WorldWideScience

Sample records for brown dwarf ulas

  1. How, Now, Brown Dwarfs?

    Science.gov (United States)

    Brecher, Kenneth

    2009-01-01

    The vocabulary of astronomy is riddled with colorful names for stars, from red giants to blue stragglers. Objects with masses between roughly .01 and .1 solar masses are called "brown dwarfs". Do they - could they - ever actually appear brown? Color is not a one-dimensional physical parameter like wavelength. It is a complex, psychophysical phenomenon involving not only three degrees of freedom - hue (often incorrectly equated with "color"), saturation and brightness - but also observational context. The perceptual nature of color has been known since Newton wrote in his "Opticks” in 1704: "For the Rays to speak properly are not coloured. In them there is nothing else than a certain Power and disposition to stir up a Sensation of this or that Colour.” To most observers, the 2000 or so naked eye stars observable from the northern hemisphere all appear white, with the half dozen exceptions which look reddish/orange like Betelgeuse, Arcturus and Antares. But what color would Betelgeuse (effective temperature 3600 K) appear at a distance of, say, 100 times the Earth-Sun separation? Not red. In fact, it has a temperature about 40% higher than that of an ordinary incandescent light bulb. It would appear white (or yellowish)! Can a very cool radiating (emissive) object ever appear brown? What is brown anyway? It is not a primary or even secondary color. In this presentation, we will explore the nature and meaning of "brown” by the use of several physical and computer demonstrations developed as part of "Project LITE- Light Inquiry Through Experiments", an educational materials development project. These demonstrations show that an isolated thermally radiating object will never appear brown. Hence the term "Brown Dwarf” is as nonsensical as the phrase "How, Now, Brown Cow?". Project LITE is supported by the NSF through DUE Grant # 0715975.

  2. 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 ...

  3. 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.

  4. Radial Velocity Variability of Field Brown Dwarfs

    Science.gov (United States)

    Prato, L.; Mace, G. N.; Rice, E. L.; McLean, I. S.; Kirkpatrick, J. Davy; Burgasser, A. J.; Kim, Sungsoo S.

    2015-07-01

    We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R ˜ 20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph at the W. M. Keck Observatory. With a radial velocity (RV) precision of ˜2 km s-1, we are sensitive to brown dwarf companions in orbits with periods of a few years or less given a mass ratio of 0.5 or greater. We do not detect any spectroscopic binary brown dwarfs in the sample. Given our target properties, and the frequency and cadence of observations, we use a Monte Carlo simulation to determine the detection probability of our sample. Even with a null detection result, our 1σ upper limit for very low mass binary frequency is 18%. Our targets included seven known, wide brown dwarf binary systems. No significant RV variability was measured in our multi-epoch observations of these systems, even for those pairs for which our data spanned a significant fraction of the orbital period. Specialized techniques are required to reach the high precisions sensitive to motion in orbits of very low-mass systems. For eight objects, including six T dwarfs, we present the first published high-resolution spectra, many with high signal to noise, that will provide valuable comparison data for models of brown dwarf atmospheres.

  5. Lightning on exoplanets and brown dwarfs

    OpenAIRE

    Hodosán, Gabriella

    2017-01-01

    Lightning is an important electrical phenomenon, known to exist in several Solar System planets. Amongst others, it carries information on convection and cloud formation, and may be important for pre-biotic chemistry. Exoplanets and brown dwarfs have been shown to host environments appropriate for the initiation of lightning discharges. In this PhD project, I aim to determine if lightning on exoplanets and brown dwarfs can be more energetic than it is known from Solar System planets, what are...

  6. The Luminosities of the Coldest Brown Dwarfs

    Science.gov (United States)

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

    2014-11-01

    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. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  7. 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.

  8. Whither do the microlensing Brown Dwarfs rove?

    CERN Document Server

    De Rújula, Alvaro; Mollerach, S; Roulet, Esteban; de Rujula, A; Giudice, G; Mollerach, S; Roulet, E

    1995-01-01

    The EROS and MACHO collaborations have reported observations of light curves of stars in the Large Magellanic Cloud that are compatible with gravitational microlensing by intervening massive objects, presumably Brown-Dwarf stars. The OGLE and MACHO teams have also seen similar events in the direction of the galactic Bulge. Current data are insufficient to decide whether the Brown-Dwarfs are dark-matter constituents of the non-luminous galactic Halo, or belong to a more conventional population, such as that of faint stars in the galactic Spheroid, in its Thin or Thick Disks, or in their possible LMC counterparts. We discuss in detail how further observations of microlensing rates and of the moments of the distribution of event durations, can help resolve the issue of the Brown-Dwarf location, and eventually provide information on the mass function of the dark objects.

