WorldWideScience

Sample records for brown dwarf companion

  1. 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 ...

  2. A USNO Search for Astrometric Companions to Brown Dwarfs IV

    Science.gov (United States)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tilleman, T.; Henden, A. A.

    2014-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m (61-in) Kaj Strand Astrometric Reflector from 2000 September through 2006 June over periods from 2.0 to 5.3 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from late M through mid-T. None of them are known binaries. Distance estimates place six of these objects within the 25-pc limit of the Solar Neighborhood, and preliminary parallaxes place another three between 25 and 35 pc. These substellar objects are located north of -15° Dec. The brown dwarfs evaluated are 2MASS J00325937+1410371, 2MASS J01514155+1244300 (BF Ari) 2MASS J02074284+0000564, 2MASS J03095345-0753156, SDSS J083717.21-000018.0, 2MASS J11101001+0116130, 2MASS J13262981-0038314 (2MUCD 11143), 2MASS J17502385+4222373, 2MASS J23391025+1352284, and 2MASS J23565477-1553111. Analyses of another 30 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  3. A USNO Search for Astrometric Companions to Brown Dwarfs III

    Science.gov (United States)

    Bartlett, Jennifer L.; Vrba, F. J.; Munn, J. A.; Luginbuhl, C. B.; Tillman, T.; Henden, A. A.

    2013-01-01

    Preliminary analyses of ten brown dwarfs observed by the U.S. Naval Observatory infrared parallax program show no clear indication of astrometric perturbations due to low mass companions. The data were collected using ASTROCAM on the 1.55-m Strand Astrometric Reflector from 2000 October through 2006 June over periods from 1.3 to 5.4 years. After our standard solution for parallax and proper motion, the residuals were subjected to a time-series analysis using the Lomb-Scargle periodogram method. The multiplicity fraction for brown dwarfs constrains theories of brown dwarf formation and evolution. Binary systems, especially those that straddle the transition between L and T spectral types, are also significant tests of atmospheric models. In addition, the identification of companions would have enabled the eventual measurement of the associated masses. This search for astrometric companions is an extension of the initial infrared parallax program. When finalized, the trigonometric parallaxes for these brown dwarfs will provide accurate distances for use in determining their luminosities and temperatures. The brown dwarfs in this subsample have spectral types that range from early L through mid-T. None are known binaries. Distance estimates place all but two within the 25-pc limit of the Solar Neighborhood; one outlier has a distance of approximately 62 pc based on its preliminary parallax. These substellar objects are located north of -25° Dec. and lie between 13h and 23h in R.A. The brown dwarfs evaluated are 2MASS J13464634-0031501, SDSS J144600.60+002452.0, 2MASS J16241436+0029158, 2MASS J17580545+4633099, 2MASS J19010601+4718136, 2MASS J21241387+0059599, 2MASS J22425317+2542573, 2MASS J22443167+2043433, 2MASS J22541892+3123498, and 2MASS J22552907-0034336. Analyses of another 20 brown dwarfs were presented earlier and the analyses of 19 more brown dwarfs are planned.

  4. 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.

  5. Combing the Brown Dwarf Desert with the APOGEE Catalog of Stellar and Substellar Companion Candidates

    Science.gov (United States)

    Troup, Nicholas William; De Lee, Nathan M.; Carlberg, Joleen K.; Nidever, David L.; Majewski, Steven R.; Stassun, Keivan; Covey, Kevin R.; Skrutskie, Michael F.; Allende-Prieto, Carlos; Hearty, Fred R.; APOGEE Substellar Companions Working Group

    2016-01-01

    While both exoplanets and stellar-mass companions have been found in extremely short-period orbits, there has been a paucity of brown dwarf (BD) companions orbiting Sun-like stars, a phenomenon known as the "Brown Dwarf Desert." However, more recent work has shown that this Desert might be limited in extent, only existing for small separation (a test this hypothesis by constraining the formation mechanisms of BD companions, and exploring their orbital evolution as their host evolves off the main sequence.

  6. A KECK LGS AO SEARCH FOR BROWN DWARF AND PLANETARY MASS COMPANIONS TO UPPER SCORPIUS BROWN DWARFS

    International Nuclear Information System (INIS)

    We searched for binary companions to 20 young brown dwarfs in the Upper Scorpius association (145 pc, 5 Myr, nearest OB association) with 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 sun 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 Jup) brown dwarfs in Upper Sco is similar to that for T dwarfs in the field; for higher mass brown dwarfs and very low mass stars, there is an excess of medium-separation (10-50 AU projected separation) young binaries with respect to the field. These medium-separation binaries will likely survive to late ages.

  7. THE SEARCH FOR PLANETARY MASS COMPANIONS TO FIELD BROWN DWARFS WITH HST/NICMOS

    International Nuclear Information System (INIS)

    We present the results of a high-resolution spectral differential imaging survey of 12 nearby, relatively young field L dwarfs (≤1 Gyr) carried out with the Hubble Space Telescope/NICMOS to search for planetary mass companions at small physical separations from their host. The survey resolved two brown dwarf binaries: the L dwarf system Kelu-1 AB and the newly discovered L/T transition system 2MASS 031059+164815 AB. For both systems, common proper motion has already been confirmed in follow-up observations which have been published elsewhere. The derived separations of the binaries are smaller than 6 AU and consistent with previous brown dwarf binary statistics. Their mass ratios of q ≥ 0.8 confirm the preference for equal-mass systems similar to a large number of other surveys. Furthermore, we found tentative evidence for a companion to the L4 dwarf 2MASSW 033703-175807, straddling the brown dwarf/planetary mass boundary and revealing an uncommonly low-mass ratio system (q ∼ 0.2) compared to the vast majority of previously found brown dwarf binaries. With a derived minimum mass of 10-15 MJup a planetary nature of the secondary cannot be ruled out yet. However, it seems more likely to be a very low mass brown dwarf secondary at the border of the spectral T/Y transition regime, primarily due to its similarities to recently found very cool T dwarfs. This would make it one of the closest resolved brown dwarf binaries (0.''087 ± 0.''015, corresponding to 2.52 ± 0.44 AU at a distance of 29 pc) with the coolest (Teff ∼ 600-630 K) and least massive companion to any L or T dwarf.

  8. 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.

  9. 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...

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

    Science.gov (United States)

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

    2016-05-01

    Interacting compact binary systems provide a natural laboratory in which to study irradiated substellar objects. As the mass-losing secondary (donor) in these systems makes a transition from the stellar to the substellar regime, it is also irradiated by the primary (compact accretor). The internal and external energy fluxes are both expected to be comparable in these objects, providing access to an unexplored irradiation regime. The atmospheric properties of donors are largely unknown, but could be modified by the irradiation. To constrain models of donor atmospheres, it is necessary to obtain accurate observational estimates of their physical properties (masses, radii, temperatures and albedos). Here we report the spectroscopic detection and characterization of an irradiated substellar donor in an accreting white-dwarf binary system. Our near-infrared observations allow us to determine a model-independent mass estimate for the donor of 0.055 ± 0.008 solar masses and an average spectral type of L1 ± 1, supporting both theoretical predictions and model-dependent observational constraints that suggest that the donor is a brown dwarf. Our time-resolved data also allow us to estimate the average irradiation-induced temperature difference between the dayside and nightside of the substellar donor (57 kelvin) and the maximum difference between the hottest and coolest parts of its surface (200 kelvin). The observations are well described by a simple geometric reprocessing model with a bolometric (Bond) albedo of less than 0.54 at the 2σ confidence level, consistent with high reprocessing efficiency, but poor lateral heat redistribution in the atmosphere of the brown-dwarf donor. These results add to our knowledge of binary evolution, in that the donor has survived the transition from the stellar to the substellar regime, and of substellar atmospheres, in that we have been able to test a regime in which the irradiation and the internal energy of a brown dwarf are

  11. Statistical Properties of Brown Dwarf Companions: Implications for Different Formation Mechanisms

    CERN Document Server

    Ma, Bo

    2013-01-01

    The mass domain where massive extrasolar planets and brown dwarfs overlap is still poorly understood due to the paucity of brown dwarfs orbiting close to solar-type stars, the so-called brown dwarf desert. In this paper we collect all of available data about close brown dwarfs around solar type stars and their host stars from literature and study the demographics of the brown dwarf desert. The data clearly show a short period and a medium mass gap in the brown dwarf period-mass distribution diagram ($ 35brown dwarf desert. Observation biases are highly unlikely to cause this gap due to its short period and medium mass, of which brown dwarfs can be easily detected by previous RV surveys. Brown dwarfs above and below this gap have significantly different eccentricity distribution, which not only confirms that this gap is real, but also implies that they may have different origins. Our further statistical study indicates t...

  12. 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...

  13. A Search for Companions to Brown Dwarfs in the Taurus and Chamaeleon Star Forming Regions

    CERN Document Server

    Todorov, K O; Konopacky, Q M; McLeod, K K; Apai, D; Ghez, A M; Pascucci, I; Robberto, M

    2014-01-01

    We present the results of a search for companions to young brown dwarfs in the Taurus and Chamaeleon I star forming regions (1/2-3 Myr). We have used WFPC2 on board HST to obtain F791W and F850LP images of 47 members of these regions that have spectral types of M6-L0 (0.01-0.1 Msun). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. We have applied PSF subtraction to the primaries and have searched the resulting images for objects that have colors and magnitudes that are indicative of young low-mass objects. Through this process, we have identified promising candidate companions to 2MASS J04414489+2301513 (rho=0.105"/15 AU), 2MASS J04221332+1934392 (rho=0.05"/7 AU), and ISO 217 (rho=0.03"/5 AU). We reported the discovery of the first candidate in a previous study, showing that it has a similar proper motion as the primary through a comparison of astrometry measured with WFPC2 and Gemini adaptive optics. We have collected an additional e...

  14. 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.

  15. 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.

  16. Discovery of a companion at the brown dwarf limit to the solar-type star Gliese 29

    Science.gov (United States)

    Chini, R.; Fuhrmann, K.; Pozo Nuñez, F.; Ramolla, M.; Kaderhandt, L.; Niedworok, N.; Hodapp, K.-W.

    2016-07-01

    Gliese 29 is a 7 to 8 Gyr old, southern Population I turnoff star with a large proper motion of 1 arcsec/yr. Using recent direct imaging observations with the 0.8 m Infrared Imaging System (IRIS) of the Universitätssternwarte Bochum near Cerro Armazones in Chile, we demonstrate that the faint source 2MASS J00402651-5927168 at a projected angular separation ρ=6.35 arcsec is a common-proper-motion companion to Gl 29. Provided this source is not part of a further subsystem, the IRIS J- and K_s-band photometry either implies a spectral type of about L2, based on its absolute magnitude, or an approximate mass M_B ≃ 0.077 M⊙, suggesting that it may even be a brown dwarf. Assuming a face-on circular orbit this faint companion orbits Gl 29 in 1880 years.

  17. 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...

  18. A brown dwarf companion to the intermediate-mass star HR6037

    CERN Document Server

    Huelamo, N; Ivanov, V D; Chauvin, G; Carraro, G; Sterzik, M F; Melo, C H F; Bonnefoy, M; Hartung, M; Haubois, X; Foellmi, C

    2010-01-01

    In the course of an imaging survey we have detected a visual companion to the intermediate-mass star HR 6037. In this letter, we present two epoch observations of the binary with NACO/VLT, and near-IR spectroscopy of the secondary with ISAAC/VLT. The NACO observations allow us to confirm HR 6037B as a co-moving companion. Its J and H band ISAAC spectra suggest the object has an spectral type of M9+-1, with a surface gravity intermediate between that of 10 Myr dwarfs and field dwarfs with identical spectral type. The comparison of its Ks-band photometry with evolutionary tracks allows us to derive a mass, effective temperature, and surface gravity of 62+-20 MJup, Teff = 2330+-200 K, and log g = 5.1+-0.2, respectively. The small mass ratio of the binary, -0.03, and its long orbital period, -5000 yr, makes HR 6037 a rare and uncommon binary system.

  19. The Brown Dwarf Kinematics Project. II. Details on Nine Wide Common Proper Motion Very Low Mass Companions to Nearby Stars

    Science.gov (United States)

    Faherty, Jacqueline K.; Burgasser, Adam J.; West, Andrew A.; Bochanski, John J.; Cruz, Kelle L.; Shara, Michael M.; Walter, Frederick M.

    2010-01-01

    We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for both stellar primaries and low-mass secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of ~25,000 AU making it one of the widest and lowest binding energy systems known to date. The system containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows Hα activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine systems have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) low-mass companions (i.e., at least a triple system) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion systems indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide low-mass systems, suggesting that weakly bound, low-to-intermediate mass (0.2 M sun meter Magellan Telescopes located at Las Campanas Observatory, Chile. This paper makes use of data obtained with

  20. THE BROWN DWARF KINEMATICS PROJECT. II. DETAILS ON NINE WIDE COMMON PROPER MOTION VERY LOW MASS COMPANIONS TO NEARBY STARS ,

    International Nuclear Information System (INIS)

    We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for both stellar primaries and low-mass secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of ∼25,000 AU making it one of the widest and lowest binding energy systems known to date. The system containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows Hα activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. Two of the nine systems have discrepant component ages that emerge from stellar or ultracool diagnostics indicating possible shortcomings in our understanding of the age diagnostics of stars and brown dwarfs. We find a resolved binary frequency for widely separated (>100 AU) low-mass companions (i.e., at least a triple system) which is at least twice the frequency found for the field ultracool dwarf population. The ratio of triples to binaries and quadruples to binaries is also high for this sample: 3:5 and 1:4, respectively, compared to 8 pc sample values of 1:4 and 1:26. The additional components in these wide companion systems indicates a formation mechanism that requires a third or fourth component to maintain gravitational stability or facilitate the exchange of angular momentum. The binding energies for the nine multiples discussed in this text are among the lowest known for wide low-mass systems, suggesting that weakly bound, low-to-intermediate mass (0.2 M sun totsun) multiples can form and survive to exist in the field (1-8 Gyr).

  1. MOA-2013-BLG-220Lb: Planetary Companion to a Possible Brown Dwarf Host

    CERN Document Server

    Yee, J C; Gould, A; Skowron, J; Bond, I A; Udalski, A; Hundertmark, M; Monard, L A G; Porritt, I; Nelson, P; Bozza, V; Albrow, M D; Choi, J -Y; Christie, G W; DePoy, D L; Gaudi, B S; Hwang, K -H; Jung, Y K; Lee, C -U; McCormick, J; Natusch, T; Ngan, H; Park, H; Pogge, R W; Shin, I -G; Tan, T -G; Abe, F; Bennett, D P; Bond, I A; Botzler, C S; Freeman, M; Fukui, A; Fukunaga, D; Itow, Y; Koshimoto, N; Larsen, P; Ling, C H; Masuda, K; Matsubara, Y; Muraki, Y; Namba, S; Ohnishi, K; Philpott, L; Rattenbury, N J; Saito, To; Sullivan, D J; Sumi, T; Sweatman, W L; Suzuki, D; Tristram, P J; Tsurumi, N; Wada, K; Yamai, N; Yock, P C M; Yonehara, A; Szymański, M K; Ulaczyk, K; Kozłowski, S; Poleski, R; Wyrzykowski, Ł; Kubiak, M; Pietrukowicz, P; Pietrzyński, G; Soszyński, I; Bramich, D M; Browne, P; Horne, K; Ipatov, S; Kains, N; Snodgrass, C; Steele, I A; Street, R; Tsapras, Y

    2014-01-01

    Based on its high proper motion $\\mu=12.5\\pm 1\\,\\masyr$, MOA-2013-BLG-220Lb is the best candidate to date for a microlensing planet with a verifiable brown dwarf host. This candidacy can be partially tested immediately and more fully tested by $\\sim 2021$, when the source and lens will have separated sufficiently to be resolved in high-resolution images even if the lens is at the bottom of the main sequence, and so extremely faint, $H\\sim 24$. The planet-star mass ratio is $q=3.01\\pm 0.02\\times 10^{-3}$. The planet could have been detected and characterized purely with follow-up data. The potential to completely characterize planetary events from followup data has far-reaching implications for microlensing surveys, both current and into the LSST era.

  2. 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...

  3. HST NICMOS Imaging of the Planetary-mass Companion to the Young Brown Dwarf 2MASS J1207334-393254

    CERN Document Server

    Song, I; Zuckerman, B; Farihi, J; Becklin, E E; Bessell, M S; Lowrance, P J; MacIntosh, B A; Song, Inseok

    2006-01-01

    Multi-band (0.9 to 1.6 um) images of the TW Hydrae Association (TWA) brown dwarf, 2MASS J1207334-393254 (also known as 2M1207), and its candidate planetary mass companion (2M1207b) were obtained on 2004 Aug 28 and 2005 Apr 26 with HST/NICMOS. The images from these two epochs unequivocally confirm the two objects as a common proper motion pair (16.0 sigma confidence). A new measurement of the proper motion of 2M1207 implies a distance to the system of 59+-7 pc and a projected separation of 46+-5 AU. The NICMOS and previously published VLT photometry of 2M1207b, extending overall from 0.9 to 3.8 um, are fully consistent with an object of a few Jupiter masses at the canonical age of a TWA member (~8 Myr) based on evolutionary models of young giant planets. These observations provide information on the physical nature of 2M1207b and unambiguously establish that the first direct image of a planetary mass companion in orbit around a self-luminous body, other than our Sun, has been secured.

  4. 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.

  5. DETECTION OF A TERTIARY BROWN DWARF COMPANION IN THE sdB-TYPE ECLIPSING BINARY HS 0705+6700

    International Nuclear Information System (INIS)

    HS 0705+6700 is a short-period (P = 2.3 hr), close binary containing a hot sdB-type primary and a fully convective secondary. We have monitored this eclipsing binary for more than two years and as a result, 32 times of light minimum were obtained. Based on our new eclipse times together with these compiled from the literature, it is discovered that the observed-calculated curve of HS 0705+6700 shows a cyclic variation with a period of 7.15 years and a semiamplitude of 92.4 s. The periodic change was analyzed for the light-travel time effect that may be due to the presence of a tertiary companion. The mass of the third body is determined to be M 3sin i' = 0.0377(±0.0043) M sun when a total mass of 0.617 M sun for HS 0705+6700 is adopted. For orbital inclinations i' ≥ 32.08, the mass of the tertiary component would be below the stable hydrogen-burning limit of M 3 ∼ 0.072 M sun, and thus it would be a brown dwarf. The third body is orbiting the sdB-type binary at a distance shorter than 3.6 AU. HS 0705+6700 was formed through the evolution of a common envelope after the primary becomes a red giant. The detection of a substellar companion in HS 0705+6700 system at this distance from the binary could give some constraints on stellar evolution in such systems and the interactions between red giants and their companions.

  6. 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.

  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

    International Nuclear Information System (INIS)

    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+0.0188-0.0187 days, an eccentricity of 0.4375 ± 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 Teff = 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☉ and 0.92 ± 0.19 R☉. The minimum mass of MARVELS-5b is 65.0 ± 2.9MJup, 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☉ at a separation larger than 40 AU

  8. The SOPHIE search for northern extrasolar planets. VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

    Science.gov (United States)

    Bouchy, F.; Ségransan, D.; 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.

    2016-01-01

    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-yr 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 MJup 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 such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging. Based on observations made with ELODIE and SOPHIE spectrographs on the 1.93-m telescope at Observatoire de Haute-Provence (CNRS/AMU), France.Tables 5-9 (RV data) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/585/A46

  9. Detection of a tertiary brown dwarf companion in the sdB-typ e eclipsing binary HS 0705+6700

    CERN Document Server

    Qian, S; Zola, S; Liao, W; Liu, L; Li, L; Winiarski, M; Kuligowska, E; Kreiner, J

    2009-01-01

    HS 0705+6700 is a short-period (P=2.3 hours), close binary containing a hot sdB-type primary and a fully convective secondary. We have monitored this eclipsing binary for more than 2 years and as a result, 32 times of light minimum were obtained. Based on our new eclipse times together with these compiled from the literature, it is discovered that the O-C curve of HS 0705+6700 shows a cyclic variation with a period of 7.15 years and a semiamplitude of 92.4 s. The periodic change was analyzed for the light-travel time effect that may be due to the presence of a tertiary companion. The mass of the third body is determined to be M3 sin i = 0.0377 (+/-0.0043) M when a total mass of 0.617 M for HS 0705+6700 is adopted. For orbital inclinations i >= 32.8, the mass of the tertiary component would be below the stable hydrogen-burning limit of M3~0.072 M, and thus it would be a brown dwarf. The third body is orbiting the sdB-type binary at a distance shorter than 3.6 astronomical units (AU). HS 0705+6700 was formed th...

  10. Analysis of two eclipsing hot subdwarf binaries with a low mass stellar and a brown dwarf companion

    OpenAIRE

    Schaffenroth, Veronika; Geier, Stephan; Heber, Ulrich; Drechsel, Horst; O̸stensen, Roy H.; Maxted, Pierre F. L.; Kupfer, Thomas; Barlow, Brad N.

    2010-01-01

    The formation of hot subdwarf stars (sdBs), which are core helium‐burning stars located on the extended horizontal branch, is still not understood. Many of the known hot subdwarf stars reside in close binary systems with short orbital periods between a few hours and a few days with either M star or white dwarf companions. Common envelope ejection is the most probable formation channel. Among these, eclipsing systems are of special importance because it is possible to constrain the parameters ...

  11. The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits . III. The frequency of brown dwarfs and giant planets as companions to solar-type stars

    Science.gov (United States)

    Reggiani, M.; Meyer, M. R.; Chauvin, G.; Vigan, A.; Quanz, S. P.; Biller, B.; Bonavita, M.; Desidera, S.; Delorme, P.; Hagelberg, J.; Maire, A.-L.; Boccaletti, A.; Beuzit, J.-L.; Buenzli, E.; Carson, J.; Covino, E.; Feldt, M.; Girard, J.; Gratton, R.; Henning, T.; Kasper, M.; Lagrange, A.-M.; Mesa, D.; Messina, S.; Montagnier, G.; Mordasini, C.; Mouillet, D.; Schlieder, J. E.; Segransan, D.; Thalmann, C.; Zurlo, A.

    2016-02-01

    Context. In recent years there have been many attempts to characterize the occurrence and distribution of stellar, brown dwarf (BD), and planetary-mass companions to solar-type stars with the aim of constraining formation mechanisms. From radial velocity observations a dearth of companions with masses between 10-40 MJupiter has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range. Aims: We present a model for the substellar companion mass function (CMF). This model consists of the superposition of the planet and BD companion mass distributions, assuming that we can extrapolate the radial velocity measured CMF for planets to larger separations and the stellar companion mass-ratio distribution over all separations into the BD mass regime. By using both the results of the VLT/NaCo large program (NaCo-LP) and the complementary archive datasets, which probe the occurrence of planets and BDs on wide orbits around solar-type stars, we place some constraints on the planet and BD distributions. Methods: We developed a Monte Carlo simulation tool to predict the outcome of a given survey, depending on the shape of the orbital parameter distributions (mass, semimajor axis, eccentricity, and inclination). Comparing the predictions with the results of the observations, we calculate the likelihood of different models and which models can be ruled out. Results: Current observations are consistent with the proposed model for the CMF, as long as a sufficiently small outer truncation radius (≲100 AU) is introduced for the planet separation distribution. Some regions of parameter space can be excluded by the observations. Conclusions: We conclude that the results of the direct imaging surveys searching for substellar companions around Sun-like stars are consistent with a combined substellar mass spectrum of planets and BDs. This mass distribution has a minimum between 10 and 50 MJupiter, in agreement

  12. New Extinction and Mass Estimates from Optical Photometry of the Very Low Mass Brown Dwarf Companion CT Chamaeleontis B with the Magellan AO System

    CERN Document Server

    Wu, Ya-Lin; Males, Jared R; Barman, Travis S; Morzinski, Katie M; Follette, Katherine B; Bailey, Vanessa; Rodigas, Timothy J; Hinz, Philip; Puglisi, Alfio; Xompero, Marco; Briguglio, Runa

    2015-01-01

    We used the Magellan adaptive optics (MagAO) system and its VisAO CCD camera to image the young low mass brown dwarf companion CT Chamaeleontis B for the first time at visible wavelengths. We detect it at r', i', z', and Ys. With our new photometry and Teff~2500 K derived from the shape its K-band spectrum, we find that CT Cha B has Av = 3.4+/-1.1 mag, and a mass of 14-24 Mj according to the DUSTY evolutionary tracks and its 1-5 Myr age. The overluminosity of our r' detection indicates that the companion has significant Halpha emission and a mass accretion rate ~6*10^-10 Msun/yr, similar to some substellar companions. Proper motion analysis shows that another point source within 2" of CT Cha A is not physical. This paper demonstrates how visible wavelength AO photometry (r', i', z', Ys) allows for a better estimate of extinction, luminosity, and mass accretion rate of young substellar companions.

  13. The Brown Dwarf Kinematics Project (BDKP). II. Details on Nine Wide Common Proper Motion Very Low-Mass Companions to Nearby Stars

    CERN Document Server

    Faherty, Jacqueline K; West, Andrew A; Bochanski, John J; Cruz, Kelle L; Shara, Michael M; Walter, Frederick M

    2009-01-01

    We report on nine wide common proper motion systems containing late-type M, L, or T companions. We confirm six previously reported companions, and identify three new systems. The ages of these systems are determined using diagnostics for both stellar primaries and low--mass secondaries and masses for the secondaries are inferred using evolutionary models. Of our three new discoveries, the M3+T6.5 pair G 204-39 and SDSS J1758+4633 has an age constrained to 0.5-1.5 Gyr making the secondary a potentially useful brown dwarf benchmark. The G5+L4 pair G 200-28 and SDSS J1416+5006 has a projected separation of ~25,000 AU making it one of the widest and lowest binding energy systems known to date. The system containing NLTT 2274 and SDSS J0041+1341 is an older M4+L0 (>4.5 Gyr) pair which shows Halpha activity in the secondary but not the primary making it a useful tracer of age/mass/activity trends. We find a resolved binary frequency for widely-separated (> 100 AU) low--mass companions (i.e. at least a triple system...

  14. A THERMAL INFRARED IMAGING STUDY OF VERY LOW MASS, WIDE-SEPARATION BROWN DWARF COMPANIONS TO UPPER SCORPIUS STARS: CONSTRAINING CIRCUMSTELLAR ENVIRONMENTS

    International Nuclear Information System (INIS)

    We present a 3-5 μm LBT/MMT adaptive optics imaging study of three Upper Scorpius stars with brown dwarf (BD) companions with very low masses/mass ratios (MBD Jup; MBD/M* ≈ 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 μm and 24 μm 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 μm excess in the system may be explained by the contribution from this disk. 1RXS 1609B exhibits no 3-4 μm excess, nor does its primary; however, the system as a whole has a modest 24 μm 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 μm 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 (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.

  15. 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.

  16. Planet or brown dwarf? Inferring the companion mass in HD 100546 from the wall shape using mid-infrared interferometry

    NARCIS (Netherlands)

    Mulders, Gijs D.; Paardekooper, Sijme-Jan; Panic, Olja; Dominik, Carsten; van Boekel, Roy; Ratzka, Thorsten

    2013-01-01

    Context. Giant planets form in protoplanetary disks while these disks are still gas-rich, and can reveal their presence through the annular gaps they carve out. HD 100546 is a gas-rich disk with a wide gap between a radius of similar to 1 and 13 AU, possibly cleared out by a planetary companion or p

  17. DISCOVERY OF TWO VERY WIDE BINARIES WITH ULTRACOOL COMPANIONS AND A NEW BROWN DWARF AT THE L/T TRANSITION

    International Nuclear Information System (INIS)

    We present the discovery and spectroscopic follow-up of a nearby late-type L dwarf (2M0614+3950), and two extremely wide very low mass binary systems (2M0525-7425AB and 2M1348-1344AB), resulting from our search for common proper motion pairs containing ultracool components in the Two Micron All Sky Survey and the Wide-field Infrared Survey Explorer catalogs. The near-infrared spectrum of 2M0614+3950 indicates a spectral type L9 ± 1 object residing at a distance of 26.0 ± 1.8 pc. The optical spectrum of 2M0525-7425A reveals an M3.0 ± 0.5 dwarf primary, accompanied by a secondary previously classified as L2. The system has an angular separation of ∼44'', equivalent to ∼2000 AU at a distance of 46.0 ± 3.0 pc. Using optical and infrared spectra, respectively, we classify the components of 2M1348-1344AB as M4.5 ± 0.5 and T5.5 ± 1. The angular separation of ∼68'' is equivalent to ∼1400 AU at a distance of 20.7 ± 1.4 pc. 2M1348-1344AB is one of only six very wide (separation >1000 AU) systems containing late T dwarfs known to date.

  18. 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...

  19. Photometric brown-dwarf classification

    CERN Document Server

    Skrzypek, N

    2013-01-01

    We have developed a method "photo-type" to identify and accurately classify L and T dwarfs, onto the standard system, from photometry alone. We combine SDSS, UKIDSS and WISE data and classify point sources by comparing the izYJHKW1W2 colours against template colours for quasars, stars, and brown dwarfs. In a sample of $6.5\\times10^6$ bright point sources, J$<$17.5, from 3150 deg$^2$, we identify and type 898 L and T dwarfs, making this the largest homogeneously selected sample of brown dwarfs to date. The sample includes 713 (125) new (previously known) L dwarfs and 21 (39) T dwarfs. For the previously-known sources, the scatter in the plot of photo-type vs spectral type indicates that our photo-types are accurate to 1.5 (1.0) sub-types rms for L (T) dwarfs. Peculiar objects and candidate unresolved binaries are identified.

  20. Can brown dwarfs survive on close orbits around convective stars?

    CERN Document Server

    Damiani, Cilia

    2016-01-01

    Brown dwarfs straddle the mass range transition from planetary to stellar objects. There is a relative paucity of brown dwarfs companions around FGKM stars compared to exoplanets for orbital periods less than a few years, but most of the short-period brown dwarf companions fully characterised by transits and radial velocities are found around F-type stars. We examine the hypothesis that brown dwarf companions could not survive on close orbit around stars with important convective envelopes because the tides and angular momentum loss through magnetic breaking should lead to a rapid orbital decay and quick engulfment of the companion. We use a classical Skumanich-type braking law, and constant time-lag tidal theory to assess the characteristic timescale for orbital decay for the brown dwarf mass range as a function of the host properties. We find that F-type stars may host massive companions for a significantly longer time than G-type stars for a given orbital period, which may explain the paucity of G-type hos...

  1. Can brown dwarfs survive on close orbits around convective stars?

    Science.gov (United States)

    Damiani, C.; Díaz, R. F.

    2016-04-01

    Context. The mass range of brown dwarfs extends across the planetary domain to stellar objects. There is a relative paucity of brown dwarfs companions around FGKM-type stars compared to exoplanets for orbital periods of less than a few years, but most of the short-period brown dwarf companions that are fully characterised by transits and radial velocities are found around F-type stars. Aims: We examine the hypothesis that brown dwarf companions could not survive on close orbit around stars with important convective envelopes because the tides and angular momentum loss, the result of magnetic braking, would lead to a rapid orbital decay with the companion being quickly engulfed. Methods: We use a classical Skumanich-type braking law and constant time-lag tidal theory to assess the characteristic timescale for orbital decay for the brown dwarf mass range as a function of the host properties. Results: We find that F-type stars may host massive companions for a significantly longer time than G-type stars for a given orbital period, which may explain the paucity of G-type hosts for brown dwarfs with an orbital period less than five days. On the other hand, we show that the small radius of early M-type stars contributes to orbital decay timescales that are only half those of F-type stars, despite their more efficient tidal dissipation and magnetic braking. For fully convective later type M-dwarfs, orbital decay timescales could be orders of magnitude greater than for F-type stars. Moreover, we find that, for a wide range of values of tidal dissipation efficiency and magnetic braking, it is safe to assume that orbital decay for massive companions can be neglected for orbital periods greater than ten days. Conclusions: For orbital periods greater than ten days, brown dwarf occurrence should largely be unaffected by tidal decay, whatever the mass of the host. On closer orbital periods, the rapid engulfment of massive companions could explain the lack of G and K-type hosts

  2. 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 (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.

  3. FIRST DIRECT EVIDENCE THAT BARIUM DWARFS HAVE WHITE DWARF COMPANIONS

    International Nuclear Information System (INIS)

    Barium II (Ba) stars are chemically peculiar F-, G-, and K-type objects that show enhanced abundances of s-process elements. Since s-process nucleosynthesis is unlikely to take place in stars prior to the advanced asymptotic giant branch (AGB) stage, the prevailing hypothesis is that each present Ba star was contaminated by an AGB companion which is now a white dwarf (WD). Unless the initial mass ratio of such a binary was fairly close to unity, the receiving star is thus at least as likely to be a dwarf as a giant. So although most known Ba stars appear to be giants, the hypothesis requires that Ba dwarfs be comparably plentiful and moreover that they should all have WD companions. However, despite dedicated searches with the IUE satellite, no WD companions have been directly detected to date among the classical Ba dwarfs, even though some 90% of those stars are spectroscopic binaries, so the contamination hypothesis is therefore presently in some jeopardy. In this paper, we analyze recent deep, near-UV and far-UV Galaxy Evolution Explorer (GALEX) exposures of four of the brightest of the class (HD 2454, 15360, 26367, and 221531), together with archived GALEX data for two newly recognized Ba dwarfs: HD 34654 and HD 114520 (which also prove to be spectroscopic binaries). The GALEX observations of the Ba dwarfs as a group show a significant far-UV excess compared to a control sample of normal F-type dwarfs. We suggest that this ensemble far-UV excess constitutes the first direct evidence that Ba dwarfs have WD companions.

  4. HIGH-CONTRAST 3.8 μm IMAGING OF THE BROWN DWARF/PLANET-MASS COMPANION TO GJ 758

    International Nuclear Information System (INIS)

    We present L'-band (3.8 μm) MMT/Clio high-contrast imaging data for the nearby star GJ 758, which was recently reported by Thalmann et al. to have one-possibly two-faint comoving companions (GJ 758B and 'C', respectively). GJ 758B is detected in two distinct data sets. Additionally, we report a possible detection of the object identified by Thalmann et al. as 'GJ 758C' in our more sensitive data set, 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 758B has an H - L' color redder than nearly all known L-T8 dwarfs. Based on comparisons with the COND evolutionary models, GJ 758B has T e ∼ 560 K+150K-90K and a mass ranging from ∼10-20 MJ if it is ∼1 Gyr old to ∼ 25-40 MJ if it is 8.7 Gyr old. GJ 758B is likely in a highly eccentric orbit, e ∼ 0.73+0.12-0.21, with a semimajor axis. Though GJ 758B 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.

  5. 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...

  6. 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...

  7. The VLT/NaCo large program to probe the occurrence of exoplanets and brown dwarfs at wide orbits. III. The frequency of brown dwarfs and giant planets as companions to solar-type stars

    CERN Document Server

    Reggiani, M; Chauvin, G; Vigan, A; Quanz, S P; Biller, B; Bonavita, M; Desidera, S; Delorme, P; Hagelberg, J; Maire, A -L; Boccaletti, A; Beuzit, J -L; Buenzli, E; Carson, J; Covino, E; Feldt, M; Girard, J; Gratton, R; Henning, T; Kasper, M; Lagrange, A -M; Mesa, D; Messina, S; Montagnier, G; Mordasini, C; Mouillet, D; Schlieder, J E; Segransan, D; Thalmann, C; Zurlo, A

    2015-01-01

    In recent years there have been many attempts to characterize the occurrence of stellar, BD and planetary-mass companions to solar-type stars, with the aim of constraining formation mechanisms. From RV observations a dearth of companions with masses between 10-40 MJup has been noticed at close separations, suggesting the possibility of a distinct formation mechanism for objects above and below this range. We present a model for the substellar companion mass function (CMF). It consists of the superposition of the planet and BD companion mass distributions, assuming that we can extrapolate the RV measured companion mass function for planets to larger separations and the stellar companion mass-ratio distribution over all separations into the BD mass regime. By using both the results of the VLT/NaCo large program and the complementary archive datasets that probe the occurrence of planets and BDs on wide orbits around solar-type stars, we place some constraints on the planet and BD distributions. We developed a MC...

  8. 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 ...

  9. Adaptive Optics Observations of Exoplanets, Brown Dwarfs, & Binary Stars

    CERN Document Server

    Hinkley, Sasha

    2011-01-01

    The current direct observations of brown dwarfs and exoplanets have been obtained using instruments not specifically designed for overcoming the large contrast ratio between the host star and any wide-separation faint companions. However, we are about to witness the birth of several new dedicated observing platforms specifically geared towards high contrast imaging of these objects. The Gemini Planet Imager, VLT-SPHERE, Subaru HiCIAO, and Project 1640 at the Palomar 5m telescope will return images of numerous exoplanets and brown dwarfs over hundreds of observing nights in the next five years. Along with diffraction-limited coronagraphs and high-order adaptive optics, these instruments also will return spectral and polarimetric information on any discovered targets, giving clues to their atmospheric compositions and characteristics. Such spectral characterization will be key to forming a detailed theory of comparative exoplanetary science which will be widely applicable to both exoplanets and brown dwarfs. Fu...

  10. 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

    International Nuclear Information System (INIS)

    We describe the discovery of a likely brown dwarf (BD) companion with a minimum mass of 31.7 ± 2.0 MJup 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☉, 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 eccentricity of 0.1442+0.0078-0.0073, and a semi-amplitude of 1644+12-13 m s–1. Moderate resolution spectroscopy of the host star has determined the following parameters: Teff = 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* = 1.11 ± 0.11 M☉ and R* = 1.06 ± 0.23 R☉ 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 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.

  11. Auroral Phenomena in Brown Dwarf Atmospheres

    Science.gov (United States)

    Pineda, J. Sebastian; Hallinan, Gregg

    2016-01-01

    Since the unexpected discovery of radio emission from brown dwarfs some 15 years ago, investigations into the nature of this emission have revealed that, despite their cool and neutral atmospheres, brown dwarfs harbor strong kG magnetic fields, but unlike the warmer stellar objects, they generate highly circularly polarized auroral radio emission, like the giant planets of the Solar System. Our recent results from Keck LRIS monitoring of the brown dwarf LSR1835+32 definitively confirm this picture by connecting the auroral radio emission to spectroscopic variability at optical wavelengths as coherent manifestations of strong large-scale magnetospheric auroral current systems. I present some of the results of my dissertation work to understand the nature brown dwarf auroral phenomena. My efforts include a survey of Late L dwarfs and T dwarfs, looking for auroral Hα emission and a concurrent survey looking for the auroral emission of H3+ from brown dwarfs with radio pulse detections. I discuss the potential connection of this auroral activity to brown dwarf weather phenomena and how brown dwarf aurorae may differ from the analogous emission of the magnetized giant planets in the Solar System.

  12. Brown dwarf disks with ALMA

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, L.; Isella, A. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Testi, L.; De Gregorio-Monsalvo, I. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Natta, A. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Scholz, A., E-mail: lricci@astro.caltech.edu [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland)

    2014-08-10

    We present Atacama Large Millimeter/submillimeter Array continuum and spectral line data at 0.89 mm and 3.2 mm for three disks surrounding young brown dwarfs and very low mass stars in the Taurus star forming region. Dust thermal emission is detected and spatially resolved for all the three disks, while CO(J = 3-2) emission is seen in two disks. We analyze the continuum visibilities and constrain the disks' physical structure in dust. The results of our analysis show that the disks are relatively large; the smallest one has an outer radius of about 70 AU. The inferred disk radii, radial profiles of the dust surface density, and disk to central object mass ratios lie within the ranges found for disks around more massive young stars. We derive from our observations the wavelength dependence of the millimeter dust opacity. In all the three disks, data are consistent with the presence of grains with at least millimeter sizes, as also found for disks around young stars, and confirm that the early stages of the solid growth toward planetesimals occur also around very low-mass objects. We discuss the implications of our findings on models of solids evolution in protoplanetary disks, the main mechanisms proposed for the formation of brown dwarfs and very low-mass stars, as well as the potential of finding rocky and giant planets around very low-mass objects.

  13. Brown Dwarfs at the Exoplanet Mass Boundary

    Science.gov (United States)

    Faherty, J. K.; Cruz, K. L.; Rice, E. L.; Riedel, A.

    2014-10-01

    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. Our team has assigned >30 brown dwarfs to 10-150 Myr nearby moving groups. In so doing, we have discovered important diversity among this extremely low-mass (10 - 30 M_{Jup}) age-calibrated sample indicating that cloud properties play a critical role in their observables.

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

    OpenAIRE

    Crepp, Justin R.; Gonzales, Erica J.; 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 i...

  16. 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

  17. NLTT 41135: A FIELD M DWARF + BROWN DWARF ECLIPSING BINARY IN A TRIPLE SYSTEM, DISCOVERED BY THE MEARTH OBSERVATORY

    International Nuclear Information System (INIS)

    We report the discovery of an eclipsing companion to NLTT 41135, a nearby M5 dwarf that was already known to have a wider, slightly more massive common proper motion companion, NLTT 41136, at 2.''4 separation. Analysis of combined-light and RV curves of the system indicates that NLTT 41135B is a (31-34) ± 3MJup brown dwarf (where the range depends on the unknown metallicity of the host star) on a circular orbit. The visual M dwarf pair appears to be physically bound, so the system forms a hierarchical triple, with masses approximately in the ratio 8:6:1. The eclipses are grazing, preventing an unambiguous measurement of the secondary radius, but follow-up observations of the secondary eclipse (e.g., with the James Webb Space Telescope) could permit measurements of the surface brightness ratio between the two objects, and thus place constraints on models of brown dwarfs.

  18. 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...

  19. OGLE-2014-BLG-0257L: A Microlensing Brown Dwarf Orbiting a Low-mass M Dwarf

    CERN Document Server

    Han, C; Udalski, A; Gould, A; Bozza, V; Szymański, M K; Soszyński, I; Poleski, R; Kozłowski, S; Pietrukowicz, P; Skowron, J; Ulaczyk, K; Wyrzykowski, Ł

    2016-01-01

    In this paper, we report the discovery of a binary composed of a brown dwarf and a low-mass M dwarf from the observation of the microlensing event OGLE-2014-BLG-0257. Resolution of the very short-lasting caustic crossing combined with the detection of subtle continuous deviation in the lensing light curve induced by the Earth's orbital motion enable us to precisely measure both the Einstein radius \\theta_E and the lens parallax pi_E, which are the two quantities needed to unambiguously determine the mass and distance to the lens. It is found that the companion is a substellar brown dwarf with a mass 0.036 +/- 0.005 Msun (37.7 +/- 5.2\\ M_J) and it is orbiting an M dwarf with a mass 0.19 +/- 0.02 Msun. The binary is located at a distance 1.25 +/- 0.13 kpc toward the Galactic bulge and the projected separation between the binary components is 0.61 +/- 0.07 AU. The separation scaled by the mass of the host is 3.2 AU/Msun. Under the assumption that separations scale with masses, then, the discovered brown dwarf is...

  20. The luminosities of the coldest brown dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Tinney, C. G. [School of Physics, UNSW Australia, NSW 2052 (Australia); Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington DC 20005 (United States); Kirkpatrick, J. Davy [Infrared Processing and Analysis Center, MS100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Mike [Department of Physics and Astronomy, The University of Toledo, OH 43606 (United States); Morley, Caroline V. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Wright, Edward L., E-mail: c.tinney@unsw.edu.au [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States)

    2014-11-20

    In recent years, brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500 K and masses in the range of 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 130 K) and both hotter T-type brown dwarfs and the hotter planets that can be imaged orbiting young nearby stars (both with effective temperatures in the range of 1500-1000 K). 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 color. The latest atmospheric models show good agreement with the majority of these Y-dwarf absolute magnitudes. This is also the case for WISE0855-0714, the coldest and closest brown dwarf to the Sun, which shows evidence for water ice clouds. However, there are also some outstanding exceptions, which suggest either binarity or the presence of condensate clouds. The former is readily testable with current adaptive optics facilities. The latter would mean that the range of cloudiness in Y dwarfs is substantial with most hosting almost no clouds—while others have dense clouds, making them prime targets for future variability observations to study cloud dynamics.

  1. Cool white dwarf companions to four millisecond pulsars

    CERN Document Server

    Bassa, C G; Camilo, F; Cognard, I; Koester, D; Kramer, M; Ransom, S R; Stappers, B W

    2015-01-01

    We report on photometric and spectroscopic observations of white dwarf companions to four binary radio millisecond pulsars, leading to the discovery of companions to PSRs J0614-3329, J1231-1411 and J2017+0603. We place limits on the brightness of the companion to PSR J0613-0200. Optical spectroscopy of the companion to PSR J0614-3329 identifies it as a DA type white dwarf with a temperature of Teff=6460+-80 K, a surface gravity log g=7.0+-0.2 cgs and a mass of Mwd=0.24+-0.04 Msun. We find that the distance to PSR J0614-3329 is smaller than previously estimated, removing the need for the pulsar to have an unrealistically high gamma-ray efficiency. Comparing the photometry with predictions from white dwarf cooling models allows us to estimate temperatures and cooling ages of the companions to PSRs J0613-0200, J1231-1411 and J2017+0603. We find that the white dwarfs in these systems are cool Teff5 Gyr. Thin Hydrogen envelopes are required for these white dwarfs to cool to the observed temperatures, and we sugges...

  2. Near-infrared spectroscopy of the very low mass companion to the hot DA white dwarf PG1234+482

    CERN Document Server

    Steele, P R; Dobbie, P D; Barstow, M A

    2007-01-01

    We present a near-infrared spectrum of the hot ($T_{\\rm eff}$ $\\approx$ 55,000 K) DA white dwarf PG 1234+482. We confirm that a very low mass companion is responsible for the previously recognised infrared photometric excess. We compare spectra of M and L dwarfs, combined with an appropriate white dwarf model, to the data to constrain the spectral type of the secondary. We find that uncertainties in the 2MASS $HK$ photometry of the white dwarf prevent us from distinguishing whether the secondary is stellar or substellar, and assign a spectral type of L0$\\pm$1 (M9-L1).Therefore, this is the hottest and youngest ($\\approx 10^6$ yr) DA white dwarf with a possible brown dwarf companion.

  3. 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 ...

  4. Mapping the shores of the brown dwarf desert. IV. Ophiuchus

    CERN Document Server

    Cheetham, Anthony C; Ireland, Michael J; Cieza, Lucas; Rizzuto, Aaron C; Tuthill, Peter G

    2015-01-01

    We conduct a multiplicity survey of members of the rho Ophiuchus cloud complex with high resolution imaging to characterize the multiple star population of this nearby star forming region and investigate the relation between stellar multiplicity and star and planet formation. Our aperture masking survey reveals the presence of 5 new stellar companions beyond the reach of previous studies, but does not result in the detection of any new substellar companions. We find that 43+/-6% of the 114 stars in our survey have stellar mass companions between 1.3-780AU, while 7 (+8 -5)% host brown dwarf companions in the same interval. By combining this information with knowledge of disk-hosting stars, we show that the presence of a close binary companion (separation < 40 AU) significantly influences the lifetime of protoplanetary disks, a phenomenon previously seen in older star forming regions. At the ~1-2Myr age of our Ophiuchus members ~2/3 of close binary systems have lost their disks, compared to only ~30% of sing...

