfs

    Science.gov (United States)

    Phan-Bao, N.; Bessell, M. S.; Nguyen-Thanh, D.; Martín, E. L.; Ho, P. T. P.; Lee, C. F.; Parsons, H.

    2017-03-01

    Context. Late M-type dwarfs in the solar neighborhood include a mixture of very low-mass stars and brown dwarfs that is difficult to disentangle due to the lack of constraints on their age, such as trigonometric parallax, lithium detection, and space velocity. Aims: We search for young brown dwarf candidates among a sample of 28 nearby late-M dwarfs with spectral types between M5.0 and M9.0, and we also search for debris disks around three of them. Methods: Based on theoretical models, we used the color I-J, the J-band absolute magnitude, and the detection of the Li I 6708 Å doublet line as a strong constraint to estimate masses and ages of our targets. For the search of debris disks, we observed three targets at submillimeter wavelength of 850 μm. Results: We report here the first clear detections of lithium absorption in four targets and a marginal detection in one target. Our mass estimates indicate that two of them are young brown dwarfs, two are young brown dwarf candidates, and one is a young very low-mass star. The closest young field brown dwarf in our sample at only 15 pc is an excellent benchmark for further studying physical properties of brown dwarfs in the range 100-150 Myr. We did not detect any debris disks around three late-M dwarfs, and we estimated upper limits to the dust mass of debris disks around them. The reduced spectra (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/600/A19

  18. Relativistic Kinematics

    CERN Document Server

    Sahoo, Raghunath

    2016-01-01

    This lecture note covers Relativistic Kinematics, which is very useful for the beginners in the field of high-energy physics. A very practical approach has been taken, which answers "why and how" of the kinematics useful for students working in the related areas.

  19. Brown Dwarf Binaries from Disintegrating Triple Systems

    CERN Document Server

    Reipurth, Bo

    2015-01-01

    We have carried out 200,000 N-body simulations of three identical stellar embryos with masses from a Chabrier IMF and embedded in a molecular core. The bodies are initially non-hierarchical and undergo chaotic motions, while accreting using Bondi-Hoyle accretion. The coupling of dynamics and accretion often leads to one or two dominant bodies controlling the center of the cloud core, while banishing the other(s) to the lower-density outskirts, leading to stunted growth. Eventually each system transforms either to a bound hierarchical configuration or breaks apart into separate single and binary components. The orbital motion is followed for 100 Myr. To illustrate the simulations we introduce the 'triple diagnostic diagram', which plots two dimensionless numbers against each other, representing the binary mass ratio and the mass ratio of the third body to the total system mass. Numerous freefloating BD binaries are formed in these simulations. The separation distribution function is in good correspondence with...

  20. On the formation of brown dwarfs

    Directory of Open Access Journals (Sweden)

    Ing Guey Jiang

    2004-01-01

    Full Text Available Las propiedades de las enanas marrones presentan problemas para la teor a de la formaci on estelar. Como sus masas son mucho menores que la masa de Jeans de las nubes interestelares, las enanas marrones se forman probablemente por fragmentaci on secundaria, y no por el colapso directo del n ucleo de la nube molecular. Para evitar la acreci on de masa posterior, las j ovenes enanas marrones deben salir de las regiones de alta densidad donde se formaron. Proponemos que las enanas marrones se forman en las regiones externas, opticamente delgadas, de los discos circunbinarios. Las interacciones din amicas subsecuentes con sus binarias causan que las enanas marrones sean dispersadas a grandes distancias, o que escapen del sistema a baja velocidad.

  1. Trigonometric Parallaxes and Proper Motions of 134 Southern Late M, L, and T Dwarfs from the Carnegie Astrometric Planet Search Program

    CERN Document Server

    Weinberger, A J; Keiser, S A; Anglada-Escudé, G; Thompson, I B; Burley, G

    2016-01-01

    We report trigonometric parallaxes for 134 low mass stars and brown dwarfs, of which 38 have no previously published measurement and 79 more have improved uncertainties. Our survey targeted nearby targets, so 119 are closer than 30 pc. Of the 38 stars with new parallaxes, 14 are within 20 pc and seven are likely brown dwarfs (spectral types later than L0). These parallaxes are useful for studies of kinematics, multiplicity, and spectrophotometric calibration. Two objects with new parallaxes are confirmed as young stars with membership in nearby young moving groups: LP 870-65 in AB Doradus and G 161-71 in Argus. We also report the first parallax for the planet-hosting star GJ 3470; this allows us to refine the density of its Neptune-mass planet. One T-dwarf, 2MASS J12590470-4336243, previously thought to lie within 4 pc, is found to be at 7.8 pc, and the M-type star 2MASS J01392170-3936088 joins the ranks of nearby stars as it is found to be within 10 pc. Five stars that are over-luminous and/or too red for th...