  9. 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....... Conclusions. As far as we are aware, this is the first detection using the microlensing technique of a binary system in our Galaxy composed of an M-star and a brown dwarf....... gives two local minima, which correspond to the theoretical degeneracy s ≡ s-1. We find that the lens is composed of a brown dwarf secondary of mass MS = 0.05 M⊙ orbiting a primary M-star of mass MP = 0.18 M⊙. We also reveal a new mass-ratio degeneracy for the central caustics of close binaries...

  10. New brown dwarf candidates in the Pleiades

    Science.gov (United States)

    Eisenbeiss, T.; Moualla, M.; Mugrauer, M.; Schmidt, T. O. B.; Raetz, St.; Neuhäuser, R.; Ginski, Ch.; Hohle, M. M.; Koeltzsch, A.; Marka, C.; Rammo, W.; Reithe, A.; Roell, T.; Vaňko, M.

    2009-05-01

    We have performed deep, wide-field imaging on a ˜ 0.4 deg2 field in the Pleiades (Melotte 22). The selected field was not yet target of a deep search for low mass stars and brown dwarfs. Our limiting magnitudes are R˜22 mag and I˜20 mag, sufficient to detect brown dwarf candidates down to 40 MJ. We found 197 objects, whose location in the (I, R-I) color magnitude diagram is consistent with the age and the distance of the Pleiades. Using CTK R and I as well as JHK photometry from our data and the 2MASS survey we were able to identify 7 new brown dwarf candidates. We present our data reduction technique, which enables us to resample, calibrate, and co-add many images by just two steps. We estimate the interstellar extinction and the spectral type from our optical and the NIR data using a two-dimensional χ2 fitting. Based on observations obtained with telescopes of the University Observatory Jena, which is operated by the Astrophysical Institute of the Friedrich- Schiller-University. Table A3 is available at the CDS via http://cdsarc.u-strasbg.fr/pub/cats/J/AN/330/439

  11. The NIRSPEC Brown Dwarf Spectroscopic Survey

    Science.gov (United States)

    McGovern, M. R.; McLean, I. S.; Prato, L.; Burgasser, A. J.; Kirkpatrick, J. D.

    2002-12-01

    The major goal of the NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS - McLean et al. 2000, ApJ, 533, L45) is to obtain a complete sample of low resolution (R ~ 2000) spectra spanning the M, L, and T dwarf sub-classes in order to extend spectral classification schemes to near-infrared wavebands and to investigate the spectral signatures of temperature, gravity, and composition by comparison to theoretical models. Additional goals include the acquisition of higher resolution spectra (R ~ 25,000) of a sub-sample of the survey for detailed comparison with models and to search for radial velocity variations. The initial phase of the survey is complete with the acquisition of low resolution J-band spectra for two objects per sub-class spanning the range M6 to T8, with one object every other sub-class, in the same range, observed from 0.9-2.35 microns to produce a complete, flux-calibrated spectrum overlapping with previously obtained Keck LRIS data from 0.5-1.0 microns. Several of the brighter sources have also been observed at high resolution at J-band. To date, over 70 objects have been studied including 17 M dwarfs, 36 L dwarfs and 18 T dwarfs. Results from the initial phase of the survey are presented along with some preliminary results from our next directed phase study into the investigation of gravity signatures in these low-mass objects based upon infrared spectral features.

  12. Brown Dwarf Like Behaviors of Jupiter

    Science.gov (United States)

    Ghosh, K.

    2007-06-01

    Jupiter is by far the most massive object in our solar system after the Sun having mass of about 10-3 M&odot, M&odot being the mass of the Sun. Its density is significantly lower than that of the inner planets; just 1.3 g cm-3 while the densities of Mercury, Venus, Earth and Mars are respectively 5.4, 5.3, 5.5 and 3.9 g cm-3. Jupiter radiates more energy into space than it receives from the Sun. It is proposed that the interior of Jupiter has excess energy stored since the time of its collapse. The heat is also generated by the Kelvin-Helmholtz mechanism, the slow gravitational compression of the configuration. This heat within Jupiter contributes to the unusual motion in the internal rotation in Jupiter. Motions in the interior of Jupiter contribute in a very special way to the development of the powerful and extensive magnetosphere of Jupiter. These observations indicate that the composition of Jupiter is basically different from that of the inner planets and these properties of Jupiter are significantly similar to the features of rotating brown dwarfs under the consideration of magnetic field which are thought to be objects having mass between stars and planets. The stellar bodies with mass less than the lower mass limit of the main sequence become completely degenerate as a consequence of gravitational contraction and consequently they cannot go through normal stellar evolution. Primarily they were named 'Black Dwarf.' The modern term for these objects is 'Brown Dwarf.' In their young age (<10^8 years) they contract rapidly and the gravitational binding energy released makes them quite luminous, but as they age they cool rapidly and make them harder to detect. Calculations show a significant similarity in this paper between the presently observed configuration of Jupiter with that of the model brown dwarf under the consideration of internal rotation and magnetic field with mass, composition and age same that of Jupiter which leads to to a conclusion that

  13. 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

  14. Brown Dwarfs: Up Close and Physical

    Science.gov (United States)

    Basri, G. B.