  5. CONFIRMATION OF ONE OF THE COLDEST KNOWN BROWN DWARFS

    International Nuclear Information System (INIS)

    Using two epochs of 4.5 μm 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 μm 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 eff = 300-345 K.

  6. 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...

  7. 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...

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

    Science.gov (United States)

    Wilson, P. A.; Hébrard, G.; 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.

    2016-04-01

    Radial velocity planet search surveys of nearby solar-type stars have shown a strong scarcity of brown dwarf companions within ~5 AU. There is presently no comprehensive explanation for 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 MJup, 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 ± 4 MJup to a mass of 0.35 ± 0.03 M⊙. The orbital parameters of two previously known substellar candidates are improved. Based on observations collected with the SOPHIE spectrograph on the 1.93 m telescope at Observatoire de Haute-Provence (CNRS), France, by the SOPHIE Consortium.The radial velocity measurements are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A144

  9. Do all barium stars have a white dwarf companion?

    Science.gov (United States)

    Dominy, J. F.; Lambert, D. L.

    1983-01-01

    International Ultraviolet Explorer short-wavelength, low-dispersion spectra were analyzed for four barium, two mild barium, and one R-type carbon star in order to test the hypothesis that the barium and related giants are produced by mass transfer from a companion now present as a white dwarf. An earlier tentative identification of a white dwarf companion to the mild barium star Zeta Cyg is confirmed. For the other stars, no ultraviolet excess attributable to a white dwarf is seen. Limits are set on the bolometric magnitude and age of a possible white dwarf companion. Since the barium stars do not have obvious progenitors among main-sequence and subgiant stars, mass transfer must be presumed to occur when the mass-gaining star is already on the giant branch. This restriction, and the white dwarf's minimum age, which is greater than 8 x 10 to the 8th yr, determined for several stars, effectively eliminates the hypothesis that mass transfer from an asymptotic giant branch star creates a barium star. Speculations are presented on alternative methods of producing a barium star in a binary system.

  10. 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

  11. 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...

  12. WASP-30b: a 61 Mjup brown dwarf transiting a V=12, F8 star

    CERN Document Server

    Anderson, D R; Hellier, C; Lendl, M; Maxted, P F L; Pollacco, D; Queloz, D; Smalley, B; Smith, A M S; Todd, I; Triaud, A H M J; West, R G; Barros, S C C; Enoch, B; Gillon, M; Lister, T A; Pepe, F; Ségransan, D; Street, R A; Udry, S

    2010-01-01

    We report the discovery of a 61-Jupiter-mass brown dwarf, which transits its F8V, rotationally-synchronised host star, WASP-30, every 4.16 days. From a range of age indicators, we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 \\pm 0.02 RJup) for the companion that is consistent with that predicted (0.914 RJup) by a model of a 1-Gyr-old, non-irradiated brown dwarf with a dusty atmosphere.

  13. The White Dwarf Binary Pathways Survey I: A sample of FGK stars with white dwarf companions

    CERN Document Server

    Parsons, S G; Schreiber, M R; Gansicke, B T; Zorotovic, M; Ren, J J

    2016-01-01

    The number of white dwarf plus main-sequence star binaries has increased rapidly in the last decade, jumping from only ~30 in 2003 to over 3000. However, in the majority of known systems the companion to the white dwarf is a low mass M dwarf, since these are relatively easy to identify from optical colours and spectra. White dwarfs with more massive FGK type companions have remained elusive due to the large difference in optical brightness between the two stars. In this paper we identify 934 main-sequence FGK stars from the Radial Velocity Experiment (RAVE) survey in the southern hemisphere and the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) survey in the northern hemisphere, that show excess flux at ultraviolet wavelengths which we interpret as the likely presence of a white dwarf companion. We obtained Hubble Space Telescope ultraviolet spectra for nine systems which confirmed that the excess is indeed caused, in all cases, by a hot compact companion, eight being white dwarfs and one ...

  14. 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

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

    Science.gov (United States)

    Faherty, Jacqueline K.; Burgasser, Adam J.; Walter, Frederick M.; Van der Bliek, Nicole; Shara, Michael M.; Cruz, Kelle L.; West, Andrew A.; Vrba, Frederick J.; Anglada-Escudé, Guillem

    2012-06-01

    We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical-mid-IR photometry to examine trends in spectral-type/absolute magnitude, and color-color diagrams. We report new polynomial relations between spectral type and MJHK . Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a "bright" (unresolved binary) and a "faint" (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in MJ where there is a [1.2-1.4] mag difference. A similar yet dampened brightening of [0.3-0.5] mag happens at MH and a plateau or dimming of [-0.2 to -0.3] mag is seen in MK . Comparison with evolutionary models that vary gravity, metallicity, and cloud thickness verifies that for L into T dwarfs, decreasing cloud thickness reproduces brown dwarf near-IR color-magnitude diagrams. However we find that a near constant temperature of 1200 ±100 K along a narrow spectral subtype of T0-T4 is required to account for the brightening and color-magnitude diagram of the L-dwarf/T-dwarf transition. There is a significant population of both L and T dwarfs which are red or potentially "ultra-cloudy" compared to the models, many of which are known to be young indicating a correlation between enhanced photospheric dust and youth. For the low surface gravity or young companion L dwarfs we find that 8 out of 10 are at least [0.2-1.0] mag underluminous in MJH and/or MK compared to equivalent spectral type objects. We speculate that this is a consequence of increased dust opacity and conclude that low surface gravity L dwarfs require a completely new spectral-type/absolute magnitude polynomial for analysis.

  16. THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS

    International Nuclear Information System (INIS)

    We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical-mid-IR photometry to examine trends in spectral-type/absolute magnitude, and color-color diagrams. We report new polynomial relations between spectral type and MJHK. Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a 'bright' (unresolved binary) and a 'faint' (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in MJ where there is a [1.2-1.4] mag difference. A similar yet dampened brightening of [0.3-0.5] mag happens at MH and a plateau or dimming of [–0.2 to –0.3] mag is seen in MK . Comparison with evolutionary models that vary gravity, metallicity, and cloud thickness verifies that for L into T dwarfs, decreasing cloud thickness reproduces brown dwarf near-IR color-magnitude diagrams. However we find that a near constant temperature of 1200 ±100 K along a narrow spectral subtype of T0-T4 is required to account for the brightening and color-magnitude diagram of the L-dwarf/T-dwarf transition. There is a significant population of both L and T dwarfs which are red or potentially 'ultra-cloudy' compared to the models, many of which are known to be young indicating a correlation between enhanced photospheric dust and youth. For the low surface gravity or young companion L dwarfs we find that 8 out of 10 are at least [0.2-1.0] mag underluminous in MJH and/or MK compared to equivalent spectral type objects. We speculate that this is a consequence of increased dust opacity and conclude that low surface gravity L dwarfs require a completely new spectral-type/absolute magnitude polynomial for analysis.

  17. THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Faherty, Jacqueline K.; Shara, Michael M.; Cruz, Kelle L. [Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034 (United States); Burgasser, Adam J. [Center of Astrophysics and Space Sciences, Department of Physics, University of California, San Diego, CA 92093 (United States); Walter, Frederick M. [Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States); Van der Bliek, Nicole [CTIO/National Optical Astronomy Observatory (Chile); West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Ave Boston, MA 02215 (United States); Vrba, Frederick J. [US Naval Observatory, Flagstaff Station, P.O. Box 1149, Flagstaff, AZ 86002 (United States); Anglada-Escude, Guillem, E-mail: jfaherty@amnh.org [Department of Terrestrial Magnetism, Carnegie Institution of Washington 5241 Broad Branch Road, NW, Washington, DC 20015 (United States)

    2012-06-10

    We report parallax measurements for 70 ultracool dwarfs (UCDs) including 11 late-M, 32 L, and 27 T dwarfs. In this sample, 14 M and L dwarfs exhibit low surface gravity features, 6 are close binary systems, and 2 are metal-poor subdwarfs. We combined our new measurements with 114 previously published UCD parallaxes and optical-mid-IR photometry to examine trends in spectral-type/absolute magnitude, and color-color diagrams. We report new polynomial relations between spectral type and M{sub JHK}. Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a 'bright' (unresolved binary) and a 'faint' (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in M{sub J} where there is a [1.2-1.4] mag difference. A similar yet dampened brightening of [0.3-0.5] mag happens at M{sub H} and a plateau or dimming of [-0.2 to -0.3] mag is seen in M{sub K} . Comparison with evolutionary models that vary gravity, metallicity, and cloud thickness verifies that for L into T dwarfs, decreasing cloud thickness reproduces brown dwarf near-IR color-magnitude diagrams. However we find that a near constant temperature of 1200 {+-}100 K along a narrow spectral subtype of T0-T4 is required to account for the brightening and color-magnitude diagram of the L-dwarf/T-dwarf transition. There is a significant population of both L and T dwarfs which are red or potentially 'ultra-cloudy' compared to the models, many of which are known to be young indicating a correlation between enhanced photospheric dust and youth. For the low surface gravity or young companion L dwarfs we find that 8 out of 10 are at least [0.2-1.0] mag underluminous in M{sub JH} and/or M{sub K} compared to equivalent spectral type objects. We speculate that this is a consequence of increased dust opacity and conclude that low surface gravity L dwarfs require a completely new

  18. Correlated spectral variability in brown dwarfs

    CERN Document Server

    Bailer-Jones, C A L

    2007-01-01

    Models of brown dwarf atmospheres suggest they exhibit complex physical behaviour. Observations have shown that they are indeed dynamic, displaying small photometric variations over timescales of hours. Here I report results of infrared (0.95-1.64 micron) spectrophotometric monitoring of four field L and T dwarfs spanning timescales of 0.1-5.5 hrs, the goal being to learn more about the physical nature of this variability. Spectra are analysed differentially with respect to a simultaneously observed reference source in order to remove Earth-atmospheric variations. The variability amplitude detected is typically 2-10%, depending on the source and wavelength. I analyse the data for correlated variations between spectral indices. This approach is more robust than single band or chisq analyses, because it does not assume an amplitude for the (often uncertain) noise level (although the significance test still assumes a shape for the noise power spectrum). Three of the four targets show significant evidence for cor...

  19. WD0837+185:the formation and evolution of an extreme mass ratio white dwarf-brown dwarf binary in Praesepe

    CERN Document Server

    Casewell, S L; Wynn, G A; Alexander, R D; Napiwotzki, R; Lawrie, K A; Dobbie, P D; Jameson, R F; Hodgkin, S T

    2012-01-01

    There is a striking and unexplained dearth of brown dwarf companions in close orbits (< 3AU) 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 ~ 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 Msun (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 ~2 AU, with common envelope evolution reducing the s...

  20. Race to the Top: Transiting Brown Dwarfs and Hot Jupiters

    Science.gov (United States)

    Beatty, Thomas G.

    2015-12-01

    There are currently twelve known transiting brown dwarfs, nine of which orbit single main-sequence stars. These systems give us one of the only ways in which we may directly measure the masses and radii brown dwarfs, which in turn provides strong constraints on theoretical models of brown dwarf interiors and atmospheres. In addition, the transiting brown dwarfs allow us to forge a link between our understanding of transiting hot Jupiters, and our understanding of the field brown dwarf population. Comparing the two gives us a unique avenue to explore the role and interaction of surface gravity and stellar irradiation in the atmospheres of sub-stellar objects. It also allows us to leverage the detailed spectroscopic information we have for field brown dwarfs to interpret the broadband colors of hot Jupiters. This provides us with insight into the L/T transition in brown dwarfs, and the atmospheric chemistry changes that occur in hot Jupiter atmospheres as they cool. I will discuss recent observational results, with a particular focus on the transiting brown dwarf KELT-1b, and suggest how more of these important systems may be discovered in the future.

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

    International Nuclear Information System (INIS)

    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

  2. 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.

  3. Chandra Captures Flare From Brown Dwarf

    Science.gov (United States)

    2000-07-01

    The first flare ever seen from a brown dwarf, or failed star, was detected by NASA's Chandra X-ray Observatory. The bright X-ray flare has implications for understanding the explosive activity and origin of magnetic fields of extremely low mass stars. Chandra detected no X-rays at all from LP 944-20 for the first nine hours of a twelve hour observation, then the source flared dramatically before it faded away over the next two hours. "We were shocked," said Dr. Robert Rutledge of the California Institute of Technology in Pasadena, the lead author on the discovery paper to appear in the July 20 issue of Astrophysical Journal Letters. "We didn't expect to see flaring from such a lightweight object. This is really the 'mouse that roared.'" Chandra LP 944-20 X-ray Image Press Image and Caption The energy emitted in the brown dwarf flare was comparable to a small solar flare, and was a billion times greater than observed X-ray flares from Jupiter. The flaring energy is believed to come from a twisted magnetic field. "This is the strongest evidence yet that brown dwarfs and possibly young giant planets have magnetic fields, and that a large amount of energy can be released in a flare," said Dr. Eduardo Martin, also of Caltech and a member of the team. Professor Gibor Basri of the University of California, Berkeley, the principal investigator for this observation, speculated that the flare "could have its origin in the turbulent magnetized hot material beneath the surface of the brown dwarf. A sub-surface flare could heat the atmosphere, allowing currents to flow and give rise to the X-ray flare -- like a stroke of lightning." LP 944-20 is about 500 million years old and has a mass that is about 60 times that of Jupiter, or 6 percent that of the Sun. Its diameter is about one-tenth that of the Sun and it has a rotation period of less than five hours. Located in the constellation Fornax in the southern skies, LP 944-20 is one of the best studied brown dwarfs because it is

  4. A 3D Search for Companions to 12 Nearby M-Dwarfs

    CERN Document Server

    Davison, Cassy L; Henry, Todd J; Riedel, Adric R; Jao, Wei-Chun; Bailey, John I; Quinn, Samuel N; Cantrell, Justin R; Subasavage, John P; Winters, Jen G

    2015-01-01

    We present a carefully vetted equatorial ($\\pm$ 30$^\\circ$ Decl.) sample of all known single (within 4'') mid M-dwarfs (M2.5V-M8.0V) extending out to 10 pc; their proximity and low masses make them ideal targets for planet searches. For this sample of 58 stars, we provide V$_J$, R$_{KC}$, I$_{KC}$ photometry, new low dispersion optical ($6000 - 9000$\\AA) spectra from which uniform spectral types are determined, multi-epoch H$\\alpha$ equivalent widths, and gravity sensitive $Na\\,I$ indices. For 12 of these 58 stars, strict limits are placed on the presence of stellar and sub-stellar companions, based on a pioneering program described here that utilizes precise infrared radial velocities and optical astrometric measurements in an effort to search for Jupiter-mass, brown dwarf and stellar-mass companions. Our infrared radial velocity precision using CSHELL at NASA's IRTF is $\\sim$90 m s$^{-1}$ over timescales from 13 days to 5 years. With our spectroscopic results the mean companion masses that we rule out of ex...

  5. Search for white dwarf companions of cool stars with peculiar element abundances

    Science.gov (United States)

    Boehm-Vitense, E.

    1984-01-01

    A search for a white dwarf companions of cool stars with peculiar element abundances was undertaken. One additional star the xi Cet, was found with a white dwarf companion. It was found that HR 1016, 56Uma, 16 Ser, have high excitation emission lines which indicate a high temperature object in the system. It is suggested that since these indications for high temperature companions were seen for all nearby Ba stars, it is highly probable that all Ba stars have white dwarf companions, and that the peculiar element abundances seen in the Ba stars are due to mass transfer. Observations, arguments and conclusions are presented. White dwarf companions were not found. Together with the Li and Be abundances and the chromospheric emission line spectra in these stars were studied. No white dwarf companions were seen for subgiant CH stars.

  6. The BANYAN All-Sky Survey for Brown Dwarf Members of Young Moving Groups

    Science.gov (United States)

    Gagné, Jonathan; Lafrenière, David; Doyon, René; Faherty, Jacqueline K.; Malo, Lison; Cruz, Kelle L.; Artigau, Étienne; Burgasser, Adam J.; Naud, Marie-Eve; Bouchard, Sandie; Gizis, John E.; Albert, Loïc

    2016-01-01

    We describe in this work the BASS survey for brown dwarfs in young moving groups of the solar neighborhood, and summarize the results that it generated. These include the discovery of the 2MASS J01033563-5515561 (AB)b and 2MASS J02192210-3925225 B young companions near the deuterium-burning limit as well as 44 new low-mass stars and 69 new brown dwarfs with a spectroscopically confirmed low gravity. Among those, ~20 have estimated masses within the planetary regime, one is a new L4 γ bona fide member of AB Doradus, three are TW Hydrae candidates with later spectral types (L1-L4) than all of its previously known members and six are among the first contenders for low-gravity >= L5 β/γ brown dwarfs, reminiscent of WISEP J004701.06+680352.1, PSO J318.5338-22.8603 and VHS J125601.92-125723.9 b. Finally, we describe a future version of this survey, BASS-Ultracool, that will specifically target >= L5 candidate members of young moving groups. First experimentations in designing the survey have already led to the discovery of a new T dwarf bona fide member of AB Doradus, as well as the serendipitous discoveries of an L9 subdwarf and an L5 + T5 brown dwarf binary.

  7. 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.

  8. Point Source Polarimetry with the Gemini Planet Imager: Sensitivity Characterization with T5.5 Dwarf Companion HD 19467 B

    Science.gov (United States)

    Jensen-Clem, Rebecca; Millar-Blanchaer, Max; Mawet, Dimitri; Graham, James R.; Wallace, J. Kent; Macintosh, Bruce; Hinkley, Sasha; Wiktorowicz, Sloane J.; Perrin, Marshall D.; Marley, Mark S.; Fitzgerald, Michael P.; Oppenheimer, Rebecca; Ammons, S. Mark; Rantakyr?o, Fredrik T.; Marchis, Franck

    2016-01-01

    Detecting polarized light from self-luminous exoplanets has the potential to provide key information about rotation, surface gravity, cloud grain size, and cloud coverage. While field brown dwarfs with detected polarized emission are common, no exoplanet or substellar companion has yet been detected in polarized light. With the advent of high contrast imaging spectro-polarimeters such as GPI and SPHERE, such a detection may now be possible with careful treatment of instrumental polarization. In this paper, we present 28 minutes of H-band GPI polarimetric observations of the benchmark T5.5 companion HD 19467 B. We detect no polarization signal from the target, and place an upper limit on the degree of linear polarization of pCL99:73% less than 1:7%. We discuss our results in the context of T dwarf cloud models and photometric variability.

  9. Point Source Polarimetry with the Gemini Planet Imager: Sensitivity Characterization with T5.5 Dwarf Companion HD 19467 B

    CERN Document Server

    Jensen-Clem, Rebecca; Mawet, Dimitri; Graham, James R; Wallace, J Kent; Macintosh, Bruce; Hinkley, Sasha; Wiktorowicz, Sloane J; Perrin, Marshall D; Marley, Mark S; Fitzgerald, Michael P; Oppenheimer, Rebecca; Ammons, S Mark; Rantakyro, Fredrik T; Marchis, Franck

    2016-01-01

    Detecting polarized light from self-luminous exoplanets has the potential to provide key information about rotation, surface gravity, cloud grain size, and cloud coverage. While field brown dwarfs with detected polarized emission are common, no exoplanet or substellar companion has yet been detected in polarized light. With the advent of high contrast imaging spectro-polarimeters such as GPI and SPHERE, such a detection may now be possible with careful treatment of instrumental polarization. In this paper, we present 28 minutes of $H$-band GPI polarimetric observations of the benchmark T5.5 companion HD 19467 B. We detect no polarization signal from the target, and place an upper limit on the degree of linear polarization of $p_{\\text{CL}99.73\\%} \\leq 2.4\\%$. We discuss our results in the context of T dwarf cloud models and photometric variability.

  10. Fundmental Parameters of Low-Mass Stars, Brown Dwarfs, and Planets

    Science.gov (United States)

    Montet, Benjamin; Johnson, John A.; Bowler, Brendan; Shkolnik, Evgenya

    2016-01-01

    Despite advances in evolutionary models of low-mass stars and brown dwarfs, these models remain poorly constrained by observations. In order to test these predictions directly, masses of individual stars must be measured and combined with broadband photometry and medium-resolution spectroscopy to probe stellar atmospheres. I will present results from an astrometric and spectroscopic survey of low-mass pre-main sequence binary stars to measure individual dynamical masses and compare to model predictions. This is the first systematic test of a large number of stellar systems of intermediate age between young star-forming regions and old field stars. Stars in our sample are members of the Tuc-Hor, AB Doradus, and beta Pictoris moving groups, the last of which includes GJ 3305 AB, the wide binary companion to the imaged exoplanet host 51 Eri. I will also present results of Spitzer observations of secondary eclipses of LHS 6343 C, a T dwarf transiting one member of an M+M binary in the Kepler field. By combining these data with Kepler photometry and radial velocity observations, we can measure the luminosity, mass, and radius of the brown dwarf. This is the first non-inflated brown dwarf for which all three of these parameters have been measured, providing the first benchmark to test model predictions of the masses and radii of field T dwarfs. I will discuss these results in the context of K2 and TESS, which will find additional benchmark transiting brown dwarfs over the course of their missions, including a description of the first planet catalog developed from K2 data and a program to search for transiting planets around mid-M dwarfs.

  11. Cold Brown Dwarfs with WISE: Y Dwarfs and the Field Mass Function

    Science.gov (United States)

    Kirkpatrick, J. Davy

    2012-01-01

    Why study Brown Dwarf stars? They re the lowest mass byproducts of star formation.. They provide time capsules across the age of the Galaxy.. They show what low-T(sub eff) atmospheres look like.. They may be some of our closest neighbors in space..WISE is a 40cm Earth-orbiting telescope. There are 211 stars and only 33 brown dwarfs in this volume.. This means that stars outnumber brown dwarfs by a factor of 6:1 currently.. The number of brown dwarfs will continue to increase if:: (a) more nearby Y dwarf candidates are confirmed, or (b) our distances to known Y s are overestimated, or (c) there are colder BDs invisible to WISE..

  12. 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 ...

  13. 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).

  14. A SUBSTELLAR COMPANION TO THE WHITE DWARF-RED DWARF ECLIPSING BINARY NN Ser

    International Nuclear Information System (INIS)

    NN Ser is a short-period (P = 3.12 hr) close binary containing a very hot white dwarf primary with a mass of 0.535 Msun and a fully convective secondary with a mass of 0.111 Msun. The changes in the orbital period of the eclipsing binary were analyzed based on our five newly determined eclipse times together with those compiled from the literature. A small-amplitude (0fd00031) cyclic period variation with a period of 7.56 years was discovered to be superimposed on a possible long-term decrease. The periodic change was plausibly explained as the light-travel time effect via the presence of a tertiary companion. The mass of the tertiary companion is determined to be M3sin i' = 0.0107(±0.0017) Msun when a total mass of 0.646 Msun for NN Ser is adopted. For orbital inclinations i' ≥ 49.056, the mass of the tertiary component was calculated to be M 3 ≤ 0.014 Msun; thus it would be an extrasolar planet. The third body is orbiting the white dwarf-red dwarf eclipsing binary at a distance shorter than 3.29 AU. Since the observed decrease rate of the orbital period is about two orders larger than that caused by gravitational radiation, it can be plausibly interpreted by magnetic braking of the fully convective component, which is driving this binary to evolve into a normal cataclysmic variable.

  15. Herschel survey of brown dwarf disks in Rho Ophiuchi

    CERN Document Server

    de Oliveira, C Alves; Marton, G; Pinte, C; Kiss, Cs; Kun, M; Kóspál, Á; André, Ph; Könyves, V

    2013-01-01

    Recent observations of the Rho Ophiuchi cluster with the Herschel Space Observatory allow us to probe the spectral energy distribution (SED) of the brown dwarf population in the far-IR, where the disk emission peaks. We performed aperture photometry at 70, 100, and 160 micron, and constructed SEDs for all previously known brown dwarfs detected. These were complemented with ancillary photometry at shorter wavelengths. We compared the observed SEDs to a grid of synthetic disks produced with the radiative transfer code MCFOST, and used the relative figure of merit estimated from the Bayesian inference of each disk parameter to analyse the structural properties. We detected 12 Class II brown dwarfs with Herschel, which corresponds to one-third of all currently known brown dwarf members of Rho Ophiuchi. We do not detect any of the known Class III brown dwarfs. Comparison to models reveals that the disks are best described by an inner radius between 0.01 and 0.07 AU, and a flared disk geometry with a flaring index ...

  16. On the properties of discs around accreting brown dwarfs

    CERN Document Server

    Mayne, Nathan

    2010-01-01

    We present a grid of models of accreting brown dwarf systems with circumstellar discs. The calculations involve a self-consistent solution of both vertical hydrostatic and radiative equilibrium along with a sophisticated treatment of dust sublimation. We have simulated observations of the spectral energy distributions and several broadband photometric systems. Analysis of the disc structures and simulated observations reveal a natural dichotomy in accretion rates, with \\logmdot $>-$9 and $\\leq -$9 classed as extreme and typical accretors respectively. Derivation of ages and masses from our simulated photometry using isochrones is demonstrated to be unreliable even for typical accretors. Although current brown dwarf disc candidate selection criteria have been shown to be largely reliable when applied to our model grid we suggest improved selection criteria in several colour indices. We show that as accretion rates increase brown dwarf disc systems are less likely to be correctly identified. This suggests that,...

  17. A global cloud map of the nearest known brown dwarf

    CERN Document Server

    Crossfield, I J M; Schlieder, J E; Deacon, N R; Bonnefoy, M; Homeier, D; Allard, F; Buenzli, E; Henning, Th; Brandner, W; Goldman, B; Kopytova, T

    2014-01-01

    Brown dwarfs -- substellar bodies more massive than planets but not massive enough to initiate the sustained hydrogen fusion that powers self-luminous stars -- are born hot and slowly cool as they age. As they cool below about 2,300 K, liquid or crystalline particles composed of calcium aluminates, silicates and iron condense into atmospheric 'dust', which disappears at still cooler temperatures (around 1,300 K). Models to explain this dust dispersal include both an abrupt sinking of the entire cloud deck into the deep, unob- servable atmosphere and breakup of the cloud into scattered patches (as seen on Jupiter and Saturn). Thus far, observations of brown dwarfs have been limited to globally integrated measurements, which can reveal surface inhomogeneities but cannot unambiguously resolve surface features. Here we report a two-dimensional map of a brown dwarf's surface that allows identification of large-scale bright and dark features, indicative of patchy clouds.

  18. Halo dark clusters of brown dwarfs and molecular clouds

    CERN Document Server

    De Paolis, F; Jetzer, Ph; Roncadelli, M; 10.1086/305692

    2009-01-01

    The discovery of Massive Astrophysical Compact Halo Objects (MACHOs) in microlensing experiments makes it compelling to understand their physical nature, as well as their formation mechanism. Within the present uncertainties, brown dwarfs are a viable candidate for MACHOs, and the present paper deals with this option. According to a recently proposed scenario, brown dwarfs are clumped along with cold molecular clouds into dark clusters -- in several respects similar to globular clusters -- which form in the outer part of the galactic halo. Here, we analyze the dynamics of these dark clusters and we address the possibility that a sizable fraction of MACHOs can be binary brown dwarfs. Moreover, we point out that Ly-$\\alpha$ absorption systems naturally fit within the present picture.

  19. Using Clustering Algorithms to Identify Brown Dwarf Characteristics

    Science.gov (United States)

    Choban, Caleb

    2016-06-01

    Brown dwarfs are stars that are not massive enough to sustain core hydrogen fusion, and thus fade and cool over time. The molecular composition of brown dwarf atmospheres can be determined by observing absorption features in their infrared spectrum, which can be quantified using spectral indices. Comparing these indices to one another, we can determine what kind of brown dwarf it is, and if it is young or metal-poor. We explored a new method for identifying these subgroups through the expectation-maximization machine learning clustering algorithm, which provides a quantitative and statistical way of identifying index pairs which separate rare populations. We specifically quantified two statistics, completeness and concentration, to identify the best index pairs. Starting with a training set, we defined selection regions for young, metal-poor and binary brown dwarfs, and tested these on a large sample of L dwarfs. We present the results of this analysis, and demonstrate that new objects in these classes can be found through these methods.

  20. 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.

  1. The Solar Neighborhood XXVIII: The Multiplicity Fraction of Nearby Stars from 5 to 70 AU and the Brown Dwarf Desert Around M Dwarfs

    CERN Document Server

    Dieterich, Sergio B; Golimowski, David A; Krist, John E; Tanner, Angelle M

    2012-01-01

    We report on our analysis of HST/NICMOS snapshot high resolution images of 255 stars in 201 systems within ~10 parsecs of the Sun. Photometry was obtained through filters F110W, F180M, F207M, and F222M using NICMOS Camera 2. These filters were selected to permit clear identification of cool brown dwarfs through methane contrast imaging. With a plate scale of 76 mas/pixel, NICMOS can easily resolve binaries with sub-arcsecond separations in the 19".5x19".5 field of view. We previously reported five companions to nearby M and L dwarfs from this search. No new companions were discovered during the second phase of data analysis presented here, confirming that stellar/substellar binaries are rare. We establish magnitude and separation limits for which companions can be ruled out for each star in the sample, and then perform a comprehensive sensitivity and completeness analysis for the subsample of 138 M dwarfs in 126 systems. We calculate a multiplicity fraction of 0.0{-0.0}^{+3.5}% for L companions to M dwarfs in...

  2. The BANYAN All-Sky Survey for Brown Dwarf Members of Young Moving Groups

    CERN Document Server

    Gagné, Jonathan; Doyon, René; Faherty, Jacqueline K; Malo, Lison; Cruz, Kelle L; Artigau, Étienne; Burgasser, Adam J; Naud, Marie-Eve; Bouchard, Sandie; Gizis, John E; Albert, Loïc

    2015-01-01

    We describe in this work the BASS survey for brown dwarfs in young moving groups of the solar neighborhood, and summarize the results that it generated. These include the discovery of the 2MASS J01033563-5515561 (AB)b and 2MASS J02192210-3925225 B young companions near the deuterium-burning limit as well as 44 new low-mass stars and 69 new brown dwarfs with a spectroscopically confirmed low gravity. Among those, ~20 have estimated masses within the planetary regime, one is a new L4 $\\gamma$ bona fide member of AB Doradus, three are TW Hydrae candidates with later spectral types (L1-L4) than all of its previously known members and six are among the first contenders to low-gravity $\\geq$ L5 $\\beta$/$\\gamma$ brown dwarfs, reminiscent of WISEP J004701.06+680352.1, PSO J318.5338-22.8603 and VHS J125601.92-125723.9 b. Finally, we describe a future version of this survey, BASS-Ultracool, that will specifically target $\\geq$ L5 candidate members of young moving groups. First experimentations in designing the survey h...

  3. 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...

  4. Epsilon Indi Ba, Bb: a spectroscopic study of the nearest known brown dwarfs

    CERN Document Server

    King, Robert R; Homeier, Derek; Allard, France; Scholz, Ralf-Dieter; Lodieu, Nicolas

    2008-01-01

    The discovery of Epsilon Indi Ba and Bb, a nearby binary brown dwarf system with a main-sequence companion, allows a concerted campaign to characterise the physical parameters of two T dwarfs providing benchmarks against which atmospheric and evolutionary models can be tested. Some recent observations suggest the models at low mass and intermediate age may not reflect reality with, however, few conclusive tests. We are carrying out a comprehensive characterisation of these, the nearest known brown dwarfs, to allow constraints to be placed upon models of cool field dwarfs. We present broadband photometry from the V- to M-band and the individual spectrum of both components from 0.6-5.1 microns at a resolution of up to R=5000. A custom analytic profile fitting routine was implemented to extract the blended spectra and photometry of both components separated by 0.7 arcsec. We confirm the spectral types to be T1 and T6, and notably, we do not detect lithium at 6708A in the more massive object which may be indicati...

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

    International Nuclear Information System (INIS)

    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–1 and lies relatively close to the Galactic plane (b = 5.02). Near-infrared photometry and spectroscopy reveals that this is one of the reddest (2MASS J – Ks 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 (Ks = 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.

  6. Temperature Fluctuations as a Source of Brown Dwarf Variability

    CERN Document Server

    Robinson, Tyler D

    2014-01-01

    A number of brown dwarfs are now known to be variable with observed amplitudes as large as 10-30% at some wavelengths. While spatial inhomogeneities in cloud coverage and thickness are likely responsible for much of the observed variability, it is possible that some of the variations arise from atmospheric temperature fluctuations instead of, or in addition to, clouds. To better understand the role that thermal variability might play we present a case study of brown dwarf variability using a newly-developed one-dimensional, time-stepping model of atmospheric thermal structure. We focus on the effects of thermal perturbations, intentionally simplifying the problem through omission of clouds and atmospheric circulation. Model results demonstrate that thermal perturbations occurring deep in the atmosphere (at pressures greater than 10 bar) of a model T-dwarf can be communicated to the upper atmosphere through radiative heating via the windows in near-infrared water opacity. The response time depends on where in ...

  7. 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 M...

  8. 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.

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

    Science.gov (United States)

    Udalski, A.; Jung, Y. K.; Han, C.; Gould, A.; Kozłowski, 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.

    2015-10-01

    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 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. Here we report 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 a star or as a scaled-up version of a moon plus a 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 to suggest that the formation processes of companions within accretion disks around stars, brown dwarfs, and planets are similar.

  10. 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...

  11. 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...

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

    OpenAIRE

    Montet, Benjamin T.; Johnson, John Asher; 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. ...

  13. A search for brown dwarf like secondaries in cataclysmic variables

    Science.gov (United States)

    Mennickent, R. E.; Diaz, M. P.

    2002-11-01

    We present VTL/ISAAC infrared spectroscopy of a sample of short-orbital-period cataclysmic variables that are candidates for harbouring substellar companions. We have detected the K I and Na I absorption lines of the companion star in VY Aqr. The overall spectral distribution in this system is best fitted with an M9.5 type dwarf spectrum, implying a distance of 100 +/- 10 pc. VY Aqr seems to fall far from the theoretical distribution of secondary star temperatures around the orbital period minimum. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. The application of such a spectral fitting procedure suggests that the continuum shape in the 1.1-2.5 μm spectral region in short-orbital-period cataclysmic variables may be a useful indicator of the companion's spectral type. SED fitting for RZ Leo and CU Vel suggests M5-type dwarf companions, and distances of 340 +/- 110 and 150 +/- 50 pc, respectively. These systems may be placed in the upper evolution branch for short-period cataclysmic variables.

  14. The First Science Results from SPHERE: Disproving the Predicted Brown Dwarf around V471 Tau

    CERN Document Server

    Hardy, A; Parsons, S G; Caceres, C; Retamales, G; Wahhaj, Z; Mawet, D; Canovas, H; Cieza, L; Marsh, T R; Bours, M C P; Dhillon, V S; Bayo, A

    2015-01-01

    Variations of eclipse arrival times have recently been detected in several post common envelope binaries consisting of a white dwarf and a main sequence companion star. The generally favoured explanation for these timing variations is the gravitational pull of one or more circumbinary substellar objects periodically moving the center of mass of the host binary. Using the new extreme-AO instrument SPHERE, we image the prototype eclipsing post-common envelope binary V471 Tau in search of the brown dwarf that is believed to be responsible for variations in its eclipse arrival times. We report that an unprecedented contrast of 12.1 magnitudes in the H band at a separation of 260 mas was achieved, but resulted in a non-detection. This implies that there is no brown dwarf present in the system unless it is three magnitudes fainter than predicted by evolutionary track models, and provides damaging evidence against the circumbinary interpretation of eclipse timing variations. In the case of V471 Tau, a more consisten...

  15. 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.

  16. 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

  17. The Brown-dwarf Atmosphere Monitoring (BAM) Project II: Multi-epoch monitoring of extremely cool brown dwarfs

    CERN Document Server

    Rajan, A; Wilson, P A; Bulger, J; De Rosa, R J; Ward-Duong, K; Morley, C; Pont, F; Windhorst, R

    2015-01-01

    With the discovery of Y dwarfs by the WISE mission, the population of field brown dwarfs now extends to objects with temperatures comparable to those of Solar System planets. To investigate the atmospheres of these newly identified brown dwarfs, we have conducted a pilot study monitoring an initial sample of three late T-dwarfs (T6.5, T8 and T8.5) and one Y-dwarf (Y0) for infrared photometric variability at multiple epochs. With J-band imaging, each target was observed for a period of 1.0h to 4.5h per epoch, which covers a significant fraction of the expected rotational period. These measurements represent the first photometric monitoring for these targets. For three of the four targets (2M1047, Ross 458C and WISE0458), multi-epoch monitoring was performed, with the time span between epochs ranging from a few hours to ~2 years. During the first epoch, the T8.5 target WISE0458 exhibited variations with a remarkable min-to-max amplitude of 13%, while the second epoch light curve taken ~2 years later did not not...

  18. 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...

  19. Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor

    OpenAIRE

    Zimmerman, Neil; Oppenheimer, Ben R.; Hinkley, Sasha; Brenner, Douglas; Parry, Ian R.; Sivaramakrishnan, Anand; Hillenbrand, Lynne; Beichman, Charles; Crepp, Justin R.; Vasisht, Gautam; Roberts Jr., Lewis C.; Burruss, Rick; King, David L.; Soummer, Rémi; Dekany, Richard

    2010-01-01

    The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of ~6 J- and H-band magnitudes and separation of 1" from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star...

  20. 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...

  1. Atmospheric Circulation of Brown Dwarfs: Jets, Vortices, and Time Variability

    CERN Document Server

    Zhang, Xi

    2014-01-01

    A variety of observational evidence demonstrates that brown dwarfs exhibit active atmospheric circulations. In this study we use a shallow-water model to investigate the global atmospheric dynamics in the stratified layer overlying the convective zone on these rapidly rotating objects. We show that the existence and properties of the atmospheric circulation crucially depend on key parameters including the energy injection rate and radiative timescale. Under conditions of strong internal heat flux and weak radiative dissipation, a banded flow pattern comprising east-west jet streams spontaneously emerges from the interaction of atmospheric turbulence with the planetary rotation. In contrast, when the internal heat flux is weak and/or radiative dissipation is strong, turbulence injected into the atmosphere damps before it can self-organize into jets, leading to a flow dominated by isotropic turbulence and vortices instead. Based on the location of the transition, we suggest that many brown dwarfs may exhibit at...

  2. 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.

  3. 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...

  4. DISCOVERY OF A WIDE BINARY BROWN DWARF BORN IN ISOLATION

    International Nuclear Information System (INIS)

    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 constructed spectral energy distributions. Both sources are young (∼1 Myr) according to their Hα emission, gravity-sensitive spectral features, and mid-infrared 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 that it is an unresolved binary. FU Tau A and B are likely to be components of a binary system based on the low probability (∼3 x 10-4) that Taurus would produce two unrelated brown dwarfs with a projected separation of a ≤ 6''. Barnard 215 contains only one other young star and is in a remote area of Taurus, making FU Tau A and B the first spectroscopically confirmed brown dwarfs discovered forming in isolation rather than in a stellar cluster or aggregate. Because they were born in isolation and comprise a weakly bound binary, dynamical interactions with stars could not have played a role in their formation, and thus are not essential for the birth of brown dwarfs.

  5. Planetesimals to brown dwarfs: What is a planet?

    OpenAIRE

    Basri, Gibor; Brown, Michael E.

    2006-01-01

    The past 15 years have brought about a revolution in our understanding of our Solar System and other planetary systems. During this time, discoveries include the first Kuiper Belt Objects, the first brown dwarfs, and the first extra-solar planets. Although discoveries continue apace, they have called into question our previous perspectives on planets, both here and elsewhere. The result has been a debate about the meaning of the word ''planet'' itself. It became clear that scientists do not h...

  6. 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.

  7. The disk around the brown dwarf KPNO Tau 3

    Energy Technology Data Exchange (ETDEWEB)

    Broekhoven-Fiene, Hannah; Matthews, Brenda; Di Francesco, James [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8W 3P6 (Canada); Duchêne, Gaspard [Department of Astronomy, University of California at Berkeley, Hearst Field Annex, B-20, Berkeley, CA 94720-3411 (United States); Scholz, Aleks [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom); Chrysostomou, Antonio [Joint Astronomy Centre, 660 North Aóhoku Place, University Park, Hilo, HI 96720 (United States); Jayawardhana, Ray [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)

    2014-07-10

    We present submillimeter observations of the young brown dwarfs KPNO Tau 1, KPNO Tau 3, and KPNO Tau 6 at 450 μm and 850 μm taken with the Submillimetre Common-User Bolometer Array on the James Clerk 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 3σ detection of cold dust around KPNO Tau 3 implies a total disk mass of (4.0 ± 1.1) × 10{sup –4} M{sub ☉} (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 × 10{sup –4} M{sub ☉} and <2.7 × 10{sup –4} M{sub ☉}, 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 for KPNO Tau 3 is congruent with the scenario that at least some brown dwarfs form via the same mechanism as low-mass stars.

  8. Epsilon Indi Ba/Bb: the nearest binary brown dwarf

    CERN Document Server

    McCaughrean, M J; Scholz, R D; Lenzen, R; Biller, B; Brandner, W; Hartung, M; Lodieu, N

    2004-01-01

    We have carried out high angular resolution near-infrared imaging and low-resolution (R~1000) spectroscopy of the nearest known brown dwarf, Eps Indi B, using the ESO VLT NAOS/CONICA adaptive optics system. We find it to be a close binary with an angular separation of 0.732 arcsec, corresponding to 2.65AU at the 3.626pc distance of the Eps Indi system, as also noted by Volk et al. (2003). In our discovery paper (Scholz et al. 2003), we concluded that Eps Indi B was a ~50Mjup T2.5 dwarf: our revised finding is that the two system components (Eps Indi Ba and Eps Indi Bb) have spectral types of T1 and T6, respectively, and estimated masses of 44 and 28Mjup, respectively, assuming an age of 1.3Gyr. Errors in the masses are +/-10 and +/-7Mjup, respectively, dominated by the uncertainty in the age determination (0.8-2Gyr range). This uniquely well-characterised T dwarf binary system should prove important in the study of low-mass, cool brown dwarfs. The two components are bright and relatively well-resolved: it is ...

  9. Formation of millisecond pulsars with CO white dwarf companions - II. Accretion, spin-up, true ages and comparison to MSPs with He white dwarf companions

    CERN Document Server

    Tauris, Thomas M; Kramer, Michael

    2012-01-01

    Millisecond pulsars (MSPs) are mainly characterised by their spin periods, B-fields and masses - quantities which are largely affected by previous interactions with a companion star in a binary system. In this paper, we investigate the formation mechanism of MSPs by considering the pulsar recycling process in both intermediate-mass X-ray binaries (IMXBs) and low-mass X-ray binaries (LMXBs). The IMXBs mainly lead to the formation of binary MSPs with a massive carbon-oxygen (CO) or an oxygen-neon-magnesium white dwarf (ONeMg WD) companion, whereas the LMXBs form recycled pulsars with a helium white dwarf (He WD) companion. We discuss the accretion physics leading to the spin-up line in the PPdot-diagram and demonstrate that such a line cannot be uniquely defined. We derive a simple expression for the amount of accreted mass needed for any given pulsar to achieve its equilibrium spin and apply this to explain the observed differences of the spin distributions of recycled pulsars with different types of companion...

  10. LHS 2803B: A VERY WIDE MID-T DWARF COMPANION TO AN OLD M DWARF IDENTIFIED FROM PAN-STARRS1

    International Nuclear Information System (INIS)

    We report the discovery of a wide (∼1400 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 Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that the primary has a spectral type of M4.5, with approximately solar metallicity and no measurable Hα 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 that the secondary has a mass of 72±47 MJup, temperature of 1120 ± 80 K, and log g = 5.4 ± 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0.

  11. 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 ...

  12. 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...

  13. The white dwarf companion of the B a 2 star zeta Cap

    Science.gov (United States)

    Boehm-Vitense, E.

    1981-01-01

    The Ba II star zeta Cap has a white dwarf companion. Its T (sub eff) is determined to be 22000 K, its mass is approximately one solar mass. The importance of this finding for the explanation of abundance peculiarities is discussed.

  14. Astrometric orbit of a low-mass companion to an ultracool dwarf

    CERN Document Server

    Sahlmann, J; Segransan, D; Martin, E L; Queloz, D; Mayor, M; Udry, S

    2013-01-01

    Little is known about the existence of extrasolar planets around ultracool dwarfs. Furthermore, binary stars with Sun-like primaries and very low-mass binaries composed of ultracool dwarfs show differences in the distributions of mass ratio and orbital separation that can be indicative of distinct formation mechanisms. Using FORS2/VLT optical imaging for high precision astrometry we are searching for planets and substellar objects around ultracool dwarfs to investigate their multiplicity properties for very low companion masses. Here we report astrometric measurements with an accuracy of two tenths of a milli-arcsecond over two years that reveal orbital motion of the nearby L1.5 dwarf DENIS-P J082303.1-491201 located at 20.77 +/- 0.08 pc caused by an unseen companion that revolves about its host on an eccentric orbit in 246.4 +/- 1.4 days. We estimate the L1.5 dwarf to have 7.5 +/- 0.7 % of the Sun's mass that implies a companion mass of 28 +/- 2 Jupiter masses. This new system has the smallest mass ratio (0....

  15. PLANETS AROUND LOW-MASS STARS (PALMS). I. A SUBSTELLAR COMPANION TO THE YOUNG M DWARF 1RXS J235133.3+312720

    International Nuclear Information System (INIS)

    We report the discovery of a brown dwarf companion to the young M dwarf 1RXS J235133.3+312720 as part of a high contrast imaging search for planets around nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2.''4 (∼120 AU) pair is confirmed to be comoving from two epochs of high-resolution imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of 1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of L0+2–1. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV activity levels comparable to young moving group members with ages of ∼10-100 Myr. UVW kinematics based the measured radial velocity of the primary and the system's photometric distance (50 ± 10 pc) indicate it is likely a member of the ∼50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology shows subtle hints of intermediate surface gravity. The spectrum is also an excellent match to the ∼200 Myr M9 brown dwarf LP 944-20. Assuming an age of 50-150 Myr, evolutionary models imply a mass of 32 ± 6 MJup for the companion, making 1RXS J2351+3127 B the second lowest-mass member of the AB Dor moving group after the L4 companion CD-35 2722 B and one of the few benchmark brown dwarfs known at young ages.

  16. Detection of a white dwarf companion to the Hyades stars HD 27483

    Science.gov (United States)

    Boehm-Vitense, Erika

    1993-01-01

    We observed with IUE a white dwarf (WD) companion to the Hyades F6 V binary stars HD 27483. This system is known to be a close binary of two nearly equal stars with an orbital period of 3.05 days. Our IUE observations revealed the presence of a third star, a white dwarf with an effective temperature of 23,000 +/- 1000 K and a mass of approximately 0.6 solar mass. Its presence in the Hyades cluster with a known age permits me to derive the mass of its progenitor, which must have been about 2.3 solar masses. The presence of the white dwarf in a binary system opens the possibility that some of the envelope material, which was expelled by the WD progenitor, may have been collected by the F6 stars. We may thus be able to study abundance anomalies of the WD progenitor with known mass on the surface of the F6 companions.