  2. Trigonometric Parallaxes and Proper Motions of 134 Southern Late M, L, and T Dwarfs from the Carnegie Astrometric Planet Search Program

    Science.gov (United States)

    Weinberger, Alycia J.; Boss, Alan P.; Keiser, Sandra A.; Anglada-Escudé, Guillem; Thompson, Ian B.; Burley, Gregory

    2016-07-01

    We report trigonometric parallaxes for 134 low-mass stars and brown dwarfs, of which 38 have no previously published measurement and 79 more have improved uncertainties. Our survey focused on nearby targets, so 119 are closer than 30 pc. Of the 38 stars with new parallaxes, 14 are within 20 pc and seven are likely brown dwarfs (spectral types later than L0). These parallaxes are useful for studies of kinematics, multiplicity, and spectrophotometric calibration. Two objects with new parallaxes are confirmed as young stars with membership in nearby young moving groups: LP 870-65 in AB Doradus and G 161-71 in Argus. We also report the first parallax for the planet-hosting star GJ 3470; this allows us to refine the density of its Neptune-mass planet. T-dwarf 2MASS J12590470-4336243, previously thought to lie within 4 pc, is found to be at 7.8 pc, and the M-type star 2MASS J01392170-3936088 joins the ranks of nearby stars as it is found to be within 10 pc. Five stars that are overluminous and/or too red for their spectral types are identified and deserve further study as possible young stars.

  3. 49 new T dwarfs identified using methane imaging

    CERN Document Server

    Cardoso, C V; Smart, R L; van Spaandonk, L; Baker, D; Smith, L C; Andrei, A H; Bucciarelli, B; Dhital, S; Jones, H R A; Lattanzi, M G; Magazzu, A; Pinfield, D J; Tinney, C G

    2015-01-01

    We present the discovery of 49 new photometrically classified T dwarfs from the combination of large infrared and optical surveys combined with follow-up TNG photometry. We used multi-band infrared and optical photometry from the UKIRT and Sloan Digital Sky Surveys to identify possible brown dwarf candidates, which were then confirmed using methane filter photometry. We have defined a new photometric conversion between CH4s - CH4l colour and spectral type for T4 to T8 brown dwarfs based on a part of the sample that has been followed up using methane photometry and spectroscopy. Using methane differential photometry as a proxy for spectral type for T dwarfs has proved to be a very efficient technique. Of a subset of 45 methane selected brown dwarfs that were observed spectroscopically, 100% were confirmed as T dwarfs. Future deep imaging surveys will produce large samples of faint brown dwarf candidates, for which spectroscopy will not be feasible. When broad wavelength coverage is unavailable, methane imaging...

  4. 49 new T dwarfs identified using methane imaging

    Science.gov (United States)

    Cardoso, C. V.; Burningham, B.; Smart, R. L.; van Spaandonk, L.; Baker, D.; Smith, L. C.; Zhang, Z. H.; Andrei, A. H.; Bucciarelli, B.; Dhital, S.; Jones, H. R. A.; Lattanzi, M. G.; Magazzú, A.; Pinfield, D. J.; Tinney, C. G.

    2015-07-01

    We present the discovery of 49 new photometrically classified T dwarfs from the combination of large infrared and optical surveys combined with follow-up Telescopio Nazionale Galileo photometry. We used multiband infrared and optical photometry from the United Kingdom Infrared Telescope and Sloan Digital Sky Surveys to identify possible brown dwarf candidates, which were then confirmed using methane filter photometry. We have defined a new photometric conversion between CH4s - CH4l colour and spectral type for T4-T8 brown dwarfs based on a part of the sample that has been followed up using methane photometry and spectroscopy. Using methane differential photometry as a proxy for spectral type for T dwarfs has proved to be a very efficient technique. Of a subset of 45 methane selected brown dwarfs that were observed spectroscopically, 100 per cent were confirmed as T dwarfs. Future deep imaging surveys will produce large samples of faint brown dwarf candidates, for which spectroscopy will not be feasible. When broad wavelength coverage is unavailable, methane imaging offers a means to efficiently classify candidates from such surveys using just a pair of near-infrared images.