    2003-12-01

    I review what has now been nearly a decade of progress in the study of brown dwarfs as physical objects. The definition of brown dwarfs as distinct from stars or planets has some subtlety, and is an amalgam of considerations. I briefly discuss their internal structure, and the evolution of luminosity sources within them. Deuterium and lithium can be used as external probes of their internal state. I next discuss the effective temperature scale for the new L and T spectral classes. Formation of dust in the atmospheres of these objects is a crucial determinant of their spectral appearance, as is the conversion of typical molecules from oxides to hydrides. Not only is the chemical formation of dust important, but proper treatment of cloud formation and dust settling is clearly important (``meteorology'' becomes a consideration). This can strongly affect the colors of the objects, and the visibility of spectral features. Finally, I summarize results on other physical properties which can be studied using high spectral and angular resolution, including angular momentum, magnetic activity, surface gravity, and binarity.

  15. 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

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

    CERN Document Server

    Reid, I. Neill

    2005-01-01

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

  17. Clouds and Hazes in Exoplanets and Brown Dwarfs

    OpenAIRE

    Morley, Caroline Victoria

    2016-01-01

    The formation of clouds significantly alters the spectra of cool substellar atmospheres from terrestrial planets to brown dwarfs. In cool planets like Earth and Jupiter, volatile species like water and ammonia condense to form ice clouds. In hot planets and brown dwarfs, iron and silicates instead condense, forming dusty clouds. Irradiated methane-rich planets may have substantial hydrocarbon hazes. During my dissertation, I have studied the impact of clouds and hazes in a variety of substell...

  18. 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..

  19. Preliminary Analysis of M and L Dwarf Surface Gravities in the NIRSPEC Brown Dwarf Spectroscopic Survey

    Science.gov (United States)

    Martin, Emily C.; Mace, Gregory N.; McLean, Ian S.; Logsdon, Sarah E.; Rice, Emily L.

    2015-01-01

    Using previously published gravity-sensitive indices, we report on the analysis of near-infrared spectra for ˜ 80 M and L dwarfs . The spectra were obtained as part of the Brown Dwarf Spectroscopic Survey (BDSS) using NIRSPEC at the Keck Observatory, and each has a resolving power of R ˜ 2000 in the J band. With established gravity indices in the J band we can disentangle the degeneracy between temperature and age for brown dwarfs of various masses. By comparing a subset of the BDSS database with gravity indices defined at lower spectral resolution, we demonstrate that these indices also work well for higher resolution spectra. We then apply these techniques to M and L dwarfs in the BDSS to classify the diverse surface gravities of this large sample in a consistent manner. This analysis provides new age estimates for many M and L dwarfs, which will guide future studies of the young and old brown dwarf populations.

  20. JVLA Observations of Young Brown Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Luis F.; Zapata, Luis A.; Palau, Aina, E-mail: l.rodriguez@crya.unam.mx, E-mail: l.zapata@crya.unam.mx, E-mail: a.palau@crya.unam.mx [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico)

    2017-05-01

    We present sensitive 3.0 cm JVLA radio continuum observations of six regions of low-mass star formation that include twelve young brown dwarfs (BDs) and four young BD candidates. We detect a total of 49 compact radio sources in the fields observed, of which 24 have no reported counterparts and are considered new detections. Twelve of the radio sources show variability in timescales of weeks to months, suggesting gyrosynchrotron emission produced in active magnetospheres. Only one of the target BDs, FU Tau A, was detected. However, we detected radio emission associated with two of the BD candidates, WL 20S and CHLT 2. The radio flux densities of the sources associated with these BD candidates are more than an order of magnitude larger than expected for a BD and suggest a revision of their classification. In contrast, FU Tau A falls on the well-known correlation between radio luminosity and bolometric luminosity, suggesting that the emission comes from a thermal jet and that this BD seems to be forming as a scaled-down version of low-mass stars.