  17. A RADIO SEARCH FOR PULSAR COMPANIONS TO SLOAN DIGITAL SKY SURVEY LOW-MASS WHITE DWARFS

    International Nuclear Information System (INIS)

    We have conducted a search for pulsar companions to 15 low-mass white dwarfs (LMWDs; M sun) at 820 MHz with the NRAO Green Bank Telescope (GBT). These LMWDs were spectroscopically identified in the Sloan Digital Sky Survey (SDSS), and do not show the photometric excess or spectroscopic signature associated with a companion in their discovery data. However, LMWDs are believed to evolve in binary systems and to have either a more massive white dwarf (WD) or a neutron star (NS) as a companion. Indeed, evolutionary models of low-mass X-ray binaries, the precursors of millisecond pulsars (MSPs), produce significant numbers of LMWDs, suggesting that the SDSS LMWDs may have NS companions. No convincing pulsar signal is detected in our data. This is consistent with the findings of van Leeuwen et al., who conducted a GBT search for radio pulsations at 340 MHz from unseen companions to eight SDSS WDs (five are still considered LMWDs; the three others are now classified as 'ordinary' WDs). We discuss the constraints our nondetections place on the probability P MSP that the companion to a given LMWD is a radio pulsar in the context of the luminosity and acceleration limits of our search; we find that P MSP +4-2%.

  18. 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...

  19. ON THE SURVIVAL OF BROWN DWARFS AND PLANETS ENGULFED BY THEIR GIANT HOST STAR

    Energy Technology Data Exchange (ETDEWEB)

    Passy, Jean-Claude; Mac Low, Mordecai-Mark [Department of Astrophysics, American Museum of Natural History, New York, NY (United States); De Marco, Orsola [Department of Physics and Astronomy, Macquarie University, Sydney, NSW (Australia)

    2012-11-10

    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 remnants of one or two Jovian-mass planets that lost extensive mass during the common envelope phase.

  20. MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS-AURIGA

    International Nuclear Information System (INIS)

    We have conducted a high-resolution imaging study of the Taurus-Auriga star-forming region in order to characterize the primordial outcome of multiple star formation and the extent of the brown dwarf desert. Our survey identified 16 new binary companions to primary stars with masses of 0.25-2.5 Msun, raising the total number of binary pairs (including components of high-order multiples) with separations of 3-5000 AU to 90. We find that ∼2/3-3/4 of all Taurus members are multiple systems of two or more stars, while the other ∼1/4-1/3 appear to have formed as single stars; the distribution of high-order multiplicity suggests that fragmentation into a wide binary has no impact on the subsequent probability that either component will fragment again. The separation distribution for solar-type stars (0.7-2.5 Msun) is nearly log-flat over separations of 3-5000 AU, but lower-mass stars (0.25-0.7 Msun) show a paucity of binary companions with separations of ∼>200 AU. Across this full mass range, companion masses are well described with a linear-flat function; all system mass ratios (q = MB /MA ) are equally probable, apparently including substellar companions. Our results are broadly consistent with the two expected modes of binary formation (free-fall fragmentation on large scales and disk fragmentation on small scales), but the distributions provide some clues as to the epochs at which the companions are likely to form.

  1. A THIRD HOT WHITE DWARF COMPANION DETECTED BY KEPLER

    International Nuclear Information System (INIS)

    We have found a system listed in the Kepler Binary Catalog (Porb = 3.273 days) that we have determined is comprised of a low-mass, thermally bloated, hot white dwarf orbiting an A star of about 2.3 Msun. In this work, we designate the object, KIC 10657664, simply as 'KHWD3' (Kepler Hot White Dwarf 3). We use the transit depth of ∼0.66%, the eclipse depth of ∼1.9%, and regular smooth periodic variations at the orbital frequency and twice the orbital frequency to analyze the system parameters. The smooth periodic variations are identified with the classical ellipsoidal light variation (ELV) and illumination (ILL) effects, and the newly utilized Doppler boosting (DB) effect. Given the measured values of R/a and inclination angle of the binary, both the ELV and DB effects are mostly sensitive to the mass ratio, q = M2/M1, of the binary. The two effects yield values of q which are somewhat inconsistent-presumably due to unidentified systematic effects-but which nonetheless provide a quite useful set of possibilities for the mass of the white dwarf (either 0.26 ± 0.04 Msun or 0.37 ± 0.08 Msun). All of the other system parameters are determined fairly robustly. In particular, we show that the white dwarf has a radius of 0.15 ± 0.01 Rsun, which is extremely bloated over the radius it would have as a fully degenerate object, and an effective temperature Teff≅14,500 K. Binary evolution scenarios and models for this system are discussed. We suggest that the progenitor binary was comprised of a primary of mass ∼2.2 Msun (the progenitor of the current hot white dwarf) and a secondary of mass ∼1.4 Msun (the progenitor of the current A star in the system). We compare this new system with three other white dwarfs in binaries that likely were formed via stable Roche-lobe overflow (KOI-74, KOI-81, and the inner Regulus binary).

  2. WASP-30b: A 61 MJup BROWN DWARF TRANSITING A V = 12, F8 STAR

    International Nuclear Information System (INIS)

    We report the discovery of a 61-Jupiter-mass brown dwarf (BD), which transits its F8V host star, WASP-30, every 4.16 days. From a range of age indicators we estimate the system age to be 1-2 Gyr. We derive a radius (0.89 ± 0.02 RJup) for the companion that is consistent with that predicted (0.914 RJup) by a model of a 1 Gyr old, non-irradiated BD with a dusty atmosphere. The location of WASP-30b in the minimum of the mass-radius relation is consistent with the quantitative prediction of Chabrier and Baraffe, thus confirming the theory.

  3. 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...

  4. Akari Observations of Brown Dwarfs. II CO2 as Probe of Carbon and Oxygen Abundances in Brown Dwarfs

    CERN Document Server

    Tsuji, Takashi; Sorahana, Satoko

    2011-01-01

    Recent observations with the infrared astronomical satellite AKARI have shown that the CO2 bands at 4.2 micron in three brown dwarfs are much stronger than expected from the unified cloudy model (UCM) based on recent solar C & O abundances. This result has been a puzzle, but we now find that this is simply an abundance effect: We show that these strong CO2 bands can be explained with the UCMs based on the classical C & O abundances (log Ac and log Ao), which are about 0.2 dex larger compared to the recent values. Since three other brown dwarfs could be well interpreted with the recent solar C & O abundances, we require at least two model sequences based on the different chemical compositions to interpret all the AKARI spectra. The reason for this is that the CO2 band is especially sensitive to C & O abundances, since the CO2 abundance depends approximately on AcAo^2 --- the cube of C & O abundances. For this reason, even low resolution spectra of very cool dwarfs, especially of CO2 cannot ...

  5. 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 ...

  6. The First Spectrum of the Coldest Brown Dwarf

    Science.gov (United States)

    Skemer, Andrew J.; Morley, Caroline V.; Allers, Katelyn N.; Geballe, Thomas R.; Marley, Mark S.; Fortney, Jonathan J.; Faherty, Jacqueline K.; Bjoraker, Gordon L.; Lupu, Roxana

    2016-08-01

    The recently discovered brown dwarf WISE 0855 presents the 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 μm 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’s. The spectrum quality is high enough to allow for the investigation of dynamical and chemical processes that have long been studied in Jupiter’s atmosphere, but now on an extrasolar world.

  7. 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.

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

    International Nuclear Information System (INIS)

    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 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 J, with a single power-law distribution. We find that p(M, a)∝M –0.65 ± 0.60 a –0.85 ± 0.39 (1σ errors) provides an adequate fit to our data, with 1.0%-3.1% (68% confidence) of stars hosting 5-70 M 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.

  9. HD 91669B: A NEW BROWN DWARF CANDIDATE FROM THE MCDONALD OBSERVATORY PLANET SEARCH

    International Nuclear Information System (INIS)

    We report the detection of a brown dwarf candidate orbiting the metal-rich K dwarf HD 91669, based on radial-velocity data from the McDonald Observatory Planet Search. HD 91669b is a substellar object in an eccentric orbit (e = 0.45) at a separation of 1.2 AU. The minimum mass of 30.6M Jup places this object firmly within the brown dwarf desert for inclinations i ∼> 230. This is the second rare close-in brown dwarf candidate discovered by the McDonald planet search program.

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

    Science.gov (United States)

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

    2015-07-01

    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 Li i-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 ± 100 K and 1670 ± 140 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 M1 ≃ 0.028-0.063 M⊙ and M2 ≃ 0.018-0.045 M⊙ with a mass ratio of q ≃ 0.64-0.74. Multi-epoch radial velocity measurements unambiguously establish the three-dimensional orbit of the system and allow us to investigate its kinematic properties. DE0823-49 emerges as a rare example of a nearby brown dwarf binary with orbit, component properties, and age that are characterised well. It is a juvenile resident of the solar neighbourhood, but does not appear to belong to a known young association or moving group. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme IDs 086.C-0680, 088.C-0679, 090.C-0786, and 092.C-0202.

  11. The First Brown Dwarf/Planetary-mass Object in the 32 Orionis Group

    Science.gov (United States)

    Burgasser, Adam J.; Lopez, Mike A.; Mamajek, Eric E.; Gagné, Jonathan; Faherty, Jacqueline K.; Tallis, Melisa; Choban, Caleb; Tamiya, Tomoki; Escala, Ivanna; Aganze, Christian

    2016-03-01

    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 measureable proper motion. We re-analyze previous data and new moderate-resolution spectroscopy from Magellan/Folded-port InfraRed Echellette to demonstrate that this source is a young near-infrared L1 brown dwarf with very low surface gravity features. Spectral model fits indicate Teff = 1880{}-70+150 K and {log}g = 3.8{}-0.2+0.2, 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}-3+4 MJ) that straddles the brown dwarf/planetary-mass object boundary. The source has a somewhat red J-W2 color compared to other L1 dwarfs, but this is likely a low-gravity-related temperature offset; we find no evidence of significant excess reddening from a disk or cool companion in the 3-5 μm waveband. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  12. 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...

  13. INDICATIONS OF WATER CLOUDS IN THE COLDEST KNOWN BROWN DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Tinney, C. G. [School of Physics, UNSW Australia, Sydney, NSW 2052 (Australia); Skemer, Andrew [Steward Observatory, Department of Astronomy, University of Arizona, Tucson, AZ 85721 (United States); Monson, Andrew J., E-mail: jfaherty@ciw.edu [Observatories of the Carnegie Institution of Washington, Pasadena, CA 91101 (United States)

    2014-09-20

    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{sub −0.35}{sup +0.53} (J {sub MKO} = 25.0{sub −0.35}{sup +0.53}) at 2.6σ—or equivalently an upper limit of J3 > 23.8 (J {sub MKO} > 24.0) at 5σ makes W0855 the reddest brown dwarf ever categorized (J {sub MKO} – W2 = 10.984{sub −0.35}{sup +0.53} at 2.6σ—or equivalently an upper limit of J {sub MKO} – W2 > 9.984 at 5σ) and refines its position on color-magnitude diagrams. Comparing the new photometry with chemical equilibrium model atmosphere predictions, we demonstrate that W0855 is 2.7σ 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.

  14. Spitzer Observations of two TW Hydrae Association Brown Dwarfs

    CERN Document Server

    Riaz, B; Hmiel, A; Riaz, Basmah; Gizis, John E.; Hmiel, Abraham

    2006-01-01

    We present Spitzer Space Telescope observations of two TW Hydrae Association brown dwarfs, 2MASSW J1207334-393254 and 2MASSW J1139511-315921, in the IRAC and MIPS 24 micron bands. Based on their IRAC colors, we have classified them as Classical and Weak-line T Tauri stars, respectively. For 2MASSW J1207334-393254, we have found that a flat disk model fits the data very well. This brown dwarf shows the presence of warm (T > 100 K) circumstellar dust close (R < 0.2 AU) to it, and does not display any signs of cleansing of dust within several AU of the star. In comparison with other TWA members that show excess in IR, we suggest that there exists a different disk evolution/dust processing mechanism for stellar and sub-stellar objects. 2MASSW J1139511-315921 does not show any significant excess in any of the IRAC bands, but a small one at 24 micron, which is not significant enough to suggest the presence of warm dust around this star. It shows signs of dust cleansing in the inner several AU, similar to most of...

  15. New Brown Dwarf Disks in the TW Hydrae Association

    CERN Document Server

    Riaz, B

    2008-01-01

    In our analysis of {\\it Spitzer}/IRS archival data on the stellar and sub-stellar members of the TW Hydrae Association (TWA), we have discovered two new brown dwarf disks: a flat optically thick disk around SSSPM J1102-3431 (SSSPM 1102), and a transition disk around 2MASS J1139511-315921 (2M1139). The disk structure for SSSPM 1102 is found to be very similar to the known brown dwarf disk 2MASSW J1207334-393254 (2M1207), with excess emission observed at wavelengths as short as 5 $\\micron$. 2M1139 shows no excess emission shortward of $\\sim$20 $\\micron$, but flares up at longer wavelengths, and is the first transition disk detected among the sub-stellar members of TWA. We also report on the {\\it Spitzer}/70 $\\micron$ observations, and the presence of a weak {\\it absorption} 10 $\\micron$ silicate feature for 2M1207. The absorption can be attributed to a close to edge-on disk at a 75$\\degr$ inclination. The 10 $\\micron$ spectrum for 2M1207 shows crystalline forsterite features, with a peak in absorption near 11.3...

  16. Search for exoplanets and brown dwarfs with VLBI.

    Science.gov (United States)

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

    2016-06-01

    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 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.

  17. 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.

  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. The Coolest Isolated Brown Dwarf Candidate Member of TWA

    CERN Document Server

    Gagné, Jonathan; Cruz, Kelle; Lafrenière, David; Doyon, René; Malo, Lison; Artigau, Étienne

    2014-01-01

    We present two new late-type brown dwarf candidate members of the TW Hydrae association (TWA) : 2MASS J12074836-3900043 and 2MASS J12474428-3816464, which were found as part of the BANYAN all-sky survey (BASS) for brown dwarf members to nearby young associations. We obtained near-infrared (NIR) spectroscopy for both objects (NIR spectral types are respectively L1 and M9), as well as optical spectroscopy for J1207-3900 (optical spectral type is L0{\\gamma}), and show that both display clear signs of low-gravity, and thus youth. We use the BANYAN II Bayesian inference tool to show that both objects are candidate members to TWA with a very low probability of being field contaminants, although the kinematics of J1247-3816 seem slightly at odds with that of other TWA members. J1207-3900 is currently the latest-type and the only isolated L-type candidate member of TWA. Measuring the distance and radial velocity of both objects is still required to claim them as bona fide members. Such late-type objects are predicted...

  20. Detectability of substellar companions around white dwarfs with Gaia

    CERN Document Server

    Silvotti, Roberto; Lattanzi, Mario; Morbidelli, Roberto

    2014-01-01

    To date not a single-bona fide planet has been identified orbiting a single white dwarf. In fact we are ignorant about the final configuration of >95% of planetary systems. Theoretical models predict a gap in the final distribution of orbital periods, due to the opposite effects of stellar mass loss (planets pushed outwards) and tidal interactions (planets pushed inwards) during the RGB and the AGB stellar expansions. Over its five year primary mission, Gaia is expected to astrometrically detect the first (few tens of) WD massive planets/BDs giving first evidence that WD planets exist, at least those in wide orbits. In this article we present preliminary results of our simulations of what Gaia should be able to find in this field.

  1. Parallactic Motion for Companion Discovery: An M-Dwarf Orbiting Alcor

    CERN Document Server

    Zimmerman, Neil; Hinkley, Sasha; Brenner, Douglas; Parry, Ian R; Sivaramakrishnan, Anand; Hillenbrand, Lynne; Beichman, Charles; Crepp, Justin R; Vasisht, Gautam; Roberts, Lewis C; Burruss, Rick; King, David L; Soummer, Rémi; Dekany, Richard; Shao, Michael; Bouchez, Antonin; Roberts, Jennifer E; Hunt, Stephanie

    2009-01-01

    The A5V star Alcor has an M3-M4 dwarf companion, as evidenced by a novel astrometric technique. Imaging spectroscopy combined with adaptive optics coronagraphy allowed for the detection and spectrophotometric characterization of the point source at a contrast of ~6 J- and H-band magnitudes and separation of 1" from the primary star. The use of an astrometric pupil plane grid allowed us to determine the projected separations between the companion and the coronagraphically occulted primary star to <=3 milliarcsecond precision at two observation epochs. Our measurements demonstrate common parallactic and proper motion over the course of 103 days, significantly shorter than the period of time needed for most companion confirmations through proper motion measurements alone. This common parallax method is potentially more rigorous than common proper motion, ensuring that the neighboring bodies lie at the same distance, rather than relying on the statistical improbability that two objects in close proximity to ea...

  2. A Third Hot White Dwarf Companion Detected by Kepler

    CERN Document Server

    Carter, Joshua A; Fabrycky, Daniel

    2010-01-01

    We have found a system listed in the Kepler Binary Catalog (3.273 day period; Prsa et al. 2010) that we have determined is comprised of a low-mass, thermally-bloated, hot white dwarf orbiting an A star of about 2.3 solar masses. In this work we designate the object, KIC 10657664, simply as KHWD3. We use the transit depth of ~0.66%, the eclipse depth of ~1.9%, and regular smooth periodic variations at the orbital frequency and twice the orbital frequency to analyze the system parameters. The smooth periodic variations are identified with the classical ellipsoidal light variation and illumination effects, and the newly utilized Doppler boosting effect. Given the measured values of R/a and inclination angle of the binary, both the ELV and DB effects are mostly sensitive to the mass ratio, q = M_2/M_1, of the binary. The two effects yield values of q which are somewhat inconsistent - presumably due to unidentified systematic effects - but which nonetheless provide a quite useful set of possibilities for the mass ...

  3. LHS 2803B: A VERY WIDE MID-T DWARF COMPANION TO AN OLD M DWARF IDENTIFIED FROM PAN-STARRS1

    Energy Technology Data Exchange (ETDEWEB)

    Deacon, Niall R. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Liu, Michael C.; Magnier, Eugene A.; Bowler, Brendan P.; Mann, Andrew W.; Burgett, William S.; Chambers, Ken C.; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S.; Tonry, John L.; Wainscoat, Richard J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Redstone, Joshua A. [Facebook, 1601 Willow Road, Menlo Park, CA 94025 (United States); Hodapp, Klaus W. [Institute for Astronomy, University of Hawaii, 640 North Aohoku Place, Hilo, HI 96720 (United States); Price, Paul A., E-mail: deacon@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-09-20

    We report the discovery of a wide ({approx}1400 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 Two Micron All Sky Survey data. Using the Infrared Telescope Facility/SpeX near-infrared spectroscopy, we classify the secondary to be spectral type T5.5. University of Hawaii 2.2 m/SuperNova Integral Field Spectrograph optical spectroscopy indicates that 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 that the secondary has a mass of 72{+-}{sup 4}{sub 7} M{sub Jup}, temperature of 1120 {+-} 80 K, and log g = 5.4 {+-} 0.1 dex. Model atmosphere fitting to the near-IR spectrum gives similar physical parameters of 1100 K and log g = 5.0.

  4. 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...

  5. A CAUTIONARY TALE: MARVELS BROWN DWARF CANDIDATE REVEALS ITSELF TO BE A VERY LONG PERIOD, HIGHLY ECCENTRIC SPECTROSCOPIC STELLAR BINARY

    International Nuclear Information System (INIS)

    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 ∼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.

  6. 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.

  7. Planetesimals To Brown Dwarfs: What is a Planet?

    CERN Document Server

    Basri, G; Basri, Gibor; Brown, Michael E.

    2006-01-01

    The past 15 years have brought about a revolution in our understanding of our Solar System and other planetary systems. During this time, discoveries include the first Kuiper Belt Objects, the first brown dwarfs, and the first extra-solar planets. Although discoveries continue apace, they have called into question our previous perspectives on planets, both here and elsewhere. The result has been a debate about the meaning of the word ''planet'' itself. It became clear that scientists do not have a widely accepted or clear definition of what a planet is, and both scientists and the public are confused (and sometimes annoyed) by its use in various contexts. Because ''planet'' is a very widely used term, it seems worth the attempt to resolve this problem. In this essay, we try to cover all the issues that have come to the fore, and bring clarity (if not resolution) to the debate.

  8. The Mass Distribution of Companions to Low-Mass White Dwarfs

    CERN Document Server

    Andrews, Jeff J; Agüeros, Marcel A

    2014-01-01

    Measuring the masses of companions to single-line spectroscopic binary stars is (in general) not possible because of the unknown orbital plane inclination. Even when the mass of the visible star can be measured, only a lower limit can be placed on the mass of the unseen companion. However, since these inclination angles should be isotropically distributed, for a large enough, unbiased sample, the companion mass distribution can be deconvolved from the distribution of observables. In this work, we construct a hierarchical probabilistic model to infer properties of unseen companion stars given observations of the orbital period and projected radial velocity of the primary star. We apply this model to three mock samples of low-mass white dwarfs (LMWDs, $M\\lesssim0.45~\\Msun$) and a sample of post-common-envelope binaries. We use a mixture of two Gaussians to model the WD and neutron star (NS) companion mass distributions. Our model successfully recovers the initial parameters of these test data sets. We then appl...

  9. A Radio Search For Pulsar Companions To SDSS Low-Mass White Dwarfs

    CERN Document Server

    Agueros, Marcel A; Silvestri, Nicole M; Kleinman, S J; Anderson, Scott F; Liebert, James W

    2009-01-01

    We have conducted a search for pulsar companions to 15 low-mass white dwarfs (LMWDs; M < 0.4 M_Sun) at 820 MHz with the NRAO Green Bank Telescope (GBT). These LMWDs were spectroscopically identified in the Sloan Digital Sky Survey (SDSS), and do not show the photometric excess or spectroscopic signature associated with a companion in their discovery data. However, LMWDs are believed to evolve in binary systems and to have either a more massive WD or a neutron star as a companion. Indeed, evolutionary models of low-mass X-ray binaries, the precursors of millisecond pulsars (MSPs), produce significant numbers of LMWDs (e.g., Benvenuto & De Vito 2005), suggesting that the SDSS LMWDs may have neutron star companions. No convincing pulsar signal is detected in our data. This is consistent with the findings of van Leeuwen et al. (2007), who conducted a GBT search for radio pulsations at 340 MHz from unseen companions to eight SDSS WDs (five are still considered LMWDs; the three others are now classified as "...

  10. 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).

  11. The Effects of Close Companions (and Rotation) on the Magnetic Activity of M Dwarfs

    CERN Document Server

    Morgan, Dylan P; Garcés, Ane; Catalán, Silvia; Dhital, Saurav; Fuchs, Miriam; Silvestri, Nicole M

    2012-01-01

    We present a study of close white dwarf and M dwarf (WD+dM) binary systems and examine the effect that a close companion has on the magnetic field generation in M dwarfs. We use a base sample of 1602 white dwarf -- main sequence binaries from Rebassa et al. to develop a set of color cuts in GALEX, SDSS, UKIDSS, and 2MASS color space to construct a sample of 1756 WD+dM high-quality pairs from the SDSS DR8 spectroscopic database. We separate the individual WD and dM from each spectrum using an iterative technique that compares the WD and dM components to best-fit templates. Using the absolute height above the Galactic plane as a proxy for age, and the H{\\alpha} emission line as an indicator for magnetic activity, we investigate the age-activity relation for our sample for spectral types \\leqM7. Our results show that early-type M dwarfs (\\leqM4) in close binary systems are more likely to be active and have longer activity lifetimes compared to their field counterparts. However, at a spectral type of M5 (just pas...

  12. The BASS survey for brown dwarfs in young moving groups

    Science.gov (United States)

    Gagne, Jonathan; Lafreniere, David; Doyon, Rene; Malo, Lison; Faherty, Jacqueline K.; Artigau, Etienne; Cruz, Kelle L.; Burgasser, Adam J.; Filippazzo, Joe; Naud, Marie-Eve; Albert, Loic; Bouchard, Sandie; Gizis, John; Robert, Jasmin; Nadeau, Daniel; Bowsher, Emily C.; Nicholls, Christine

    2016-01-01

    I will present in this dissertation talk the construction and follow-up of the BANYAN All-Sky Survey (BASS) that we led to identify dozens of new isolated young brown dwarfs in the Solar neighborhood, several of which have physical properties such as mass, age and temperature that make them similar to exoplanets that were recently discovered using the method of direct imaging.Such isolated analogs of the giant, gaseous exoplanets are precious benchmarks that will allow a deep characterization of their atmospheres using high-resolution and high signal-to-noise spectroscopy, which is made possible due to the absence of a nearby and bright host star.I will end by describing BASS-Ultracool, an extension of BASS that focuses on the identification of extremely cool isolated exoplanet analogs that display methane in their atmospheres. This survey has already uncovered the first bonafide T dwarf member of a moving group, the ~150 Myr AB Doradus T5, SDSS1110+0116.

  13. KOI 1224, a Fourth Bloated Hot White Dwarf Companion Found With Kepler

    CERN Document Server

    Breton, Rene P; van Kerkwijk, Marten H; Carter, Josh A

    2011-01-01

    We present an analysis and interpretation of the Kepler binary system KOI 1224. This is the fourth binary found with Kepler that consists of a thermally bloated, hot white dwarf in a close orbit with a more or less normal star of spectral class A or F. As we show, KOI 1224 contains a white dwarf with Teff = 14400 +/- 1100 K, mass = 0.20 +/- 0.02 Msun, and radius = 0.103 +/- 0.004 Rsun, and an F-star companion of mass = 1.59 +/- 0.07 Msun that is somewhat beyond its terminal-age main sequence. The orbital period is quite short at 2.69802 days. The ingredients that are used in the analysis are the Kepler binary light curve, including the detection of the Doppler boosting effect; the NUV and FUV fluxes from the Galex images of this object; an estimate of the spectral type of the F-star companion; and evolutionary models of the companion designed to match its effective temperature and mean density. The light curve is modelled with a new code named Icarus which we describe in detail. Its features include the full ...

  14. Variability of Two Young L/T Transition Brown Dwarfs

    Science.gov (United States)

    Allers, Katelyn; Biller, Beth; Gallimore, Jack; Crossfield, Ian

    2015-10-01

    We propose for photometric monitoring observations of WISEP J004701.06+680352 (hereinafter W0047) and 2MASSWJ2244316+204343 (hereinafter 2M2244) using Spitzer/IRAC. Both objects are kinematically confirmed L7 members of the 150 Myr old AB Doradus moving group and show remarkable spectral similarity in both the near-IR and optical. The WoW survey found that L/T transition brown dwarfs having detected mid-IR variability are redder than the typical J - K color for their spectral type. A Cycle 11 exploration program (P.I. Metchev) is investigating the geometrical dependence of color and variability by expanding the original WoW sample. If inclination and J - K color are correlated (as predicted by Metchev et al.), then the spectral and photometric diversity seen across the L/T transition could be explained by geometry rather than diversity in atmospheric chemistry and dynamics. This would have wide ranging implications for the way we model cloud dissipation for brown dwarfs and extrasolar planets. Our proposed observations will provide an important test of the Metchev et al. prediction complementary to their Cycle 11 program. W0047 and 2M2244 are the same age, and have remarkably similar colors (J - K = 2.55 and 2.46 mags, respectively) and underlying spectra. Thus, if Metchev's prediction about the correlation of inclination and spectral morphology holds true, we would expect that W0047 and 2M2244 should have similar inclinations. However, the measured v sin(i) values for W0047 and 2M2244 are quite different. This difference in v sin(i) could be due to spin-axis inclination (with W0047 having a smaller i) or orbital period (with W0047 having a longer period), both of which we will determine from our proposed observations. This test is a unique opportunity, as there are no other free-floating L/T transition dwarfs known to be both coeval and spectrally similar. Our proposed observations will also extend the spectral type range for young objects surveyed for variability

  15. The hot white-dwarf companions of HR 1608, HR 8210, and HD 15638

    Science.gov (United States)

    Landsman, Wayne; Simon, Theodore; Bergeron, P.

    1993-01-01

    We have obtained low-dispersion IUE spectra of the late-type stars HD 15638 (F3 V), HR 1608 (=63 Eridani, KO IV), and HR 8210 (A8m). Each of these stars had been detected as a strong EUV source with the Wide Field Camera aboard the ROSAT satellite. The short-wavelength IUE spectrum of each star reveals the presence of a hot white-dwarf companion. We have fit the Lyman-alpha profile and UV continuum of each white dwarf using pure hydrogen models. The excellent fit of the data to the models provides confirmation of the Finley and Koester absolute calibration of the SWP camera of IUE. The UV data alone are insufficient to constrain the model gravity, but an additional constraint is provided by the photometric distance to the late-type primary. The most interesting of the three white dwarfs is the companion to HR 8210 for which our results imply a mass of 1.15 +0.05/-0.15 solar mass. This result is in good agreement with the lower limit on the mass derived from the spectroscopic orbit (greater than 1.1 solar mass), provided that the inclination is close to 90 deg.

  16. Extending the Canada-France Brown Dwarf Survey to the near infrared

    Directory of Open Access Journals (Sweden)

    Bertin E.

    2011-07-01

    Full Text Available We present the first results of the Canada-France Brown Dwarfs Survey-InfraRed, hereafter CFBDSIR, our near infrared extension to the optical wide field survey CFBDS. Our final objectives are to constrain ultracool atmosphere physics by finding a statistically significant sample of objects cooler than 600K and to explore the ultracool brown dwarf mass function building on a well defined sample of such objects. We identify candidates in CFHT/Wircam J and CFHT/MegaCam z′ images using optimized psf-fitting within Source Extractor, and follow them up with pointed near infrared imaging with SOFI at NTT. We have so far analysed and followed up all candidates on the first 66 square degrees of the 280 square degrees survey. We identified 64 T dwarfs candidates with z′− J > 3.5 and have confirmed 3 of them as ultracool brown dwarfs (later than T7 dwarfs and Y dwarfs candidates, and 14 of them as early and mid-T dwarfs based on their far red and NIR colours. We also present here the NIR spectra of one of these ultracool dwarfs, CFBDSIR1458 which confirms it as one of the coldest brown dwarf known, in the 500–600 K temperature range.

  17. Fundamental properties of the new dwarf galaxy And VI - alias "Pegasus Dwarf" - another companion of M31

    CERN Document Server

    Hopp, U; Greggio, L; Mehlert, D; Hopp, Ulrich; Schulte-Ladbeck, Regina E.; Greggio, Laura; Mehlert, Dorte

    1998-01-01

    We present medium deep CCD imaging in B, V, and I of the Pegasus Dwarf galaxy (And VI) which was recently found by Karachentsev & Karachentseva (1998), and independently also by Armandroff et al. (1999). The Calar Alto 2.2m images show a low surface brightness galaxy. Its structure resembles that of the other known dSph companions of M31 And I, II, III, and V. The brightest stars are resolved in all three colors. Color-magnitude diagrams in either B-V or V-I show the tip of the red giant branch which allows us to estimate a true distance modulus of $24.5 \\pm 0.2$. The color-magnitude diagrams and the structure show no evidence for recent star formation, thus, a classification as spheroidal dwarf galaxy with a rather old population seems appropriate. The total absolute magnitude of this dwarf is $M_{V,0} = -10.4\\pm0.2$.

  18. 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 ...

  19. KOI 1224: A FOURTH BLOATED HOT WHITE DWARF COMPANION FOUND WITH KEPLER

    International Nuclear Information System (INIS)

    We present an analysis and interpretation of the Kepler binary system KOI 1224. This is the fourth binary found with Kepler that consists of a thermally bloated, hot white dwarf in a close orbit with a more or less normal star of spectral class A or F. As we show, KOI 1224 contains a white dwarf with Teff = 14, 700 ± 1000 K, mass = 0.22 ± 0.02 M☉, and radius = 0.103 ± 0.002 R☉, and an F-star companion of mass 1.59 ± 0.06 M☉ that is somewhat beyond its terminal-age main sequence. The orbital period is quite short at 2.69802 days. The ingredients that are used in the analysis are the Kepler binary light curve, including the detection of the Doppler boosting effect; the NUV and FUV fluxes from the GALEX images of this object; an estimate of the spectral type of the F-star companion; and evolutionary models of the companion designed to match its effective temperature and mean density. The light curve is modeled with a new code named Icarus which we describe in detail. Its features include the full treatment of orbital phase-resolved spectroscopy, Doppler boosting, irradiation effects, and transits/eclipses, which are particularly suited to irradiated eclipsing binaries. We interpret the KOI 1224 system in terms of its likely evolutionary history. We infer that this type of system, containing a bloated hot white dwarf, is the direct descendant of an Algol-type binary. In spite of this basic understanding of the origin of KOI 1224, we discuss a number of problems associated with producing a system with an orbital period this short.

  20. Microarcsecond VLBI pulsar astrometry with PSRPI I. Two binary millisecond pulsars with white dwarf companions

    CERN Document Server

    Deller, A T; Kaplan, D L; Goss, W M; Brisken, W F; Chatterjee, S; Cordes, J M; Janssen, G H; Lazio, T J W; Petrov, L; Stappers, B W; Lyne, A

    2016-01-01

    Model-independent distance constraints to binary millisecond pulsars (MSPs) are of great value to both the timing observations of the radio pulsars, and multiwavelength observations of their companion stars. Very Long Baseline Interferometry (VLBI) astrometry can be employed to provide these model-independent distances with very high precision via the detection of annual geometric parallax. Using the Very Long Baseline Array, we have observed two binary millisecond pulsars, PSR J1022+1001 and J2145-0750, over a two-year period and measured their distances to be 700 +14 -10 pc and 613 +16 -14 pc respectively. We use the well-calibrated distance in conjunction with revised analysis of optical photometry to tightly constrain the nature of their massive (M ~ 0.85 Msun) white dwarf companions. Finally, we show that several measurements of their parallax and proper motion obtained by pulsar timing array projects are incorrect, and investigate possible causes for the discrepancy.

  1. Planets around Low-mass Stars (PALMS). I. A Substellar Companion to the Young M Dwarf 1RXS J235133.3+312720

    Science.gov (United States)

    Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Dupuy, Trent J.; Cieza, Lucas A.; Kraus, Adam L.; Tamura, Motohide

    2012-07-01

    We report the discovery of a brown dwarf companion to the young M dwarf 1RXS J235133.3+312720 as part of a high contrast imaging search for planets around nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2farcs4 (~120 AU) pair is confirmed to be comoving from two epochs of high-resolution imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of 1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of L0+2 -1. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV activity levels comparable to young moving group members with ages of ~10-100 Myr. UVW kinematics based the measured radial velocity of the primary and the system's photometric distance (50 ± 10 pc) indicate it is likely a member of the ~50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology shows subtle hints of intermediate surface gravity. The spectrum is also an excellent match to the ~200 Myr M9 brown dwarf LP 944-20. Assuming an age of 50-150 Myr, evolutionary models imply a mass of 32 ± 6 M Jup for the companion, making 1RXS J2351+3127 B the second lowest-mass member of the AB Dor moving group after the L4 companion CD-35 2722 B and one of the few benchmark brown dwarfs known at young ages. Some of 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.

  2. 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.

  3. The Limiting Effects of Dust in Brown Dwarf Model Atmospheres

    CERN Document Server

    Allard, F; Alexander, D R; Tamanai, A; Schweitzer, A; Allard, France; Hauschildt, Peter H.; Alexander, David R.; Tamanai, Akemi; Schweitzer, Andreas

    2001-01-01

    We present opacity sampling model atmospheres, synthetic spectra and colors for brown dwarfs and very low mass stars in two limiting case of dust grain formation: 1) inefficient gravitational settling i.e. the dust is distributed according to the chemical equilibrium predictions, 2) efficient gravitational settling i.e. the dust forms and depletes refractory elements from the gas, but their opacity does not affect the thermal structure. The models include the formation of over 600 gas phase species, and 1000 liquids and crystals, and the opacities of 30 different types of grains including corundum (Al$_2$O$_3$), the magnesium aluminum spinel MgAl$_2$O$_4$, iron, enstatite (MgSiO$_3$), forsterite (Mg$_2$SiO$_4$), amorphous carbon, SiC, and a number of calcium silicates. The models extend from the beginning of the grain formation regime well into the condensation regime of water ice ($\\teff= 3000 - 100$ K) and encompasses the range of $\\log g= 2.5 - 6.0$ at solar metallicity. We find that silicate dust grains c...

  4. 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...

  5. 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...

  6. 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

  7. 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...

  8. 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 ...

  9. 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...

  10. Planets Around Low-Mass Stars (PALMS). II. A Low-Mass Companion to the Young M Dwarf GJ 3629 Separated By 0.2"

    CERN Document Server

    Bowler, Brendan P; Shkolnik, Evgenya L; Tamura, Motohide

    2012-01-01

    We present the discovery of a 0.2" companion to the young M dwarf GJ 3629 as part of our high contrast adaptive optics imaging search for giant planets around low-mass stars with the Keck-II and Subaru telescopes. Two epochs of imaging confirm the pair is co-moving and reveal signs of orbital motion. The primary exhibits saturated X-ray emission, which together with its UV photometry from GALEX point to an age younger than ~300 Myr. At these ages the companion lies below the hydrogen burning limit with a model-dependent mass of 46 +/- 16 Mjup based on the system's photometric distance of 22 +/- 3 pc. Resolved YJHK photometry of the pair indicates a spectral type of M7 +/- 2 for GJ 3629 B. With a projected separation of 4.4 +/- 0.6 AU and an estimated orbital period of 21 +/- 5 yr, GJ 3629 AB is likely to yield a dynamical mass in the next several years, making it one of only a handful of brown dwarfs to have a measured mass and an age constrained from the stellar primary.

  11. 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.

  12. 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.

  13. On the mass segregation of stars and brown dwarfs in Taurus

    CERN Document Server

    Parker, Richard J; Goodwin, Simon P; Moraux, Estelle; Allison, Richard J; Guieu, Sylvain; Guedel, Manuel

    2010-01-01

    We use the new minimum spanning tree (MST) method to look for mass segregation in the Taurus association. The method computes the ratio of MST lengths of any chosen subset of objects, including the most massive stars and brown dwarfs, to the MST lengths of random sets of stars and brown dwarfs in the cluster. This mass segregation ratio (Lambda_MSR) enables a quantitative measure of the spatial distribution of high-mass and low-mass stars, and brown dwarfs to be made in Taurus. We find that the most massive stars in Taurus are inversely mass segregated, with Lambda_MSR = 0.70 +/- 0.10 (Lambda_MSR = 1 corresponds to no mass segregation), which differs from the strong mass segregation signatures found in more dense and massive clusters such as Orion. The brown dwarfs in Taurus are not mass segregated, although we find evidence that some low-mass stars are, with an Lambda_MSR = 1.25 +/- 0.15. Finally, we compare our results to previous measures of the spatial distribution of stars and brown dwarfs in Taurus, and...

  14. 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 ...

  15. Is beryllium ultra-depletion in solar-type stars linked to the presence of a white dwarf companion?

    CERN Document Server

    Desidera, S; Lugaro, M

    2015-01-01

    Abundance studies of solar-type stars revealed a small fraction of objects with extreme depletion of beryllium. We investigate the possible link between the beryllium depletion and the presence of companions. The classical methods (radial velocity, astrometry, imaging) used to search for binary companions were exploited. We also performed a chemical analysis to identify binaries by the alteration in abundances that is produced by the accretion of material lost by a former evolved companion. We found that all the four previously investigated stars that were found to be ultra--depleted in Be are binaries. In two cases the companion is a white dwarf, and in the other two cases the companion might be a white dwarf or a main-sequence star. One new barium star was identified. We speculate that the interaction with the white dwarf progenitor caused an alteration in the abundance pattern of the star, which resulted in severe beryllium depletion. Possible mechanisms such as thermohaline mixing, episodic accretion, and...

  16. Discovery of a young planetary mass companion to the nearby M dwarf VHS J125601.92-125723.9

    CERN Document Server

    Gauza, Bartosz; Pérez-Garrido, Antonio; Osorio, Maria Rosa Zapatero; Lodieu, Nicolas; Rebolo, Rafael; Pallé, Enric; Nowak, Grzegorz

    2015-01-01

    In a search for common proper motion companions using the VISTA Hemisphere Survey and 2MASS catalogs we have identified a very red (J-Ks=2.47 mag) late-L dwarf companion of a previously unrecognized M dwarf VHS J125601.92-125723.9, located at a projected angular separation of 8.06"+/-0.03". From low-resolution optical and near-IR spectroscopy we classified the primary and the companion as an M7.5+/-0.5 and L7+/-1.5, respectively. The primary shows weaker alkali lines than field dwarfs of similar spectral type, but still consistent with either a high-gravity dwarf or a younger object of hundreds of millions of years. The secondary shows spectral features characteristic for low surface gravity objects at ages below several hundred Myr, like the triangular shape of the H-band continuum and alkali lines weaker than in field dwarfs of the same spectral type. The absence of lithium in the atmosphere of the primary and the likely membership to the Local Association allowed us to constrain the age of the system to th...

  17. DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER

    International Nuclear Information System (INIS)

    Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7 Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler stars were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history

  18. DETECTION OF WHITE DWARF COMPANIONS TO BLUE STRAGGLERS IN THE OPEN CLUSTER NGC 188: DIRECT EVIDENCE FOR RECENT MASS TRANSFER

    Energy Technology Data Exchange (ETDEWEB)

    Gosnell, Natalie M.; Mathieu, Robert D. [Department of Astronomy, University of Wisconsin - Madison, 475 N. Charter St., Madison, WI 53706 (United States); Geller, Aaron M. [Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA) and Department of Physics and Astronomy, Northwestern University, 2145 Sheridan Rd, Evanston, IL 60208 (United States); Sills, Alison [Department of Physics and Astronomy, McMaster University, 1280 Main St. W, Hamilton, ON L8S 4M1 (Canada); Leigh, Nathan [Department of Physics, University of Alberta, CCIS 4-183, Edmonton, AB T6G 2E1 (Canada); Knigge, Christian, E-mail: gosnell@astro.wisc.edu [School of Physics and Astronomy, University of Southampton, Highfield, Southampton, SO17 IBJ (United Kingdom)

    2014-03-01

    Several possible formation pathways for blue straggler stars have been developed recently, but no one pathway has yet been observationally confirmed for a specific blue straggler. Here we report the first findings from a Hubble Space Telescope Advanced Camera for Surveys/Solar Blind Channel far-UV photometric program to search for white dwarf companions to blue straggler stars. We find three hot and young white dwarf companions to blue straggler stars in the 7 Gyr open cluster NGC 188, indicating that mass transfer in these systems ended less than 300 Myr ago. These companions are direct and secure observational evidence that these blue straggler stars were formed through mass transfer in binary stars. Their existence in a well-studied cluster environment allows for observational constraints of both the current binary system and the progenitor binary system, mapping the entire mass transfer history.

  19. The TRENDS High-Contrast Imaging Survey. III. A Faint White Dwarf Companion Orbiting HD 114174

    CERN Document Server

    Crepp, Justin R; Howard, Andrew W; Marcy, Geoffrey W; Gianninas, Alexandros; Kilic, Mukremin; Wright, Jason T

    2013-01-01

    The nearby Sun-like star HD 114174 exhibits a strong and persistent Doppler acceleration indicating the presence of an unseen distant companion. We have acquired high-contrast imaging observations of this star using NIRC2 at Keck and report the direct detection of the body responsible for causing the "trend". HD 114174 B has a projected separation of 692+/-9 mas (18.1 AU) and is 10.75+/-0.12 magnitudes (contrast of 5x10{-5}) fainter than its host in the K-band, requiring aggressive point-spread function subtraction to identify. Our astrometric time baseline of 1.4 years demonstrates physical association through common proper motion. We find that the companion has absolute magnitude, M_J=13.97+/-0.11, and colors, J-K= 0.12+/-0.16 mag. These characteristics are consistent with an ~T3 dwarf, initially leading us to believe that HD 114174 B was a substellar object. However, a dynamical analysis that combines radial velocity measurements with available imaging data indicates a minimum mass of m=0.260+/-0.010Msun. ...

  20. Evolutionary Constraints on the Planet-Hosting Subgiant Epsilon Reticulum from its White Dwarf Companion

    CERN Document Server

    Farihi, J; Holberg, J B; Casewell, S L; Barstow, M A

    2011-01-01

    The planet-hosting and Sirius-type binary system epsilon Reticulum (HD 27442) is examined from the perspective of its more evolved white dwarf secondary. The stellar parameters are determined from a combination of Balmer line spectroscopy, gravitational redshift, and solid angle. These three methods conspire to yield the most accurate physical description of the companion to date: Teff=15,310 \\pm 350 K and M=0.60 \\pm 0.02 Msol. Post-main sequence mass loss indicates the current binary separation has increased by a factor of 1.6 from its primordial state when the current primary was forming its planet(s), implying a0 > 150 AU and constraining stable planets to within 15-20 AU for a binary eccentricity of e=0.5. Almost 80 years have passed since the first detection of the stellar companion, and marginal orbital motion may be apparent in the binary, suggesting a near edge-on configuration with i > 70 deg, albeit with substantial uncertainty. If correct, the mass of the planet HD 27442b is bound between 1.66 and ...

  1. HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS

    Energy Technology Data Exchange (ETDEWEB)

    Apai, Daniel [Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Radigan, Jacqueline; Jayawardhana, Ray [Department of Astronomy, University of Toronto, 50 St. George Street, Toronto M5S 3H4 (Canada); Buenzli, Esther [Department of Astronomy and Steward Observatory, 933 N. Cherry Avenue, University of Arizona, Tucson, AZ 85721 (United States); Burrows, Adam [Department of Astrophysical Sciences, 105 Peyton Hall, Princeton University, Princeton, NJ 08544 (United States); Reid, Iain Neill, E-mail: apai@as.arizona.edu [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21212 (United States)

    2013-05-10

    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 a linear combination of only two different spectra, i.e., the entire surface is covered by two distinct types of regions. Modeling the color changes and spectral variations together reveal patchy cloud covers consisting of a spatially heterogeneous mix of low-brightness, low-temperature thick clouds and brighter, thin, and warm clouds. We show that the same thick cloud patches seen in our varying brown dwarf targets, if extended to the entire photosphere, predict near-infrared colors/magnitudes matching the range occupied by the directly imaged exoplanets that are cooler and less luminous than brown dwarfs with similar spectral types. This supports the models in which thick clouds are responsible for the near-infrared properties of these ''underluminous'' exoplanets.

  2. The Rotation of Young Low-Mass Stars and Brown Dwarfs

    CERN Document Server

    Herbst, W; Mundt, R; Scholz, A

    2006-01-01

    We review the current state of our knowledge concerning the rotation and angular momentum evolution of young stellar objects and brown dwarfs from a primarily observational view point. Periods are typically accurate to 1% and available for about 1700 stars and 30 brown dwarfs in young clusters. Discussion of angular momentum evolution also requires knowledge of stellar radii, which are poorly known for pre-main sequence stars. It is clear that rotation rates at a given age depend strongly on mass; higher mass stars (0.4-1.2 M$_\\odot$) have longer periods than lower mass stars and brown dwarfs. On the other hand, specific angular momentum is approximately independent of mass for low mass pre-main sequence stars and young brown dwarfs. A spread of about a factor of 30 is seen at any given mass and age. The evolution of rotation of solar-like stars during the first 100 Myr is discussed. A broad, bimodal distribution exists at the earliest observable phases ($\\sim$1 Myr) for stars more massive than 0.4 M$_\\odot$....

  3. Evolution of Young Brown Dwarf Disks in the Mid-Infrared

    CERN Document Server

    Sterzik, M F; Apai, D; Van der Bliek, N; Dullemond, C P; Sterzik, Michael F.; Pascucci, Ilaria; Apai, Daniel; Bliek, Nicole van der; Dullemond, Cornelis P.