  5. Water Clouds in Y Dwarfs and Exoplanets

    CERN Document Server

    Morley, Caroline V; Fortney, Jonathan J; Lupu, Roxana; Saumon, Didier; Greene, Tom; Lodders, Katharina

    2014-01-01

    The formation of clouds affects brown dwarf and planetary atmospheres of nearly all effective temperatures. Iron and silicate condense in L dwarf atmospheres and dissipate at the L/T transition. Minor species such as sulfides and salts condense in mid-late T dwarfs. For brown dwarfs below Teff=450 K, water condenses in the upper atmosphere to form ice clouds. Currently over a dozen objects in this temperature range have been discovered, and few previous theoretical studies have addressed the effect of water clouds on brown dwarf or exoplanetary spectra. Here we present a new grid of models that include the effect of water cloud opacity. We find that they become optically thick in objects below Teff=350-375 K. Unlike refractory cloud materials, water ice particles are significantly non-gray absorbers; they predominantly scatter at optical wavelengths through J band and absorb in the infrared with prominent features, the strongest of which is at 2.8 microns. H2O, NH3, CH4, and H2 CIA are dominant opacity source...

  6. 2MASS Data Mining and the M, L, and T Dwarf Archives

    CERN Document Server

    Kirkpatrick, J D

    2002-01-01

    Studies of brown dwarfs as a distinct galactic population have been largely pioneered by dedicated, vast-area surveys at deep optical and near-infrared wavebands. The Two Micron All Sky Survey has, because of its full-sky coverage and depth, been the most successful at providing new targets for further study. The author briefly reviews some of the ways in which 2MASS data have been used by brown dwarf researchers. One of the by-products -- namely the 2MASS Team's follow-up spectroscopy of brown dwarf candidates -- is potentially valuable as a scientific resource itself and is also being released to the public.

  7. White dwarf-red dwarf binaries in the Galaxy

    NARCIS (Netherlands)

    Besselaar, E.J.M. van den

    2007-01-01

    This PhD thesis shows several studies on white dwarf - red dwarf binaries. White dwarfs are the end products of most stars and red dwarfs are normal hydrogen burning low-mass stars. White dwarf - red dwarf binaries are both blue (white dwarf) and red (red dwarf). Together with the fact that they are

  8. THE DISCOVERY OF Y DWARFS USING DATA FROM THE WIDE-FIELD INFRARED SURVEY EXPLORER (WISE)

    Energy Technology Data Exchange (ETDEWEB)

    Cushing, Michael C.; Mainzer, A.; Eisenhardt, Peter R. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, MS 321-520, Pasadena, CA 91109 (United States); Kirkpatrick, J. Davy; Gelino, Christopher R.; Griffith, Roger L.; Marsh, Kenneth A.; Beichman, Charles A. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Skrutskie, Michael F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Prato, Lisa A. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Simcoe, Robert A. [Massachusetts Institute of Technology, 77 Massachusetts Avenue, Building 37, Cambridge, MA 02139 (United States); Marley, Mark S.; Freedman, Richard S. [NASA Ames Research Center, MS 254-3, Moffett Field, CA 94035 (United States); Saumon, D. [Los Alamos National Laboratory, MS F663, Los Alamos, NM 87545 (United States); Wright, Edward L., E-mail: michael.cushing@gmail.com [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095 (United States)