    2004-01-01

    We have imaged two bona-fide brown dwarfs with TReCS/GEMINI-S and find mid-infrared excess emission that can be explained by optically thick dust disk models. In the case of the young ($\\approx$2Myr) Cha H$\\alpha$1 we measure fluxes at 10.4$\\mu$m and 12.3$\\mu$m that are fully consistent with a standard flared disk model and prominent silicate emission. For the $\\approx$ 10Myr old brown dwarf 2MASS1207-3932 located in the TW Hydrae association we find photospheric excess emission at 8.7$\\mu$m and 10.4$\\mu$m, and confirm disk accretion as likely cause of its strong activity. Disks around brown dwarfs likely last at least as long as their low-mass stellar counterparts in the T-Tauri phase. Grain growth, dust settling, and evolution of the geometry of brown dwarfs disks may appear on a timescale of 10Myr and can be witnessed by observations in the mid-infrared.

  4. A magnetic field evolution scenario for brown dwarfs and giant planets

    CERN Document Server

    Reiners, Ansgar

    2010-01-01

    Very little is known about magnetic fields of extrasolar planets and brown dwarfs. We use the energy flux scaling law presented by Christensen et al. (2009) to calculate the evolution of average magnetic fields in extrasolar planets and brown dwarfs under the assumption of fast rotation, which is probably the case for most of them. We find that massive brown dwarfs of about 70 M_Jup can have fields of a few kilo-Gauss during the first few hundred Million years. These fields can grow by a factor of two before they weaken after deuterium burning has stopped. Brown dwarfs with weak deuterium burning and extrasolar giant planets start with magnetic fields between ~100G and ~1kG at the age of a few Myr, depending on their mass. Their magnetic field weakens steadily until after 10Gyr it has shrunk by about a factor of 10. We use observed X-ray luminosities to estimate the age of the known extrasolar giant planets that are more massive than 0.3M_Jup and closer than 20pc. Taking into account the age estimate, and ass...

  5. The Gemini NICI Planet-Finding Campaign : Discovery of a Substellar L Dwarf Companion to the Nearby Young M Dwarf CD-35 2722

    CERN Document Server

    Wahhaj, Zahed; Biller, Beth A; Clarke, Fraser; Nielsen, Eric L; Close, Laird M; Hayward, Thomas L; Mamajek, Eric E; Cushing, Michael; Dupuy, Trent; Tecza, Matthias; Thatte, Niranjan; Chun, Mark; Ftaclas, Christ; Hartung, Markus; Reid, I Neill; Shkolnik, Evgenya L; Alencar, Silvia H P; Artymowicz, Pawel; Boss, Alan; Pino, Elisabethe de Gouveia Dal; Gregorio-Hetem, Jane; Ida, Shigeru; Kuchner, Marc; Lin, Douglas N C; Toomey, Douglas W

    2011-01-01

    We present the discovery of a wide (67 AU) substellar companion to the nearby (21 pc) young solar-metallicity M1 dwarf CD-35 2722, a member of the ~100 Myr AB Doradus association. Two epochs of astrometry from the NICI Planet-Finding Campaign confirm that CD-35 2722 B is physically associated with the primary star. Near-IR spectra indicate a spectral type of L4\\pm1 with a moderately low surface gravity, making it one of the coolest young companions found to date. The absorption lines and near-IR continuum shape of CD-35 2722 B agree especially well the dusty field L4.5 dwarf 2MASS J22244381-0158521, while the near-IR colors and absolute magnitudes match those of the 5 Myr old L4 planetary-mass companion, 1RXS J160929.1-210524 b. Overall, CD-35 2722 B appears to be an intermediate-age benchmark for L-dwarfs, with a less peaked H-band continuum than the youngest objects and near-IR absorption lines comparable to field objects. We fit Ames-Dusty model atmospheres to the near-IR spectra and find T=1700-1900 K and...

  6. 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

  7. 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.

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

    Science.gov (United States)

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

    2016-01-01

    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 Very Large Telescope. 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 type. In our sample, we measured minimum binary fraction of 9.1^{+9.9}_{-3.0} per cent. From the best fit of the BT-Settl models 2014 to the observed spectra, we derived the atmospheric parameters for the single objects. The BT-Settl models were able to reproduce the majority of the spectral energy distributions from our objects, and the variation of the equivalent width of the Rb I (794.8 nm) and Cs I (852.0 nm) lines with the spectral type. None the less, these models did not reproduce the evolution of the equivalent widths of the Na I (818.3 and 819.5 nm) and K I (1253 nm) lines with the spectral type.

  9. A submillimetre search for pre- and proto-brown dwarfs in Chamaeleon II

    Science.gov (United States)

    de Gregorio-Monsalvo, I.; Barrado, D.; Bouy, H.; Bayo, A.; Palau, A.; Morales-Calderón, M.; Huélamo, N.; Morata, O.; Merín, B.; Eiroa, C.

    2016-05-01

    Context. The Chamaeleon II molecular cloud is an active star-forming region that offers an excellent opportunity to study the formation of brown dwarfs in the southern hemisphere. Aims: Our aims are to identify a population of pre- and proto-brown dwarfs (5σ mass limit threshold of ~0.015 M⊙) and provide information on the formation mechanisms of substellar objects. Methods: We performed high sensitivity observations at 870 μm using the LABOCA bolometer at the APEX telescope towards an active star-forming region in Chamaeleon II. The data are complemented by an extensive multiwavelength catalogue of sources, which covers the optical to the far-infrared, to study the nature of the LABOCA detections. Results: We detect 15 cores at 870 μm, and 11 of them show masses in the substellar regime. The most intense objects in the surveyed field correspond to the submillimetre counterparts of the well-known young stellar objects DK Cha and IRAS 12500-7658. We identify a possible proto-brown dwarf candidate (ChaII-APEX-L) with IRAC emission at 3.6 and 4.5 μm. Conclusions: Our analysis indicates that most of the spatially resolved cores are transient, and that the point-like starless cores in the substellar regime (with masses between 0.016 M⊙ and 0.066 M⊙) could be pre-brown dwarfs cores that are gravitationally unstable if they have radii less than 220 AU to 907 AU (1.2'' to 5'' at 178 pc), respectively, for different masses. ALMA observations will be key to revealing the energetic state of these pre-brown dwarfs candidates.

  10. The atomic and molecular content of disks around very low-mass stars and brown dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Pascucci, I. [Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Herczeg, G. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Carr, J. S. [Naval Research Laboratory, Code 7211, Washington, DC 20375 (United States); Bruderer, S., E-mail: pascucci@lpl.arizona.edu [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748 Garching (Germany)

    2013-12-20

    There is growing observational evidence that disk evolution is stellar-mass-dependent. Here, we show that these dependencies extend to the atomic and molecular content of disk atmospheres. We analyze a unique dataset of high-resolution Spitzer/IRS spectra from eight very low mass star and brown dwarf disks. We report the first detections of Ne{sup +}, H{sub 2}, CO{sub 2}, and tentative detections of H{sub 2}O toward these faint and low-mass disks. Two of our [Ne II] 12.81 μm emission lines likely trace the hot (≥5000 K) disk surface irradiated by X-ray photons from the central stellar/sub-stellar object. The H{sub 2} S(2) and S(1) fluxes are consistent with arising below the fully or partially ionized surface traced by the [Ne II] emission in gas at ∼600 K. We confirm the higher C{sub 2}H{sub 2}/HCN flux and column density ratio in brown dwarf disks previously noted from low-resolution IRS spectra. Our high-resolution spectra also show that the HCN/H{sub 2}O fluxes of brown dwarf disks are on average higher than those of T Tauri disks. Our LTE modeling hints that this difference extends to column density ratios if H{sub 2}O lines trace warm ≥600 K disk gas. These trends suggest that the inner regions of brown dwarf disks have a lower O/C ratio than those of T Tauri disks, which may result from a more efficient formation of non-migrating icy planetesimals. An O/C = 1, as inferred from our analysis, would have profound implications on the bulk composition of rocky planets that can form around very low mass stars and brown dwarfs.

  11. OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?

    Energy Technology Data Exchange (ETDEWEB)

    Dong, S; Gould, A; Udalski, A; Anderson, J; Christie, G W; Gaudi, B S; Jaroszynski, M; Kubiak, M; Szymanski, M K; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; DePoy, D L; Fox, D B; Gal-Yam, A; Han, C; Lepine, S; McCormick, J; Ofek, E; Park, B; Pogge, R W; Abe, F; Bennett, D P; Bond, I A; Britton, T R; Gilmore, A C; Hearnshaw, J B; Itow, Y; Kamiya, K; Kilmartin, P M; Korpela, A; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Ohnishi, K; Okada, C; Rattenbury, N; Saito, T; Sako, T; Sasaki, M; Sullivan, D; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P M; Yoshoika, T; Albrow, M D; Beaulieu, J P; Brillant, S; Calitz, H; Cassan, A; Cook, K H; Coutures, C; Dieters, S; Prester, D D; Donatowicz, J; Fouque, P; Greenhill, J; Hill, K; Hoffman, M; Horne, K; J?rgensen, U G; Kane, S; Kubas, D; Marquette, J B; Martin, R; Meintjes, P; Menzies, J; Pollard, K R; Sahu, K C; Vinter, C; Wambsganss, J; Williams, A; Bode, M; Bramich, D M; Burgdorf, M; Snodgrass, C; Steele, I; Doublier, V; Foelmi, C

    2008-04-18

    We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher-order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is a foreground M dwarf, with mass M = 0.46 {+-} 0.04M{sub {circle_dot}}, distance D{sub l} = 3.3 {+-} 0.4 kpc, and thick-disk kinematics {nu}{sub LSR} {approx} 103 km s{sup -1}. From the best-fit model, the planet has mass M{sub p} = 3.5 {+-} 0.3 M{sub Jupiter}, lies at a projected separation r{sub {perpendicular}} = 3.6 {+-} 0.2 AU from its host and has an equilibrium temperature of T {approx} 50 K, i.e., similar to Neptune. A degenerate model less favored by {Delta}{sub {chi}}{sup 2} {approx} 4 gives essentially the same planetary mass M{sub p} = 3.3 {+-} 0.3 M{sub Jupiter} with a smaller projected separation, r{sub {perpendicular}} = 2.1 {+-} 0.1 AU, and higher equilibrium temperature T {approx} 68 K. These results from the primary analysis suggest that OGLE-2005-BLG-071Lb is likely to be the most massive planet yet discovered that is hosted by an M dwarf. However, the formation of such high-mass planetary companions in the outer regions of M-dwarf planetary systems is predicted to be unlikely within the core-accretion scenario. There are a number of caveats to this analysis, but these could mostly be resolved by a single astrometric measurement a few years after the event.

  12. The nature of the companion of PSR J1719-1438:a white dwarf or an exotic object?

    Institute of Scientific and Technical Information of China (English)

    J.E.Horvath

    2012-01-01

    We raise the possibility that the very dense,compact companion of PSR J1719-1438,which has a Jupiter-like mass,is an exotic quark object rather than a light helium or carbon white dwarf.The exotic hypothesis naturally explains some of the observed features,and provides quite strong predictions for this system,to be confirmed or refuted in feasible future studies.

  13. Timing of a Young Mildly Recycled Pulsar with a Massive White Dwarf Companion

    CERN Document Server

    Lazarus, P; Knispel, B; Freire, P C C; Deneva, J S; Kaspi, V M; Allen, B; Bogdanov, S; Chatterjee, S; Stairs, I H; Zhu, W W

    2013-01-01

    We report on timing observations of the recently discovered binary pulsar PSR J1952+2630 using the Arecibo Observatory. The mildly recycled 20.7-ms pulsar is in a 9.4-hr orbit with a massive, M_WD > 0.93 M_sun, white dwarf (WD) companion. We present, for the first time, a phase-coherent timing solution, with precise spin, astrometric, and Keplerian orbital parameters. This shows that the characteristic age of PSR J1952+2630 is 77 Myr, younger by one order of magnitude than any other recycled pulsar-massive WD system. We derive an upper limit on the true age of the system of 50 Myr. We investigate the formation of PSR J1952+2630 using detailed modelling of the mass-transfer process from a naked helium star on to the neutron star following a common-envelope phase (Case BB Roche-lobe overflow). From our modelling of the progenitor system, we constrain the accretion efficiency of the neutron star, which suggests a value between 100 and 300% of the Eddington accretion limit. We present numerical models of the chem...

  14. Planets Around Low-Mass Stars (PALMS). I. A Substellar Companion to the Young M Dwarf 1RXS J235133.3+312720

    CERN Document Server

    Bowler, Brendan P; Shkolnik, Evgenya L; Dupuy, Trent J; Cieza, Lucas A; Kraus, Adam L; Tamura, Motohide

    2012-01-01

    We report the discovery of a brown dwarf companion to the young M dwarf 1RXS J235133.3+312720 as part of a high contrast imaging search for planets around nearby young low-mass stars with Keck-II/NIRC2 and Subaru/HiCIAO. The 2.4" (~120 AU) pair is confirmed to be comoving from two epochs of high resolution imaging. Follow-up low- and moderate-resolution near-infrared spectroscopy of 1RXS J2351+3127 B with IRTF/SpeX and Keck-II/OSIRIS reveals a spectral type of L0$^{+2}_{-1}$. The M2 primary star 1RXS J2351+3127 A exhibits X-ray and UV activity levels comparable to young moving group members with ages of ~10-100 Myr. UVW kinematics based the measured radial velocity of the primary and the system's photometric distance (50 +/- 10 pc) indicate it is likely a member of the ~50-150 Myr AB Dor moving group. The near-infrared spectrum of 1RXS J2351+3127 B does not exhibit obvious signs of youth, but its H-band morphology shows subtle hints of intermediate surface gravity. The spectrum is also an excellent match to t...

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

    OpenAIRE

    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 ...

  16. 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...

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

    Science.gov (United States)

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

    2015-12-01

    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, because 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, which allows 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 1.54 m 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 ± 0.02 mag and 0.34 ± 0.02 mag for Luhman 16A and 16B, respectively. Results: We used the 16-night time-series data to estimate the rotation period of the two components. We found that Luhman 16B rotates with a period of 5.1 ± 0.1 h, in very good agreement with previous measurements. For Luhman 16A, we report that it rotates more slowly than its companion, and even though we were not able to get a robust determination, our data indicate a rotation period of roughly 8 h. This implies that the rotation axes of the two components are well aligned and suggests a scenario in which the two objects underwent the same accretion process. The 2-year complete data set was used to study the astrometric motion of Luhman 16AB. We predict a motion of the system that is not consistent with a previous estimate based on two months of monitoring, but cannot confirm or refute the presence of additional planetary-mass bodies in the system. Based on data collected by MiNDSTEp with the Danish 1.54 m telescope at the ESO La

  18. The Surface Densities of Disk Brown Dwarfs in JWST Surveys

    Science.gov (United States)

    Ryan, R. E., Jr.; Reid, I. N.

    2016-04-01

    We present predictions for the surface density of ultracool dwarfs (with spectral types M8-T8) for a host of deep fields that are likely to be observed with the James Webb Space Telescope. Based on simple thin and thick/thin disk (exponential) models, we show that the typical distance modulus is μ ≈ 9.8 mag, which at high Galactic latitude is 5{log}(2 {z}{scl})-5. Since this is a property of the density distribution of an exponential disk, it is independent of spectral type or stellar sample. Using the published estimates of the ultracool dwarf luminosity function, we show that their number counts typically peak around J˜ 24 mag with a total surface density of {{Σ }}˜ 0.3 arcmin-2, but with a strong dependence on galactic coordinate and spectral type. Owing to the exponential shape of the disk, the ultracool dwarfs are very rare at faint magnitudes (J≥slant 27 mag), with typical densities of {{Σ }}˜ 0.005 arcmin-2 (or ˜ 20% of the total contribution within the field). Therefore, in very narrow and deep fields, we predict there are only a few ultracool dwarfs, and hence these stars are likely not a severe contaminant in searches for high-redshift galaxies. Furthermore, the ultracool dwarfs are expected to be considerably brighter than the high-redshift galaxies, so samples near the faint end of the high-redshift galaxy population will be the purest. We present the star-count formalism in a simplified way so that observers may easily predict the number of stars for their conditions (field, depth, wavelength, etc.).

  19. Go Long! Identifying Distant Brown Dwarfs in HST/WFC3 Parallel Field

    Science.gov (United States)

    Aganze, Christian; Burgasser, Adam J.; Malkan, Matthew Arnold; Masters, Daniel C.; Mercado, Gretel; Suarez, Adrian; Tamiya, Tomoki

    2016-01-01

    The spatial distribution of brown dwarfs beyond the local Solar Neighborhood is crucial for understanding their Galactic formation, dynamical and evolutionary history. Wide-field red optical and infrared surveys (e.g., 2MASS, SDSS, WISE) have enabled measures of the local density of brown dwarfs, but probe a relatively shallow (˜100 parsecs) volume; few constraints exist for the scale height or radial distributions of these low mass and low luminosity objects. We have searched ~1400 square arcminutes of WFC3 Infrared Spectroscopic Parallel Survey (WISPS) data to identify distant brown dwarfs (d > 300 pc) with near-infrared grism spectra from the the Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3). Using spectral indices to identify candidates, measure spectral types and estimate distances, and comparing the WFC3 spectra to spectral templates in the SpeX Prism Library, we report our first results from this work, the discovery of ~50 late-M, L and T dwarfs with distances of 30 - 1000+ pc. We compare the distance and spectral type distribution to population simulations, and discuss current selection biases.The material presented here is based on work supported by the National Aeronautics and Space Administration under Grant No. NNX15AI75G

  20. 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, ...

  1. A search for brown-dwarf like secondaries in cataclysmic variables

    CERN Document Server

    Mennickent, R E

    2002-01-01

    We present VTL/ISAAC infrared spectroscopy of a sample of short orbital period cataclysmic variables which are candidates for harboring substellar companions. We have detected the KI and NaI absorption lines of the companion star in VY Aqr. The overall spectral distribution in this system is best fit with a M9.5 type dwarf spectra, implying a distance of $100 \\pm 10$ pc. VY Aqr seems to fall far from the theoretical distribution of secondary star temperatures around the orbital period minimum. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. The application of such a spectral fitting procedure suggests that the continuum shape in the 1.1-2.5 $\\mu$m spectral region in short orbital period cataclysmic variables may be an useful indicator of the companion spectral type. The SED fitting for RZ Leo and CU Vel suggests M5 type dwarf companions, and distances of 340 $\\pm$ 110 and 150 $\\pm$ 50 pc, respectively. These systems may be placed ...

  2. 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...

  3. 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...

  4. The Surface Densities of Disk Brown Dwarfs in JWST Surveys

    CERN Document Server

    Ryan, R E

    2015-01-01

    We present predictions for the surface density of ultracool dwarfs (with spectral types M8-T8) for a host of deep fields that are likely to be observed with the James Webb Space Telescope. Based on simple thin and thick/thin disk (exponential) models, we show the typical distance modulus is mu~9.8 mag, which at high Galactic latitude is 5log(2 z_scl)-5. Since this is a property of the density distribution of an exponential disk, it is independent of spectral type or stellar sample. Using the published estimates of the ultracool dwarf luminosity function, we show that their number counts typically peak around J~24 mag with a total surface density of Sigma ~ 0.3 arcmin^-2, but with a strong dependence on galactic coordinate and spectral type. Owing to the exponential shape of the disk, the ultracool dwarfs are very rare at faint magnitudes (J>~27 mag), with typical densities of Sigma~0.005 arcmin^-2 (or ~20% of the total contribution within the field). Therefore in the very narrow and deep fields, we predict th...

  5. Brown dwarf photospheres are patchy: A Hubble space telescope near-infrared spectroscopic survey finds frequent low-level variability

    International Nuclear Information System (INIS)

    Condensate clouds strongly impact the spectra of brown dwarfs and exoplanets. Recent discoveries of variable L/T transition dwarfs argued for patchy clouds in at least some ultracool atmospheres. This study aims to measure the frequency and level of spectral variability in brown dwarfs and to search for correlations with spectral type. We used Hubble Space Telescope/Wide Field Camera 3 to obtain spectroscopic time series for 22 brown dwarfs of spectral types ranging from L5 to T6 at 1.1-1.7 μm for ≈40 minutes per object. Using Bayesian analysis, we find six brown dwarfs with confident (p > 95%) variability in the relative flux in at least one wavelength region at sub-percent precision, and five brown dwarfs with tentative (p > 68%) variability. We derive a minimum variability fraction fmin=27−7+11% over all covered spectral types. The fraction of variables is equal within errors for mid-L, late-L, and mid-T spectral types; for early-T dwarfs we do not find any confident variable but the sample is too small to derive meaningful limits. For some objects, the variability occurs primarily in the flux peak in the J or H band, others are variable throughout the spectrum or only in specific absorption regions. Four sources may have broadband peak-to-peak amplitudes exceeding 1%. Our measurements are not sensitive to very long periods, inclinations near pole-on and rotationally symmetric heterogeneity. The detection statistics are consistent with most brown dwarf photospheres being patchy. While multiple-percent near-infrared variability may be rare and confined to the L/T transition, low-level heterogeneities are a frequent characteristic of brown dwarf atmospheres.

  6. Brown dwarf photospheres are patchy: A Hubble space telescope near-infrared spectroscopic survey finds frequent low-level variability

    Energy Technology Data Exchange (ETDEWEB)

    Buenzli, Esther; Apai, Dániel [Department of Astronomy and Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Radigan, Jacqueline; Reid, I. Neill [Space Telescope Science Institute, Baltimore, MD 21218 (United States); Flateau, Davin, E-mail: ebuenzli@email.arizona.edu [Department of Planetary Sciences and Lunar and Planetary Laboratory, University of Arizona, Tucson, AZ 85721 (United States)

    2014-02-20

    Condensate clouds strongly impact the spectra of brown dwarfs and exoplanets. Recent discoveries of variable L/T transition dwarfs argued for patchy clouds in at least some ultracool atmospheres. This study aims to measure the frequency and level of spectral variability in brown dwarfs and to search for correlations with spectral type. We used Hubble Space Telescope/Wide Field Camera 3 to obtain spectroscopic time series for 22 brown dwarfs of spectral types ranging from L5 to T6 at 1.1-1.7 μm for ≈40 minutes per object. Using Bayesian analysis, we find six brown dwarfs with confident (p > 95%) variability in the relative flux in at least one wavelength region at sub-percent precision, and five brown dwarfs with tentative (p > 68%) variability. We derive a minimum variability fraction f{sub min}=27{sub −7}{sup +11}% over all covered spectral types. The fraction of variables is equal within errors for mid-L, late-L, and mid-T spectral types; for early-T dwarfs we do not find any confident variable but the sample is too small to derive meaningful limits. For some objects, the variability occurs primarily in the flux peak in the J or H band, others are variable throughout the spectrum or only in specific absorption regions. Four sources may have broadband peak-to-peak amplitudes exceeding 1%. Our measurements are not sensitive to very long periods, inclinations near pole-on and rotationally symmetric heterogeneity. The detection statistics are consistent with most brown dwarf photospheres being patchy. While multiple-percent near-infrared variability may be rare and confined to the L/T transition, low-level heterogeneities are a frequent characteristic of brown dwarf atmospheres.

  7. UKIDSS detections of cool brown dwarfs - proper motions of 14 known $>$T5 dwarfs and discovery of three new T5.5-T6 dwarfs

    CERN Document Server

    Scholz, Ralf-Dieter; Schnurr, Olivier; Storm, Jesper

    2012-01-01

    AIMS: We contribute to improving the census of cool brown dwarfs (late-T and Y dwarfs) in the immediate solar neighbourhood. METHODS: By combining near-infrared (NIR) data of UKIDSS with mid-infrared WISE and other available NIR (2MASS) and red optical (SDSS $z$-band) multi-epoch data we detect high proper motion (HPM) objects with colours typical of late spectral types ($>$T5). We use NIR low-resolution spectroscopy for the classification of new candidates. RESULTS: We determined new proper motions for 14 known T5.5-Y0 dwarfs, many of them being significantly ($>$2-10 times) more accurate than previous ones. We detected three new candidates, ULAS J0954+0623, ULAS J1152+0359, and ULAS J1204-0150, by their HPMs and colours. Using previously published and new UKIDSS positions of the known nearby T8 dwarf WISE J0254+0223 we improved its trigonometric parallax to 165$\\pm$20 mas. For the three new objects we obtained NIR spectroscopic follow-up with LBT/LUCIFER classifying them as T5.5 and T6 dwarfs. With their es...

  8. Brown Dwarf Photospheres are Patchy: A Hubble Space Telescope Near-infrared Spectroscopic Survey Finds Frequent Low-level Variability

    CERN Document Server

    Buenzli, Esther; Radigan, Jacqueline; Reid, I Neill; Flateau, Davin

    2013-01-01

    Condensate clouds strongly impact the spectra of brown dwarfs and exoplanets. Recent discoveries of variable L/T transition dwarfs argued for patchy clouds in at least some ultracool atmospheres. This study aims to measure the frequency and level of spectral variability in brown dwarfs and to search for correlations with spectral type. We used HST/WFC3 to obtain spectroscopic time series for 22 brown dwarfs of spectral types ranging from L5 to T6 at 1.1-1.7 $\\mu$m for $\\approx$40 min per object. Using Bayesian analysis, we find 6 brown dwarfs with confident $(p>95\\%)$ variability in the relative flux in at least one wavelength region at sub-percent precision, and 5 brown dwarfs with tentative $(p>68\\%)$ variability. We derive a minimum variability fraction $f_{min}=27^{+11}_{-7}\\%$ over all covered spectral types. The fraction of variables is equal within errors for mid L, late L and mid T spectral types; for early T dwarfs we do not find any confident variable but the sample is too small to derive meaningful...

  9. 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...

  10. 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 ...

  11. 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.

  12. 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...

  13. ALMA and CARMA observations of Brown Dwarfs disks: testing the models of dust evolution

    CERN Document Server

    Ricci, L; Natta, A; Scholz, A; de Gregorio-Monsalvo, I; Isella, A; Carpenter, J M

    2013-01-01

    The first steps toward planet formation involve the coagulation of small microscopic grains into larger and larger pebbles and rocks in gas-rich disks around young stars and brown dwarfs. Observations in the sub-millimeter can trace mm/cm-sized pebbles in the outer disks, and investigate the mechanisms of coagulation/fragmentation and radial migration of these solids. These represent key, yet not fully understood ingredients for our understanding of the formation of planetesimals, the building blocks of planets. Here we present the first results from an observational program using the ALMA and CARMA sub-mm/mm interferometers aimed at characterizing the dust properties and disk structure of young disks around brown dwarfs and very low mass stars. Given the physical conditions expected for these disks, they represent critical test beds for the models of the early stages of planet formation in proto-planetary disks.

  14. 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.

  15. A HIGHLY INCLINED ORBIT FOR THE 110 DAY PERIOD M-DWARF COMPANION KOI-368.01

    International Nuclear Information System (INIS)

    We report the detection of asymmetry in the transit light curves of the 110 day period companion to KOI-368, a rapidly rotating A-dwarf. The significant distortion in the transit light curve is attributed to spin-orbit misalignment between the transiting companion and the gravity darkened host star. Our analysis was based on 11 long cadence and 2 short cadence transits of KOI-368.01 from the Kepler mission, as well as stellar parameters determined from our follow-up spectroscopic observation. We measured the true obliquity between the orbit normal and the stellar rotation axis to be 69-10+9o. We also find a secondary eclipse event with depth 29 ± 3 ppm at phase 0.59, from which the temperature of the companion is constrained to 3060 ± 50 K, indicating that KOI-368.01 is a late M-dwarf. The eccentricity is also calculated from the eclipse to be 0.1429 ± 0.0007. The long period, high obliquity, and low eccentricity of KOI-368.01 allow us to limit a number of proposed theories for the misalignment of binary systems

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

    International Nuclear Information System (INIS)

    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 CH4 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 CH4 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 CH4/CO, the NH3/N2 ratio is insensitive to mixing, which makes NH3 a potential proxy for gravity. HCN may become interesting in high-gravity brown dwarfs with very strong vertical mixing. Detailed analysis of the CO-CH4 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, CH4, NH3, HCN, and CO2 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).

  17. Characterization of a Brown Rot Fungus Isolated from Dwarf Flowering Almond in Korea

    OpenAIRE

    Shim, Myoung Yong; Jeon, Young Jae; Kim, Seong Hwan

    2007-01-01

    The fruits showing brown rot symptom on dwarf flowering almond were found in Gongju, Chungchungnam-Do in Korea in July 2005. Small water-soaked lesions on the fruits were initiated, and gradually developed to soft rot covered with gray conidia. Then the diseased fruits were shrunk and became grayish-black mummies. A fungus was isolated from the diseased fruit and its morphological, cultural and molecular genetic characteristics were investigated. Typical blastospores of Monilinia spp. were ob...

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

    Science.gov (United States)

    Zahnle, Kevin J.; Marley, Mark S.

    2014-12-01

    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 CH4 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 CH4 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 CH4/CO, the NH3/N2 ratio is insensitive to mixing, which makes NH3 a potential proxy for gravity. HCN may become interesting in high-gravity brown dwarfs with very strong vertical mixing. Detailed analysis of the CO-CH4 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, CH4, NH3, HCN, and CO2 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).

  19. 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...

  20. 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...

  1. Young, Low-Mass Brown Dwarfs with Mid-Infrared Excesses

    CERN Document Server

    Allers, K N; Jaffe, D T; Kessler-Silacci, J E

    2006-01-01

    We have combined new I, J, H, and Ks imaging of portions of the Chamaeleon II, Lupus I, and Ophiuchus star-forming clouds with 3.6 to 24 micron imaging from the Spitzer Legacy Program, "From Molecular Clouds to Planet Forming Disks", to identify a sample of 19 young stars, brown dwarfs and sub-brown dwarfs showing mid-infrared excess emission. The resulting sample includes sources with luminosities of 0.5>log(L/Lsun)>-3.1. Six of the more luminous sources in our sample have been previously identified by other surveys for young stars and brown dwarfs. Five of the sources in our sample have nominal masses at or below the deuterium burning limit (~12 M_J). Over three decades in luminosity, our sources have an approximately constant ratio of excess to stellar luminosity. We compare our observed SEDs to theoretical models of a central source with a passive irradiated circumstellar disk and test the effects of disk inclination, disk flaring, and the size of the inner disk hole on the strength/shape of the excess. T...

  2. Rotation Periods of Young Brown Dwarfs: K2 Survey in Upper Scorpius

    CERN Document Server

    Scholz, Aleks; Jayawardhana, Ray; Muzic, Koraljka

    2015-01-01

    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 Kepler space telescope's K2 mission. The periods range from a few hours to two days (plus one outlier at 5 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 lightcurves. 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 provide an important constraint on the mass dependence of the braking mechanism.

  3. Mid-Infrared Selection of Brown Dwarfs and High-Redshift Quasars

    CERN Document Server

    Stern, D; Allen, L; Bian, C; Blain, A; Brand, K; Brodwin, M; Brown, M J I; Cool, R; Desai, V; Dey, A; Eisenhardt, P; González, A; Jannuzi, B T; Menendez-Delmestre, K; Smith, H A; Soifer, B T; Tiede, G P; Wright, E

    2006-01-01

    We discuss color selection of rare objects in a wide-field, multiband survey spanning from the optical to the mid-infrared. Simple color criteria simultaneously identify and distinguish two of the most sought after astrophysical sources: the coolest brown dwarfs and the most distant quasars. We present spectroscopically-confirmed examples of each class identified in the IRAC Shallow Survey of the Bootes field of the NOAO Deep Wide-Field Survey. ISS J142950.9+333012 is a T4.5 brown dwarf at a distance of approximately 42 pc, and ISS J142738.5+331242 is a radio-loud quasar at redshift z=6.12. Our selection criteria identify a total of four candidates over 8 square degrees of the Bootes field. The other two candidates are both confirmed 5.5brown dwarfs and higher redshift quasars.

  4. X-ray emission from young brown dwarfs in the Orion Nebula Cluster

    CERN Document Server

    Preibisch, T; Grosso, N; Feigelson, E D; Flaccomio, E; Getman, K; Hillenbrand, L A; Meeus, G; Micela, G; Sciortino, S; Stelzer, B; Preibisch, Thomas; Caughrean, Mark J. Mc; Grosso, Nicolas; Feigelson, Eric D.; Flaccomio, Ettore; Getman, Konstantin; Hillenbrand, Lynne A.; Meeus, Gwendolyn; Micela, Giusi; Sciortino, Salvatore; Stelzer, Beate

    2005-01-01

    We use the sensitive X-ray data from the Chandra Orion Ultradeep Project (COUP) to study the X-ray properties of 34 spectroscopically-identified brown dwarfs with near-infrared spectral types between M6 and M9 in the core of the Orion Nebula Cluster. Nine of the 34 objects are clearly detected as X-ray sources. The apparently low detection rate is in many cases related to the substantial extinction of these brown dwarfs; considering only the BDs with $A_V \\leq 5$ mag, nearly half of the objects (7 out of 16) are detected in X-rays. Our 10-day long X-ray lightcurves of these objects exhibit strong variability, including numerous flares. While one of the objects was only detected during a short flare, a statistical analysis of the lightcurves provides evidence for continuous (`quiescent') emission in addition to flares for all other objects. Of these, the $\\sim$ M9 brown dwarf COUP 1255 = HC 212 is one of the coolest known objects with a clear detection of quiescent X-ray emission. The X-ray properties (spectra...

  5. 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...

  6. 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...

  7. 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 ...

  8. The Brown dwarf Atmosphere Monitoring (BAM) Project I: The largest near-IR monitoring survey of L- & T-dwarfs

    CERN Document Server

    Wilson, P A; Patience, J

    2014-01-01

    Using SofI on the 3.5m New Technology Telescope, we have conducted an extensive near-infrared monitoring survey of an unbiased sample of 69 brown dwarfs spanning the L0 and T8 spectral range, with at least one example of each spectral type. Each target was observed for a 2-4 hour period in the Js-band, and the median photometric precision of the data is ~0.7%. A total of 14 brown dwarfs were identified as variables with min-to-max amplitudes ranging from 1.7% to 10.8% over the observed duration. All variables satisfy a statistical significance threshold with a p-value <5% based on comparison with the median reference star light curve. Approximately half of the variables show sinusoidal amplitude variations similar to 2M2139, and the remainder shows short timescale evolving light curves similar to SIMP0136. The L/T transition has been suggested to be a region of a higher degree of variability if patchy clouds are present and this survey was designed to test the patchy cloud model with photometric monitoring...

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

    OpenAIRE

    Faherty, Jacqueline K.; Burgasser, Adam J.; Walter, Frederick M.; van der Bliek, Nicole; Shara, Michael M.; Cruz, Kelle L.; West, Andrew A.; Vrba, Frederick J.; Anglada-Escud, Guillem

    2012-01-01

    We report parallax measurements for 70 ultracool dwarfs (UCDs). Using both literature values and our sample, we report new polynomial relations between spectral type and M$_{JHK}$. Including resolved L/T transition binaries in the relations, we find no reason to differentiate between a "bright" (unresolved binary) and "faint" (single source) sample across the L/T boundary. Isolating early T dwarfs, we find that the brightening of T0-T4 sources is prominent in M$_{J}$ where there is a [1.2 - 1...

  10. Final Fates of Rotating White Dwarfs and Their Companions in the Single Degenerate Model of Type Ia Supernovae

    CERN Document Server

    Hachisu, Izumi; Nomoto, Ken'ichi

    2012-01-01

    Taking into account the rotation of mass-accreting white dwarfs (WDs) whose masses exceed the Chandrasekhar mass, we extend our new single degenerate model for the progenitors of Type Ia supernovae (SNe Ia) to both types of binary systems with the main-sequence and red-giant (RG) companions. We present a mass distribution of WDs exploding as SNe Ia, where the WD mass ranges from 1.38 to 2.3 M_sun. These progenitor models are assigned to various types of SNe Ia. A lower mass range of WDs (1.38 M_sun 1.5 M_sun), which are supported by differential rotation, correspond to brighter SNe Ia such as SN 1991T. In this case, a variety of the WD mass may lead to a variation of brightness. We also show the evolutionary states of the companion stars at SN Ia explosions and pose constraints on the unseen companions. In the WD+RG systems, in particular, most of the RG companions have evolved to helium/carbon-oxygen WDs in the spin-down phase before the SN Ia explosions. In such a case, we do not expect any prominent signa...

  11. QATAR-2: A K DWARF ORBITED BY A TRANSITING HOT JUPITER AND A MORE MASSIVE COMPANION IN AN OUTER ORBIT

    International Nuclear Information System (INIS)

    We report the discovery and initial characterization of Qatar-2b, a hot Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short period, Pb = 1.34 days. The mass and radius of Qatar-2b are MP = 2.49 MJ and RP = 1.14 RJ, respectively. Radial-velocity monitoring of Qatar-2 over a span of 153 days revealed the presence of a second companion in an outer orbit. The Systemic Console yielded plausible orbits for the outer companion, with periods on the order of a year and a companion mass of at least several MJ. Thus, Qatar-2 joins the short but growing list of systems with a transiting hot Jupiter and an outer companion with a much longer period. This system architecture is in sharp contrast to that found by Kepler for multi-transiting systems, which are dominated by objects smaller than Neptune, usually with tightly spaced orbits that must be nearly coplanar.

  12. Qatar-2: A K dwarf orbited by a transiting hot Jupiter and a more massive companion in an outer orbit

    CERN Document Server

    Bryan, Marta L; Latham, David W; Parley, Neil R; Cameron, Andrew Collier; Quinn, Samuel N; Carter, Joshua A; Fulton, Benjamin J; Berlind, Perry; Brown, Warren R; Buchhave, Lars A; Calkins, Michael L; Esquerdo, Gilbert A; Furesz, Gabor; Jorgensen, Uffe Grae; Horne, Keith D; Stefanik, Robert P; Street, Rachel A; Torres, Guillermo; West, Richard G; Dominik, Martin; Harpsoe, Kennet B W; Liebig, Christine; Novati, Sebastiano Calchi; Ricci, Davide; Skottfelt, Jesper F

    2011-01-01

    We report the discovery and initial characterization of Qatar-2b, a hot Jupiter transiting a V = 13.3 mag K dwarf in a circular orbit with a short period, P_ b = 1.34 days. The mass and radius of Qatar-2b are M_p = 2.49 M_j and R_p = 1.14 R_j, respectively. Radial-velocity monitoring of Qatar-2 over a span of 153 days revealed the presence of a second companion in an outer orbit. The Systemic Console yielded plausible orbits for the outer companion, with periods on the order of a year and a companion mass of at least several M_j. Thus Qatar-2 joins the short but growing list of systems with a transiting hot Jupiter and an outer companion with a much longer period. This system architecture is in sharp contrast to that found by Kepler for multi-transiting systems, which are dominated by objects smaller than Neptune, usually with tightly spaced orbits that must be nearly coplanar.

  13. An M dwarf Companion to an F-type Star in a young main-sequence binary

    CERN Document Server

    Eigmüller, Ph; Csizmadia, Sz; Lehmann, H; Erikson, A; Fridlund, M; Hartmann, M; Hatzes, A; Pasternacki, Th; Rauer, H; Tkachenko, A; Voss, H

    2016-01-01

    Only a few well characterized very low-mass M dwarfs are known today. Our understanding of M dwarfs is vital as these are the most common stars in our solar neighborhood. We aim to characterize the properties of a rare F+dM stellar system for a better understanding of the low-mass end of the Hertzsprung-Russel diagram. We used photometric light curves and radial velocity follow-up measurements to study the binary. Spectro- scopic analysis was used in combination with isochrone fitting to characterize the primary star. The primary star is an early F-type main-sequence star with a mass of (1.493 +- 0.073) Msun and a radius of (1.474 +- 0.040) Rsun. The companion is an M dwarf with a mass of (0.188 +- 0.014) Msun and a radius of (0.234 +- 0.009) Rsun. The orbital period is (1.35121 +- 0:00001)d. The secondary star is among the lowest-mass M dwarfs known to date. The binary has not reached a 1:1 spin-orbit synchronization. This indicates a young main-sequence binary with an age below ~250 Myrs. The mass-radius re...

  14. Discovery of four new low-mass white-dwarf companions in the Kepler data

    Science.gov (United States)

    Faigler, Simchon; Kull, Ilya; Mazeh, Tsevi; Kiefer, Flavien; Latham, David W.; Bloemen, Steven

    2015-12-01

    We report the discovery of four new short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white-dwarf (WD) secondary (dA+WD) - KIC 4169521, KOI-3818, KIC 2851474 and KIC 9285587. These add to the 6 Kepler, and 19 non-Kepler, previously known short-period eclipsing dA+WD binaries.The discoveries were made through searching the light curves of bright Kepler stars for BEaming, Ellipsoidal and Reflection (BEER) modulations that are consistent with a compact companion, using the BEER search algorithm. This was followed by inspection of the search top hits, looking for eclipsing systems with a secondary eclipse deeper than the primary one, as expected for a WD that is hotter than the primary star. Follow-up spectroscopic radial-velocity (RV) observations confirmed the binarity of the systems. We derive the systems' parameters through analyses of the light curves' eclipses and phase modulations, combined with RV orbital solutions and stellar evolution models.The four systems' orbital periods of 1.17-3.82 days and WD masses of 0.19-0.22 Msun are similar to those reported for the previously known systems. These values are consistent with evolution models of such systems, that undergo a stable mass transfer from the WD progenitor to the current A star.For KIC 4169521 we derive a bloated WD radius of 0.09 Rsun that is well within the WD radius range of 0.04-0.43 Rsun of the known systems. For the remaining three systems we report WD radii of 0.026-0.035 Rsun, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries.As suggested before, the previously known systems, together with KIC 4169521, all with hot and bloated WD secondaries, represent young systems probably at a proto-WD, or initial WD cooling track stage. The other three new systems - KOI-3818, KIC 2851474, and KIC 9285587, are probably positioned further along the WD cooling track, and extend the known population to older systems with cooler

  15. 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...

  16. 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, A.; 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. A.; Tsai, Chao-Wei; Bailey, Vanessa; Beichman, Charles A.; Bloom, Joshua S.; 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-Calderón, 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.

    2011-12-01

    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 μm (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+1.3 -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 ~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 these objects and discuss

  17. UKIDSS detections of cool brown dwarfs. Proper motions of 14 known >T5 dwarfs and discovery of three new T5.5-T6 dwarfs

    Science.gov (United States)

    Scholz, R.-D.; Bihain, G.; Schnurr, O.; Storm, J.

    2012-05-01

    Aims: We contribute to improving the census of cool brown dwarfs (late-T and Y dwarfs) in the immediate solar neighbourhood. Methods: By combining near-infrared (NIR) data of UKIDSS with mid-infrared WISE and other available NIR (2MASS) and red optical (SDSS z-band) multi-epoch data we detected high proper motion (HPM) objects with colours typical of late spectral types (>T5). We used NIR low-resolution spectroscopy for the classification of new candidates. Results: We determined new proper motions for 14 known T5.5-Y0 dwarfs, many of which are significantly (>2-10 times) more accurate than previous ones. We detected three new candidates, ULAS J0954+0623, ULAS J1152+0359, and ULAS J1204-0150, by their HPMs and colours. Using previously published and new UKIDSS positions of the known nearby T8 dwarf WISE J0254+0223 we improved its trigonometric parallax to 165 ± 20 mas. For the three new objects we obtained NIR spectroscopic follow-up with LBT/LUCIFER classifying them as T5.5 and T6 dwarfs. With their estimated spectroscopic distances of about 25-30 pc, their proper motions of about 430-650 mas/yr lead to tangential velocities of about 50-80 km s-1, typical of the Galactic thin-disk population. Based on observations with the Large Binocular Telescope (LBT)Tables 1-5 are available in electronic form at http://www.aanda.org

  18. SDSS J001641-000925: THE FIRST STABLE RED DWARF CONTACT BINARY WITH A CLOSE-IN STELLAR COMPANION

    International Nuclear Information System (INIS)

    SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of P-dot ∼8 s yr−1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O–C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M 3sin i' ∼ 0.14 M ☉. The orbital separation between the third body and the central binary is about 2.8 AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary

  19. SDSS J001641-000925: The First Stable Red Dwarf Contact Binary with a Close-in Stellar Companion

    Science.gov (United States)

    Qian, S.-B.; Jiang, L.-Q.; Fernández Lajús, E.; Soonthornthum, B.; Zhu, L.-Y.; Zhao, E. G.; He, J.-J.; Liao, W.-P.; Wang, J.-J.; Liu, L.; Rattanasoon, S.; Aukkaravittayapun, S.; Zhou, X.; Liu, N. P.

    2015-01-01

    SDSS J001641-000925 is the first red dwarf contact binary star with an orbital period of 0.19856 days that is one of the shortest known periods among M-dwarf binary systems. The orbital period was detected to be decreasing rapidly at a rate of \\dot{P}˜ {8} s yr-1. This indicated that SDSS J001641-000925 was undergoing coalescence via a dynamical mass transfer or loss and thus this red dwarf contact binary is dynamically unstable. To understand the properties of the period change, we monitored the binary system photometrically from 2011 September 2 to 2014 October 1 by using several telescopes in the world and 25 eclipse times were determined. It is discovered that the rapid decrease of the orbital period is not true. This is contrary to the prediction that the system is merging driven by rapid mass transfer or loss. Our preliminary analysis suggests that the observed minus calculated (O-C) diagram shows a cyclic oscillation with an amplitude of 0.00255 days and a period of 5.7 yr. The cyclic variation can be explained by the light travel time effect via the presence of a cool stellar companion with a mass of M 3sin i' ~ 0.14 M ⊙. The orbital separation between the third body and the central binary is about 2.8 AU. These results reveal that the rarity of red dwarf contact binaries could not be explained by rapidly dynamical destruction and the presence of the third body helps to form the red dwarf contact binary.

  20. 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...

  1. Signatures of Cloud, Temperature, and Gravity From Spectra of the Closest Brown Dwarfs

    CERN Document Server

    Faherty, Jacqueline K; Burgasser, Adam J; Tinney, Chris; Osip, David J; Filippazzo, Joseph C; Simcoe, Robert A

    2014-01-01

    We present medium resolution optical and NIR spectral data for components of the newly discovered WISE J104915.57-531906.1AB (Luhman 16AB) brown dwarf binary. The optical spectra reveal strong 6708 A Li I absorption in both Luhman 16A (8.0+/-0.4 A) and Luhman 16B (3.8+/-0.4 A). Interestingly, this is the first detection of Li I absorption in a T dwarf. Combined with the lack of surface gravity features, the Li I detection constrains the system age to 0.1 - 3 Gyr. In the NIR data, we find strong KI absorption at 1.168, 1.177, 1.243, and 1.254 {\\mu}m in both components. Compared to the strength of KI 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 {\\mu}m and 1.25 {\\mu}m regions than Luhman 16A. Converting flux units to a brightness temperature...

  2. K-H2 line shapes for the spectra of cool brown dwarfs

    Science.gov (United States)

    Allard, N. F.; Spiegelman, F.; Kielkopf, J. F.