    2011-12-10

    We present the discovery of seven ultracool brown dwarfs identified with the Wide-field Infrared Survey Explorer (WISE). Near-infrared spectroscopy reveals deep absorption bands of H{sub 2}O and CH{sub 4} that indicate all seven of the brown dwarfs have spectral types later than UGPS J072227.51-054031.2, the latest-type T dwarf currently known. The spectrum of WISEP J182831.08+265037.8 is distinct in that the heights of the J- and H-band peaks are approximately equal in units of f{sub {lambda}}, so we identify it as the archetypal member of the Y spectral class. The spectra of at least two of the other brown dwarfs exhibit absorption on the blue wing of the H-band peak that we tentatively ascribe to NH{sub 3}. These spectral morphological changes provide a clear transition between the T dwarfs and the Y dwarfs. In order to produce a smooth near-infrared spectral sequence across the T/Y dwarf transition, we have reclassified UGPS 0722-05 as the T9 spectral standard and tentatively assign WISEP J173835.52+273258.9 as the Y0 spectral standard. In total, six of the seven new brown dwarfs are classified as Y dwarfs: four are classified as Y0, one is classified as Y0 (pec?), and WISEP J1828+2650 is classified as >Y0. We have also compared the spectra to the model atmospheres of Marley and Saumon and infer that the brown dwarfs have effective temperatures ranging from 300 K to 500 K, making them the coldest spectroscopically confirmed brown dwarfs known to date.

  9. Rational kinematics

    CERN Document Server

    Angeles, Jorge

    1988-01-01

    A rational study of kinematics is a treatment of the subject based on invariants, i.e., quantities that remain essentially unchanged under a change of observer. An observer is understood to be a reference frame supplied with a clock (Truesdell 1966). This study will therefore include an introduction to invariants. The language of these is tensor analysis and multilinear algebra, both of which share many isomorphic relations, These subjects are treated in full detail in Ericksen (1960) and Bowen and Wang (1976), and hence will not be included here. Only a short account of notation and definitions will be presented. Moreover, definitions and basic concepts pertaining to the kinematics of rigid bodies will be also included. Although the kinematics of rigid bodies can be regarded as a particular case of the kinematics of continua, the former deserves attention on its own merits for several reasons. One of these is that it describes locally the motions undergone by continua. Another reason is that a whole area of ...

  10. The Onset of Methane in L Dwarfs

    CERN Document Server

    Noll, K S; Leggett, S K; Marley, M S; Noll, Keith S.; Marley, Mark S.

    2000-01-01

    We have detected weak absorption features produced by the strong nu(3) methane band at 3.3 microns in two L dwarfs, 2MASSW J1507476-162738 and 2MASSI J0825196+211552, classified by Kirkpatrick et al. (2000) as spectral types L5 and L7.5 respectively. These absorptions occur in objects warmer than any in which methane previously has been detected, and mark the first appearance of methane in the ultracool star-to-brown dwarf spectral sequence.

  11. The Missing Link: Early Methane ("T") Dwarfs in the Sloan Digital Sky Survey

    OpenAIRE

    Leggett, S. K.; Geballe, T. R.; Fan, Xiaohui

    2000-01-01

    We report the discovery of three cool brown dwarfs which fall in the effective temperature gap between the latest L dwarfs currently known, with no methane absorption bands in the 1-2.5um range, and the previously known methane (T) dwarfs, whose spectra are dominated by methane and water. The newly discovered objects were detected as very red objects in the Sloan Digital Sky Survey imaging data and have JHK colors between the red L dwarfs and the blue Gl229B-like T dwarfs. They show both CO a...

  12. ORIGIN AND KINEMATICS OF THE ERUPTIVE FLOW FROM XZ TAU REVEALED BY ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Zapata, Luis A.; Galván-Madrid, Roberto; Carrasco-González, Carlos; Palau, Aina; Rodríguez, Luis F.; Kurtz, Stan E.; Tafoya, Daniel; Loinard, Laurent [Centro de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Curiel, Salvador [Instituto de Astronomía, Universidad Nacional Autónoma de México, Ap. 70-264, 04510 DF, México (Mexico)

    2015-09-20

    We present high angular resolution (∼0.″94) {sup 12}CO(1-0) Atacama Large Millimeter/submillimeter Array (ALMA) observations obtained during the 2014 long baseline campaign from the eruptive bipolar flow from the multiple XZ Tau stellar system discovered by the Hubble Space Telescope (HST). These observations reveal, for the first time, the kinematics of the molecular flow. The kinematics of the different ejections close to XZ Tau reveal a rotating and expanding structure with a southeast–northwest velocity gradient. The youngest eruptive bubbles unveiled in the optical HST images are inside of this molecular expanding structure. Additionally, we report a very compact and collimated bipolar outflow emanating from XZ Tau A, which indicates that the eruptive outflow is indeed originating from this object. The mass (3 × 10{sup −7} M{sub ⊙}) and energetics (E{sub kin} = 3 × 10{sup 37} erg) for the collimated outflow are comparable to those found in molecular outflows associated with young brown dwarfs.