    2016-04-01

    Observations of cooler and cooler brown dwarfs show that the contribution from broadening at many bars pressure is becoming important. The opacity in the red optical to near-IR region under these conditions is dominated by the extremely pressure-broadened wings of the alkali resonance lines, in particular, the K I resonance doublet at 0.77 μm. Collisions with H2 are preponderant in brown dwarf atmospheres at an effective temperature of about 1000 K; the H2 perturber densities reach several 1019 even in Jupiter-mass planets and exceed 1020 for super-Jupiters and older Y dwarfs. As a consequence, it appears that when the far wing absorption due to alkali atoms in a dense H2 atmosphere is significant, accurate pressure broadened profiles that are valid at high densities of H2 should be incorporated into spectral models. The opacity tables are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A21

  3. 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...

  4. Epsilon Indi Ba, Bb: a detailed study of the nearest known brown dwarfs

    CERN Document Server

    King, Robert R; Homeier, Derek; Allard, France; Scholz, Ralf-Dieter; Lodieu, Nicolas

    2009-01-01

    The discovery of epsilon Indi Ba, Bb, a binary brown dwarf system very close to the Sun, makes possible a concerted campaign to characterise the physical parameters of two T dwarfs. Recent observations suggest substellar atmospheric and evolutionary models may be inconsistent with observations, but there have been few conclusive tests to date. We therefore aim to characterise these benchmark brown dwarfs to place constraints on such models. We have obtained high angular resolution optical, near-infrared, and thermal-infrared imaging and medium-resolution (up to R~5000) spectroscopy of epsilon Indi Ba, Bb with the ESO VLT and present VRIzJHKL'M' broad-band photometry and 0.63--5.1 micron spectroscopy of the individual components. Furthermore, we use deep AO-imaging to place upper limits on the (model-dependent) mass of any further system members. We derive luminosities of log L/L_sun = -4.699+/-0.017 and -5.232+/-0.020 for epsilon Indi Ba, Bb, respectively, and using the dynamical system mass and COND03 evolut...

  5. A Close Companion Search around L Dwarfs using Aperture Masking Interferometry and Palomar Laser Guide Star Adaptive Optics

    CERN Document Server

    Bernat, David; Ireland, Michael; Tuthill, Peter; Martinache, Frantz; Angione, John; Burruss, Rick S; Cromer, John L; Dekany, Richard G; Guiwits, Stephen R; Henning, John R; Hickey, Jeff; Kibblewhite, Edward; McKenna, Daniel L; Moore, Anna M; Petrie, Harold L; Roberts, Jennifer; Shelton, J Chris; Thicksten, Robert P; Trinh, Thang; Tripathi, Renu; Troy, Mitchell; Truong, Tuan; Velur, Viswa; Lloyd, James P

    2010-01-01

    We present a close companion search around sixteen known early-L dwarfs using aperture masking interferometry with Palomar laser guide star adaptive optics. The use of aperture masking allows the detection of close binaries, corresponding to projected physical separations of 0.6-10.0 AU for the targets of our survey. This survey achieved median contrast limits of Delta_K ~ 2.3 for separations between 1.2 - 4 lambda/D, and Delta_K ~ 1.4 at (2/3)lambda/D. We present four candidate binaries detected with moderate to high confidence (90-98%). Two have projected physical separations less than 1.5 AU. This may indicate that tight-separation binaries contribute more significantly to the binary fraction than currently assumed, consistent with spectroscopic and photometric overluminosity studies. Ten targets of this survey have previously been observed with the Hubble Space Telescope as part of companion searches. We use the increased resolution of aperture masking to search for close or dim companions that would be o...

  6. 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.

  7. DANCING IN THE DARK: NEW BROWN DWARF BINARIES FROM KERNEL PHASE INTERFEROMETRY

    International Nuclear Information System (INIS)

    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 ∼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 pc, we report a binary fraction of at least ϵb = 17.2−3.7+5.7%. The results reported here provide new insights into the population of nearby ultracool binaries, while also offering an incisive case study of the benefits conferred by the kernel phase approach in the recovery of companions within a few resolution elements of the point-spread function core.

  8. DANCING IN THE DARK: NEW BROWN DWARF BINARIES FROM KERNEL PHASE INTERFEROMETRY

    Energy Technology Data Exchange (ETDEWEB)

    Pope, Benjamin; Tuthill, Peter [Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2226 (Australia); Martinache, Frantz, E-mail: bjsp@physics.usyd.edu.au, E-mail: p.tuthill@physics.usyd.edu.au, E-mail: frantz@naoj.org [National Astronomical Observatory of Japan, Subaru Telescope, Hilo, HI 96720 (United States)

    2013-04-20

    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 {approx}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 pc, we report a binary fraction of at least #Greek Lunate Epsilon Symbol#{sub b} = 17.2{sub -3.7}{sup +5.7}%. The results reported here provide new insights into the population of nearby ultracool binaries, while also offering an incisive case study of the benefits conferred by the kernel phase approach in the recovery of companions within a few resolution elements of the point-spread function core.

  9. 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...

  10. 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...

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

    International Nuclear Information System (INIS)

    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–1 and a parallax of 0.454 ± 0.045'' (2.20−0.20+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 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 Jup for the age range of 1-10 Gyr that encompasses most nearby stars

  12. Dynamical masses for the nearest brown dwarf binary: Epsilon Indi Ba, Bb

    CERN Document Server

    Cardoso, C V; King, R R; Close, L M; Scholz, R -D; Lenzen, R; Brandner, W; Lodieu, N; Zinnecker, H

    2008-01-01

    We present preliminary astrometric results for the closest known brown dwarf binary to the Sun: Epsilon Indi Ba, Bb at a distance of 3.626 pc. Via ongoing monitoring of the relative separation of the two brown dwarfs (spectral types T1 and T6) with the VLT NACO near-IR adaptive optics system since June 2004, we obtain a model-independent dynamical total mass for the system of 121 MJup, some 60% larger than the one obtained by McCaughrean et al. (2004), implying that the system may be as old as 5 Gyr. We have also been monitoring the absolute astrometric motions of the system using the VLT FORS2 optical imager since August 2005 to determine the individual masses. We predict a periastron passage in early 2010, by which time the system mass will be constrained to < 1 MJup and we will be able to determine the individual masses accurately in a dynamical, model-independent manner.

  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. Spitzer IRS Observations of Disks around Brown Dwarfs in the TW Hydra Association

    CERN Document Server

    Morrow, A L; Espaillat, C; D'Alessio, P; Adame, L; Calvet, N; Forrest, W J; Sargent, B; Hartmann, L; Watson, D M; Bohac, C J

    2008-01-01

    Using SpeX at the NASA Infrared Telescope Facility and the Spitzer Infrared Spectrograph, we have obtained infrared spectra from 0.7 to 30um for three young brown dwarfs in the TW Hydra Association (~10 Myr), 2M J1207-3932, 2M J1139-3159, and SS J1102-3431. The spectral energy distribution for 2M J1139-3159 is consistent with a stellar photosphere for the entire wavelength range of our data while the other two objects exhibit significant excess emission at >5um. We are able to reproduce the excess emission from each brown dwarf using our models of irradiated accretion disks. According to our model fits, both disks have experienced a high degree of dust settling. We also find that silicate emission at 10 and 20um is absent from the spectra of these disks, indicating that grains in the upper disk layers have grown to sizes larger than ~5um. Both of these characteristics are consistent with previous observations of decreasing silicate emission with lower stellar masses and older ages. These trends suggest that e...

  15. 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...

  16. 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.

  17. The cool atmospheres of the binary brown dwarf eps Indi B

    CERN Document Server

    Sterzik, M F; Hartung, M; Huélamo, N; Kaufer, A; Käufl, H U; Melo, C; Nürnberger, D; Siebenmorgen, R; Smette, A

    2005-01-01

    We have imaged $\\epsilon$ Indi B, the closest brown dwarf binary known, with VISIR at the VLT in three narrow-band mid-infrared bandpasses located around 8.6$\\mu$m, 10.5$\\mu$m and 11.3$\\mu$m. We are able to spatially resolve both components, and determine accurate mid-infrared photometry for both components independently. In particular, our VISIR observations allow to probe the NH$_3$ feature in the atmospheres of the cooler and warmer brown dwarfs. For the first time, we can disentangle the contributions of the two components, and find that % our photometry of $\\epsilon$ IndiBb is in good agreement with recent ``cloud-free'' atmosphere models having an effective temperature of $T_\\mathrm{eff}=800$ K. Component Ba agrees more with $T_\\mathrm{eff} \\approx 1100$ K rather than with $T_\\mathrm{eff}=1200$ K, as suggested by SPITZER spectroscopic observations of the combined $\\epsilon$ Indi B system (Roellig et al., 2004). Even higher effective temperatures appear inconsistent with our absolute photometry, as they ...

  18. 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 ...

  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. DEUTERIUM BURNING IN MASSIVE GIANT PLANETS AND LOW-MASS BROWN DWARFS FORMED BY CORE-NUCLEATED ACCRETION

    International Nuclear Information System (INIS)

    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⊕, 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 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 M50. For masses above M50, 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.

  1. Astrometric planet search around southern ultracool dwarfs III. Discovery of a brown dwarf in a 3-year orbit around DE0630-18

    CERN Document Server

    Sahlmann, J; Segransan, D; Martin, E L; Mayor, M; Queloz, D; Udry, S

    2015-01-01

    Using astrometric measurements obtained with the FORS2/VLT camera, we are searching for low-mass companions around 20 nearby ultracool dwarfs. With a single-measurement precision of 0.1 milli-arcseconds, our survey is sensitive to a wide range of companion masses from planetary companions to binary systems. Here, we report the discovery and orbit characterisation of a new ultracool binary at a distance of 19.5 pc from Earth that is composed of the M8.5-dwarf primary DE0630-18 and a substellar companion. The nearly edge-on orbit is moderately eccentric (e=0.23) with an orbital period of 1120 d, which corresponds to a relative separation in semimajor axis of approximately 1.1 AU. We obtained a high-resolution optical spectrum with UVES/VLT and measured the system's heliocentric radial velocity. The spectrum does not exhibit lithium absorption at 670.8 nm, indicating that the system is not extremely young. A preliminary estimate of the binary's physical parameters tells us that it is composed of a primary at the...

  2. Near-infrared imaging survey of faint companions around young dwarfs in the Pleiades cluster

    Institute of Scientific and Technical Information of China (English)

    Yoichi Itoh; Yumiko Oasa; Hitoshi Funayama; Masahiko Hayashi; Misato Fukagawa; Toshio Hashiguchi; Thayne Currie

    2011-01-01

    We conducted a near-infrared imaging survey of 11 young dwarfs in the Pleiades cluster using the Subaru Telescope and the near-infrared coronagraph imager.We found ten faint point sources, with magnitudes as faint as 20 mag in the K-band,with around seven dwarfs. Comparison with the Spitzer archive images revealed that a pair of the faint sources around V 1171 Tau is very red in infrared wavelengths, which indicates very low-mass young stellar objects. However, the results of our follow-up proper motion measurements implied that the central star and the faint sources do not share common proper motions, suggesting that they are not physically associated.

  3. A Signature of Chromospheric Activity in Brown Dwarfs Revealed by 2.5-5.0 Micron AKARI Spectra

    CERN Document Server

    Sorahana, Satoko; Yamamura, Issei

    2014-01-01

    We propose that the 2.7 micron H_2O, 3.3 micron CH_4 and 4.6 micron CO absorption bands can be good tracers of chromospheric activity in brown dwarfs. In our previous study, we found that there are difficulties in explaining entire spectra between 1.0 and 5.0 microns with the Unified Cloudy Model (UCM), a brown dwarf atmosphere model. Based on simple radiative equilibrium, temperature in a model atmosphere usually decreases monotonically with height. However, if a brown dwarf has a chromosphere, as inferred by some observations, the temperature in the upper atmosphere is higher. We construct a simple model that takes into account heating due to chromospheric activity by setting a temperature floor in an upper atmosphere, and find that the model spectra of 3 brown dwarfs with moderate H-alpha emission, an indicator of chromospheric activity, are considerably improved to match the AKARI spectra. Because of the higher temperatures in the upper atmospheres, the amount of CH_4 molecules is reduced and the absorpti...

  4. ALMA OBSERVATIONS OF {rho}-Oph 102: GRAIN GROWTH AND MOLECULAR GAS IN THE DISK AROUND A YOUNG BROWN DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Ricci, L. [Department of Astronomy, California Institute of Technology, MC 249-17, Pasadena, CA 91125 (United States); Testi, L. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Natta, A. [INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze (Italy); Scholz, A. [School of Cosmic Physics, Dublin Institute for Advanced Studies, 31 Fitzwilliam Place, Dublin 2 (Ireland); De Gregorio-Monsalvo, I., E-mail: lricci@astro.caltech.edu [Joint ALMA Observatory (JAO)/ESO, Alonso de Cordova 3107, Vitacura 763 0335, Santiago de Chile (Chile)

    2012-12-20

    We present ALMA continuum and spectral line observations of the young brown dwarf {rho}-Oph 102 at about 0.89 mm and 3.2 mm. We detect dust emission from the disk at these wavelengths and derive an upper limit on the radius of the dusty disk of {approx}40 AU. The derived variation of the dust opacity with frequency in the millimeter (mm) provides evidence for the presence of mm-sized grains in the disk's outer regions. This result demonstrates that mm-sized grains are found even in the low-density environments of brown dwarf disks and challenges our current understanding of dust evolution in disks. The CO map at 345 GHz clearly reveals molecular gas emission at the location of the brown dwarf, indicating a gas-rich disk as typically found for disks surrounding young pre-main-sequence stars. We derive a disk mass of {approx}0.3%-1% of the mass of the central brown dwarf, similar to the typical values found for disks around more massive young stars.

  5. AKARI OBSERVATIONS OF BROWN DWARFS. III. CO, CO2, AND CH4 FUNDAMENTAL BANDS AND PHYSICAL PARAMETERS

    International Nuclear Information System (INIS)

    We investigate variations in the strengths of three molecular bands, CH4 at 3.3 μm, CO at 4.6 μm, and CO2 at 4.2 μm, in 16 brown dwarf spectra obtained by AKARI. Spectral features are examined along the sequence of source classes from L1 to T8. We find that the CH4 3.3 μm band is present in the spectra of brown dwarfs later than L5, and the CO 4.6 μm band appears in all spectral types. The CO2 absorption band at 4.2 μm is detected in late-L and T-type dwarfs. To better understand brown dwarf atmospheres, we analyze the observed spectra using the Unified Cloudy Model. The physical parameters of the AKARI sample, i.e., atmospheric effective temperature T eff, surface gravity log g, and critical temperature T cr, are derived. We also model IRTF/SpeX and UKIRT/CGS4 spectra in addition to the AKARI data in order to derive the most probable physical parameters. Correlations between the spectral type and the modeled parameters are examined. We confirm that the spectral-type sequence of late-L dwarfs is not related to T eff, but instead originates as a result of the effect of dust.

  6. The spectrum of the recycled PSR J0437-4715 and its white dwarf companion

    CERN Document Server

    Durant, M; Pavlov, G G; Kowalski, P M; Posselt, B; van Kerkwijk, M H; Kaplan, D L

    2011-01-01

    We present extensive spectral and photometric observations of the recycled pulsar/white-dwarf binary containing PSR J0437-4715, which we analyzed together with archival X-ray and gamma-ray data, to obtain the complete mid-infrared to gamma-ray spectrum. We first fit each part of the spectrum separately, and then the whole multi-wavelength spectrum. We find that the optical-infrared part of the spectrum is well fit by a cool white dwarf atmosphere model with pure hydrogen composition. The model atmosphere (Teff = 3950pm150K, log g=6.98pm0.15, R_WD=(1.9pm0.2)e9 cm) fits our spectral data remarkably well for the known mass and distance (M=0.25pm0.02Msun, d=156.3pm1.3pc), yielding the white dwarf age (tau=6.0pm0.5Gyr). In the UV, we find a spectral shape consistent with thermal emission from the bulk of the neutron star surface, with surface temperature between 1.25e5 and 3.5e5K. The temperature of the thermal spectrum suggests that some heating mechanism operates throughout the life of the neutron star. The temp...

  7. A nearby young M dwarf with a wide, possibly planetary-mass companion

    CERN Document Server

    Deacon, Niall R; Murphy, Simon J

    2016-01-01

    We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the $\\sim$45 Myr old Tucana Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708~\\AA~absorption consistent with M dwarfs younger than TucHor but older than the $\\sim$10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the $\\sim$24 Myr old $\\beta$ Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6--...

  8. 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...

  9. 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.

  10. 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...

  11. NEW H2 COLLISION-INDUCED ABSORPTION AND NH3 OPACITY AND THE SPECTRA OF THE COOLEST BROWN DWARFS

    International Nuclear Information System (INIS)

    We present new cloudy and cloudless model atmospheres for brown dwarfs using recent ab initio calculations of the line list of ammonia (NH3) and of the collision-induced absorption of molecular hydrogen (H2). We compare the new synthetic spectra with models based on an earlier description of the H2 and NH3 opacities. We find a significant improvement in fitting the nearly complete spectral energy distribution of the T7p dwarf Gliese 570D and in near-infrared color-magnitude diagrams of field brown dwarfs. We apply these new models to the identification of NH3 absorption in the H-band peak of very late T dwarfs and the new Y dwarfs and discuss the observed trend in the NH3-H spectral index. The new NH3 line list also allows a detailed study of the medium-resolution spectrum of the T9/T10 dwarf UGPS J072227.51–054031.2 where we identify several specific features caused by NH3.

  12. A nearby young M dwarf with a wide, possibly planetary-mass companion

    Science.gov (United States)

    Deacon, N. R.; Schlieder, J. E.; Murphy, S. J.

    2016-04-01

    We present the identification of two previously known young objects in the solar neighbourhood as a likely very wide binary. TYC 9486-927-1, an active, rapidly rotating early-M dwarf, and 2MASS J21265040-8140293, a low-gravity L3 dwarf previously identified as candidate members of the ˜45 Myr old Tucana-Horologium association (TucHor). An updated proper motion measurement of the L3 secondary, and a detailed analysis of the pair's kinematics in the context of known nearby, young stars, reveals that they share common proper motion and are likely bound. New observations and analyses reveal the primary exhibits Li 6708 Å absorption consistent with M dwarfs younger than TucHor but older than the ˜10 Myr TW Hydra association yielding an age range of 10-45 Myr. A revised kinematic analysis suggests the space motions and positions of the pair are closer to, but not entirely in agreement with, the ˜24 Myr old β Pictoris moving group. This revised 10-45 Myr age range yields a mass range of 11.6-15 MJ for the secondary. It is thus likely 2MASS J2126-8140 is the widest orbit planetary-mass object known (>4500 au) and its estimated mass, age, spectral type, and Teff are similar to the well-studied planet β Pictoris b. Because of their extreme separation and youth, this low-mass pair provide an interesting case study for very wide binary formation and evolution.

  13. Studies of the Coldest Brown Dwarfs with the James Webb Space Telescope

    Science.gov (United States)

    Roellig, Thomas L.

    2016-01-01

    The coolest T and Y-class Brown Dwarf objects are very faint and are therefore very poorly understood, since they are barely detectable with the current astronomical instrumentation. The upcoming James Webb Space Telescope now in development for a launch in the Fall of 2018 will have vastly increased sensitivity in the near and mid-infrared compared to any current facilities and will not be affected by telluric absorption over its entire wavelength range of operations. As a result it will be an ideal tool to obtain information about the composition and temperature-pressure structure in these objects' atmospheres. This presentation will outline the JWST guaranteed time observing plans for these studies.

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

    International Nuclear Information System (INIS)

    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☉ and 0.034 M☉, 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 ∼0.02 M☉. 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.

  15. 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

  16. New Ideas in the Theory of Extrasolar Giant Planets and Brown Dwarfs

    CERN Document Server

    Burrows, A; Lunine, J I; Marley, M S; Saumon, D S; Burrows, Adam

    1998-01-01

    We summarize and extend recent work on the theory of extrasolar giant planets (EGPs) and brown dwarfs, paying particular attention to Gliese 229 B, the albedos of EGPs, the compositions of substellar atmospheres, the connections with the giant planets in the solar system, cloud physics, and non-gray spectral synthesis. The role of condensates in altering the optical spectrum of Gliese 229 B is explored, as are the systematics of the reflection spectra from extrasolar giant planets near their primaries. In addition, we discuss the role of convection and disequilibrium chemistry in explaining the anomalous detection of CO in Gliese 229 B. Throughout, we highlight the distinctive chemistry that defines this new class of objects and set goals for future study.

  17. 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.

  18. 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.

  19. 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.

  20. A faint type of supernova from a white dwarf with a helium-rich companion.

    Science.gov (United States)

    Perets, H B; Gal-Yam, A; Mazzali, P A; Arnett, D; Kagan, D; Filippenko, A V; Li, W; Arcavi, I; Cenko, S B; Fox, D B; Leonard, D C; Moon, D-S; Sand, D J; Soderberg, A M; Anderson, J P; James, P A; Foley, R J; Ganeshalingam, M; Ofek, E O; Bildsten, L; Nelemans, G; Shen, K J; Weinberg, N N; Metzger, B D; Piro, A L; Quataert, E; Kiewe, M; Poznanski, D

    2010-05-20

    Supernovae are thought to arise from two different physical processes. The cores of massive, short-lived stars undergo gravitational core collapse and typically eject a few solar masses during their explosion. These are thought to appear as type Ib/c and type II supernovae, and are associated with young stellar populations. In contrast, the thermonuclear detonation of a carbon-oxygen white dwarf, whose mass approaches the Chandrasekhar limit, is thought to produce type Ia supernovae. Such supernovae are observed in both young and old stellar environments. Here we report a faint type Ib supernova, SN 2005E, in the halo of the nearby isolated galaxy, NGC 1032. The 'old' environment near the supernova location, and the very low derived ejected mass ( approximately 0.3 solar masses), argue strongly against a core-collapse origin. Spectroscopic observations and analysis reveal high ejecta velocities, dominated by helium-burning products, probably excluding this as a subluminous or a regular type Ia supernova. We conclude that it arises from a low-mass, old progenitor, likely to have been a helium-accreting white dwarf in a binary. The ejecta contain more calcium than observed in other types of supernovae and probably large amounts of radioactive (44)Ti. PMID:20485429

  1. THE FIRST ULTRA-COOL BROWN DWARF DISCOVERED BY THE WIDE-FIELD INFRARED SURVEY EXPLORER

    International Nuclear Information System (INIS)

    We report the discovery of the first new ultra-cool brown dwarf (BDs) 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 μm 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 BD is easily detected by WISE, with a signal-to-noise ratio of ∼36 at 4.6 μm. Current estimates place it at a distance of 6-10 pc. This object represents the first in what will likely be hundreds of nearby BDs 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, closest stars to our Sun; the discovery of this new BD proves that WISE is capable of fulfilling this objective.

  2. The First Ultra-cool Brown Dwarf Discovered by the Wide-field Infrared Survey Explorer

    Science.gov (United States)

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

    2011-01-01

    We report the discovery of the first new ultra-cool brown dwarf (BDs) 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 μm 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 BD is easily detected by WISE, with a signal-to-noise ratio of ~36 at 4.6 μm. Current estimates place it at a distance of 6-10 pc. This object represents the first in what will likely be hundreds of nearby BDs 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, closest stars to our Sun; the discovery of this new BD proves that WISE is capable of fulfilling this objective.

  3. 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...

  4. 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

    International Nuclear Information System (INIS)

    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.

  5. Probing Substellar Companions of AGB Stars through Spirals and Arcs

    CERN Document Server

    Kim, Hyosun

    2011-01-01

    Recent observations of strikingly well-defined spirals in the circumstellar envelopes of asymptotic giant branch (AGB) stars point to the existence of binary companions in these objects. In the case of planet or brown dwarf mass companions, we investigate the observational properties of the spiral-onion shell wakes due to the gravitational interaction of these companions with the outflowing circumstellar matter. Three dimensional hydrodynamical simulations at high resolution show that the substellar mass objects produce detectable signatures at 100 AU distance, for the wake induced by a Jupiter to brown dwarf mass object orbiting a solar mass AGB star. In particular, the arm pattern propagates with a speed depending on the local wind and sound speeds, implying possible variations in the arm separation in the wind acceleration region and/or in a slow wind with significant temperature variation. The pattern propagation speeds of the inner and outer boundaries differ by twice the sound speed, leading to the over...

  6. The solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry

    Energy Technology Data Exchange (ETDEWEB)

    Lurie, John C. [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Henry, Todd J.; Ianna, Philip A. [RECONS Institute, Chambersburg, PA 17201 (United States); Jao, Wei-Chun; Quinn, Samuel N.; Winters, Jennifer G. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States); Koerner, David W. [Department of Physics and Astronomy, Northern Arizona University, Flagstaff, AZ 86011 (United States); Riedel, Adric R. [Department of Astrophysics, American Museum of Natural History, New York, NY 10034 (United States); Subasavage, John P., E-mail: lurie@uw.edu [United States Naval Observatory, Flagstaff, AZ 86001 (United States)

    2014-11-01

    Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD-10 -3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of 3 to 13 years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9 m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods of 2–12 years. For the six more astrometrically favorable M dwarfs, we conclude that none have brown dwarf companions, and are sensitive to companions with masses as low as 1 M{sub Jup} for periods longer than two years. In particular, we conclude that Proxima Centauri has no Jovian companions at orbital periods of 2–12 years. These results complement previously published M dwarf planet occurrence rates by providing astrometrically determined upper mass limits on potential super-Jupiter companions at orbits of two years and longer. As part of a continuing survey, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the over 250 red dwarfs within 25 pc observed longer than five years in our astrometric program.

  7. The solar neighborhood. XXXIV. A search for planets orbiting nearby M dwarfs using astrometry

    International Nuclear Information System (INIS)

    Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD-10 -3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of 3 to 13 years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9 m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods of 2–12 years. For the six more astrometrically favorable M dwarfs, we conclude that none have brown dwarf companions, and are sensitive to companions with masses as low as 1 MJup for periods longer than two years. In particular, we conclude that Proxima Centauri has no Jovian companions at orbital periods of 2–12 years. These results complement previously published M dwarf planet occurrence rates by providing astrometrically determined upper mass limits on potential super-Jupiter companions at orbits of two years and longer. As part of a continuing survey, these results are consistent with the paucity of super-Jupiter and brown dwarf companions we find among the over 250 red dwarfs within 25 pc observed longer than five years in our astrometric program.

  8. New frontiers of high-resolution spectroscopy: Probing the atmospheres of brown dwarfs and reflected light from exoplanets

    Science.gov (United States)

    Birkby, Jayne; Alonso, Roi; Brogi, Matteo; Charbonneau, David; Fortney, Jonathan; Hoyer, Sergio; Johnson, John Asher; de Kok, Remco; Lopez-Morales, Mercedes; Montet, Ben; Snellen, Ignas

    2015-12-01

    High-resolution spectroscopy (R>25,000) is a robust and powerful tool in the near-infrared characterization of exoplanet atmospheres. It has unambiguously revealed the presence of carbon monoxide and water in several hot Jupiters, measured the rotation rate of beta Pic b, and suggested the presence of fast day-to-night winds in one atmosphere. The method is applicable to transiting, non-transiting, and directly-imaged planets. It works by resolving broad molecular bands in the planetary spectrum into a dense, unique forest of individual lines and tracing them directly by their Doppler shift, while the star and tellurics remain essentially stationary. I will focus on two ongoing efforts to expand this technique. First, I will present new results on 51 Peg b revealing its infrared atmospheric compositional properties, then I will discuss an ongoing optical HARPS-N/TNG campaign (due mid October 2015) to obtain a detailed albedo spectrum of 51 Peg b at 387-691 nm in bins of 50nm. This spectrum would provide strong constraints on the previously claimed high albedo and potentially cloudy nature of this planet. Second, I will discuss preliminary results from Keck/NIRSPAO observations (due late September 2015) of LHS 6343 C, a 1000 K transiting brown dwarf with an M-dwarf host star. The high-resolution method converts this system into an eclipsing, double-lined spectroscopic binary, thus allowing dynamical mass and radius estimates of the components, free from astrophysical assumptions. Alongside probing the atmospheric composition of the brown dwarf, these data would provide the first model-independent study of the bulk properties of an old brown dwarf, with masses accurate to <5%, placing a crucial constraint on brown dwarf evolution models.

  9. 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.

  10. 2MASS J035523.37+113343.7: A YOUNG, DUSTY, NEARBY, ISOLATED BROWN DWARF RESEMBLING A GIANT EXOPLANET

    International Nuclear Information System (INIS)

    We present parallax and proper motion measurements, near-infrared spectra, and Wide-field Infrared Survey Explorer photometry for the low surface gravity L5γ 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 ∼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 μm, 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.

  11. A Substellar Companion to the Dusty Pleiades Star HD 23514

    CERN Document Server

    Rodriguez, David R; Zuckerman, B; Macintosh, Bruce; Melis, Carl

    2011-01-01

    With adaptive optics imaging at Keck observatory, we have discovered a substellar companion to the F6 Pleiades star HD 23514, one of the dustiest main-sequence stars known to date (L_{IR}/L_{*}~2%). This is one of the first brown dwarfs discovered as a companion to a star in the Pleiades. The 0.06 M$_\\odot$ late-M secondary has a projected separation of ~360 AU. The scarcity of substellar companions to stellar primaries in the Pleiades combined with the extremely dusty environment make this a unique system to study.

  12. Planets Around Low-Mass Stars (PALMS). III. A Young Dusty L Dwarf Companion at the Deuterium-Burning Limit

    CERN Document Server

    Bowler, Brendan P; Shkolnik, Evgenya L; Dupuy, Trent J

    2013-01-01

    We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.45" (~52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R~3800) 1.5-2.4 $\\mu$m spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the ~120 Myr AB Dor young moving group based on the photometric distance to the primary (36 +/- 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I $\\lambda$6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of ~10-120 Myr is possible. The age...

  13. 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...

  14. First results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low Mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    CERN Document Server

    Carlin, Jeffrey L; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F; Brodie, Jean P; Crnojević, Denija; Forbes, Duncan A; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H G; Romanowsky, Aaron J; Strader, Jay

    2016-01-01

    We report the discovery of the faintest known dwarf galaxy satellite of an LMC stellar-mass host beyond the Local Group, based on deep imaging with Subaru/Hyper Suprime-Cam. MADCASH J074238+652501-dw lies $\\sim$35 kpc in projection from NGC 2403, a dwarf spiral galaxy at $D$$\\approx$3.2 Mpc. This new dwarf has $M_{g} = -7.4\\pm0.4$ and a half-light radius of $168\\pm70$ pc, at the calculated distance of $3.39\\pm0.41$ Mpc. The color-magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low luminosity dwarfs in the Local Group. The lack of either detected HI gas ($M_{\\rm HI}/L_{V} < 0.69 M_\\odot/L_\\odot$, based on Green Bank Telescope observations) or $GALEX$ NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH (Magellanic Analog Dwarf Companions And Stellar Halos) survey, which is conducting a census of the stellar substructure and faint satellites in the halos...

  15. OGLE-2005-BLG-071Lb, the Most Massive M-Dwarf Planetary Companion?

    CERN Document Server

    Dong, Subo; Udalski, Andrzej; Anderson, Jay; Christie, G W; Gaudi, B S; Jaroszynski, M; Kubiak, M; Szymanski, M K; Pietrzynski, G; Soszynski, I; Szewczyk, O; Ulaczyk, K; Wyrzykowski, L; De Poy, D L; Fox, D B; Gal-Yam, A; Han, C; Lepine, S; McCormick, J; Ofek, E; Park, B -G; Pogge, R W; Abe, F; Bennett, D P; Bond, I A; Britton, T R; Gilmore, A C; Hearnshaw, J B; Itow, Y; Kamiya, K; Kilmartin, P M; Korpela, A; Masuda, K; Matsubara, Y; Motomura, M; Muraki, Y; Nakamura, S; Ohnishi, K; Okada, C; Rattenbury, N; Saito, To; Sako, T; Sasaki, M; Sullivan, D; Sumi, T; Tristram, P J; Yanagisawa, T; Yock, P C M; Yoshoika, T; Albrow, M D; Beaulieu, J P; Brillant, S; Calitz, H; Cassan, A; Cook, K H; Coutures, Ch; Dieters, S; Prester, D Dominis; Donatowicz, J; Fouqué, P; Greenhill, J; Hill, K; Hoffman, M; Horne, K; Jørgensen, U G; Kane, S; Kubas, D; Marquette, J B; Martin, R; Meintjes, P; Menzies, J; Pollard, K R; Sahu, K C; Vinter, C; Wambsganss, J; Williams, A; Bode, M; Bramich, D M; Burgdorf, M; Snodgrass, C; Steele, I; Doublier, Vanessa; Foelmi, Cedric

    2008-01-01

    We combine all available information to constrain the nature of OGLE-2005-BLG-071Lb, the second planet discovered by microlensing and the first in a high-magnification event. These include photometric and astrometric measurements from Hubble Space Telescope, as well as constraints from higher-order effects extracted from the ground-based light curve, such as microlens parallax, planetary orbital motion and finite-source effects. Our primary analysis leads to the conclusion that the host of Jovian planet OGLE-2005-BLG-071Lb is a foreground M dwarf, with mass M = 0.46 +/- 0.04 Msun, distance D_lens = 3.3 +/- 0.4 kpc, and thick-disk kinematics v_LSR ~ 103 km/s. From the best-fit model, the planet has mass M_p = 3.5 +/- 0.3 M_Jup, lies at a projected separation r_perp = 3.6 +/- 0.2 AU from its host and has an equilibrium temperature of T ~ 50 K, i.e., similar to Neptune. A degenerate model less favored by \\Delta\\chi^2 ~ 4 gives essentially the same planetary mass M_p = 3.3 +/- 0.4 M_Jup with a smaller projected s...

  16. On the formation of eccentric millisecond pulsars with helium white-dwarf companions

    CERN Document Server

    Antoniadis, John

    2014-01-01

    Millisecond pulsars (MSPs) orbiting helium white-dwarfs (WD) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris (2014) recently proposed that these binary MSPs may instead form from the rotationally-delayed accretion-induced collapse of a massive WD. This scenario predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities -- in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (10^4-10^5 yrs disk can result to eccentricities of e ~ 0.01-0.15 for orbital per...

  17. ON THE FORMATION OF ECCENTRIC MILLISECOND PULSARS WITH HELIUM WHITE-DWARF COMPANIONS

    International Nuclear Information System (INIS)

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire and Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ≅ 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range

  18. On the Formation of Eccentric Millisecond Pulsars with Helium White-dwarf Companions

    Science.gov (United States)

    Antoniadis, John

    2014-12-01

    Millisecond pulsars (MSPs) orbiting helium white dwarfs (WDs) in eccentric orbits challenge the established binary-evolution paradigm that predicts efficient orbital circularization during the mass-transfer episode that spins up the pulsar. Freire & Tauris recently proposed that these binary MSPs may instead form from the rotationally delayed accretion-induced collapse of a massive WD. However, their hypothesis predicts that eccentric systems preferably host low-mass pulsars and travel with small systemic velocities—in tension with new observational constraints. Here, I show that a substantial growth in eccentricity may alternatively arise from the dynamical interaction of the binary with a circumbinary disk. Such a disk may form from ejected donor material during hydrogen flash episodes, when the neutron star is already an active radio pulsar and tidal forces can no longer circularize the binary. I demonstrate that a short-lived (104-105 yr) disk can result in eccentricities of e ~= 0.01-0.15 for orbital periods between 15 and 50 days. Finally, I propose that, more generally, the disk hypothesis may explain the lack of circular binary pulsars for the aforementioned orbital-period range.

  19. An eccentric binary millisecond pulsar with a helium white dwarf companion in the Galactic Field

    CERN Document Server

    Antoniadis, John; Stovall, Kevin; Freire, Paulo C; Deneva, Julia S; Koester, Detlev; Jenet, Frederick; Martinez, Jose

    2016-01-01

    Low-mass white dwarfs (LMWDs) are believed to be exclusive products of binary evolution, as the Universe is not yet old enough to produce them from single stars. Because of the strong tidal forces operating during the binary interaction phase, the remnant host systems observed today are expected to have negligible eccentricities. Here, we report on the first unambiguous identification of a LMWD in an eccentric (e=0.13) orbit with a millisecond pulsar, which directly contradicts this picture. We use our spectra and radio-timing solution (derived elsewhere) to infer the WD temperature T_eff = 8600 +/- 190 K) and 3D systemic velocity (179.5 km\\s). We also place model-independent constraints on the WD radius (R_WD = 0.024+/- 0.004/0.002 R_sun) and surface gravity (log g = 7.11 +/- 0.08/0.16 dex). The WD and kinematic properties are consistent with the expectations for low-mass X-ray binary evolution and disfavour a three-body formation channel. In the case of the high eccentricity being the result of a spontaneou...

  20. Assessing nucleation in cloud formation modelling for Brown Dwarf and Exoplanet atmospheres

    Science.gov (United States)

    Lee, Graham; Helling, Christiane; Giles, Helen; Bromley, Stefan

    2015-04-01

    Context. Substellar objects such as Brown Dwarfs and hot Jupiter exoplanets are cool enough that clouds can form in their atmospheres (Helling & Casewell 2014; A&ARv 22)). Unlike Earth, where cloud condensation nuclei are provided by the upward motion of sand or ash, in Brown Dwarf and hot Jupiters these condensation seeds form from the gas phase. This process proceeds in a stepwise chemical reaction of single monomer addition of a single nucleation species, referred to as homogeneous nucleation. The rate at which these seeds form is determined by the local thermodynamic conditions and the chemical composition of the local gas phase. Once the seed particles have formed, multiple materials are thermally stable and grow almost simultaneously by chemical surface reactions. This results in the growth of the condensation seeds to macroscopic particles of μm size. At the same time, the gas phase becomes depleted. Once temperatures become too high for thermal stability of the cloud particle, it evaporates until its constituents return to the gas phase. Convection from deeper atmospheric layers provides element replenishment to upper, cooler layers allowing the cloud formation process to reach a stationary state (Woitke & Helling 2003; A&A 399). Aims. The most efficient nucleation is a 'winner takes all' process as the losing molecules will condense on the surface of the faster nucleating seed particle. We apply new molecular (TiO2)N-cluster and SiO vapour data to our cloud formation model in order to re-asses the question of the primary nucleation species. Methods. We apply density functional theory (B3LYP, 6-311G(d)) 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 both TiO2 and SiO as primary nucleates assuming a homogeneous nucleation process and by solving a system of dust moment equations and element conservation for a pre-scribed Brown Dwarf

  1. A search for brown dwarf like secondaries in cataclysmic variables - II

    Science.gov (United States)

    Mennickent, R. E.; Diaz, M. P.; Tappert, C.

    2004-02-01

    We have examined VTL/ISAAC 1-2.5 μm spectroscopy of a sample of short-orbital-period cataclysmic variables which are candidates for harbouring substellar companions. We provide descriptions of the infrared spectra of EI Psc, V834 Cen, WX Cet, VW Hyi, TY PsA and BW Scl. Fitting of the infrared (IR) spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. Absorption features of the secondary star were detected in EI Psc and V834 Cen, consistent with dwarf secondaries of spectral type K 5 +/- 1 and M 8 +/- 0.5, respectively. In addition, we report the first detection of the secondary star in VW Hyi. The SED in this case is well matched by an L 0 +/- 2 type secondary contributing 23 per cent to the overall flux at λ= 1.15 μm. This is a surprising result for a system with a relatively high mass transfer rate. We discuss the implication of our findings on the current scenarios for cataclysmic variable star evolution.

  2. Search for brown-dwarf like secondaries in cataclysmic variables II

    CERN Document Server

    Mennickent, R E; Tappert, C

    2004-01-01

    We have examined VTL/ISAAC 1-2.5 $\\umu$m spectroscopy of a sample of short orbital period cataclysmic variables which are candidates for harboring substellar companions. We provide descriptions of the infrared spectrum of \\hbox{EI Psc}, \\hbox{V834 Cen}, \\hbox{WX Cet}, \\hbox{VW Hyi}, \\hbox{TY PsA} and \\hbox{BW Scl}. Fitting of the IR spectral energy distribution (SED) was performed by comparing the observed spectrum with late-type templates. Absorption features of the secondary star were detected in \\hbox{EI Psc} and \\hbox{V834 Cen}, consistent with dwarf secondaries of spectral type K 5 $\\pm$ 1 and M 8 $\\pm$ 0.5, respectively. In addition, we report the first detection of the secondary star in \\hbox{VW Hyi}. The SED in this case is well matched by an L 0 $\\pm$ 2 type secondary contributing 23 per cent to the overall flux at $\\lambda$ = 1.15 $\\umu$m. This is a surprising result for a system with a relatively high mass transfer rate. We discuss the implication of our findings on the current scenarios for catacl...

  3. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION

    International Nuclear Information System (INIS)

    Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor 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 Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (≥10–7) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén 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 neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10–6-1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H2, or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks

  4. IONIZATION IN ATMOSPHERES OF BROWN DWARFS AND EXTRASOLAR PLANETS. V. ALFVÉN IONIZATION

    Energy Technology Data Exchange (ETDEWEB)

    Stark, C. R.; Helling, Ch.; Rimmer, P. B. [SUPA, School of Physics and Astronomy, University of St Andrews, St Andrews, KY16 9SS (United Kingdom); Diver, D. A., E-mail: craig.stark@st-andrews.ac.uk [SUPA, School of Physics and Astronomy, Kelvin Building, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

    2013-10-10

    Observations of continuous radio and sporadic X-ray emission from low-mass objects suggest they harbor 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 Alfvén ionization as a mechanism for producing localized pockets of ionized gas in the atmosphere, having sufficient degrees of ionization (≥10{sup –7}) that they constitute plasmas. We outline the criteria required for Alfvén ionization and demonstrate its applicability in the atmospheres of low-mass objects such as giant gas planets, brown dwarfs, and M dwarfs with both solar and sub-solar metallicities. We find that Alfvén 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 neutral flows are the smallest. For the model atmospheres considered, our results show that degrees of ionization of 10{sup –6}-1 can be obtained as a result of Alfvén ionization. Observable consequences include continuum bremsstrahlung emission, superimposed with spectral lines from the plasma ion species (e.g., He, Mg, H{sub 2}, or CO lines). Forbidden lines are also expected from the metastable population. The presence of an atmospheric plasma opens the door to a multitude of plasma and chemical processes not yet considered in current atmospheric models. The occurrence of Alfvén ionization may also be applicable to other astrophysical environments such as protoplanetary disks.

  5. A CHANDRA OBSERVATION OF THE TW HYDRAE ASSOCIATION BROWN DWARF 2MASSW J1139511-315921

    International Nuclear Information System (INIS)

    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 3σ confidence level. We find an X-ray luminosity of LX = 1.4+2.7-1.0 x 1026 erg s-1 or log LX/Lbol = -4.8 ± 0.3. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B): both have Hα 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 LX = 4 x 1027 erg s-1 or log LX/Lbol = -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 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 explained by rotation alone. We also examine two X-ray bright objects in the field of view of our Chandra observations and find one to be of spectral type K0IV and identify it as a possible RS Canum Venaticorum, and another X-ray bright object whose light curve clearly shows the decay phase of an X-ray flare.

  6. 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...

  7. 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...

  8. 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...

  9. 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.

  10. 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 ...

  11. 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...

  12. Constraints on the binary Properties of mid to late T dwarfs from Hubble Space Telescope WFC3 Observations

    CERN Document Server

    Aberasturi, M; Mora, A; Solano, E; Mart\\'\\in, E L; Reid, I N; Looper, D

    2014-01-01

    We used HST/WFC3 observations of a sample of 26 nearby ($\\le$20 pc) mid to late T dwarfs to search for cooler companions and measure the multiplicity statistics of brown dwarfs. Tightly-separated companions were searched for using a double-PSF fitting algorithm. We also compared our detection limits based on simulations to other prior T5+ brown dwarf binary programs. No new wide or tight companions were identified, which is consistent with the number of known T5+ binary systems and the resolution limits of WFC3. We use our results to add new constraints to the binary fraction of T-type brown dwarfs. Modeling selection effects and adopting previously derived separation and mass ratio distributions, we find an upper limit total binary fraction of <16% and <25% assuming power law and flat mass ratio distributions respectively, which are consistent with previous results. We also characterize a handful of targets around the L/T transition.

  13. Wide, Cool and Ultracool Companions to Nearby Stars from Pan-STARRS1

    CERN Document Server

    Deacon, Niall R; Magnier, Eugene A; Aller, Kimberly M; Best, William M J; Dupuy, Trent; Bowler, Brendan P; Mann, Andrew W; Redstone, Joshua A; Burgett, William S; Chambers, Kenneth C; Draper, Peter W; Flewelling, H; Hodapp, Klaus W; Kaiser, Nick; Kudritzki, Rolf-Peter; Morgan, Jeff S; Metcalfe, Nigel; Price, Paul A; Tonry, John L; Wainscoat, Richard J

    2014-01-01

    We present the discovery of 61 wide (>5 arcsecond) separation, low-mass (stellar and substellar) companions to stars in the solar neighborhood identified from Pan-STARRS\\,1 (PS1) data and the spectral classification of 27 previously known companions. Our companions represent a selective subsample of promising candidates and span a range in spectral type of K7-L9 with the addition of one DA white dwarf. These were identified primarily from a dedicated common proper motion search around nearby stars, along with a few as serendipitous discoveries from our Pan-STARRS1 brown dwarf search. Our discoveries include 24 new L dwarf companions and one known L dwarf not previously identified as a companion. The primary stars around which we searched for companions come from a list of bright stars with well-measured parallaxes and large proper motions from the Hipparcos catalog (8583 stars, mostly A-K~dwarfs) and fainter stars from other proper motion catalogues (79170 stars, mostly M~dwarfs). We examine the likelihood th...

  14. 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...

  15. 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...

  16. 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...

  17. 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...

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

    Science.gov (United States)

    Simon, Amy A.; 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.

    2016-02-01

    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.

  19. 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. ...

  20. 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...

  1. Evolution of brown dwarf disks: A Spitzer survey in Upper Scorpius

    CERN Document Server

    Scholz, A; Wood, K; Meeus, G; Stelzer, B; Walker, C; O'Sullivan, M; Scholz, Alexander; Jayawardhana, Ray; Wood, Kenneth; Meeus, Gwendolyn; Stelzer, Beate; Walker, Christina; Sullivan, Mark O'

    2007-01-01

    We have carried out a Spitzer survey for brown dwarf (BD) disks in the ~5 Myr old Upper Scorpius (UpSco) star forming region, using IRS spectroscopy from 8 to 12\\mu m and MIPS photometry at 24\\mu m. Our sample consists of 35 confirmed very low mass members of UpSco. Thirteen objects in this sample show clear excess flux at 24\\mu m, explained by dust emission from a circum-sub-stellar disk. Objects without excess emission either have no disks at all or disks with inner opacity holes of at least ~5 AU radii. Our disk frequency of 37\\pm 9% is higher than what has been derived previously for K0-M5 stars in the same region (on a 1.8 sigma confidence level), suggesting a mass-dependent disk lifetime in UpSco. The clear distinction between objects with and without disks as well as the lack of transition objects shows that disk dissipation inside 5 AU occurs rapidly, probably on timescales of <~10^5 years. For the objects with disks, most SEDs are uniformly flat with flux levels of a few mJy, well modeled as emiss...

  2. 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...