  13. Naming Disney's Dwarfs.

    Science.gov (United States)

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  14. The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries

    CERN Document Server

    Burgasser, A J; Kirkpatrick, J D; McElwain, M W; Reid, I N; Tinney, C G; Burgasser, Adam J.; Elwain, Michael W. Mc; Cruz, Kelle L.; Tinney, Chris G.

    2004-01-01

    We present the discovery of seven new T dwarfs identified in the Two Micron All Sky Survey. Low-resolution (R$\\sim$150) 0.8--2.5 micron spectroscopy obtained with the IRTF SpeX instrument reveal the characteristic H$_2$O and CH$_4$ bands in the spectra of these brown dwarfs. Comparison to spectral standards observed with the same instrument enable us to derive classifications of T3 to T7 for the objects in this sample. Moderate-resolution (R$\\sim$1200) near-infrared spectroscopy for a subset of these discoveries reveal K I line strengths consistent with previously observed trends with spectral type. Follow-up imaging observations provide proper motion measurements for these sources, ranging from $<$ 0$\\farcs$1 to 1$\\farcs$55 yr$^{-1}$. One object, 2MASS 0034+0523, has a spectrophotometric distance placing it within 10 pc of the Sun. This source also exhibits a depressed K-band peak reminiscent of the peculiar T dwarf 2MASS 0937+2931, and may be a metal-poor or old, high-mass brown dwarf. We also present lo...

  15. How chameleons core dwarfs with cusps

    CERN Document Server

    Lombriser, Lucas

    2014-01-01

    The presence of a scalar field that couples nonminimally and universally to matter can enhance gravitational forces on cosmological scales while restoring general relativity in the Solar neighborhood. In the intermediate regime, kinematically inferred masses experience an additional radial dependence with respect to the underlying distribution of matter, which is caused by the increment of gravitational forces with increasing distance from the Milky Way center. The same effect can influence the internal kinematics of subhalos and cause cuspy matter distributions to appear core-like. Specializing to the chameleon model as a worked example, we demonstrate this effect by tracing the scalar field from the outskirts of the Milky Way halo to its interior, simultaneously fitting observed velocity dispersions of chemo-dynamically discriminated red giant populations in the Fornax and Sculptor dwarf spheroidals. Whereas in standard gravity these observations suggest that the matter distribution of the dwarfs is cored, ...

  16. A Survey for H-alpha Emission from Late L dwarfs and T dwarfs

    CERN Document Server

    Pineda, J Sebastian; Kirkpatrick, J Davy; Cotter, Garret; Kao, Melodie M; Mooley, Kunal

    2016-01-01

    Recently, studies of brown dwarfs have demonstrated that they possess strong magnetic fields and have the potential to produce radio and optical auroral emissions powered by magnetospheric currents. This emission provides the only window on magnetic fields in the coolest brown dwarfs and identifying additional benchmark objects is key to constraining dynamo theory in this regime. To this end, we conducted a new red optical (6300 - 9700 Angstrom) survey with the Keck telescopes looking for H-alpha emission from a sample of late L dwarfs and T dwarfs. Our survey gathered optical spectra for 29 targets, 18 of which did not have previous optical spectra in the literature, greatly expanding the number of moderate resolution (R~2000) spectra available at these spectral types. Combining our sample with previous surveys, we confirm an H-alpha detection rate of 9.2 (+3.5/-2.1) % for L and T dwarfs in the optical spectral range of L4 - T8. This detection rate is consistent with the recently measured detection rate for ...

  17. Youth Indicators of Late-M Dwarfs

    Science.gov (United States)

    Feldman, Daniel; Cruz, K.; Lépine, S.; Alpert, N.