  3. Spitzer and z' Secondary Eclipse Observations of the Highly Irradiated Transiting Brown Dwarf KELT-1b

    CERN Document Server

    Beatty, Thomas G; Fortney, Jonathan; Knutson, Heather; Gaudi, B Scott; Bruns, Jacob M; Showman, Adam P; Eastman, Jason; Pepper, Joshua; Siverd, Robert; Stassun, Keivan G; Kielkopf, John F

    2013-01-01

    We present secondary eclipse observations of the highly irradiated transiting brown dwarf KELT-1b. Using the Spitzer Space Telescope, we measure secondary eclipse depths of 0.195+/-0.010% at 3.6um and 0.200+/-0.012% at 4.5um, corresponding to a fairly grey color of [3.6]-[4.5]=0.07+/-0.11. Using four separate ground-based light curves, we find tentative evidence for the secondary eclipse in the z' band with a depth of 0.049+/-0.023%. These observations suggest that the amount of heat redistribution in the atmosphere to the night side is very low, and prefer a model in which there is no TiO inversion and a strong substellar hotspot. However, models with no TiO and a more mild hotspot, or with TiO absorption and complete dayside redistribution, are only marginally disfavored. The eclipse timings and durations indicate that the orbital eccentricity of KELT-1b is consistent with circular to better than a percent. These observations represent the first constraints on the atmospheric dynamics of a highly irradiated...

  4. Characterizing the disk around the TW Hydrae Association brown dwarf 2MASSW J1207334-393254

    CERN Document Server

    Gizis, B R J E

    2007-01-01

    We present detailed modeling of the disk around the TW Hydrae Association (TWA) brown dwarf 2MASSW J1207334-393254 (2M1207), using {\\it Spitzer} observations from 3.6 to 24 $\\micron$. The spectral energy distribution (SED) does not show a high amount of flaring. We have obtained a good fit using a flat disk of mass between $10^{-4}$ and $10^{-6}$ $M_{\\sun}$, $\\dot{M}$ $\\la10^{-11} M_{\\sun}$/yr and a large inclination angle between 60$\\degr$ and 70$\\degr$. We have used three different grain models to fit the 10 $\\micron$ Si emission feature, and have found the results to be consistent with ISM-like dust. In comparison with other TWA members, this suggests lesser dust processing for 2M1207 which could be explained by mechanisms such as aggregate fragmentation and/or turbulent mixing. We have found a good fit using an inner disk radius equal to the dust sublimation radius, which indicates the absence of an inner hole in the disk. This suggests the presence of a small K-$L^{\\prime}$ excess, similar to the observe...

  5. 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

  6. 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...

  7. 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...

  8. 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...

  9. 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...

  10. 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...

  11. 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...

  12. PLANETS AROUND LOW-MASS STARS. III. A YOUNG DUSTY L DWARF COMPANION AT THE DEUTERIUM-BURNING LIMIT ,

    International Nuclear Information System (INIS)

    We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.''45 (≈52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R ≈ 3800) 1.5-2.4 μm spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the ∼120 Myr AB Dor young moving group based on the photometric distance to the primary (36 ± 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I λ6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of ∼10-120 Myr is possible. The age and luminosity of 2MASS 0122-2439 B fall in a strip where ''hot-start'' evolutionary model mass tracks overlap as a result of deuterium burning. Several known substellar companions also fall in this region (2MASS J0103-5515 ABb, AB Pic b, κ And b, G196-3 B, SDSS 2249+0044 B, LP 261-75 B, HD 203030 B, and HN Peg B), but their dual-valued mass predictions have largely been unrecognized. The implied mass of 2MASS 0122-2439 B is ≈12-13 MJup or ≈22-27 MJup if it is an AB Dor member, or possibly as low as 11 MJup if the wider age range is adopted. Evolutionary models predict an effective temperature for 2MASS 0122-2439 B that corresponds to spectral types near the L/T transition (≈1300-1500 K) for field objects. However, we find a mid-L near-infrared spectral type, indicating that 2MASS 0122-2439 B represents another case of photospheric dust being retained to cooler temperatures at low surface gravities, as seen in the spectra of young (8-30 Myr) planetary

  13. Planets around Low-mass Stars. III. A Young Dusty L Dwarf Companion at the Deuterium-burning Limit

    Science.gov (United States)

    Bowler, Brendan P.; Liu, Michael C.; Shkolnik, Evgenya L.; Dupuy, Trent J.

    2013-09-01

    We report the discovery of an L-type companion to the young M3.5V star 2MASS J01225093-2439505 at a projected separation of 1.''45 (≈52 AU) as part of our adaptive optics imaging search for extrasolar giant planets around young low-mass stars. 2MASS 0122-2439 B has very red near-infrared colors similar to the HR 8799 planets and the reddest known young/dusty L dwarfs in the field. Moderate-resolution (R ≈ 3800) 1.5-2.4 μm spectroscopy reveals a near-infrared spectral type of L4-L6 and an angular H-band shape, confirming its cool temperature and young age. The kinematics of 2MASS 0122-2439 AB are marginally consistent with members of the ~120 Myr AB Dor young moving group based on the photometric distance to the primary (36 ± 4 pc) and our radial velocity measurement of 2MASS 0122-2439 A from Keck/HIRES. We adopt the AB Dor group age for the system, but the high energy emission, lack of Li I λ6707 absorption, and spectral shape of 2MASS 0122-2439 B suggest a range of ~10-120 Myr is possible. The age and luminosity of 2MASS 0122-2439 B fall in a strip where "hot-start" evolutionary model mass tracks overlap as a result of deuterium burning. Several known substellar companions also fall in this region (2MASS J0103-5515 ABb, AB Pic b, κ And b, G196-3 B, SDSS 2249+0044 B, LP 261-75 B, HD 203030 B, and HN Peg B), but their dual-valued mass predictions have largely been unrecognized. The implied mass of 2MASS 0122-2439 B is ≈12-13 M Jup or ≈22-27 M Jup if it is an AB Dor member, or possibly as low as 11 M Jup if the wider age range is adopted. Evolutionary models predict an effective temperature for 2MASS 0122-2439 B that corresponds to spectral types near the L/T transition (≈1300-1500 K) for field objects. However, we find a mid-L near-infrared spectral type, indicating that 2MASS 0122-2439 B represents another case of photospheric dust being retained to cooler temperatures at low surface gravities, as seen in the spectra of young (8-30 Myr) planetary

  14. The kinematics of very low mass dwarfs: splinter session summary

    CERN Document Server

    Burgasser, Adam J; Schmidt, Sarah; West, Andrew A; Osorio, Maria Rosa Zapatero; Pineda, J Sebastian; Burningham, Ben; Nicholls, C; Sanderson, Robyn; Shkolnik, Evgenya; Rodriguez, David; Riedel, Adric; Joergens, Viki

    2013-01-01

    Kinematic investigations are being increasingly deployed in studies of the lowest mass stars and brown dwarfs to investigate their origins, characterize their atmospheres, and examine the evolution of their physical parameters. This article summarizes the contributions made at the Kinematics of Very Low Mass Dwarfs Splinter Session. Results discussed include analysis of kinematic distributions of M, L and T dwarfs; theoretical tools for interpreting these distributions; identifications of very low mass halo dwarfs and wide companions to nearby stars; radial velocity variability among young and very cool brown dwarfs; and the search and identification of M dwarfs in young moving groups. A summary of discussion points at the conclusion of the Splinter is also presented.

  15. Discovery of a 0.15" Binary Brown Dwarf 2MASSJ 1426316+155701 With Gemini/Hokupa'a Adaptive Optics

    CERN Document Server

    Close, L M; Brandner, W; Lloyd-Hart, M; Liebert, J; Burrows, A; Siegler, N

    2002-01-01

    Use of the highly sensitive Hokupa'a curvature wavefront sensor has allowed for the first time direct adaptive optics (AO) guiding on brown dwarfs and VLM stars (SpT=M7-L2). An initial survey of 9 such objects discovered one 0.15" binary (2MASSJ 1426316+155701). The companion is about half as bright as the primary (Delta K = 0.61+/-0.05$, Delta H = 0.70+/-0.05) and has even redder colors H-K=0.59+/-0.14 than the primary. The blended spectrum of the binary has been previously determined to be M9.0. We modeled a blend of an M8.5 template and a L1-L3 template reproducing a M9.0 spectrum in the case of Delta K = 0.61+/-0.05,Delta H = 0.70\\pm0.05$. These spectral types also match the observed H-K colors of each star. Based the previously observed low space motion and $H_{\\alpha}$ activity we assign an age of $0.8^{+6.7}_{-0.3} Gyr$. Utilizing this age range and the latest DUSTY models of the Lyon group we assign a photometric distance of $18.8^{+1.44}_{-1.02} pc$ and masses of $M_{A}=0.074^{+0.005}_{-0.011} M_\\odo...

  16. First Light LBT AO Images of HR 8799 bcde at 1.65 and 3.3 Microns: New Discrepancies between Young Planets and Old Brown Dwarfs

    CERN Document Server

    Skemer, Andrew J; Esposito, Simone; Burrows, Adam; Leisenring, Jarron; Skrutskie, Michael; Desidera, Silvano; Mesa, Dino; Arcidiacono, Carmelo; Mannucci, Filippo; Rodigas, Timothy J; Close, Laird; McCarthy, Don; Kulesa, Craig; Agapito, Guido; Apai, Daniel; Argomedo, Javier; Bailey, Vanessa; Boutsia, Konstantina; Briguglio, Runa; Brusa, Guido; Busoni, Lorenzo; Claudi, Riccardo; Eisner, Joshua; Fini, Luca; Follette, Katherine B; Garnavich, Peter; Gratton, Raffaele; Guerra, Juan Carlos; Hill, John M; Hoffmann, William F; Jones, Terry; Krejny, Megan; Males, Jared; Masciadri, Elena; Meyer, Michael R; Miller, Douglas L; Morzinski, Katie; Nelson, Matthew; Pinna, Enrico; Puglisi, Alfio; Quanz, Sascha P; Quiros-Pacheco, Fernando; Riccardi, Armando; Stefanini, Paolo; Vaitheeswaran, Vidhya; Wilson, John C; Xompero, Marco

    2012-01-01

    As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H-band and 3.3 microns with the new LBT adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3$ micron photometry of the innermost planet (for the first time) and put strong upper-limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 microns compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 microns due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres, but find that removing CH4 to fit the 3.3 micron photometry increases the predicted L' (3.8 microns) flux enough that it is inconsistent with observations. In an effort to fit the ...

  17. 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.

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

    International Nuclear Information System (INIS)

    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 ☉, 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 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

  19. Deep Near-IR Observations of the Globular Cluster M4: Hunting for Brown Dwarfs

    Science.gov (United States)

    Dieball, A.; Bedin, L. R.; Knigge, C.; Rich, R. M.; Allard, F.; Dotter, A.; Richer, H.; Zurek, D.

    2016-01-01

    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.

  20. 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...

  1. 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...

  2. 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...

  3. First Results from the MADCASH Survey: A Faint Dwarf Galaxy Companion to the Low-mass Spiral Galaxy NGC 2403 at 3.2 Mpc

    Science.gov (United States)

    Carlin, Jeffrey L.; Sand, David J.; Price, Paul; Willman, Beth; Karunakaran, Ananthan; Spekkens, Kristine; Bell, Eric F.; Brodie, Jean P.; Crnojević, Denija; Forbes, Duncan A.; Hargis, Jonathan; Kirby, Evan; Lupton, Robert; Peter, Annika H. G.; Romanowsky, Aaron J.; Strader, Jay

    2016-09-01

    We report the discovery of the faintest known dwarf galaxy satellite of a Large Magellanic Cloud (LMC) stellar-mass host beyond the Local Group (LG), based on deep imaging with Subaru/Hyper Suprime-Cam. Magellanic Analog Dwarf Companions And Stellar Halos (MADCASH) J074238+652501-dw lies ˜35 kpc in projection from NGC 2403, a dwarf spiral galaxy at D ≈ 3.2 Mpc. This new dwarf has {M}g=-7.4+/- 0.4 and a half-light radius of 168 ± 70 pc, at the calculated distance of 3.39 ± 0.41 Mpc. The color–magnitude diagram reveals no evidence of young stellar populations, suggesting that MADCASH J074238+652501-dw is an old, metal-poor dwarf similar to low-luminosity dwarfs in the LG. The lack of either detected HI gas ({M}{HI}/{L}V\\lt 0.69 {M}ȯ /{L}ȯ , based on Green Bank Telescope observations) or GALEX NUV/FUV flux enhancement is consistent with a lack of young stars. This is the first result from the MADCASH survey, which is conducting a census of the stellar substructure and faint satellites in the halos of Local Volume LMC analogs via resolved stellar populations. Models predict a total of ˜4–10 satellites at least as massive as MADCASH J074238+652501-dw around a host with the mass of NGC 2403, with 2–3 within our field of view, slightly more than the one such satellite observed in our footprint. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  4. A HERSCHEL SURVEY OF COLD DUST IN DISKS AROUND BROWN DWARFS AND LOW-MASS STARS

    International Nuclear Information System (INIS)

    We report the complete photometric results from our Herschel study which is the first comprehensive program to search for far-infrared emission from cold dust around young brown dwarfs (BDs). We surveyed 50 fields containing 51 known or suspected BDs and very low mass stars that have evidence of circumstellar disks based on Spitzer photometry and/or spectroscopy. The objects with known spectral types range from M3 to M9.5. Four of the candidates were subsequently identified as extragalactic objects. Of the remaining 47 we have successfully detected 36 at 70 μm and 14 at 160 μm with signal-to-noise ratio (S/N) greater than 3, as well as several additional possible detections with low S/N. The objects exhibit a range of [24]-[70] μm colors suggesting a range in mass and/or structure of the outer disk. We present modeling of the spectral energy distributions of the sample and discuss trends visible in the data. Using two Monte Carlo radiative transfer codes we investigate disk masses and geometry. We find a very wide range in modeled total disk masses from less than 10–6 M☉ up to 10–3 M☉ with a median disk mass of the order of 3 × 10–5 M☉, suggesting that the median ratio of disk mass to central object mass may be lower than for T Tauri stars. The disk scale heights and flaring angles, however, cover a range consistent with those seen around T Tauri stars. The host clouds in which the young BDs and low-mass stars are located span a range in estimated age from ∼1-3 Myr to ∼10 Myr and represent a variety of star-forming environments. No obvious dependence on cloud location or age is seen in the disk properties, though the statistical significance of this conclusion is not strong.

  5. DETECTION OF BROWN DWARF LIKE OBJECTS IN THE CORE OF NGC 3603

    International Nuclear Information System (INIS)

    We used near-infrared data obtained with the Wide Field Camera 3 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 a combination of narrow- and medium-band filters which span the J and H bands and are particularly sensitive to the presence of the 1.3-1.5 μm H2O molecular band unique to BDs. We provide a calibration of the relationship between effective temperature and color for both field stars and BDs. This photometric method provides effective temperatures for BDs to an accuracy of ±350 K 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 temperatures between 1700 and 2200 K, typical of BDs, observed J-band magnitudes in the range 19.5-21.5, and that are strongly clustered toward the luminous core of NGC 3603. However, if these are located at the distance of the cluster, they are far too luminous to be normal BDs. We argue that it is unlikely that these objects are either artifacts of our data set, normal field BDs/M-type giants, or extragalactic contaminants and, therefore, might represent a new class of stars having the effective temperatures of BDs but with luminosities of more massive stars. We explore the interesting scenario in which these objects would be normal stars that have recently tidally ingested a hot Jupiter, the remnants of which are providing a short-lived extended photosphere to the central star. In this case, we would expect them to show the signature of fast rotation.

  6. 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...

  7. 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.

  8. Hubble Space Telescope Observations of Binary Very-Low-Mass Stars and Brown Dwarfs

    OpenAIRE

    Gizis, J. E.; Reid, I N; Knapp, G. R.; Liebert, J.; Kirkpatrick, J. D.; Koerner, D. W.; Burgasser, A. J.

    2003-01-01

    We present analysis of Hubble Space Telescope images of 82 nearby field late-M and L dwarfs. We resolve 13 of these systems into double M/L dwarf systems and identify an additional possible binary. Combined with previous observations of 20 L dwarfs, we derive an observed binary fraction for ultracool dwarfs of 17+4-3%, where the statistics included systems with separations in the range 1.6-16 A.U. We argue that accounting for biases and incompleteness leads to an estimated binary fraction 15+...

  9. Substellar Companions to Evolved Intermediate-Mass Stars: HD 145457 and HD 180314

    CERN Document Server

    Sato, Bun'ei; Liu, Yujuan; Harakawa, Hiroki; Izumiura, Hideyuki; Kambe, Eiji; Toyota, Eri; Murata, Daisuke; Lee, Byeong-Cheol; Masuda, Seiji; Takeda, Yoichi; Yoshida, Michitoshi; Itoh, Yoichi; Ando, Hiroyasu; Kokubo, Eiichiro; Ida, Shigeru; Zhao, Gang; Han, Inwoo

    2010-01-01

    We report the detections of two substellar companions orbiting around evolved intermediate-mass stars from precise Doppler measurements at Subaru Telescope and Okayama Astrophysical Observatory. HD 145457 is a K0 giant with a mass of 1.9 M_sun and has a planet of minimum mass m_2sini=2.9 M_J orbiting with period of P=176 d and eccentricity of e=0.11. HD 180314 is also a K0 giant with 2.6 M_sun and hosts a substellar companion of m_2sin i=22 M_J, which falls in brown-dwarf mass regime, in an orbit with P=396 d and e=0.26. HD 145457 b is one of the innermost planets and HD 180314 b is the seventh candidate of brown-dwarf-mass companion found around intermediate-mass evolved stars.

  10. Characterization of the atmosphere of the hot Jupiter HAT-P-32Ab and the M-dwarf companion HAT-P-32B

    CERN Document Server

    Zhao, Ming; Wright, Jason T; Knutson, Heather A; Burrows, Adam; Fortney, Johnathan; Ngo, Henry; Fulton, Benjamin J; Baranec, Christoph; Riddle, Reed; Law, Nicholas M; Muirhead, Philip S; Hinkley, Sasha; Showman, Adam P; Curtis, Jason; Burruss, Rick

    2014-01-01

    We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/WIRC in H and Ks bands and with Spitzer/IRAC at 3.6 and 4.5 micron. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.923" +/- 0. 004" and a position angle 110.64 deg +/- 0.12 deg. We measure the flux ratios of the binary in g' r' i' z' and H & Ks bands, and determine Teff = 3565 +/- 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090 +/- 0.033%, 0.178 +/- 0.057%, 0.364 +/- 0.016%, and 0.438 +/- 0.020% i...

  11. AN ASTROMETRIC SEARCH FOR A SUB-STELLAR COMPANION OF THE M8.5 DWARF TVLM 513–46546 USING VERY LONG BASELINE INTERFEROMETRY

    International Nuclear Information System (INIS)

    We conducted multi-epoch very long baseline interferometry observations to search for astrometric reflex motion that would be caused by a sub-stellar companion of the M8.5 dwarf TVLM 513–46546. The observations yield an absolute parallax corresponding to a distance of 10.762 ± 0.027 pc and a proper motion of 78.09 ± 0.17 mas yr–1. The averaged flux density per epoch varies by a factor of at least three. From the absence of significant residual motion, we place an upper limit on any reflex motion caused by a companion, extending the parameter space covered by previous near-infrared direct-imaging searches. The data exclude a phase space of companion masses and orbital periods ranging from 3.8 MJup with an orbital radius of ∼0.05 AU (and an orbital period of 16 days) to 0.3 MJup with an orbital radius of ∼0.7 AU (and an orbital period of 710 days)

  12. A Massive Substellar Companion to the Massive Giant HD 119445

    CERN Document Server

    Omiya, Masashi; Han, Inwoo; Lee, Byeong-Cheol; Sato, Bun'ei; Kambe, Eiji; Kim, Kang-Min; Yoon, Tae Seog; Yoshida, Michitoshi; Masuda, Seiji; Toyota, Eri; Urakawa, Seitaro; Takada-Hidai, Masahide

    2009-01-01

    We detected a brown dwarf-mass companion around the intermediate-mass giant star HD 119445 (G6III) using the Doppler technique. This discovery is the first result from a Korean-Japanese planet search program based on precise radial velocity measurements. The radial velocity of this star exhibits a periodic Keplerian variation with a period, semi-amplitude and eccentricity of 410.2 days, 413.5 m/s and 0.082, respectively. Adopting a stellar mass of 3.9 M_solar, we were able to confirm the presence of a massive substellar companion with a semimajor axis of 1.71 AU and a minimum mass of 37.6 M_Jup, which falls in the middle of the brown dwarf-mass region. This substellar companion is the most massive ever discovered within 3 AU of a central intermediate-mass star. The host star also ranks among the most massive stars with substellar companions ever detected by the Doppler technique. This result supports the current view of substellar systems that more massive substellar companions tend to exist around more massi...

  13. 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...

  14. $Extrasolar~Storms$: 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. ...

  15. 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.

  16. New evidence for a substellar luminosity problem: Dynamical mass for the brown dwarf binary Gl 417BC

    Energy Technology Data Exchange (ETDEWEB)

    Dupuy, Trent J. [The University of Texas at Austin, Department of Astronomy, 2515 Speedway C1400, Austin, TX 78712 (United States); Liu, Michael C. [Institute for Astronomy, University of Hawai' i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Ireland, Michael J. [Department of Physics and Astronomy, Macquarie University, NSW 2109 (Australia)

    2014-08-01

    We present new evidence for a problem with cooling rates predicted by substellar evolutionary models that implies that 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 (≈50-55 M{sub Jup}) and age (≈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 overluminosity could be caused by opacity holes (i.e., patchy clouds) in these objects. Moreover, from hybrid substellar evolutionary models that account for cloud disappearance, we infer the corresponding phase of overluminosity may extend from a few hundred million years up to a few gigayears and cause masses to be overestimated by up to 25%, even well after clouds disappear from view entirely. Thus, the range of ages and spectral types affected by this potential systematic shift in luminosity evolution would encompass most known directly imaged gas-giants and field brown dwarfs.

  17. Membership, binarity and accretion among very low-mass stars and brown dwarfs of the σ Orionis cluster

    Science.gov (United States)

    Kenyon, M. J.; Jeffries, R. D.; Naylor, Tim; Oliveira, J. M.; Maxted, P. F. L.

    2005-01-01

    Intermediate-resolution (R~ 7000) spectroscopy is presented for 76 photometrically selected very low-mass (0.04 consistent with the cluster mean. Photometric selection alone therefore appears to be very effective in identifying cluster members in this mass range. Only six objects appear to be certain non-members; however, a substantial subset of 13 candidates have ambiguous or contradictory indications of membership and lack Li absorption. Together with an observed spread in the equivalent width of the Li absorption feature in the cooler stars of our sample, this indicates that there may be deficiencies in our understanding of the formation of this line in cool, low-gravity objects. Four candidate binary cluster members are identified. Consideration of sampling and radial velocity measurement precision leads us to conclude that either the fraction of very low-mass stars and brown dwarfs in small separation (a < 1 au) binary systems is larger than in field M-dwarfs, or the distribution of separations is much less skewed towards large separations. This conclusion hinges critically on the correct identification of the small number of binary candidates, although it remains significant even when only the candidate members displaying Li absorption are considered. Broadened Hα emission, indicative of circum(sub)stellar accretion discs is found in five or six of the candidate cluster members, three of which probably have substellar masses. The fraction of accretors (10 +/- 5 per cent) is similar to that found in stars of higher mass in the σ Ori cluster using Hα emission as a diagnostic, but much lower than found for very low-mass stars and brown dwarfs of younger clusters. The time-scale for accretion rates to drop to <~10-11 Msolar yr-1 is hence less than the age of the σ Ori cluster (3-7 Myr) for most low-mass objects.

  18. New evidence for a substellar luminosity problem: Dynamical mass for the brown dwarf binary Gl 417BC

    International Nuclear Information System (INIS)

    We present new evidence for a problem with cooling rates predicted by substellar evolutionary models that implies that 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 (≈50-55 MJup) and age (≈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 overluminosity could be caused by opacity holes (i.e., patchy clouds) in these objects. Moreover, from hybrid substellar evolutionary models that account for cloud disappearance, we infer the corresponding phase of overluminosity may extend from a few hundred million years up to a few gigayears and cause masses to be overestimated by up to 25%, even well after clouds disappear from view entirely. Thus, the range of ages and spectral types affected by this potential systematic shift in luminosity evolution would encompass most known directly imaged gas-giants and field brown dwarfs.

  19. A Substellar Companion in a 1.3 yr Nearly-circular Orbit of HD 16760

    CERN Document Server

    Sato, Bunei; Ida, Shigeru; Harakawa, Hiroki; Omiya, Masashi; Johnson, John A; Marcy, Geoffrey W; Toyota, Eri; Hori, Yasunori; Isaacson, Howard; Howard, Andrew W; Peek, Kathryn M G

    2009-01-01

    We report the detection of a substellar companion orbiting the G5 dwarf HD 16760 from the N2K sample. Precise Doppler measurements of the star from Subaru and Keck revealed a Keplerian velocity variation with a period of 466.47+-0.35 d, a semiamplitude of 407.71+-0.84 m/s, and an eccentricity of 0.084+-0.003. Adopting a stellar mass of 0.78+-0.05 M_Sun, we obtain a minimum mass for the companion of 13.13+-0.56 M_JUP, which is close to the planet/brown-dwarf transition, and the semimajor axis of 1.084+-0.023 AU. The nearly circular orbit despite the large mass and intermediate orbital period makes this companion unique among known substellar companions.

  20. Mapping the Shores of the Brown Dwarf Desert III: Young Moving Groups

    CERN Document Server

    Evans, Thomas M; Kraus, Adam L; Martinache, Frantz; Stewart, Paul; Tuthill, Peter G; Lacour, Sylvestre; Carpenter, John M; Hillenbrand, Lynne A

    2011-01-01

    We present the results of an aperture masking interferometry survey for substellar companions around 67 members of the young (~8-200Myr) nearby (~5-86pc) AB Doradus, Beta Pictoris, Hercules-Lyra, TW Hya, and Tucana-Horologium stellar associations. Observations were made at near infrared wavelengths between 1.2-3.8 microns using the adaptive optics facilities of the Keck II, VLT UT4, and Palomar Hale Telescopes. Typical contrast ratios of ~100-200 were achieved at angular separations between ~40-320mas, with our survey being 100% complete for companions with masses below 0.25\\msolar across this range. We report the discovery of a $0.52 \\pm 0.09$\\msolar companion to HIP14807, as well as the detections and orbits of previously known stellar companions to HD16760, HD113449, and HD160934. We show that the companion to HD16760 is in a face-on orbit, resulting in an upward revision of its mass from $M_2 \\sin i \\sim 14$\\mjupiter to $M_2 = 0.28 \\pm 0.04$\\msolar. No substellar companions were detected around any of our...

  1. 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...

  2. A Search for Planets and Brown Dwarfs around Post Main Sequence Stars

    Science.gov (United States)

    Otani, Tomomi; Oswalt, Terry D.

    2016-06-01

    The most promising current theory for the origin of subdwarf B (sdB) stars is that they were formed during binary star evolution. This project was conducted to test this hypothesis by searching for companions around six sdB pulsators using the Observed-minus-Calculated (O-C) method. A star’s position in space will wobble due to the gravitational forces of any companion. If it is emitting a periodic signal, the orbital motion of the star around the system’s center of mass causes periodic changes in the light pulse arrival times. O-C diagrams for six sdB pulsators were constructed from several years’ observations, providing useful limits on suspected companions’ minimum masses and semimajor axes. The results were constrained by “period vs. amplitude” and “mass vs. semimajor axis” models to quantify companion masses and semimajor axes that are consistent with the observational data, if any. Two of our targets, V391 Peg and HS0702+6043, are noted in previous publications to have substellar companions. These were used to validate the method used in this research. The results of this study yielded the same masses and semimajor axes for these two stars as the published values, within the uncertainties. Another of the targets, EC20117-4014, is noted in the literature as a binary system containing an sdB and F5V star, however the orbital period and separation were unknown. The new data obtained in this study contain the signal of a companion candidate with a period of 158.01 days. Several possible mass and semimajor axis combinations for the companion are consistent with the observations. One of the other targets in this study displayed preliminary evidence for a companion that will require further observation. Though still a small sample, these results suggest that planets often survive the post-main-sequence evolution of their parent stars.

  3. A spectral differential approach to characterizing low-mass companions to late-type stars

    CERN Document Server

    Kostogryz, N M; Yakobchuk, T M; Lyubchik, Y; Kuznetsov, M K

    2013-01-01

    In this paper, we develop a spectral differential technique with which the dynamical mass of low-mass companions can be found. This method aims at discovering close companions to late-type stars by removing the stellar spectrum through a subtraction of spectra obtained at different orbital phases and discovering the companion spectrum in the difference spectrum in which the companion lines appear twice (positive and negative signal). The resulting radial velocity difference of these two signals provides the true mass of the companion, if the orbital solution for the radial velocities of the primary is known. We select the CO line region in the K-band for our study, because it provides a favourable star-to-companion brightness ratio for our test case GJ1046, an M2V dwarf with a low-mass companion that most likely is a brown dwarf. Furthermore, these lines remain largely unblended in the difference spectrum so that the radial velocity amplitude of the companion can be measured directly. Only if the companion ro...

  4. FIRST RESULTS FROM THE SWARMS SURVEY. SDSS 1257+5428: A NEARBY, MASSIVE WHITE DWARF BINARY WITH A LIKELY NEUTRON STAR OR BLACK HOLE COMPANION

    International Nuclear Information System (INIS)

    We present the first results from the SWARMS survey, an ongoing project to identify compact white dwarf (WD) binaries in the spectroscopic catalog of the Sloan Digital Sky Survey (SDSS). The first object identified by SWARMS, SDSS 1257+5428, is a single-lined spectroscopic binary in a circular orbit with a period of 4.56 hr and a semiamplitude of 322.7 ± 6.3 km s-1. From the spectrum and photometry, we estimate a WD mass of 0.92+0.28-0.32 Msun. Together with the orbital parameters of the binary, this implies that the unseen companion must be more massive than 1.62+0.20-0.25 Msun, and is in all likelihood either a neutron star or a black hole. At an estimated distance of 48+10-19 pc, this would be the closest known stellar remnant of a supernova explosion.

  5. DISCOVERY OF AN ∼23 MJup BROWN DWARF ORBITING ∼700 AU FROM THE MASSIVE STAR HIP 78530 IN UPPER SCORPIUS

    International Nuclear Information System (INIS)

    We present the discovery of a substellar companion on a wide orbit around the ∼ 2.5 Msun star HIP 78530, which is a member of the 5 Myr old Upper Scorpius association. We have obtained follow-up imaging over two years and show that the companion and primary share common proper motion. We have also obtained JHK spectroscopy of the companion and confirm its low surface gravity, in accordance with the young age of the system. A comparison with DRIFT-PHOENIX synthetic spectra indicates an effective temperature of 2800 ± 200 K and a comparison with template spectra of young and old dwarfs indicates a spectral type of M8 ± 1. The mass of the companion is estimated to be 19-26 MJup based on its bolometric luminosity and the predictions of evolutionary models. The angular separation of the companion is 4.''5, which at the distance of the primary star, 156.7 pc, corresponds to a projected separation of ∼710 AU. This companion features one of the lowest mass ratios (∼0.009) of any known companion at separations greater than 100 AU.

  6. 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.

  7. Deep infrared imaging of close companions to austral A- and F-type stars

    CERN Document Server

    Ehrenreich, David; Montagnier, Guillaume; Chauvin, Gaël; Galland, Franck; Beuzit, Jean-Luc; Rameau, Julien

    2010-01-01

    The search for substellar companions around stars with different masses along the main sequence is critical to understand the different processes leading to the formation of low-mass stars, brown dwarfs, and planets. In particular, the existence of a large population of low-mass stars and brown dwarfs physically bound to early-type main-sequence stars could imply that the massive planets recently imaged at wide separations (10-100 AU) around A-type stars are disc-born objects in the low-mass tail of the binary distribution. Our aim is to characterize the environment of early-type main-sequence stars by detecting brown dwarf or low-mass star companions between 10 and 500 AU. High contrast and high angular resolution near-infrared images of a sample of 38 southern A- and F-type stars have been obtained between 2005 and 2009 with the instruments VLT/NaCo and CFHT/PUEO. Multi-epoch observations were performed to discriminate comoving companions from background contaminants. About 41 companion candidates were imag...

  8. MagAO Imaging of Long-period Objects (MILO). I. A Benchmark M Dwarf Companion Exciting a Massive Planet around the Sun-like Star HD 7449

    CERN Document Server

    Rodigas, Timothy J; Faherty, Jackie; Anglada-Escude, Guillem; Kaib, Nathan; Butler, R Paul; Shectman, Stephen; Weinberger, Alycia; Males, Jared R; Morzinski, Katie M; Close, Laird M; Hinz, Philip M; Crane, Jeffrey D; Thompson, Ian; Teske, Johanna; Diaz, Matias; Minniti, Dante; Lopez-Morales, Mercedes; Adams, Fred C; Boss, Alan P

    2015-01-01

    We present high-contrast Magellan adaptive optics (MagAO) images of HD 7449, a Sun-like star with one planet and a long-term radial velocity (RV) trend. We unambiguously detect the source of the long-term trend from 0.6-2.15 \\microns ~at a separation of \\about 0\\fasec 54. We use the object's colors and spectral energy distribution to show that it is most likely an M4-M5 dwarf (mass \\about 0.1-0.2 \\msun) at the same distance as the primary and is therefore likely bound. We also present new RVs measured with the Magellan/MIKE and PFS spectrometers and compile these with archival data from CORALIE and HARPS. We use a new Markov chain Monte Carlo procedure to constrain both the mass ($> 0.17$ \\msun ~at 99$\\%$ confidence) and semimajor axis (\\about 18 AU) of the M dwarf companion (HD 7449B). We also refine the parameters of the known massive planet (HD 7449Ab), finding that its minimum mass is $7.8^{+3.7}_{-1.35}$ \\mj, its semimajor axis is $2.33^{+0.01}_{-0.02}$ AU, and its eccentricity is $0.8^{+0.08}_{-0.06}$. ...

  9. 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.

  10. Structure and evolution of the first CoRoT exoplanets: Probing the Brown Dwarf/Planet overlapping mass regime

    CERN Document Server

    Leconte, J; Chabrier, G; Barman, T; Levrard, B

    2009-01-01

    We present detailed structure and evolution calculations for the first transiting extrasolar planets discovered by the space-based CoRoT mission. Comparisons between theoretical and observed radii provide information on the internal composition of the CoRoT objects. We distinguish three different categories of planets emerging from these discoveries and from previous ground-based surveys: (i) planets explained by standard planetary models including irradiation, (ii) abnormally bloated planets and (iii) massive objects belonging to the overlapping mass regime between planets and brown dwarfs. For the second category, we show that tidal heating can explain the relevant CoRoT objects, providing non-zero eccentricities. We stress that the usual assumption of a quick circularization of the orbit by tides, as usually done in transit light curve analysis, is not justified a priori, as suggested recently by Levrard et al. (2009), and that eccentricity analysis should be carefully redone for some observations. Finally...

  11. 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...

  12. Searching for Binary Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS)

    CERN Document Server

    Opitz, Daniela; Faherty, Jacqueline; Sweet, Sarah; Gelino, Christopher R; Kirkpatrick, J Davy

    2016-01-01

    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 (GeMS). We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or...

  13. 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...

  14. Cloud structure of the nearest brown dwarfs: Spectroscopic variability of Luhman 16AB from the Hubble Space Telescope

    CERN Document Server

    Buenzli, Esther; Marley, Mark S; Apai, Daniel; Radigan, Jacqueline; Bedin, Luigi R; Reid, I Neill; Morley, Caroline V

    2014-01-01

    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 only 2 pc distance. Luhman 16B is a known variable whose light curves evolve rapidly. We present spatially resolved spectroscopic time-series of Luhman 16A and B covering 6.5 h using HST/WFC3 at 1.1 to 1.66 $\\mu$m. 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 $\\approx$0.4%. Its spectrum is well fit by a single cloud layer with intermediate cloud thickness (f_sed=2, Teff=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 $\\mu$m, otherwise it mostly decreases gradually from the blue to the red edge of the spectrum. This is very...

  15. Mid infrared observations of Van Maanen 2: no substellar companion.

    Energy Technology Data Exchange (ETDEWEB)

    Farihi, J; Becklin, E; Macintosh, B

    2004-11-03

    The results of a comprehensive infrared imaging search for the putative 0.06 M{sub {circle_dot}} astrometric companion to the 4.4 pc white dwarf van Mannen 2 are reported. Adaptive optics images acquired at 3.8 {micro}m reveal a diffraction limited core of 0.09 inch and no direct evidence of a secondary. Models predict that at 5 Gyr, a 50 M{sub J} brown dwarf would be only 1 magnitude fainter than van Maanen 2 at this wavelength and the astrometric analysis suggested a separation of 0.2 inch. In the case of a chance alignment along the line of sight, a 0.4 mag excess should be measured. An independent photometric observation at the same wavelength reveals no excess. In addition, there exist published ISO observations of van Maanen 2 at 6.8 {micro}m and 15.0 {micro}m which are consistent with photospheric flux of a 6750 K white dwarf. If recent brown dwarf models are correct, there is no substellar companion with T{sub eff} {approx}> 500 K.

  16. FIRST LIGHT LBT AO IMAGES OF HR 8799 bcde AT 1.6 AND 3.3 μm: NEW DISCREPANCIES BETWEEN YOUNG PLANETS AND OLD BROWN DWARFS

    International Nuclear Information System (INIS)

    As the only directly imaged multiple planet system, HR 8799 provides a unique opportunity to study the physical properties of several planets in parallel. In this paper, we image all four of the HR 8799 planets at H band and 3.3 μm with the new Large Binocular Telescope adaptive optics system, PISCES, and LBTI/LMIRCam. Our images offer an unprecedented view of the system, allowing us to obtain H and 3.3 μm photometry of the innermost planet (for the first time) and put strong upper limits on the presence of a hypothetical fifth companion. We find that all four planets are unexpectedly bright at 3.3 μm compared to the equilibrium chemistry models used for field brown dwarfs, which predict that planets should be faint at 3.3 μm due to CH4 opacity. We attempt to model the planets with thick-cloudy, non-equilibrium chemistry atmospheres but find that removing CH4 to fit the 3.3 μm photometry increases the predicted L' (3.8 μm) flux enough that it is inconsistent with observations. In an effort to fit the spectral energy distribution of the HR 8799 planets, we construct mixtures of cloudy atmospheres, which are intended to represent planets covered by clouds of varying opacity. In this scenario, regions with low opacity look hot and bright, while regions with high opacity look faint, similar to the patchy cloud structures on Jupiter and L/T transition brown dwarfs. Our mixed-cloud models reproduce all of the available data, but self-consistent models are still necessary to demonstrate their viability.

  17. Two very nearby (d ~ 5 pc) ultracool brown dwarfs detected by their large proper motions from WISE, 2MASS, and SDSS data

    CERN Document Server

    Scholz, R -D; Schnurr, O; Storm, J

    2011-01-01

    Aims: WISE provides an infrared all-sky survey which aims at completing our knowledge on the possibly dramatically increasing number of brown dwarfs with lower temperatures. We search for the nearest representatives of the coolest brown dwarfs, which will be very interesting for detailed follow-up observations, once they haven been discovered. Methods: We have used the preliminary data release from WISE, selected bright candidates with colours typical of late-T dwarfs, tried to match them with faint 2MASS and SDSS objects, to determine their proper motions, and to follow-up them spectroscopically. Results: We have identified two new ultracool brown dwarfs, WISE J0254+0223 and WISE J1741+2553, with large proper motions of about 2.5 and 1.5 arcsec/yr, respectively. With their w1-w2~3.0 and J-w2~4.0 colour indices we expect them both to have a spectral type of ~T9-T10 and absolute magnitude of M_{w2}~14. For WISE J1741+2553 we confirm a spectral type of T10 from near-infrared spectroscopy with LBT/LUCIFER1. From...

  18. The Size and Shape of the Milky Way Disk and Halo from M-type Brown Dwarfs in the BoRG Survey

    CERN Document Server

    van Vledder, Isabel; Holwerda, B W; Kenworthy, M A; Bouwens, R J; Trenti, M

    2016-01-01

    We have identified 274 M-type Brown Dwarfs in the Hubble Space Telescope's Wide Field Camera 3 (WFC3) pure parallel fields from the Brightest of Reionizing Galaxies (BoRG) survey for high redshift galaxies. These are near-infrared observations with multiple lines-of-sight out of our Milky Way. Using these observed M-type Brown Dwarfs we fitted a Galactic disk and halo model with a Markov chain Monte Carlo (MCMC) analysis. This model worked best with the scale length of the disk fixed at $h$ = 2.6 kpc. For the scale height of the disk, we found $z_0 = 0.29^{+0.02}_{-0.019}$ kpc and for the central number density $\\rho_0 = 0.29^{+0.20}_{-0.13}$ \\#/pc$^3$. For the halo we derived a flattening parameter $\\kappa$ = 0.45$\\pm{0.04}$ and a power-law index $p$ = 2.4$\\pm{0.07}$. We found the fraction of M-type brown dwarfs in the local density that belong to the halo to be $f_{h}$ = 0.0075$^{+0.0025}_{-0.0019}$. We found no correlation between subtype of M-dwarf and any model parameters. The total number of M-type Brow...

  19. An Infrared Coronagraphic Survey for Substellar Companions

    CERN Document Server

    Lowrance, P J; Schneider, G; Kirkpatrick, D; Weinberger, A; Zuckerman, B; Dumas, C; Beuzit, J L; Plait, P; Malumuth, E; Heap, S; Terrile, R J; Hines, D

    2005-01-01

    We have used the F160W filter (1.4-1.8 um) and the coronagraph on the Near-InfraRed Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope (HST) to survey 45 single stars with a median age of 0.15 Gyr, an average distance of 30 pc, and an average H-magnitude of 7 mag. For the median age we were capable of detecting a 30 M_Jup companion at separations between 15 and 200 AU. A 5 M_Jup object could have been detected at 30 AU around 36% of our primaries. For several of our targets that were less than 30 Myr old, the lower mass limit was as low as a Jupiter mass, well into the high mass planet region. Results of the entire survey include the proper motion verification of five low-mass stellar companions, two brown dwarfs (HR7329B and TWA5B) and one possible brown dwarf binary (Gl 577B/C).

  20. The parsec program: a large sample of brown dwarf trigonometric parallaxes

    Science.gov (United States)

    Andrei, Alexandre H.; Smart, Richard L.; Bucciarelli, Beatrice; Penna, Jucira L.; Marocco, Federico; Lattanzi, Mario G.; Crosta, Mariateresa; Teixeira, Ramakrishna

    2013-02-01

    We report on the parsec program, which observed 140 L and T dwarfs on a regular basis from 2007 to 2011, using the WIFI camera on the ESO/2.2 m telescope. Trigonometric parallaxes at 5 mas precision are derived for 49 objects, and mas yr-1-level proper motions are derived for approximately 200,000 objects in the same fields. We discuss image cleaning, object centroiding, and astrometric methods, in particular three different approaches for trigonometric parallax determination.

  1. CROWDING-OUT OF GIANTS BY DWARFS: AN ORIGIN FOR THE LACK OF COMPANION PLANETS IN HOT JUPITER SYSTEMS

    International Nuclear Information System (INIS)

    We investigate the formation of close-in terrestrial planets from planetary embryos under the influence of a hot Jupiter (HJ) using gravitational N-body simulations that include gravitational interactions between the gas disk and the terrestrial planet (e.g., type I migration). Our simulations show that several terrestrial planets efficiently form outside the orbit of the HJ, making a chain of planets, and all of them gravitationally interact directly or indirectly with the HJ through resonance, which leads to inward migration of the HJ. We call this mechanism of induced migration of the HJ ''crowding-out''. The HJ is eventually lost through collision with the central star, and only several terrestrial planets remain. We also find that the efficiency of the crowding-out effect depends on the model parameters; for example, the heavier the disk is, the more efficient the crowding-out is. When planet formation occurs in a massive disk, the HJ can be lost to the central star and is never observed. On the other hand, for a less massive disk, the HJ and terrestrial planets can coexist; however, the companion planets may be below the detection limit of current observations. In both cases, systems with a HJ and terrestrial planets have little chance of detection. Therefore, our model naturally explains the lack of companion planets in HJ systems regardless of the disk mass. In effect, our model provides a theoretical prediction for future observations; additional planets can be discovered just outside the HJ, and their masses should generally be small

  2. J-Band Infrared Spectroscopy of a Sample of Brown Dwarfs Using NIRSPEC on Keck II.

    Science.gov (United States)

    McLean; Wilcox; Becklin; Figer; Gilbert; Graham; Larkin; Levenson; Teplitz; Kirkpatrick

    2000-04-10

    Near-infrared spectroscopic observations of a sample of very cool, low-mass objects are presented with higher spectral resolution than in any previous studies. Six of the objects are L dwarfs, ranging in spectral class from L2 to L8/9, and the seventh is a methane or T dwarf. These new observations were obtained during commissioning of the near-infrared spectrometer (NIRSPEC), the first high-resolution near-infrared cryogenic spectrograph for the Keck II 10 m telescope on Mauna Kea, Hawaii. Spectra with a resolving power of R approximately 2500 from 1.135 to 1.360 µm (approximately J band) are presented for each source. At this resolution, a rich spectral structure is revealed, much of which is due to blending of unresolved molecular transitions. Strong lines due to neutral potassium (K i) and bands due to iron hydride (FeH) and steam (H2O) change significantly throughout the L sequence. Iron hydride disappears between L5 and L8, the steam bands deepen, and the K i lines gradually become weaker but wider because of pressure broadening. An unidentified feature occurs at 1.22 µm that has a temperature dependence like FeH but has no counterpart in the available FeH opacity data. Because these objects are 3-6 mag brighter in the near-infrared compared with the I band, spectral classification is efficient. One of the objects studied (2MASSW J1523+3014) is the coolest L dwarf discovered so far by the 2 Micron All-Sky Survey (2MASS), but its spectrum is still significantly different from the methane-dominated objects such as Gl 229B or SDSS 1624+0029. PMID:10727388

  3. Accretion onto Planetary Mass Companions of Low-Mass Young Stars

    OpenAIRE

    Zhou, Yifan; Herczeg, Gregory J.; Kraus, Adam L.; Metchev, Stanimir; Cruz, Kelle

    2014-01-01

    Measurements of accretion rates onto planetary mass objects may distinguish between different planet formation mechanisms, which predict different accretion histories. In this Letter, we use \\HST/WFC3 UVIS optical photometry to measure accretion rates onto three accreting objects, GSC06214-00210 b, GQ Lup b, and DH Tau b, that are at the planet/brown dwarf boundary and are companions to solar mass stars. The excess optical emission in the excess accretion continuum yields mass accretion rates...