    2011-01-01

    We present a study in which we searched for a correlation between weak Na absorption doublet (8183Å, 8194Å) and strong H-Alpha emission (6563Å) in late-M dwarf stars (M6-M9), as both are indicative of youth. Our sample consists of late-M Dwarfs from the LSPM Survey (Lépine and Shara, 2005), which contain stars with measured proper motions of mu > 40 mas/yr. Measurements for emission and absorption strength were made using spectral indices. Our preliminary results are presented; future work will include a similar analysis of early type M Dwarfs, as well as kinematics. This work was funded by the CUNY Summer Undergraduate Research Program, as well as the CUNY Macaulay Honors College, and we acknowledge the hospitality of the American Museum of Natural History.

  18. Could Ultracool Dwarfs Have Sun-Like Activity?

    Science.gov (United States)

    Kohler, Susanna

    2016-11-01

    Solar-like stars exhibit magnetic cycles; our Sun, for instance, displays an 11-year period in its activity, manifesting as cyclic changes in radiation levels, the number of sunspots and flares, and ejection of solar material. Over the span of two activity cycles, the Suns magnetic field flips polarity and then returns to its original state.An artists illustration comparing the Sun to TRAPPIST-1, an ultracool dwarf star known to host several planets. [ESO]But what about the magnetic behavior of objects near the cooler end of the stellar main sequence do they exhibit similar activity cycles?Effects of a Convecting InteriorDwarf stars have made headlines in recent years due to their potential to harbor exoplanets. Because these cooler stars have lower flux levels compared to the Sun, their habitable zones lie much closer to the stars. The magnetic behavior of these stars is therefore important to understand: could ultracool dwarfs exhibit solar-like activity cycles that would affect planets with close orbits?The differences in internal structure between different mass stars. Ultracool dwarfs have fully convective interiors. [www.sun.org]Theres a major difference between ultracool dwarfs (stars of spectral type higher than M7 and brown dwarfs) and Sun-like stars: their internal structures. Sun-like stars have a convective envelope that surrounds a radiative core. The interiors of cool, low-mass objects, on the other hand, are fully convective.Based on theoretical studies of how magnetism is generated in stars, its thought that the fully convective interiors of ultracool dwarfs cant support large-scale magnetic field formation. This should prevent these stars from exhibiting activity cycles like the Sun. But recent radio observations of dwarf stars have led scientist Matthew Route (ITaP Research Computing, Purdue University) to question these models.A Reversing Field?During observations of the brown dwarf star J1047+21 in 20102011, radio flares were detected with

  19. The Late-Type Extension to MoVeRS (LaTE-MoVeRS): Proper Motion Verified Low-mass Stars and Brown Dwarfs from SDSS, 2MASS, and WISE

    Science.gov (United States)

    Theissen, Christopher A.; West, Andrew A.; Shippee, Guillaume; Burgasser, Adam J.; Schmidt, Sarah J.

    2017-03-01

    We present the Late-Type Extension to the Motion Verified Red Stars (LaTE-MoVeRS) catalog, containing 46,463 photometric late-type (>M5) dwarfs within the Sloan Digital Sky Survey (SDSS) footprint. Proper motions were computed for objects combining astrometry from the SDSS Data Release 12 (DR12), the Two-micron All-Sky Survey (2MASS) Point Source Catalog, and the Wide-field Infrared Survey Explorer (WISE) AllWISE data sets. LaTE-MoVeRS objects were required to have significant proper motion ({μ }{tot}≥slant 2{σ }{μ {tot}}). Using the LaTE-MoVeRS sample and Gaia Data Release 1, we estimate Gaia will be ∼64% complete for very low-mass objects (>M5) in comparison to the combined SDSS+2MASS+WISE data set (iSDSS CasJobs and VizieR.

  20. SEARCHING FOR BINARY Y DWARFS WITH THE GEMINI MULTI-CONJUGATE ADAPTIVE OPTICS SYSTEM (GeMS)

    Energy Technology Data Exchange (ETDEWEB)

    Opitz, Daniela; Tinney, C. G. [School of Physics, University of New South Wales, NSW 2052 (Australia); Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Sweet, Sarah [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Gelino, Christopher R.; Kirkpatrick, J. Davy, E-mail: daniela.opitz@student.unsw.edu.au [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States)

    2016-03-01

    The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs also hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System. We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than ∼0.5–1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e., 10{sup 42} erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.