  4. Characterization of the atmosphere of the hot Jupiter HAT-P-32Ab and the M-dwarf companion HAT-P-32B

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Ming; Wright, Jason T.; Curtis, Jason [Department of Astronomy and Astrophysics, Pennsylvania State University, PA 16802 (United States); O' Rourke, Joseph G.; Knutson, Heather A.; Ngo, Henry [Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125 (United States); Burrows, Adam [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States); Fortney, Johnathan [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Fulton, Benjamin J.; Baranec, Christoph [Institute for Astronomy, University of Hawai' i at Mānoa, Hilo, HI 96720-2700 (United States); Riddle, Reed; Hinkley, Sasha [Division of Physics, Mathematics, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Law, Nicholas M. [Department of Physics and Astronomy, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-3255 (United States); Muirhead, Philip S. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Showman, Adam P. [Department of Planetary Sciences and Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721 (United States); Burruss, Rick, E-mail: mingzhao@psu.edu [Jet Propulsion Laboratory, California Institute of Technology, CA 91109 (United States)

    2014-12-01

    We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/Wide-field Infra-Red Camera (WIRC) in H and K{sub S} bands and with Spitzer/IRAC at 3.6 and 4.5 μm. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.''923 ± 0.''004 and a position angle 110.°64 ± 0.°12. We measure the flux ratios of the binary in g'r'i'z' and H and K{sub S} bands, and determine T {sub eff}= 3565 ± 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090% ± 0.033%, 0.178% ± 0.057%, 0.364% ± 0.016%, and 0.438% ± 0.020% in the H, K{sub S} , 3.6 and 4.5 μm bands, respectively. We compare these with planetary atmospheric models, and find they prefer an atmosphere with a temperature inversion and inefficient heat redistribution. However, we also find that the data are equally well described by a blackbody model for the planet with T {sub p} = 2042 ± 50 K. Finally, we measure a secondary eclipse timing offset of 0.3 ± 1.3 minutes from the predicted mid-eclipse time, which constrains e = 0.0072{sub −0.0064}{sup +0.0700} when combined with radial velocity data and is more consistent with a circular orbit.

  5. Characterization of the atmosphere of the hot Jupiter HAT-P-32Ab and the M-dwarf companion HAT-P-32B

    International Nuclear Information System (INIS)

    We report secondary eclipse photometry of the hot Jupiter HAT-P-32Ab, taken with Hale/Wide-field Infra-Red Camera (WIRC) in H and KS bands and with Spitzer/IRAC at 3.6 and 4.5 μm. We carried out adaptive optics imaging of the planet host star HAT-P-32A and its companion HAT-P-32B in the near-IR and the visible. We clearly resolve the two stars from each other and find a separation of 2.''923 ± 0.''004 and a position angle 110.°64 ± 0.°12. We measure the flux ratios of the binary in g'r'i'z' and H and KS bands, and determine T eff= 3565 ± 82 K for the companion star, corresponding to an M1.5 dwarf. We use PHOENIX stellar atmosphere models to correct the dilution of the secondary eclipse depths of the hot Jupiter due to the presence of the M1.5 companion. We also improve the secondary eclipse photometry by accounting for the non-classical, flux-dependent nonlinearity of the WIRC IR detector in the H band. We measure planet-to-star flux ratios of 0.090% ± 0.033%, 0.178% ± 0.057%, 0.364% ± 0.016%, and 0.438% ± 0.020% in the H, KS , 3.6 and 4.5 μm bands, respectively. We compare these with planetary atmospheric models, and find they prefer an atmosphere with a temperature inversion and inefficient heat redistribution. However, we also find that the data are equally well described by a blackbody model for the planet with T p = 2042 ± 50 K. Finally, we measure a secondary eclipse timing offset of 0.3 ± 1.3 minutes from the predicted mid-eclipse time, which constrains e = 0.0072−0.0064+0.0700 when combined with radial velocity data and is more consistent with a circular orbit.

  6. J-Band Infrared Spectroscopy of a Sample of Brown Dwarfs Using Nirspec on Keck II

    CERN Document Server

    McLean, I S; Becklin, E E; Figer, D F; Gilbert, A M; Graham, J R; Larkin, J E; Levenson, N A; Teplitz, H I; Kirkpatrick, J D; Lean, Ian S. Mc; Wilcox, Mavourneen K.; Figer, Donald F.; Gilbert, Andrea M.; Graham, James R.; Larkin, James E.; Teplitz, Harry I.

    2000-01-01

    Near-infrared spectroscopic observations of a sample of very cool, low-massobjects are presented with higher spectral resolution than in any previousstudies. Six of the objects are L-dwarfs, ranging in spectral class from L2 toL8/9, and the seventh is a methane or T-dwarf. These new observations wereobtained during commissioning of NIRSPEC, the first high-resolutionnear-infrared cryogenic spectrograph for the Keck II 10-meter telescope onMauna Kea, Hawaii. Spectra with a resolving power of R=2500 from 1.135 to 1.360microns (approximately J-band) are presented for each source. At thisresolution, a rich spectral structure is revealed, much of which is due toblending of unresolved molecular transitions. Strong lines due to neutralpotassium (K I), and bands due to iron hydride (FeH) and steam (H2O) changesignificantly throughout the L sequence. Iron hydride disappears between L5 andL8, the steam bands deepen and the K I lines gradually become weaker but widerdue to pressure broadening. An unidentified feature occ...

  7. CLOUD STRUCTURE OF THE NEAREST BROWN DWARFS: SPECTROSCOPIC VARIABILITY OF LUHMAN 16AB FROM THE HUBBLE SPACE TELESCOPE

    International Nuclear Information System (INIS)

    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 sed = 2, T 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 eff = 1300 K, f sed = 3) and a cooler, thicker cloud (T eff = 1000-1100 K, f 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

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

    OpenAIRE

    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...

  9. Low-Mass Star Formation: Initial Conditions, Disk Instabilities, and the Brown Dwarf Desert

    CERN Document Server

    Matzner, C D; Matzner, Christopher D.; Levin, Yuri

    2004-01-01

    We develop a simple theory to predict the initial conditions for low-mass star formation and relate these to instabilities of protostellar accretion disks that may produce stellar or substellar companions. We first account for the effects of a turbulent velocity field on the cores that form stars. Revised scales for mass, radius, turbulent velocity, and angular momentum are derived from the gas temperature of the prestellar core and the column density of the parent cloud. The full distribution angular momentum around its characteristic scale is derived from an idealized but reasonable set of assumptions. Second, we examine the criterion for fragmentation to occur during star formation, concentrating on the self-gravitational instabilities of protostellar accretion disks in their main accretion phase. Disk instability can develop from rotating initial conditions even if they are axisymmetric; therefore it provides a conservative bound for the criterion of fragmentation. Self-gravitational instabilities are str...

  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. 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).

  12. 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.

  13. Ionization in atmospheres of brown dwarfs and extrasolar planets VI: Properties of large-scale discharge events

    International Nuclear Information System (INIS)

    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 (108-1010 m3) than in a giant gas planet (104-106 m3). Our results suggest that the total dissipated energy in one event is <1012 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 CH2 at the expense of CO and CH4. 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.

  14. Emission Line Variability of the Accreting Young Brown Dwarf 2MASSW J1207334-393254: From Hours to Years

    CERN Document Server

    Stelzer, Beate; Jayawardhana, Ray

    2007-01-01

    We have obtained a series of high-resolution optical spectra for the brown dwarf 2MASSW J1207334-393254 (2M1207) using the ESO Very Large Telescope with the UVES spectrograph during two consecutive observing nights (time resolution of ~12 min) and the Magellan Clay telescope with the MIKE spectrograph. Combined with previously published results, these data allow us to investigate changes in the emission line spectrum of 2M1207 on timescales of hours to years. Most of the emission line profiles of 2M1207 are broad, in particular that of Halpha, indicating that the dominant fraction of the emission must be attributed to disk accretion rather than to magnetic activity. From the Halpha 10% width we deduce a relatively stable accretion rate between 10^(-10.1...-9.8) Msun/yr for two nights of consecutive observations. Therefore, either the accretion stream is nearly homogeneous over (sub-)stellar longitude or the system is seen face-on. Small but significant variations are evident throughout our near-continuous obs...

  15. 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...

  16. 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...

  17. Korean-Japanese Planet Search Program: Substellar Companions around Intermediate-Mass Giants

    CERN Document Server

    Omiya, Masashi; Izumiura, Hideyuki; Lee, Byeong-Cheol; Sato, Bun'ei; Kim, Kang-Min; Yoon, Tae Seog; Kambe, Eiji; Yoshida, Michitoshi; Masuda, Seiji; Toyota, Eri; Urakawa, Seitaro; Takada-Hidai, Masahide

    2011-01-01

    A Korean-Japanese planet search program has been carried out using the 1.8m telescope at Bohyunsan Optical Astronomy Observatory (BOAO) in Korea, and the 1.88m telescope at Okayama Astrophysical Observatory (OAO) in Japan to search for planets around intermediate-mass giant stars. The program aims to show the properties of planetary systems around such stars by precise Doppler survey of about 190 G or K type giants together with collaborative surveys of the East-Asian Planet Search Network. So far, we detected two substellar companions around massive intermediate-mass giants in the Korean-Japanese planet search program. One is a brown dwarf-mass companion with 37.6 $M_{\\mathrm{J}}$ orbiting a giant HD 119445 with 3.9 $M_{\\odot}$, which is the most massive brown dwarf companion among those found around intermediate-mass giants. The other is a planetary companion with 1.8 $M_{\\mathrm{J}}$ orbiting a giant star with 2.4 $M_{\\odot}$, which is the lowest-mass planetary companion among those detected around giant s...

  18. HD 5388 b is a 69 M_Jup companion instead of a planet

    CERN Document Server

    Sahlmann, Johannes; Queloz, Didier; Segransan, Damien

    2011-01-01

    We examined six exoplanet host stars with non-standard Hipparcos astrometric solution, which may be indicative of unrecognised orbital motion. Using Hipparcos intermediate astrometric data, we detected the astrometric orbit of HD 5388 at a significance level of 99.4 % (2.7 sigma). HD 5388 is a metal-deficient star and hosts a planet candidate with a minimum mass of 1.96 M_J discovered in 2010. We determined its orbit inclination to be i = 178.3 +0.4/-0.7 deg and the corresponding mass of its companion HD 5388 b to be M_2 = 69 +/- 20 M_J. The orbit is seen almost face-on and the companion mass lies at the upper end of the brown-dwarf mass range. A mass lower than 13 M_J was excluded at the 3-sigma level. The astrometric motions of the five other stars had been investigated by other authors revealing two planetary companions, one stellar companion, and two statistically insignificant orbits. We conclude that HD 5388 b is not a planet but most likely a brown-dwarf companion. In addition, we find that the inclina...

  19. 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.

  20. HST ROTATIONAL SPECTRAL MAPPING OF TWO L-TYPE BROWN DWARFS: VARIABILITY IN AND OUT OF WATER BANDS INDICATES HIGH-ALTITUDE HAZE LAYERS

    International Nuclear Information System (INIS)

    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

  1. The not-so-extreme white dwarf of the CV GD 552

    International Nuclear Information System (INIS)

    GD 552 is a cataclysmic binary which was previously believed to be composed of an M-star and a white dwarf, the latter having an extreme mass of 1.4 solar masses. In a recent paper we showed that this is not compatible with new observational evidence and presented an alternative model in which the white dwarf has a typical mass and the companion is a brown dwarf, making the system a likely member of the elusive group of CVs which have already evolved through minimum orbital period. Here we present additional spectroscopical evidence supporting this conclusion by means of skew mapping.

  2. 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...

  3. Stars and brown dwarfs in the sigma Orionis cluster. II. A proper motion study

    CERN Document Server

    Caballero, Jose A

    2010-01-01

    AIMS. I seek to fully know the stellar and substellar populations in the young sigma Orionis open cluster, which is a benchmark for star-forming studies. Because of the very low proper motion of the cluster, late-type dwarfs with appreciable proper motion in the foreground of sigma Orionis can be easily discarded for expensive spectroscopic follow-up. METHODS. I use the Aladin sky atlas, USNO-B1, public astrometric catalogues, and photographic plate digitisations to identify stars with proper motions inconsistent with cluster membership in a circular area of radius 30 arcmin centred on the early-type multiple system sigma Ori. Mostly due to the long time baseline, of more than half a century, the errors in the measured proper motions are lower than 2 mas/a. RESULTS. Of the 42 stars selected for astrometric follow-up, 37 of them are proper-motion cluster interlopers. Some USNO-B1 measurements were affected by partially resolved (visual) multiplicity and target faintness. Because of their late spectral types an...

  4. 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...

  5. A search for a distant companion to the sun with the wide-field infrared survey explorer

    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); Center for Exoplanets and Habitable Worlds, The Pennsylvania State University, University Park, PA 16802 (United States)

    2014-01-20

    I have used multi-epoch astrometry from the Wide-field Infrared Survey Explorer to perform a search for a distant companion to the Sun via its parallactic motion. I have not found an object of this kind down to W2 = 14.5. This limit corresponds to analogs of Saturn and Jupiter at 28,000 and 82,000 AU, respectively, according to models of the Jovian planets by Fortney and coworkers. Models of brown dwarfs by Burrows and coworkers predict fainter fluxes at a given mass for the age of the solar system, producing a closer distance limit of 26,000 AU for a Jupiter-mass brown dwarf. These constraints exclude most combinations of mass and separation at which a solar companion has been suggested to exist by various studies over the years.

  6. Whole-genome expression analysis of Rice black-streaked dwarf virus in different plant hosts and small brown planthopper.

    Science.gov (United States)

    Xu, Qiufang; Ni, Haiping; Zhang, Jinfeng; Lan, Ying; Ren, Chunmei; Zhou, Yijun

    2015-11-10

    Rice black-streaked dwarf virus (RBSDV) can infect a number of gramineous plants and cause severe crop yield losses in southeast Asian countries. The virus is transmitted by small brown planthopper (SBPH) in a persistent circulative manner. The interactions between RBSDV and its different hosts remain unknown. Besides, how the virus adjusts itself to infect different hosts is unclear. In the present study, the relative RNA levels of the thirteen RBSDV genes in rice, maize, wheat, and SBPH were measured by real-time quantitative PCR. P7-1 and P10 genes were predominantly expressed whereas P8 and P7-2 genes were expressed at low levels in plant hosts. Similar to the expression in rice, P7-1 was the most abundantly expressed gene and P8 was expressed at the lowest level in SBPH, indicating that RBSDV adopts the same strategy to infect distinct hosts. The high expression levels of the P7-1 gene in both plants and insect suggest that it can be used as the target gene for disease diagnostics. However, the expression levels of some genes varied from host to host. P5-1, P6 and P9-1, the components of the RBSDV viroplasm, are differentially expressed in different hosts. Moreover, western blot analysis showed that the quantity of the P9-1 protein was more abundant in SBPH than in plant hosts. These data indicate that the virus may adjust its own gene expression to replicate in different hosts. Analysis of time course of gene expression revealed that P7-1 stands out as the only gene highly expressed at the earliest time point and its expression precedes all others throughout infection from 8 to 24days post-inoculation. The high expression levels of the P7-1 gene suggest that it plays a significant role in RBSDV-host interactions. PMID:26149652

  7. 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.

  8. 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.

  9. 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

    Science.gov (United States)

    David, Trevor J.; Hillenbrand, Lynne A.; Cody, Ann Marie; Carpenter, John M.; Howard, Andrew W.

    2016-01-01

    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 ˜78 days. The orbital periods of all three systems are K2 photometry plus multiple Keck/HIRES radial velocities (RVs) 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 ˜25 MJup 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=0.1183+/- 0.0028{M}⊙ , {M}2=0.1076+/- 0.0031{M}⊙ and {R}1=0.417+/- 0.010{R}⊙ , {R}2=0.450+/- 0.012{R}⊙ ) from combination of the light curve and RV time series. These stars have the lowest masses of any stellar mass double-lined eclipsing binary to date. Comparing our derived stellar parameters with evolutionary models, we suggest an age of ˜10-11 Myr for this system, in contrast to the canonical age of 3-5 Myr for the association. Finally, EPIC 203476597 is a compact single-lined system with a G8-K0 primary and a likely mid-K secondary whose lines are revealed in spectral ratios. Continued measurement of RVs and spectroscopic flux ratios will better constrain fundamental parameters and should elevate the objects to benchmark status. We also present revised parameters for the double-lined eclipsing binary UScoCTIO 5 ({M}1=0.3336+/- 0.0022{M}⊙ , {M}2=0.3200+/- 0.0022{M}⊙ and {R}1=0.862+/- 0.012, {R}2=0.852+/- 0.013{R}⊙ ), which are suggestive of a system age younger than previously reported. We discuss the implications of our

  10. 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

    ‐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......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......, efficient and sensitive, (2) rather common weak features intrinsically come with ambiguities that are not easily resolved from photometric light curves, (3) a modelling approach that finds all features of parameter space rather than just the ‘favourite model’ is required and (4) the data quality is most...

  11. EARLY STAR-FORMING PROCESSES IN DENSE MOLECULAR CLOUD L328; IDENTIFICATION OF L328-IRS AS A PROTO-BROWN DWARF

    International Nuclear Information System (INIS)

    This paper presents the results of millimeter to sub-millimeter observations of CO, HCN, N2H+, and HCO+ lines in the dense molecular cloud L328, which harbors L328-IRS, a Very Low Luminosity Object (VeLLO). Our analysis of the line width finds that 13CO and N2H+ lines are broadened right over the smallest sub-core S2 where L328-IRS is located, while they are significantly narrower in other regions of L328. Thus, L328-IRS has a direct association with the sub-core. CO observations show a bipolar outflow from this VeLLO with an extent of ∼0.08 pc. The outflow momentum flux and efficiency are much less than those of low-mass protostars. The most likely mass accretion rate (∼3.6 × 10–7 M☉ yr–1) inferred from the analysis of the CO outflow is an order of magnitude smaller than the canonical value for a protostar. If the main accretion lasts during the typical Class 0 period of a protostar, L328-IRS will accrete the mass of a brown dwarf, but not that of a star. Given that its envelope mass is small (∼0.09 M☉) and 100% star formation rate is unlikely, we suggest that L328-IRS is likely a proto-brown dwarf. Inward motions are found in global scale in the L328 cloud and its sub-cores with a typical infall speed found in starless cores. L328 is found to be fairly well isolated from other nearby clouds and seems to be forming three sub-cores simultaneously through a gravitational fragmentation process. Altogether, these all leave L328-IRS as the best example supporting the idea that a brown dwarf forms like a normal star

  12. Dark companions of stars - Astrometric commentary on the lower end of the Main Sequence

    Science.gov (United States)

    van de Kamp, P.

    1986-04-01

    The smaller the mass of a star, the lower its central temperature and the lower its luminosity. The zero-age Main Sequence is thus explained down to its lower, red dwarf section; there is, however, a critical mass value below which the central temperature is too low to permit conventional nuclear energy production, and the resulting objects are designated substellar, black, brown, or even 'dark red' stars. The present consideration of the dark companions of stars gives attention to visible and invisible dark dwarfs, as well as to the stars Sirius and Procyon, the planets Neptune and Pluto, spectroscopic, photometric, and eclipsing companion stars, the serendipitously discovered cases of Ross 614 and VW Cephei C, and astrometric study results for Barnard's star.

  13. Characterization of the Nearby L/T Binary Brown Dwarf WISE J104915.57-531906.1 at 2 Parsecs from the Sun

    CERN Document Server

    Kniazev, A Y; Muzic, K; Mehner, A; Boffin, H M J; Kurtev, R; Melo, C; Ivanov, V D; Girard, J; Mawet, D; Schmidtobreick, L; Huelamo, N; Borissova, J; Minniti, D; Ishibashi, K; Potter, S B; Beletsky, Y; Buckley, D A H; Crawford, S; Gulbis, A A S; Kotze, P; Miszalski, B; Pickering, T E; Colmenero, E Romero; Williams, T B

    2013-01-01

    WISE J104915.57-531906.1 is a candidate L/T brown dwarf binary located 2pc from the Sun. The pair contains the closest known brown dwarfs and is the third closest known system, stellar or sub-stellar. Here we report the first comprehensive follow-up observations of this newly uncovered system. We have determined the spectral types of both components (L8+/-1, T1+/-2) and their radial velocities (V_rad~23.1, 19.5 km/s) using the Southern African Large Telescope (SALT) and other facilities located at the South African Astronomical Observatory (SAAO). The relative radial velocity of the two components is smaller than the range of orbital velocities for theoretically predicted masses, implying that they form a gravitationally bound system. We report resolved near-infrared $JHK_S$ photometry from the IRSF telescope at the SAAO which yields colors consistent with the spectroscopically derived spectral types. Our apparent magnitudes predict a distance of ~2.25pc, similar to the previous measurement. The available kin...

  14. 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...

  15. Aeolus: A Markov--Chain Monte Carlo code for mapping ultracool atmospheres. An application on Jupiter and brown dwarf HST light curves

    CERN Document Server

    Karalidi, Theodora; Schneider, Glenn; Hanson, Jake R; Pasachoff, Jay M

    2015-01-01

    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 5um 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-bands HST light curves of 2MASSJ21392676+0220226 and 2MASSJ0136565+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.

  16. Database Cross-Correlation at Scale: A Complete Census of Cool and Peculiar Brown Dwarfs in the 2MASS/SDSS Overlap

    Science.gov (United States)

    Metchev, Stanimir

    Cross-correlation of surveys at different wavelengths is an effective way to leverage existing data for the generation of new science. We propose to perform a cross-match of the complete 2MASS and SDSS surveys as a demonstration of database cross-correlation at scale. The specific science case focuses on identifying cool brown dwarfs. Hundreds of L and T dwarfs have been discovered in the solar neighborhood, ~90% of which from 2MASS or SDSS. These have offered an unprecedented empirical context for the creation of sophisticated substellar phenomenology. A few dozen peculiar L and T dwarfs have also emerged from the larger sample. Their unusual spectral energy distributions have been particularly informative about the ranges of temperature, surface gravity, and dust content in ultra-cool atmospheres. Nevertheless, fundamental aspects of our knowledge of substellar astrophysics remain fragmented. The local space density of T dwarfs is hardly known to better than a factor of several. In fact, some of the nearest cool brown dwarfs may have escaped detection. Dust and cloud dynamics in ultra-cool atmospheres, and their dependence on temperature, gravity, and metallicity remain poorly understood. And in all likelihood, the few known examples of peculiar L and T dwarfs represent merely the extremes of a broad range of existing atmospheric conditions that have yet to be revealed. A combined search on 2MASS and SDSS is an effective way to generate a large, complete sample of L and T dwarfs to address these shortcomings. Cross-correlation of the two surveys can probe deeper, to cooler effective temperatures, and to a higher completeness level than searches on either survey alone. We validated this approach through a test cross-match of the 2099 sq.deg overlap area between 2MASS and SDSS Data Release 1. The demonstration project resulted not only in the first unbiased estimate of the space density and luminosity function of T0-T8 dwarfs, but also in doubling of the then known

  17. Photometric brown-dwarf classification. II. A homogeneous sample of 1361 L and T dwarfs brighter than J = 17.5 with accurate spectral types

    Science.gov (United States)

    Skrzypek, N.; Warren, S. J.; Faherty, J. K.

    2016-04-01

    We present a homogeneous sample of 1361 L and T dwarfs brighter than J = 17.5 (of which 998 are new), from an effective area of 3070 deg2, classified by the photo-type method to an accuracy of one spectral sub-type using izYJHKW1W2 photometry from SDSS+UKIDSS+WISE. Other than a small bias in the early L types, the sample is shown to be effectively complete to the magnitude limit, for all spectral types L0 to T8. The nature of the bias is an incompleteness estimated at 3% because peculiar blue L dwarfs of type L4 and earlier are classified late M. There is a corresponding overcompleteness because peculiar red (likely young) late M dwarfs are classified early L. Contamination of the sample is confirmed to be small: so far spectroscopy has been obtained for 19 sources in the catalogue and all are confirmed to be ultracool dwarfs. We provide coordinates and izYJHKW1W2 photometry of all sources. We identify an apparent discontinuity, Δm ~ 0.4 mag, in the Y - K colour between spectral types L7 and L8. We present near-infrared spectra of nine sources identified by photo-type as peculiar, including a new low-gravity source ULAS J005505.68+013436.0, with spectroscopic classification L2γ. We provide revised izYJHKW1W2 template colours for late M dwarfs, types M7 to M9. The catalogue is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/589/A49

  18. KELT-1b: A Strongly Irradiated, Highly Inflated, Short Period, 27 Jupiter-mass Companion Transiting a mid-F Star

    CERN Document Server

    Siverd, Robert J; Pepper, Joshua; Eastman, Jason D; Collins, Karen; Bieryla, Allyson; Latham, David W; Buchhave, Lars A; Jensen, Eric L N; Crepp, Justin R; Street, Rachel; Stassun, Keivan G; Gaudi, B Scott; Berlind, Perry; Calkins, Michael L; DePoy, D L; Esquerdo, Gilbert A; Fulton, Benjamin J; Furesz, Gabor; Geary, John C; Gould, Andrew; Hebb, Leslie; Kielkopf, John F; Marshall, Jennifer L; Pogge, Richard; Stanek, K Z; Stefanik, Robert P; Szentgyorgyi, Andrew H; Trueblood, Mark; Trueblood, Patricia; Stutz, Amelia M; van Saders, Jennifer L

    2012-01-01

    We present the discovery of KELT-1b, the first transiting low-mass companion from the wide-field Kilodegree Extremely Little Telescope-North (KELT-North) survey. The V=10.7 primary is a mildly evolved, solar-metallicity, mid-F star. The companion is a low-mass brown dwarf or super-massive planet with mass of 27.23+/-0.50 MJ and radius of 1.110+0.037-0.024 RJ, on a very short period (P=1.21750007) circular orbit. KELT-1b receives a large amount of stellar insolation, with an equilibrium temperature assuming zero albedo and perfect redistribution of 2422 K. Upper limits on the secondary eclipse depth indicate that either the companion must have a non-zero albedo, or it must experience some energy redistribution. Comparison with standard evolutionary models for brown dwarfs suggests that the radius of KELT-1b is significantly inflated. Adaptive optics imaging reveals a candidate stellar companion to KELT-1, which is consistent with an M dwarf if bound. The projected spin-orbit alignment angle is consistent with ...

  19. Discovery of an M9.5 Candidate Brown Dwarf in the TW Hydrae Association - DENIS J124514.1-442907

    CERN Document Server

    Looper, Dagny L; Kirkpatrick, J Davy; Swift, Brandon J

    2007-01-01

    We report the discovery of a fifth candidate substellar system in the ~5-10 Myr TW Hydrae Association - DENIS J124514.1-442907. This object has a NIR spectrum remarkably similar to that of 2MASS J1139511-315921, a known TW Hydrae brown dwarf, with low surface gravity features such as a triangular-shaped H-band, deep H2O absorption, weak alkali lines, and weak hydride bands. We find an optical spectral type of M9.5 and estimate a mass of <24 M_Jup, assuming an age of ~5-10 Myr. While the measured proper motion for DENIS J124514.1-442907 is inconclusive as a test for membership, its position in the sky is coincident with the TW Hydrae Association. A more accurate proper motion measurement, higher resolution spectroscopy for radial velocity, and a parallax measurement are needed to derive the true space motion and to confirm its membership.

  20. New spectroscopic binary companions of giant stars and updated metallicity distribution for binary systems

    CERN Document Server

    Bluhm, P; Vanzi, L; Soto, M G; Vos, J; Wittenmyer, R A; Olivares, F; Drass, H; Mennickent, R E; Vuckovic, M; Rojo, P; Melo, C H F

    2016-01-01

    We report the discovery of 24 spectroscopic binary companions to giant stars. We fully constrain the orbital solution for 6 of these systems. We cannot unambiguously derive the orbital elements for the remaining stars because the phase coverage is incomplete. Of these stars, 6 present radial velocity trends that are compatible with long-period brown dwarf companions.The orbital solutions of the 24 binary systems indicate that these giant binary systems have a wide range in orbital periods, eccentricities, and companion masses. For the binaries with restricted orbital solutions, we find a range of orbital periods of between $\\sim$ 97-1600 days and eccentricities of between $\\sim$ 0.1-0.4. In addition, we studied the metallicity distribution of single and binary giant stars. We computed the metallicity of a total of 395 evolved stars, 59 of wich are in binary systems. We find a flat distribution for these binary stars and therefore conclude that stellar binary systems, and potentially brown dwarfs, have a diffe...

  1. The slow spin of the young sub-stellar companion GQ Lupi b and its orbital configuration

    CERN Document Server

    Schwarz, Henriette; de Kok, Remco J; Snellen, Ignas A G; Brogi, Matteo; Birkby, Jayne L

    2016-01-01

    The spin of a planet or brown dwarf is related to the accretion process, and therefore studying spin can help promote our understanding of the formation of such objects. We present the projected rotational velocity of the young sub-stellar companion GQ Lupi b, along with its barycentric radial velocity. The directly imaged exoplanet or brown dwarf companion joins a small but growing ensemble of wide-orbit sub-stellar companions with a spin measurement. The GQ Lupi system was observed at high spectral resolution (R ~ 100000), and in the analysis we made use of both spectral and spatial filtering to separate the signal of the companion from that of the host star. We detect both CO (S/N=11.6) and H2O (S/N=7.7) in the atmosphere of GQ Lupi b by cross-correlating with model spectra, and we find it to be a slow rotator with a projected rotational velocity of $5.3^{+0.9}_{-1.0}$ km/s. The slow rotation is most likely due to its young age of < 5 Myr, as it is still in the process of accreting material and angular ...

  2. CHARACTERIZATION OF THE NEARBY L/T BINARY BROWN DWARF WISE J104915.57–531906.1 AT 2 pc FROM THE SUN

    International Nuclear Information System (INIS)

    WISE J104915.57–531906.1 is a L/T brown dwarf binary located 2 pc from the Sun. The pair contains the closest known brown dwarfs and is the third closest known system, stellar or sub-stellar. We report comprehensive follow-up observations of this newly uncovered system. We have determined the spectral types of both components (L8 ± 1, for the primary, agreeing with the discovery paper; T1.5 ± 2 for the secondary, which was lacking spectroscopic type determination in the discovery paper) and, for the first time, their radial velocities (Vrad ∼ 23.1, 19.5 km s–1) using optical spectra obtained at the Southern African Large Telescope and other facilities located at the South African Astronomical Observatory (SAAO). The relative radial velocity of the two components is smaller than the range of orbital velocities for theoretically predicted masses, implying that they form a gravitationally bound system. We report resolved near-infrared JHKS photometry from the Infrared Survey Facility telescope at the SAAO which yields colors consistent with the spectroscopically derived spectral types. The available kinematic and photometric information excludes the possibility that the object belongs to any of the known nearby young moving groups or associations. Simultaneous optical polarimetry observations taken at the SAAO 1.9 m give a non-detection with an upper limit of 0.07%. For the given spectral types and absolute magnitudes, 1 Gyr theoretical models predict masses of 0.04-0.05 M☉ for the primary, and 0.03-0.05 M☉ for the secondary.

  3. 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...

  4. 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.,...

  5. Astrometric and photometric monitoring of GQ Lup and its sub-stellar companion

    CERN Document Server

    Neuhaeuser, Ralph; Seifahrt, Andreas; Schmidt, Tobias; Vogt, Nikolaus

    2008-01-01

    Neuhaeuser et al. (2005) presented direct imaging evidence for a sub-stellar companion to the young T Tauri star GQ Lup. Common proper motion was highly significant, but no orbital motion was detected. Faint luminosity, low gravity, and a late-M/early-L spectral type indicated that the companion is either a planet or a brown dwarf. We have monitored GQ Lup and its companion in order to detect orbital and parallactic motion and variability in its brightness. We also search for closer and fainter companions. We have taken six more images with the VLT Adaptive Optics instrument NACO from May 2005 to Feb 2007, always with the same calibration binary from Hipparcos for both astrometric and photometric calibration. By adding up all the images taken so far, we search for additional companions. The position of GQ Lup A and its companion compared to a nearby non-moving background object varies as expected for parallactic motion by about one pixel (2 \\pi with parallax \\pi). We could not find evidence for variability of...

  6. SUB-STELLAR COMPANIONS AND STELLAR MULTIPLICITY IN THE TAURUS STAR-FORMING REGION

    Energy Technology Data Exchange (ETDEWEB)

    Daemgen, Sebastian [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5H 3H4 (Canada); Bonavita, Mariangela [The University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Jayawardhana, Ray [Physics and Astronomy, York University, Toronto, Ontario L3T 3R1 (Canada); Lafrenière, David [Department of Physics, University of Montréal, Montréal, QC (Canada); Janson, Markus, E-mail: daemgen@astro.utoronto.ca [Department of Astronomy, Stockholm University, Stockholm (Sweden)

    2015-02-01

    We present results from a large, high-spatial-resolution near-infrared imaging search for stellar and sub-stellar companions in the Taurus-Auriga star-forming region. The sample covers 64 stars with masses between those of the most massive Taurus members at ∼3 M {sub ☉} and low-mass stars at ∼0.2 M {sub ☉}. We detected 74 companion candidates, 34 of these reported for the first time. Twenty-five companions are likely physically bound, partly confirmed by follow-up observations. Four candidate companions are likely unrelated field stars. Assuming physical association with their host star, estimated companion masses are as low as ∼2 M {sub Jup}. The inferred multiplicity frequency within our sensitivity limits between ∼10-1500 AU is 26.3{sub −4.9}{sup +6.6}%. Applying a completeness correction, 62% ± 14% of all Taurus stars between 0.7 and 1.4 M {sub ☉} appear to be multiple. Higher order multiples were found in 1.8{sub −1.5}{sup +4.2}% of the cases, in agreement with previous observations of the field. We estimate a sub-stellar companion frequency of ∼3.5%-8.8% within our sensitivity limits from the discovery of two likely bound and three other tentative very low-mass companions. This frequency appears to be in agreement with what is expected from the tail of the stellar companion mass ratio distribution, suggesting that stellar and brown dwarf companions share the same dominant formation mechanism. Further, we find evidence for possible evolution of binary parameters between two identified sub-populations in Taurus with ages of ∼2 Myr and ∼20 Myr, respectively.

  7. Very Low Mass Stellar and Substellar Companions to Solar-like Stars from MARVELS. I. A Low-mass Ratio Stellar Companion to TYC 4110-01037-1 in a 79 Day Orbit

    Science.gov (United States)

    Wisniewski, John P.; Ge, Jian; Crepp, Justin R.; De Lee, Nathan; Eastman, Jason; Esposito, Massimiliano; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; Gonzalez Hernandez, Jonay I.; Lee, Brian L.; Stassun, Keivan G.; Agol, Eric; Allende Prieto, Carlos; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N.; Porto De Mello, G. F.; Femenía, Bruno; 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; Ogando, Ricardo L. C.; Oravetz, Daniel J.; Paegert, Martin; Pan, Kaike; Pepper, Joshua; Rebolo, Rafael; Santiago, Basilio; Schneider, Donald P.; Shelden, Alaina C.; Simmons, Audrey; Tofflemire, Benjamin M.; Wan, Xiaoke; Wang, Ji; Zhao, Bo

    2012-05-01

    TYC 4110-01037-1 has a low-mass stellar companion, whose small mass ratio and short orbital period are atypical among binary systems with solar-like (T eff =0.087 ± 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (T eff tertiary body has been identified in the system via single-epoch, high contrast imagery. If this object is confirmed to be comoving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of low-mass stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.

  8. Very Low-Mass Stellar and Substellar Companions to Solar-Like Stars from MARVELS I: A Low Mass Ratio Stellar Companion to TYC 4110-01037-1 in a 79-day Orbit

    CERN Document Server

    Wisniewski, John P; Crepp, Justin R; De Lee, Nathan; Eastman, Jason; Esposito, Massimiliano; Fleming, Scott W; Gaudi, B Scott; Ghezzi, Luan; Hernandez, Jonay I Gonzalez; Lee, Brian L; Stassun, Keivan G; Agol, Eric; Prieto, Carlos Allende; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N; De Mello, G F Porto; Femenia, Bruno; 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; Ogando, Ricardo L C; Oravetz, Daniel J; Paegert, Martin; Pan, Kaike; Pepper, Joshua; Rebolo, Rafael; Santiago, Basilio; Schneider, Donald P; Shelden, Alaina C; Simmons, Audrey; Tofflemire, Benjamin M; Wan, Xiaoke; Wang, Ji; Zhao, Bo

    2012-01-01

    TYC 4110-01037-1 has a low-mass stellar companion, whose small mass ratio and short orbital period are atypical amongst solar-like (Teff ~0.087 +/- 0.003, places it at the lowest end of observed values for short period stellar companions to solar-like (Teff ~< 6000 K) stars. One possible way to create such a system would be if a triple-component stellar multiple broke up into a short period, low q binary during the cluster dispersal phase of its lifetime. A candidate tertiary body has been identified in the system via single-epoch, high contrast imagery. If this object is confirmed to be co-moving, we estimate it would be a dM4 star. We present these results in the context of our larger-scale effort to constrain the statistics of low mass stellar and brown dwarf companions to FGK-type stars via the MARVELS survey.

  9. Companions to APOGEE Stars I: A Milky Way-Spanning Catalog of Stellar and Substellar Companion Candidates and their Diverse Hosts

    CERN Document Server

    Troup, Nicholas W; De Lee, Nathan; Carlberg, Joleen; Majewski, Steven R; Fernandez, Martin; Covey, Kevin; Chojnowski, S Drew; Pepper, Joshua; Nguyen, Duy T; Stassun, Keivan; Nguyen, Duy Cuong; Wisniewski, John P; Fleming, Scott W; Bizyaev, Dmitry; Frinchaboy, Peter M; García-Hernández, D A; Ge, Jian; Hearty, Fred; Meszaros, Szabolcs; Pan, Kaike; Prieto, Carlos Allende; Schneider, Donald P; Shetrone, Matthew D; Wilson, John; Zamora, Olga

    2016-01-01

    In its three years of operation, the Sloan Digital Sky Survey (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE-1) observed $>$14,000 stars with enough epochs over a sufficient temporal baseline for the fitting of Keplerian orbits. We present the custom orbit-fitting pipeline used to create this catalog, which includes novel quality metrics that account for the phase and velocity coverage of a fitted Keplerian orbit. With a typical RV precision of $\\sim100-200$ m s$^{-1}$, APOGEE can probe systems with small separation companions down to a few Jupiter masses. Here we present initial results from a catalog of 382 of the most compelling stellar and substellar companion candidates detected by APOGEE, which orbit a variety of host stars in diverse Galactic environments. Of these, 376 have no previously known small separation companion. The distribution of companion candidates in this catalog shows evidence for an extremely truncated brown dwarf (BD) desert with a paucity of BD companions o...

  10. A Dark Spot on a Massive White Dwarf

    CERN Document Server

    Kilic, Mukremin; Bell, Keaton J; Curd, Brandon; Brown, Warren R; Hermes, J J; Dufour, Patrick; Wisniewski, John P; Winget, D E; Winget, K I

    2015-01-01

    We present the serendipitous discovery of eclipse-like events around the massive white dwarf SDSS J152934.98+292801.9 (hereafter J1529+2928). We selected J1529+2928 for time-series photometry based on its spectroscopic temperature and surface gravity, which place it near the ZZ Ceti instability strip. Instead of pulsations, we detect photometric dips from this white dwarf every 38 minutes. Follow-up optical spectroscopy observations with Gemini reveal no significant radial velocity variations, ruling out stellar and brown dwarf companions. A disintegrating planet around this white dwarf cannot explain the observed light curves in different filters. Given the short period, the source of the photometric dips must be a dark spot that comes into view every 38 min due to the rotation of the white dwarf. Our optical spectroscopy does not show any evidence of Zeeman splitting of the Balmer lines, limiting the magnetic field strength to B<70 kG. Since up to 15% of white dwarfs display kG magnetic fields, such ecli...

  11. The Solar Neighborhood. XXXIV. A Search for Planets Orbiting Nearby M Dwarfs using Astrometry

    CERN Document Server

    Lurie, John C; Jao, Wei-Chun; Quinn, Samuel N; Winters, Jennifer G; Ianna, Philip A; Koerner, David W; Riedel, Adric R; Subasavage, John P

    2014-01-01

    Astrometric measurements are presented for seven nearby stars with previously detected planets: six M dwarfs (GJ 317, GJ 667C, GJ 581, GJ 849, GJ 876, and GJ 1214) and one K dwarf (BD $-$10 3166). Measurements are also presented for six additional nearby M dwarfs without known planets, but which are more favorable to astrometric detections of low mass companions, as well as three binary systems for which we provide astrometric orbit solutions. Observations have baselines of three to thirteen years, and were made as part of the RECONS long-term astrometry and photometry program at the CTIO/SMARTS 0.9m telescope. We provide trigonometric parallaxes and proper motions for all 16 systems, and perform an extensive analysis of the astrometric residuals to determine the minimum detectable companion mass for the 12 M dwarfs not having close stellar secondaries. For the six M dwarfs with known planets, we are not sensitive to planets, but can rule out the presence of all but the least massive brown dwarfs at periods o...

  12. AN ALMA DISK MASS FOR THE CANDIDATE PROTOPLANETARY COMPANION TO FW TAU

    Energy Technology Data Exchange (ETDEWEB)

    Kraus, Adam L. [Department of Astronomy, The University of Texas at Austin, Austin, TX 78712 (United States); Andrews, Sean M. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Bowler, Brendan P. [California Institute of Technology, Division of Geological and Planetary Sciences, 1200 East California Boulevard, Pasadena, CA 91101 (United States); Herczeg, Gregory [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871 (China); Ireland, Michael J. [Research School of Astronomy and Astrophysics, Australian National University, Canberra ACT 2611 (Australia); Liu, Michael C. [Institute for Astronomy, University of Hawai' i, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Metchev, Stanimir [Department of Physics and Astronomy, The University of Western Ontario, London, ON N6A 3K7 (Canada); Cruz, Kelle L. [Department of Physics and Astronomy, Hunter College, City University of New York, New York, NY 10065 (United States)

    2015-01-01

    We present ALMA observations of the FW Tau system, a close binary pair of M5 stars with a wide-orbit (300 AU projected separation) substellar companion. The companion is extremely faint and red in the optical and near-infrared, but boasts a weak far-infrared excess and optical/near-infrared emission lines indicative of a primordial accretion disk of gas and dust. The component-resolved 1.3 mm continuum emission is found to be associated only with the companion, with a flux (1.78 ± 0.03 mJy) that indicates a dust mass of 1-2 M {sub ⊕}. While this mass reservoir is insufficient to form a giant planet, it is more than sufficient to produce an analog of the Kepler-42 exoplanetary system or the Galilean satellites. The mass and geometry of the disk-bearing FW Tau companion remains unclear. Near-infrared spectroscopy shows deep water bands that indicate a spectral type later than M5, but substantial veiling prevents a more accurate determination of the effective temperature (and hence mass). Both a disk-bearing ''planetary-mass'' companion seen in direct light or a brown dwarf tertiary viewed in light scattered by an edge-on disk or envelope remain possibilities.

  13. A possible substellar companion to the intermediate-mass giant HD 175679

    International Nuclear Information System (INIS)

    We report the discovery of a substellar companion around the intermediate-mass giant HD 175679. Precise radial velocity data of the star from the Xinglong Station and the Okayama Astrophysical Observatory revealed a Keplerian velocity variation with an orbital period of 1366.8 ± 5.7 d, a semiamplitude of 380.2 ± 3.2ms−1 and an eccentricity of 0.378 ± 0.008. Adopting a stellar mass of 2.7 ± 0.3 Mo-dot, we obtain that the minimum mass of the HD 175679 b is 37.3 ± 2.8 MJ and the semimajor axis is 3.36 ± 0.12 AU. This discovery is the second brown dwarf companion candidate from a joint planet-search program between China and Japan. (research papers)

  14. A NEW SUB-STELLAR COMPANION AROUND THE YOUNG STAR HD 284149

    International Nuclear Information System (INIS)

    Even though only a handful of sub-stellar companions have been found via direct imaging, each of these discoveries has had a tremendous impact on our understanding of the star formation process and the physics of cool atmospheres. Young stars are prime targets for direct imaging searches for planets and brown dwarfs due to the favorable brightness contrast expected at such ages and also because it is often possible to derive relatively good age estimates for these primaries. Here we present the direct imaging discovery of HD 284149 b, a 18-50 M Jup companion at a projected separation of 400 AU from a young (2510+25 Myr) F8 star, with which it shares common proper motion

  15. Sparse aperture masking at the VLT I. Faint companion detection limits for the two debris disk stars HD 92945 and HD 141569

    CERN Document Server

    Lacour, S; Amico, P; Ireland, M; Ehrenreich, D; Huelamo, N; Lagrange, A -M

    2011-01-01

    Observational data on companion statistics around young stellar systems is needed to flesh out the formation pathways for extrasolar planets and brown dwarfs. Aperture masking is a new technique that is able to address an important part of this discovery space. We observed the two debris disk systems HD 92945 and HD 141569 with sparse aperture masking (SAM), a new mode offered on the NaCo instrument at the VLT. A search for faint companions was performed using a detection strategy based on the analysis of closure phases recovered from interferograms recorded on the Conica camera. Our results demonstrate that SAM is a very competitive mode in the field of companion detection. We obtained 5 sigma high-contrast detection limits at lambda/D of 2.5x10^{-3} (\\Delta L' = 6.5) for HD 92945 and 4.6x10^{-3} (\\Delta L' = 5.8) for HD 141569. According to brown dwarf evolutionary models, our data impose an upper mass boundary for any companion for the two stars to, respectively, 18 and 22 Jupiter masses at minimum separat...

  16. Radio Emission and Orbital Motion from the Close-Encounter Star-Brown Dwarf Binary WISE J072003.20-084651.2

    CERN Document Server

    Burgasser, Adam J; Todd, Jacob; Gelino, Christopher R; Hallinan, Gregg; Gagliuffi, Daniella Bardalez

    2015-01-01

    We report the detection of radio emission and orbital motion from the nearby star-brown dwarf binary WISE J072003.20-084651.2AB. Radio observations across the 4.5-6.5 GHz band with the Very Large Array identify at the position of the system quiescent emission with a flux density of 15$\\pm$3 $\\mu$Jy, and a highly-polarized radio source that underwent a 2-3 min burst with peak flux density 300$\\pm$90 $\\mu$Jy. The latter emission is likely a low-level magnetic flare similar to optical flares previously observed for this source. No outbursts were detected in separate narrow-band H$\\alpha$ monitoring observations. We report new high-resolution imaging and spectroscopic observations that confirm the presence of a co-moving T5.5 secondary and provide the first indications of three-dimensional orbital motion. We used these data to revise our estimates for the orbital period (4.1$^{+2.7}_{-1.3}$ yr) and tightly constrain the orbital inclination to be nearly edge-on (93.6\\deg$^{+1.6\\deg}_{-1.4\\deg}$), although robust m...

  17. Testing Model Atmospheres for Young Very Low Mass Stars and Brown Dwarfs in the Infrared: Evidence for Significantly Underestimated Dust Opacities

    CERN Document Server

    Tottle, Jonathan

    2014-01-01

    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 {\\mu}m 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 (Teff) several hundred Kelvin lower than predicted by the standard Pre-Main Sequence spectral type-Teff conversion scale (where the latter is based on theoretical evolutionary models). It is only in the mid-M types that the two temperature estimates agree. (2) The Teff discrepancy in the early M types (corresponding to stellar masses above 0.6 Msol at a few Myr) probably arises from remaining uncertainties in the treatment of atmospheric convection. The agreement in the mid-M types implies a reasonably good atmospheric modeling of H2O opacities, which dominate in the infrared at these spectral types. Conversely, the Teff discrepancy in the late M types is...

  18. 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.

  19. 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.

  20. Weather on the Nearest Brown Dwarfs: Resolved Simultaneous Multi-Wavelength Variability Monitoring of WISE J104915.57-531906.1AB

    CERN Document Server

    Biller, Beth A; Mancini, Luigi; Ciceri, Simona; Southworth, John; Kopytova, Taisiya G; Bonnefoy, Mickaël; Deacon, Niall R; Schlieder, Joshua E; Buenzli, Esther; Brandner, Wolfgang; Allard, France; Homeier, Derek; Freytag, Bernd; Bailer-Jones, Coryn A L; Greiner, Jochen; Henning, Thomas; Goldman, Bertrand

    2013-01-01

    We present two epochs of MPG/ESO 2.2m GROND simultaneous 6-band ($r'i'z'JHK$) photometric monitoring of the closest known L/T transition brown dwarf binary WISE J104915.57-531906.1AB. We report here the first resolved variability monitoring of both the T0.5 and L7.5 components. We obtained 4 hours of focused observations on the night of UT 2013-04-22, as well as 4 hours of defocused (unresolved) observations on the night of UT 2013-04-16. We note a number of robust trends in our light curves. The $r'$ and $i'$ light curves appear to be anticorrelated with $z'$ and $H$ for the T0.5 component and in the unresolved lightcurve. In the defocused dataset, $J$ appears correlated with $z'$ and $H$ and anticorrelated with $r'$ and $i'$, while in the focused dataset we measure no variability for $J$ at the level of our photometric precision, likely due to evolving weather phenomena. In our focused T0.5 component lightcurve, the $K$ band lightcurve displays a significant phase offset relative to both $H$ and $z'$. We ar...

  1. AB INITIO EQUATIONS OF STATE FOR HYDROGEN (H-REOS.3) AND HELIUM (He-REOS.3) AND THEIR IMPLICATIONS FOR THE INTERIOR OF BROWN DWARFS

    International Nuclear Information System (INIS)

    We present new equations of state (EOSs) for hydrogen and helium covering a wide range of temperatures from 60 K to 107 K and densities from 10–10 g cm–3 to 103 g cm–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

  2. Measuring M dwarf Winds with DAZ White Dwarfs

    CERN Document Server

    Debes, J H

    2006-01-01

    Hydrogen atmosphere white dwarfs with metal lines, so-called DAZs, show evidence for ongoing accretion of material onto their surfaces. Some DAZs are known to have unresolved M dwarf companions, which could account for the observed accretion through a stellar wind. I combine observed Ca abundances of the DAZs with information on the orbital separation of their M dwarf companions to infer the mass loss rate of the M dwarfs. I find that for three of the six known DAZs with M dwarf companions, a stellar wind can plausibly explain the observed accretion on the white dwarfs assuming Bondi-Hoyle accretion of solar abundance stellar winds on the order of 10$^{-14}-10^{-16}\\Msun$ yr$^{-1}$. The rest of the sample have companions with orbits $\\gtorder$ 1~AU, and require companion mass loss rates of $> 10^{-11}\\Msun$ yr$^{-1}$. I conclude that there must be an alternative explanation for accretion of material onto DAZs with widely separated companions. The inferred winds for two of the close binaries are orders of magn...

  3. The Kappa Andromedae System: New Constraints on the Companion Mass, System Age & Further Multiplicity

    CERN Document Server

    Hinkley, Sasha; Faherty, Jacqueline K; Oppenheimer, Ben R; Mamajek, Eric E; Kraus, Adam L; Rice, Emily L; Ireland, Michael J; David, Trevor; Hillenbrand, Lynne A; Vasisht, Gautam; Cady, Eric; Brenner, Douglas; Veicht, Aaron; Nilsson, Ricky; Zimmerman, Neil; Parry, Ian R; Beichman, Charles; Dekany, Richard; Roberts, Jennifer E; Roberts, Lewis C; Baranec, Christoph; Crepp, Justin R; Burruss, Rick; Wallace, J Kent; King, David; Zhai, Chengxing; Lockhart, Thomas; Shao, Michael; Soummer, Remi; Sivaramakrishnan, Anand; Wilson, Louis A

    2013-01-01

    Kappa Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55 AU was recently announced. In this work, we present the first spectrum of the companion, "kappa And B," using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution YJH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ~2000K, as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and effective temperature measurements of the host star to argue that the kappa And system has an isochronal age of 220 +/- 100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of kappa And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive....

  4. An astrometric search for a stellar companion to the sun

    International Nuclear Information System (INIS)

    A companion star within 0.8 pc of the Sun has been postulated to explain a possible 26 Myr periodicity in mass extinctions of species on the Earth. Such a star would already be catalogued in the Yale Bright Star catalogue unless it is fainter than m/sub nu/ = 6.5; this limits the possible stellar types for an unseen companion to red dwarfs, brown dwarfs, or compact objects. Red dwarfs account for about 75% of these possible stars. We describe here the design and development of an astrometric search for a nearby red dwarf companion with a six-month peak-to-peak parallax of ≥2.5 arcseconds. We are measuring the parallax of 2770 candidate faint red stars selected from the Dearborn Observatory catalogue. An automated 30-inch telescope and CCD camera system collect digitized images of the candidate stars, along with a 13' x 16' surrounding field of background stars. Second-epoch images, taken a few months later, are registered to the first epoch images using the background stars as fiducials. An apparent motion, m/sub a/, of the candidate stars is found to a precision of σ/sub m//sub a/ ≅ 0.08 pixel ≅ 0.2 arcseconds for fields with N/sub fiducial/ ≥ 10 fiducial stars visible above the background noise. This precision is sufficient to detect the parallactic motion of a star at 0.8 pc with a two month interval between the observation epochs. Images with fewer fiducial stars above background noise are observed with a longer interval between epochs. If a star is found with high parallactic motion, we will confirm its distance with further parallax measurements, photometry, and spectral studies, and will measure radial velocity and proper motion to establish its orbit. We have demonstrated the search procedure with observations of 41 stars, and have shown that none of these is a nearby star. 37 refs., 16 figs., 3 tabs

  5. BEER analysis of Kepler and CoRoT light curves: IV. Discovery of four new low-mass white-dwarf companions in the Kepler data

    CERN Document Server

    Faigler, Simchon; Mazeh, Tsevi; Kiefer, Flavien; Latham, David W; Bloemen, Steven

    2015-01-01

    We report the discovery of four short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white-dwarf (WD) secondary (dA+WD) - KIC 4169521, KOI-3818, KIC 2851474 and KIC 9285587. The systems show BEaming, Ellipsoidal and Reflection (BEER) phase modulations together with primary and secondary eclipses. These add to the 6 Kepler, and 18 WASP, previously known short-period eclipsing dA+WD binaries. The light curves together with follow-up spectroscopic observations allow us to derive the masses, radii and effective temperatures of the two components of the four systems. The orbital periods, of 1.17-3.82 d, and WD masses, of 0.19-0.22 Msun, are similar to those of the previously known systems. The WD radii of KOI-3818, KIC 2851474, and KIC 9285587 are 0.026, 0.035 and 0.026 Rsun, respectively, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries. These three binaries extend the previously known population to older systems with cooler and sm...

  6. BEER Analysis of Kepler and CoRoT Light Curves. IV. Discovery of Four New Low-mass White-Dwarf Companions in the Kepler Data

    Science.gov (United States)

    Faigler, S.; Kull, I.; Mazeh, T.; Kiefer, F.; Latham, D. W.; Bloemen, S.

    2015-12-01

    We report the discovery of four short-period eclipsing systems in the Kepler light curves, consisting of an A-star primary and a low-mass white dwarf (WD) secondary (dA+WD)—KIC 4169521, KOI-3818, KIC 2851474, and KIC 9285587. The systems show BEaming, Ellipsoidal and Reflection (BEER) phase modulations together with primary and secondary eclipses. These add to the 6 Kepler and 18 WASP short-period eclipsing dA+WD binaries that were previously known. The light curves, together with follow-up spectroscopic observations, allow us to derive the masses, radii, and effective temperatures of the two components of the four systems. The orbital periods, of 1.17-3.82 days, and WD masses, of 0.19-0.22 M⊙, are similar to those of the previously known systems. The WD radii of KOI-3818, KIC 2851474, and KIC 9285587 are 0.026, 0.035, and 0.026 R⊙, respectively, the smallest WD radii derived so far for short-period eclipsing dA+WD binaries. These three binaries extend the previously known population to older systems with cooler and smaller WD secondaries. KOI-3818 displays evidence for a fast-rotating primary and a minute but significant eccentricity, ˜1.5 × 10-3. These features are probably the outcome of the mass-transfer process.

  7. Identification of the pathogen causing brown rot of Chinese Dwarf Cherry( Cerasus humilis%欧李褐腐病病原菌鉴定

    Institute of Scientific and Technical Information of China (English)

    徐成楠; 周宗山; 吴玉星; 迟福梅; 张红军

    2011-01-01

    欧李[ Cerasus humilis( Bge.) Sok.]为蔷薇科樱桃属果树,别名钙果,原产中国,分布于我国的黑龙江、辽宁、内蒙古、河北、山东、山西等省区.多生长在向阳山坡或沙丘边缘,资源相当丰富.欧李株高0.3~1.5m,多为0.5~0.7m左右,是目前世界上最矮小的木本果树.果实可鲜食或加工,含糖、蛋白质、维生素C,特别是矿质元素铁和钙的含量很高,每100果肉干分别含有58和360 mg种仁可作药用,中药称之为"郁李仁"可消毒化肿.%One serious disease happened on the fruit of Chinese Dwarf Cherry in Liaoning Province recently. The typical symptom was brown spot formed on the fruit surface. The spot spread quickly through the whole fruits, then the fruits were rotten. There were tomentum round shaped mildew formed on the surface of symptomatic fruits. The pathogen was isolated from infected fruits. After pathogenicity tests in lab and field and re-isolation, the isolate HI was determined to be responsible for the disease. HI colony on PDA was 70 -75 mm in diameter, with concentric rings in grayish or light brown color after 7 days incubation at 221 with illumination of 12 h near-UV/12 h dark. The conidia were one-celled, hyaline, lemon-shaped, (10-27) jun x (7-17) jun on PDA, produced in branched monilioid chains. The rDNA ITS sequence of islolates HI and Gl had 100% similarity with those of Monilinia fructicola in GenBank. The amplification results with three Monilinia specific primer pairs showed that only primer pair ITSlMfcl and ITS4Mfcl could amplify a 356 bp fragment. Based on the morphological characteristics and rDNA molecular analysis, the pathogen was finally identified as M. Fructicola.

  8. Radio Emission and Orbital Motion from the Close-encounter Star-Brown Dwarf Binary WISE J072003.20-084651.2

    Science.gov (United States)

    Burgasser, Adam J.; Melis, Carl; Todd, Jacob; Gelino, Christopher R.; Hallinan, Gregg; Bardalez Gagliuffi, Daniella

    2015-12-01

    We report the detection of radio emission and orbital motion from the nearby star-brown dwarf binary WISE J072003.20-084651.2AB. Radio observations across the 4.5-6.5 GHz band with the Very Large Array identify at the position of the system quiescent emission with a flux density of 15 ± 3 μJy, and a highly polarized radio source that underwent a 2-3 minute burst with peak flux density 300 ± 90 μJy. The latter emission is likely a low-level magnetic flare similar to optical flares previously observed for this source. No outbursts were detected in separate narrow-band Hα monitoring observations. We report new high-resolution imaging and spectroscopic observations that confirm the presence of a co-moving T5.5 secondary and provide the first indications of three-dimensional orbital motion. We used these data to revise our estimates for the orbital period (4.1{}-1.3+2.7 year) and tightly constrain the orbital inclination to be nearly edge-on (93.°6+1.°6-1.°4), although robust measures of the component and system masses will require further monitoring. The inferred orbital motion does not change the high likelihood that this radio-emitting very low-mass binary made a close pass to the Sun in the past 100 kyr. Some of 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.

  9. WEATHER ON THE NEAREST BROWN DWARFS: RESOLVED SIMULTANEOUS MULTI-WAVELENGTH VARIABILITY MONITORING OF WISE J104915.57–531906.1AB

    Energy Technology Data Exchange (ETDEWEB)

    Biller, Beth A.; Crossfield, Ian J. M.; Mancini, Luigi; Ciceri, Simona; Kopytova, Taisiya G.; Bonnefoy, Mickaël; Deacon, Niall R.; Schlieder, Joshua E.; Buenzli, Esther; Brandner, Wolfgang; Bailer-Jones, Coryn A. L.; Henning, Thomas; Goldman, Bertrand [Max-Planck-Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Southworth, John [Astrophysics Group, Keele University, Staffordshire, ST5 5BG (United Kingdom); Allard, France; Homeier, Derek; Freytag, Bernd [Centre de Recherche Astrophysique de Lyon, Ecole Normale Supérieure de Lyon, 46 allée d' Italie, F-69364 Lyon cedex 07 (France); Greiner, Jochen [Max-Planck Institute for extraterrestrische Physik, D-85748 Garching, Giessenbachstr (Germany)

    2013-11-20

    We present two epochs of MPG/ESO 2.2 m GROND simultaneous six-band (r'i'z' JHK) photometric monitoring of the closest known L/T transition brown dwarf binary WISE J104915.57–531906.1AB. We report here the first resolved variability monitoring of both the T0.5 and L7.5 components. We obtained 4 hr of focused observations on the night of 2013 April 22 (UT), as well as 4 hr of defocused (unresolved) observations on the night of 2013 April 16 (UT). We note a number of robust trends in our light curves. The r' and i' light curves appear to be anti-correlated with z' and H for the T0.5 component and in the unresolved light curve. In the defocused dataset, J appears correlated with z' and H and anti-correlated with r' and i', while in the focused dataset we measure no variability for J at the level of our photometric precision, likely due to evolving weather phenomena. In our focused T0.5 component light curve, the K band light curve displays a significant phase offset relative to both H and z'. We argue that the measured phase offsets are correlated with atmospheric pressure probed at each band, as estimated from one-dimensional atmospheric models. We also report low-amplitude variability in i' and z' intrinsic to the L7.5 component.

  10. WEATHER ON THE NEAREST BROWN DWARFS: RESOLVED SIMULTANEOUS MULTI-WAVELENGTH VARIABILITY MONITORING OF WISE J104915.57–531906.1AB

    International Nuclear Information System (INIS)

    We present two epochs of MPG/ESO 2.2 m GROND simultaneous six-band (r'i'z' JHK) photometric monitoring of the closest known L/T transition brown dwarf binary WISE J104915.57–531906.1AB. We report here the first resolved variability monitoring of both the T0.5 and L7.5 components. We obtained 4 hr of focused observations on the night of 2013 April 22 (UT), as well as 4 hr of defocused (unresolved) observations on the night of 2013 April 16 (UT). We note a number of robust trends in our light curves. The r' and i' light curves appear to be anti-correlated with z' and H for the T0.5 component and in the unresolved light curve. In the defocused dataset, J appears correlated with z' and H and anti-correlated with r' and i', while in the focused dataset we measure no variability for J at the level of our photometric precision, likely due to evolving weather phenomena. In our focused T0.5 component light curve, the K band light curve displays a significant phase offset relative to both H and z'. We argue that the measured phase offsets are correlated with atmospheric pressure probed at each band, as estimated from one-dimensional atmospheric models. We also report low-amplitude variability in i' and z' intrinsic to the L7.5 component

  11. Synthesizing Exoplanet Demographics: A Single Population of Long-period Planetary Companions to M Dwarfs Consistent with Microlensing, Radial Velocity, and Direct Imaging Surveys

    Science.gov (United States)

    Clanton, Christian; Gaudi, B. Scott

    2016-03-01

    We present the first study to synthesize results from five different exoplanet surveys using three independent detection methods: microlensing, radial velocity, and direct imaging. The constraints derived herein represent the most comprehensive picture of the demographics of large-separation (≳2 AU) planets orbiting the most common stars in our Galaxy that has been constructed to date. We assume a simple, joint power-law planet distribution function of the form {d}2{N}{{pl}}/(d{log} {m}p d{log} a)={ A }{({m}p/{M}{{Sat}})}α {(a/2.5{{AU}})}β with an outer cutoff radius of the separation distribution function of aout. Generating populations of planets from these models and mapping them into the relevant observables for each survey, we use actual or estimated detection sensitivities to determine the expected observations for each survey. Comparing with the reported results, we derive constraints on the parameters \\{α ,β ,{ A },{a}{{out}}\\} that describe a single population of planets that is simultaneously consistent with the results of microlensing, radial velocity, and direct imaging surveys. We find median and 68% confindence intervals of α =-{0.86}-0.19+0.21 (-{0.85}-0.19+0.21), β ={1.1}-1.4+1.9 ({1.1}-1.3+1.9), { A }={0.21}-0.15+0.20 {{dex}}-2 ({0.21}-0.15+0.20 {{dex}}-2), and {a}{{out}}={10}-4.7+26 AU ({12}-6.2+50 AU) assuming “hot-start” (“cold-start”) planet evolutionary models. These values are consistent with all current knowledge of planets on orbits beyond ∼2 AU around single M dwarfs.

  12. On Lithium-Rich Red Giants. I. Engulfment of Sub-Stellar Companions

    CERN Document Server

    Aguilera-Gómez, Claudia; Pinsonneault, Marc; Carlberg, Joleen

    2016-01-01

    A small fraction of red giants are known to be lithium (Li) rich, in contradiction with expectations from stellar evolutionary theory. A possible explanation for these atypical giants is the engulfment of a Li-rich planet or brown dwarf by the star. In this work, we model the evolution of Li abundance in canonical red giants including the accretion of a sub-stellar mass companion. We consider a wide range of stellar and companion masses, Li abundances, stellar metallicities, and planetary orbital periods. Based on our calculations, companions with masses lower than 15 M_J dissolve in the convective envelope and can induce Li enrichment in regimes where extra mixing does not operate. Our models indicate that the accretion of a substellar companion can explain abundances up to A(Li)~2.2, setting an upper limit for Li-rich giants formed by this mechanism. Giants with higher abundances need another mechanism to be explained. For reasonable planetary distributions, we predict the Li abundance distribution of low-m...

  13. Low-mass stellar and substellar companions to sdB stars

    CERN Document Server

    Geier, S; Bruenner, P; Nagel, K; Schaffenroth, V; Heuser, C; Heber, U; Drechsel, H; Edelmann, H; Koen, C; O'Toole, S J; Morales-Rueda, L

    2011-01-01

    It has been suggested that besides stellar companions, substellar objects in close orbits may be able to trigger mass loss in a common envelope phase and form hot subdwarfs. In an ongoing project we search for close substellar companions combining time resolved high resolution spectroscopy with photometry. We determine the fraction of as yet undetected radial velocity variable systems from a sample of 27 apparently single sdB stars to be 16%. We discovered low-mass stellar companions to the He-sdB CPD-20 1123 and the pulsator KPD 0629-0016. The brown dwarf reported to orbit the eclipsing binary SDSS J0820+0008 could be confirmed by an analysis of high resolution spectra taken with UVES. Reflection effects have been detected in the light curves of the known sdB binaries CPD-64 481 and BPS CS 22169-0001. The inclinations of these systems must be much higher than expected and the most likely companion masses are in the substellar regime. Finally, we determined the orbit of the sdB binary PHL 457, which has a ver...

  14. REVEALING COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION

    Energy Technology Data Exchange (ETDEWEB)

    Tokovinin, Andrei [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Hartung, Markus; Hayward, Thomas L. [Gemini Observatory, Southern Operations Center, Casilla 603, La Serena (Chile); Makarov, Valeri V., E-mail: atokovinin@ctio.noao.edu, E-mail: mhartung@gemini.edu, E-mail: thayward@gemini.edu, E-mail: valeri.makarov@usno.navy.mil [US Naval Observatory, 3450 Massachusetts Sve. NW, Washington, DC 20392-5420 (United States)

    2012-07-15

    A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67 pc has been surveyed with the Near-Infrared Coronagraphic Imager adaptive optics system at Gemini-S, directly resolving for the first time 17 subarcsecond companions and 7 wider ones. Using these data together with published speckle interferometry of 57 stars, we compare the statistics of resolved astrometric companions with those of a simulated binary population. The fraction of resolved companions is slightly lower than expected from binary statistics. About 10% of astrometric companions could be 'dark' (white dwarfs and close pairs of late M-dwarfs). To our surprise, several binaries are found with companions too wide to explain the acceleration. Re-analysis of selected intermediate astrometric data shows that some acceleration solutions in the original Hipparcos catalog are spurious.

  15. Revealing companions to nearby stars with astrometric acceleration

    CERN Document Server

    Tokovinin, Andrei; Hayward, Thomas L; Makarov, Valeri V

    2012-01-01

    A subset of 51 Hipparcos astrometric binaries among FG dwarfs within 67pc has been surveyed with the NICI adaptive optics system at Gemini-S, directly resolving for the first time 17 sub-arcsecond companions and 7 wider ones. Using these data together with published speckle interferometry of 57 stars, we compare the statistics of resolved astrometric companions with those of a simulated binary population. The fraction of resolved companions is slightly lower than expected from binary statistics. About 10% of astrometric companions could be "dark" (white dwarfs and close pairs of late M-dwarfs). To our surprise, several binaries are found with companions too wide to explain the acceleration. Re-analysis of selected intermediate astrometric data shows that some acceleration solutions in the original Hipparcos catalog are spurious.

  16. First light of the VLT planet finder SPHERE. I. Detection and characterization of the substellar companion GJ 758 B

    Science.gov (United States)

    Vigan, A.; Bonnefoy, M.; Ginski, C.; Beust, H.; Galicher, R.; Janson, M.; Baudino, J.-L.; Buenzli, E.; Hagelberg, J.; D'Orazi, V.; Desidera, S.; Maire, A.-L.; Gratton, R.; Sauvage, J.-F.; Chauvin, G.; Thalmann, C.; Malo, L.; Salter, G.; Zurlo, A.; Antichi, J.; Baruffolo, A.; Baudoz, P.; Blanchard, P.; Boccaletti, A.; Beuzit, J.-L.; Carle, M.; Claudi, R.; Costille, A.; Delboulbé, A.; Dohlen, K.; Dominik, C.; Feldt, M.; Fusco, T.; Gluck, L.; Girard, J.; Giro, E.; Gry, C.; Henning, T.; Hubin, N.; Hugot, E.; Jaquet, M.; Kasper, M.; Lagrange, A.-M.; Langlois, M.; Le Mignant, D.; Llored, M.; Madec, F.; Martinez, P.; Mawet, D.; Mesa, D.; Milli, J.; Mouillet, D.; Moulin, T.; Moutou, C.; Origné, A.; Pavlov, A.; Perret, D.; Petit, C.; Pragt, J.; Puget, P.; Rabou, P.; Rochat, S.; Roelfsema, R.; Salasnich, B.; Schmid, H.-M.; Sevin, A.; Siebenmorgen, R.; Smette, A.; Stadler, E.; Suarez, M.; Turatto, M.; Udry, S.; Vakili, F.; Wahhaj, Z.; Weber, L.; Wildi, F.

    2016-03-01

    GJ 758 B is a brown dwarf companion to a nearby (15.76%) solar-type, metal-rich (M / H = + 0.2 dex) main-sequence star (G9V) that was discovered with Subaru/HiCIAO in 2009. From previous studies, it has drawn attention as being the coldest (~600 K) companion ever directly imaged around a neighboring star. We present new high-contrast data obtained during the commissioning of the SPHERE instrument at the Very Large Telescope (VLT). The data was obtained in Y-, J-, H-, and Ks-bands with the dual-band imaging (DBI) mode of IRDIS, thus providing a broad coverage of the full near-infrared (near-IR) range at higher contrast and better spectral sampling than previously reported. In this new set of high-quality data, we report the re-detection of the companion, as well as the first detection of a new candidate closer-in to the star. We use the new eight photometric points for an extended comparison of GJ 758 B with empirical objects and four families of atmospheric models. From comparison to empirical object, we estimate a T8 spectral type, but none of the comparison objects can accurately represent the observed near-IR fluxes of GJ 758 B. From comparison to atmospheric models, we attribute a Teff = 600 ± 100 K, but we find that no atmospheric model can adequately fit all the fluxes of GJ 758 B. The lack of exploration of metal enrichment in model grids appears as a major limitation that prevents an accurate estimation of the companion physical parameters. The photometry of the new candidate companion is broadly consistent with L-type objects, but a second epoch with improved photometry is necessary to clarify its status. The new astrometry of GJ 758 B shows a significant proper motion since the last epoch. We use this result to improve the determination of the orbital characteristics using two fitting approaches: Least-Squares Monte Carlo and Markov chain Monte Carlo. We confirm the high-eccentricity of the orbit (peak at 0.5), and find a most likely semi-major axis of

  17. Search for light curve modulations among Kepler candidates. Three very low-mass transiting companions

    Science.gov (United States)

    Lillo-Box, J.; Ribas, A.; Barrado, D.; Merín, B.; Bouy, H.

    2016-07-01

    Context. Light curve modulations in the sample of Kepler planet candidates allows the disentangling of the nature of the transiting object by photometrically measuring its mass. This is possible by detecting the effects of the gravitational pull of the companion (ellipsoidal modulations) and in some cases, the photometric imprints of the Doppler effect when observing in a broad band (Doppler beaming). Aims: We aim to photometrically unveil the nature of some transiting objects showing clear light curve modulations in the phase-folded Kepler light curve. Methods: We selected a subsample among the large crop of Kepler objects of interest (KOIs) based on their chances to show detectable light curve modulations, i.e., close (a< 12 R⋆) and large (in terms of radius, according to their transit signal) candidates. We modeled their phase-folded light curves with consistent equations for the three effects, namely, reflection, ellipsoidal and beaming (known as REB modulations). Results: We provide detailed general equations for the fit of the REB modulations for the case of eccentric orbits. These equations are accurate to the photometric precisions achievable by current and forthcoming instruments and space missions. By using this mathematical apparatus, we find three close-in very low-mass companions (two of them in the brown dwarf mass domain) orbiting main-sequence stars (KOI-554, KOI-1074, and KOI-3728), and reject the planetary nature of the transiting objects (thus classifying them as false positives). In contrast, the detection of the REB modulations and transit/eclipse signal allows the measurement of their mass and radius that can provide important constraints for modeling their interiors since just a few cases of low-mass eclipsing binaries are known. Additionally, these new systems can help to constrain the similarities in the formation process of the more massive and close-in planets (hot Jupiters), brown dwarfs, and very low-mass companions.

  18. Google+ companion

    CERN Document Server

    Hattersley, Mark

    2012-01-01

    Get the inside scoop on the newest social networking site: Google+ If you think you've seen it all when it comes to social networking sites, you haven't seen Google+ yet! Built from the ground up to be useful to both desktop and mobile users, Google+ offers the same great features as other popular social network sites?yet, Google+ goes one step further by integrating popular Google technologies and introducing exciting new and unique features such as "Circles," "Hang," and "Sparks." Using clear, step-by-step instructions, Google+ Companion helps you master this amazing new social networking te

  19. Droid Companion

    CERN Document Server

    Butow, Eric

    2011-01-01

    New owner of a Droid? Enjoy it even more with this perfect guide Congratulations on owning one of the hottest smartphones on the planet—more than 400,000 new Android phones are activated every day! Now get the very most out your new Droid with this handy companion by your side. Covering several versions of the Droid phones in one comprehensive guide, this book provides you with helpful information on everything from setup to the fun features of each Droid model. You'll quickly get up to speed on everything from email, browsing, and calendars to photos, maps, apps, security, and more. Hig

  20. THE PROPERTIES OF THE 500 K DWARF UGPS J072227.51–054031.2 AND A STUDY OF THE FAR-RED FLUX OF COLD BROWN DWARFS

    International Nuclear Information System (INIS)

    We present i and z photometry for 25 T dwarfs and 1 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 Teff ≈ 600 K. We present new 0.7-1.0 μm and 2.8-4.2 μm 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 new and published data, with Saumon and Marley models, shows that the dwarf has Teff = 505 ± 10 K, a mass of 3-11 MJupiter, 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 4.5 μm photometry and the Saumon and Marley models. The optical spectrum for this 500 K object shows clearly detected lines of the neutral alkalis Cs and Rb, which are emitted from deep atmospheric layers with temperatures of 900-1200 K.

  1. 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...

  2. A Mid-Infrared Search for Substellar Companions of Nearby Planet-Host Stars

    CERN Document Server

    Hulsebus, Alan; Carson, Joe; Stapelfeldt, Karl

    2014-01-01

    Determining the presence of widely separated substellar-mass companion is crucial to understand the dynamics of inner planets in extrasolar planetary systems (e.g. to explain their high mean eccentricity as inner planets are perturbed by the Kozai mechanism). We report the results of our $\\textit{Spitzer}$/Infrared Array Camera (IRAC) imaging search for widely separated (10 to 25$^{\\prime\\prime}$) substellar-mass companions for 14 planet-host stars within 15 pc of the Sun. Using deep 3.6 and 4.5 $\\mu$m observations in subarray mode, we found one object in the field of 47 UMa with [3.6]$-$[4.5] color similar to a T5 dwarf, which is, however, unlikely to share common proper motion with 47 UMa. We also found three objects with brown-dwarf-like [3.6]$-$[4.5] color limits in the fields of GJ 86, HD 160691, and GJ 581, as well as another in the field of HD 69830 for which we have excluded common proper motion. We provide model-based upper mass limits for unseen objects around all stars in our sample, with typical s...

  3. Overlooked wide companions of nearby F stars

    Science.gov (United States)

    Scholz, R.-D.

    2016-03-01

    Aims: We checked a sample of 545 F stars within 50 pc for wide companions using existing near-infrared and optical sky surveys. Methods: Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120 arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in proper motion catalogues. Final proper motions were measured by involving positional measurements from up to eleven surveys. Spectral types of red CPM companions were estimated from their absolute J-band magnitudes based on the Hipparcos distances of the primaries. Results: In addition to about 100 known CPM objects, we found 19 new CPM companions and confirmed 31 previously known candidates. A few CPM objects are still considered as candidates according to their level of proper motion agreement. Among the new objects there are nine M0-M4, eight M5-M6, one ≈L3.5 dwarf (HD 3861B), and one white dwarf (WD) (HD 2726B), whereas we confirmed two K, 19 M0-M4, six M5-M6, two early-L dwarfs, and two DA WDs as CPM companions. In a few cases, previous spectral types were available that all agree well with our estimates. Two companions (HD 22879B and HD 49933B) are associated with moderately metal-poor Gaia benchmark stars. One doubtful CPM companion, spectroscopically classified as WD but found to be very bright (J = 11.1) by others, should either be a very nearby foreground WD or a different kind of object associated with HD 165670. Tables A.1, B.1, and C.1 are also available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/587/A51

  4. 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...

  5. Mystery of a Dimming White Dwarf

    Science.gov (United States)

    Kohler, Susanna

    2015-12-01

    In the wake of the recent media attention over an enigmatic, dimming star, another intriguing object has been discovered: J1529+2928, a white dwarf that periodically dims. This mystery, however, may have a simple solution with interesting consequences for future surveys of white dwarfs.Unexpected VariabilityJ1529+2928 is an isolated white dwarf that appears to have a mass of slightly more than the Sun. But rather than radiating steadily, J1529+2928 dims once every 38 minutes almost as though it were being eclipsed.The team that discovered these variations, led by Mukremin Kilic (University of Oklahoma), used telescopes at the Apache Point Observatory and the McDonald Observatory to obtain follow-up photometric data of J1529+2928 spread across 66 days. The team also took spectra of the white dwarf with the Gemini North telescope.Kilic and collaborators then began, one by one, to rule out possible causes of this objects variability.Eliminating OptionsThe period of the variability is too long for J1529+2928 to be a pulsating white dwarf with luminosity variation caused by gravity-wave pulsations.The variability cant be due to an eclipse by a stellar or brown-dwarf companion, because there isnt any variation in J1529+2928s radial velocity.Its not due to the orbit of a solid-body planetary object; such a transit would be too short to explain observations.It cant be due to the orbit of a disintegrated planet; this wouldnt explain the light curves observed in different filters plus the light curve doesnt change over the 66-day span.Spotty SurfaceTop and middle two panels: light curves from three different nights observing J1529+2928s periodic dimming. Bottom panel: The Fourier transform shows a peak at 37.7 cycles/day (and another, smaller peak at its first harmonic). [Kilic et al. 2015]So what explanation is left? The authors suggest that J1529+2928s variability is likely caused by a starspot on the white dwarfs surface that rotates into and out of our view. Estimates

  6. ACCRETION ONTO PLANETARY MASS COMPANIONS OF LOW-MASS YOUNG STARS

    International Nuclear Information System (INIS)

    Measurements of accretion rates onto planetary mass objects may distinguish between different planet formation mechanisms, which predict different accretion histories. In this Letter, we use Hubble Space Telescope (HST)/WFC3 UVIS optical photometry to measure accretion rates onto three accreting objects, GSC 06214–00210 b, GQ Lup b, and DH Tau b, that are at the planet/brown dwarf boundary and are companions to solar mass stars. The excess optical emission in the excess accretion continuum yields mass accretion rates of 10–9-10–11 M ☉ yr–1 for these three objects. Their accretion rates are an order of magnitude higher than expected from the correlation between mass and accretion rates measured from the UV excess, which is applicable if these wide planetary mass companions formed by protostellar core fragmentation. The high accretion rates and large separation from the central star demonstrate the presence of massive disks around these objects. Models for the formation and evolution of wide planetary mass companions should account for their large accretion rates. High ratios of Hα luminosity over accretion luminosity for objects with low accretion rates suggest that searches for Hα emission may be an efficient way to find accreting planets

  7. A Substellar Companion to the Intermediate-Mass Giant 11 Com

    CERN Document Server

    Liu, Y J; Zhao, G; Noguchi, Kunio; Wang, H; Kambe, Eiji; Ando, Hiroyasu; Izumiura, Hideyuki; Chen, Y Q; Okada, Norio; Toyota, Eri; Omiya, Masashi; Masuda, Seiji; Takeda, Yoichi; Murata, Daisuke; Itoh, Yoichi; Yoshida, Michitoshi; Kokubo, Eiichiro; Ida, Shigeru

    2007-01-01

    We report the detection of a substellar companion orbiting the intermediate-mass giant star 11 Com (G8 III). Precise Doppler measurements of the star from Xinglong station and Okayama Astrophysical Observatory (OAO) revealed Keplerian velocity variations with an orbital period of 326.03 +/- 0.32 days, a semiamplitude of 302.8 +/- 2.6 m/s, and an eccentricity of 0.231 +/- 0.005. Adopting a stellar mass of 2.7 +/- 0.3 M_solar, the minimum mass of the companion is 19.4 +/- 1.5 M_Jup, well above the deuterium burning limit, and the semimajor axis is 1.29 +/- 0.05 AU. This is the first result from the joint planet search program between China and Japan aiming at revealing statistics of substellar companions around intermediate-mass giants. 11 Com b emerged from 300 targets of the planet search program at OAO. The current detection rate of a brown dwarf candidate seems to be comparable to that around solar-type stars within orbital separations of $\\sim$3 AU.

  8. AA Doradus and its Cool Companion - The Influence of Enhanced Metal Line Blanketing and the Reflection Effect

    CERN Document Server

    Müller, Sebastian; Heber, Ulrich

    2010-01-01

    AA Dor is one of only twelve so called HW-Vir systems, which are perfectly suited to determine fundamental properties like radii and masses of the components. These systems are hot subdwarf binaries which additionally show eclipses in their light curves. So far AA Dor has been studied in many investigations, however, a controversy about the nature of the unseen companion still persists. Since the influence of substellar companions on the evolution of hot subdwarfs is still unclear, the question whether the companion is a brown dwarf or a low mass main sequence star is a crucial one. To reveal the companions nature, we re-analysed high resolution spectra using metal enhanced LTE model atmospheres. Since the optical spectra are polluted by reflected light from the secondary component, we used only spectra taken during epochs when the secondary was eclipsed. Besides the atmospheric parameters effective temperature T_eff, surface gravity log(g), the helium abundance log(y) and the projected rotational velocity v_...

  9. COMPANIONS TO NEARBY STARS WITH ASTROMETRIC ACCELERATION. II

    Energy Technology Data Exchange (ETDEWEB)

    Tokovinin, Andrei [Cerro Tololo Inter-American Observatory, Casilla 603, La Serena (Chile); Hartung, Markus; Hayward, Thomas L., E-mail: atokovinin@ctio.noao.edu, E-mail: mhartung@gemini.edu, E-mail: thayward@gemini.edu [Gemini Observatory, Southern Operations Center, Casilla 603, La Serena (Chile)

    2013-07-01

    Hipparcos astrometric binaries were observed with the NICI adaptive optics system at Gemini-S, completing the work of Paper I. Among the 65 F, G, and K dwarfs within 67 pc of the Sun studied here, we resolve 18 new subarcsecond companions, remeasure 7 known astrometric pairs, and establish the physical nature of yet another 3 wider companions. The 107 astrometric binaries targeted at Gemini so far have 38 resolved companions with separations under 3''. Modeling shows that bright enough companions with separations on the order of an arcsecond can perturb the Hipparcos astrometry when they are not accounted for in the data reduction. However, the resulting bias of parallax and proper motion is generally below formal errors and such companions cannot produce fake acceleration. This work contributes to the multiplicity statistics of nearby dwarfs by bridging the gap between spectroscopic and visual binaries and by providing estimates of periods and mass ratios for many astrometric binaries.

  10. 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...

  11. Observational Constraints on the Origin of Metals in Cool DA-type White Dwarfs

    CERN Document Server

    Chary, R R; Becklin, E E

    1998-01-01

    We present ISOCAM 7 micron and 15 micron observations of 12 nearby white dwarfs, 6 of which have been found to have metals such as Ca, Mg and Fe in their photospheres. Our purpose was to search for an excess of infrared emission above the stellar photospheres. We find that none of the white dwarfs other than G29-38 shows a detectable infrared excess and this places strong constraints on the existence of a dusty disk around these stars. We conclude that ongoing accretion of the interstellar medium seems an unlikely explanation for the existence of metals in the photospheres of cool hydrogen atmosphere white dwarfs. The excess associated with G29-38 is 3.8+/-1.0 mJy and 2.9+/-0.6 mJy at 7 micron and 15 micron respectively. The broadband spectrum of this star strengthens the hypothesis that the infrared excess arises from a disk of particulate matter surrounding the white dwarf rather than from a cool brown dwarf companion.

  12. New Extinction and Mass Estimates of the Low-mass Companion 1RXS 1609 B with the Magellan AO System: Evidence of an Inclined Dust Disk

    CERN Document Server

    Wu, Ya-Lin; Males, Jared R; Barman, Travis S; Morzinski, Katie M; Follette, Katherine B; Bailey, Vanessa P; Rodigas, Timothy J; Hinz, Philip; Puglisi, Alfio; Xompero, Marco; Briguglio, Runa

    2015-01-01

    We used the Magellan adaptive optics system to image the 11 Myr substellar companion 1RXS 1609 B at the bluest wavelengths to date (z' and Ys). Comparison with synthetic spectra yields a higher temperature than previous studies of $T_\\mathrm{eff}=2000\\pm100\\mathrm{K}$ and significant dust extinction of $A_V=4.5^{+0.5}_{-0.7}$ mag. Mass estimates based on the DUSTY tracks gives 0.012-0.015 Msun, making the companion likely a low-mass brown dwarf surrounded by a dusty disk. Our study suggests that 1RXS 1609 B is one of the 25% of Upper Scorpius low-mass members harboring disks, and it may have formed like a star and not a planet out at 320 AU.

  13. White Dwarf Planets from GAIA

    OpenAIRE

    Silvotti, Roberto; Sozzetti, Alessandro; Lattanzi, Mario

    2010-01-01

    We investigate the potential of high-precision astrometry with GAIA for detection of giant planetary companions to nearby white dwarfs. If one considers that, to date, no confirmed planets around single white dwarfs are known, the results from GAIA will be crucial to study the late-stage evolution of planetary systems and to verify the possibility that 2nd-generation planets are formed.

  14. Evidence for a solar companion star

    International Nuclear Information System (INIS)

    Periodicity seen in both the mass extinctions and large impact cratering on earth can be explained if one postulates that the sun has a companion star, orbiting in a moderately eccentric orbit with a major axis of 2.8 light-years. No other explanations that have been suggested are compatible with known facts of physics and astronomy. If the companion is a red dwarf star, the most common kind in the galaxy, then no previous astronomical observations would have found it. A search for red objects with large parallax is now underway at Berkeley, and has a good chance of identifying the star in the near future

  15. Merging White Dwarfs and Thermonuclear Supernovae

    OpenAIRE

    van Kerkwijk, Marten H.

    2012-01-01

    Thermonuclear supernovae result when interaction with a companion reignites nuclear fusion in a carbon-oxygen white dwarf, causing a thermonuclear runaway, a catastrophic gain in pressure, and the disintegration of the whole white dwarf. It is usually thought that fusion is reignited in near-pycnonuclear conditions when the white dwarf approaches the Chandrasekhar mass. I briefly describe two long-standing problems faced by this scenario, and our suggestion that these supernovae instead resul...

  16. Planets Around Low-Mass Stars (PALMS). IV. The Outer Architecture of M Dwarf Planetary Systems

    CERN Document Server

    Bowler, Brendan P; Shkolnik, Evgenya L; Tamura, Motohide

    2014-01-01

    We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (>1 MJup) around 122 newly identified nearby (<40 pc) young M dwarfs. Half of our targets are younger than 135 Myr and 90% are younger than the Hyades (620 Myr). Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14 mag and 9-13 mag at 1", respectively, which corresponds to limiting planet masses of 0.5-10 MJup at 5-33 AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720 B (32 $\\pm$ 6 MJup; L0$^{+2}_{-1}$; 120 $\\pm$ 20 AU), GJ 3629 B (64$^{+30}_{-23}$ MJup; M7.5 $\\pm$ 0.5; 6.5 $\\pm$ 0.5 AU), 1RXS J034231.8+121622 B (35 $\\pm$ 8 MJup; L0 $\\pm$ 1; 19.8 $\\pm$ 0.9 AU), and 2MASS J15594729+4403595 B (43 $\\pm$ 9 MJup; M8.0 $\\pm$ 0.5; 190 $\\pm$ 20 AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of...

  17. Discovery of the Accretion-Powered Millisecond Pulsar SWIFT 51756.9-2508 with a Low-Mass Companion

    Science.gov (United States)

    Krimm, H.A.; Markwardt, C.B.; Deloye, C.J.; Romano, P.; Chakrabarty, S.; Campana. S.; Cummings, J.C.; Galloway, D.K.; Gehrels, N.; Hartman, J.M.; Kaaret, P.; Morgan, E.H.; Tueller, J

    2007-01-01

    We report on the discovery by the Swift Gamma-Ray Burst Explorer of the eighth known transient accretion-powered millisecond pulsar: SWIFT J1756.9-2508, as part of routine observations with the Swift Burst Alert Telescope hard X-ray transient monitor. The pulsar was subsequently observed by both the X-Ray Telescope on Swift and the Rossi X-Ray Timing Explorer Proportional Counter Array. It has a spin frequency of 182 Hz (5.5 ms) and an orbital period of 54.7 minutes. The minimum companion mass is between 0.0067 and 0.0086 Solar Mass, depending on the mass of the neutron star, and the upper limit on the mass is 0.030 Solar Mass (95% confidence level). Such a low mass is inconsistent with brown dwarf models. and comparison with white dwarf models suggests that the companion is a He-dominated donor whose thermal cooling has been at least modestly slowed by irradiation from the accretion flux. No X-ray bursts. dips, eclipses or quasi-periodic oscillations were detected. The current outburst lasted approx. 13 days and no earlier outbursts were found in archival data.

  18. Gas-Rich Companions of Isolated Galaxies

    CERN Document Server

    Pisano, D J; Wilcots, Eric M.

    1999-01-01

    We have used the VLA to search for gaseous remnants of the galaxy formation process around six extremely isolated galaxies. We found two distinct HI clouds around each of two galaxies in our sample (UGC 9762 & UGC 11124). These clouds are rotating and appear to have optical counterparts, strongly implying that they are typical dwarf galaxies. The companions are currently weakly interacting with the primary galaxy, but have short dynamical friction timescales (~1 Gyr) suggesting that these triple galaxy systems will shortly collapse into one massive galaxy. Given that the companions are consistent with being in circular rotation about the primary galaxy, and that they have small relative masses, the resulting merger will be a minor one. The companions do, however, contain enough gas that the merger will represent a significant infusion of fuel to drive future star formation, bar formation, or central activity, while building up the mass of the disk thus making these systems important pieces of the galaxy f...

  19. Overlooked wide companions of nearby F stars

    CERN Document Server

    Scholz, Ralf-Dieter

    2016-01-01

    AIMS: We checked a sample of 545 F stars within 50 pc for wide companions using existing near-infrared and optical sky surveys. METHODS: Applying the common proper motion (CPM) criterion, we detected wide companion candidates with 6-120 arcsec angular separations by visual inspection of multi-epoch finder charts and by searching in proper motion catalogues. Final proper motions were measured by involving positional measurements from up to eleven surveys. Spectral types of red CPM companions were estimated from their absolute $J$-band magnitudes based on the Hipparcos distances of the primaries. RESULTS: In addition to about 100 known CPM objects, we found 19 new CPM companions and confirmed 31 previously known candidates. A few CPM objects are still considered as candidates according to their level of proper motion agreement. Among the new objects there are nine M0-M4, eight M5-M6, one $\\approx$L3.5 dwarf (HD 3861B), and one white dwarf (WD) (HD 2726B), whereas we confirmed two K, 19 M0-M4, six M5-M6, two ear...

  20. PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS

    International Nuclear Information System (INIS)

    We present results from a high-contrast adaptive optics imaging search for giant planets and brown dwarfs (≳1 M Jup) around 122 newly identified nearby (≲40 pc) young M dwarfs. Half of our targets are younger than 135 Myr and 90% are younger than the Hyades (620 Myr). After removing 44 close stellar binaries (implying a stellar companion fraction of >35.4% ± 4.3% within 100 AU), 27 of which are new or spatially resolved for the first time, our remaining sample of 78 single M dwarfs makes this the largest imaging search for planets around young low-mass stars (0.1-0.6 M ☉) to date. Our H- and K-band coronagraphic observations with Keck/NIRC2 and Subaru/HiCIAO achieve typical contrasts of 12-14 mag and 9-13 mag at 1'', respectively, which correspond to limiting planet masses of 0.5-10 M Jup at 5-33 AU for 85% of our sample. We discovered four young brown dwarf companions: 1RXS J235133.3+312720 B (32 ± 6 M Jup; L0−1+2; 120 ± 20 AU), GJ 3629 B (64−23+30 M Jup; M7.5 ± 0.5; 6.5 ± 0.5 AU), 1RXS J034231.8+121622 B (35 ± 8 M Jup; L0 ± 1; 19.8 ± 0.9 AU), and 2MASS J15594729+4403595 B (43 ± 9 M Jup; M8.0 ± 0.5; 190 ± 20 AU). Over 150 candidate planets were identified; we obtained follow-up imaging for 56% of these but all are consistent with background stars. Our null detection of planets enables strong statistical constraints on the occurrence rate of long-period giant planets around single M dwarfs. We infer an upper limit (at the 95% confidence level) of 10.3% and 16.0% for 1-13 M Jup planets between 10-100 AU for hot-start and cold-start (Fortney) evolutionary models, respectively. Fewer than 6.0% (9.9%) of M dwarfs harbor massive gas giants in the 5-13 M Jup range like those orbiting HR 8799 and β Pictoris between 10-100 AU for a hot-start (cold-start) formation scenario. The frequency of brown dwarf (13-75 M Jup) companions to single M dwarfs between 10-100 AU is 2.8−1.5+2.4%. Altogether we find that