  1. An HST/STIS spectroscopic investigation: is Kelu-1 AB a brown dwarf - brown dwarf binary?

    Science.gov (United States)

    Stumpf, Micaela

    2009-07-01

    We propose to obtain resolved HST/STIS spectroscopy for the benchmark binary brown dwarf Kelu-1 AB. Dynamical masses are being obtained by monitoring the orbital motion using ground-based telescopes with adaptive optics. The main goal of this program is to study the Li I resonance line at 670.8 nm and investigate if only one or even both components bear lithium. This observation will be compared to model predictions of lithium depletion as a function of age and mass, and including our model independent ground-based mass estimations, hence will provide an observational test to the theory of substellar objects. Spin-offs will be the measurement of the strength of H-alpha emission, an indicator of chromospheric activity in cool atmospheres, and comparing the shape of the optical continuum with model spectra with different dust opacities. Thus our program will be an important step towards the understanding of brown dwarf atmospheres and to establish precise models for their formation and evolution.

  2. Examining Cloud, Metallicity, and Gravity signatures in Brown Dwarfs

    Science.gov (United States)

    Gonzales, Eileen; Faherty, Jacqueline K.; Gagné, Jonathan; Artigau, Étienne; BDNYC

    2018-01-01

    The nearby solar neighborhood is littered with low mass, low temperature objects called brown dwarfs. This population of ultracool objects do not have enough mass to sustain stable hydrogen burning so they never enter the main sequence and simply cool through time. Brown dwarfs span effective temperatures in the range 250 to 3000K. They also have age dependent observable properties. Young brown dwarfs appear to have redder near infrared colors than field age sources, while old objects tend to have bluer colors. Over the past several years, the research group entitled “Brown Dwarfs in New York City” (BDNYC) has been collecting optical, near and mid-infrared spectra, as well as photometry for sources that have well defined distances. In this poster, I will compare the distance calibrated spectral energy distributions of a sample of old, young, and field age brown dwarfs of the same effective temperature. In so doing, I will discern observables linked to gravity, atmosphere, metallicity and age effects.

  3. Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey

    OpenAIRE

    Martin, Emily C.; Mace, Gregory N.; McLean, Ian S.; Logsdon, Sarah E.; Rice, Emily L.; Kirkpatrick, J. Davy; Burgasser, Adam J.; McGovern, Mark R.; Prato, Lisa

    2017-01-01

    We combine 131 new medium-resolution (R ~ 2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5–T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all of the M6–L7 objects in our sample by measuring the equivalent widths (EW) of the...

  4. Characterization of the Mysteriously Cool Brown Dwarf HD 4113

    Science.gov (United States)

    Ednie, Michaela; Follette, Katherine; Ward-Duong, Kimberly

    2018-01-01

    Characterizing the physical properties of brown dwarfs is necessary to expand and improve our understanding of low mass companions, including exoplanets. Systems with both close radial velocity companions and distant directly imaged companions are particularly powerful in understanding planet formation mechanisms. Early in 2017, members of the SPHERE team discovered a companion brown dwarf in the HD 4113 system, which also contains a known RV planet. Atmospheric model fits to the Y and J-band spectra and H2/H3 photometry of the brown dwarf suggested it is unusually cool. We obtained new Magellan data in the Z and K’ bands in mid-2017. This data will help us to complete a more detailed atmospheric and astrometric characterization of this unusually cool companion. Broader wavelength coverage will help in accurate spectral typing and estimations of luminosity, temperature, surface gravity, radius, and composition. Additionally, a second astrometric epoch will help constrain the architecture of the system.

  5. Brown Dwarfs: A New Class of Stellar Lighthouse

    Science.gov (United States)

    2007-04-01

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

  6. BROWN DWARF BINARIES FROM DISINTEGRATING TRIPLE SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-04-15

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

  7. Follow-up of MARVELS Brown Dwarf Candidates using EXPERT

    Science.gov (United States)

    Ma, Bo; Ge, Jian; Li, Rui; Sithajan, Sirinrat; Thomas, Neil; Wang, Ji; De Lee, Nathan

    2013-02-01

    The SDSS-III MARVELS survey is a comprehensive radial velocity survey of 3,300 nearby F-K stars, between 7.6 < V < 12.0 in 2008-2012. All of the survey data for 2580 FGK stars from the first two and half years have been processed with the latest data pipeline. A total of 26 new brown dwarfs (BD) candidates have been identified in the processed RV data. We expect to have 8 more BD candidates from the ~800 stars currently under processing, which will make a total of 34 BD candidates. This proposal requests KPNO 2.1m telescope time with the EXPERT instrument, to follow up all of these BD candidates to confirm the detections and characterize the orbits. The results will be used to (1) reveal the overall distribution of the new BDs in the parameter space; (2) measure the occurrence rate of BD around FGK type stars; (3) measure dryness of the brown dwarf desert around stars with different mass and metallicity; (4) constrain theoretical models regarding the formation of brown dwarfs; (5) confirm the discovery of `desert in the brown dwarf desert'; (6) identify additional companions associated with the detected systems.

  8. Brown dwarf Atmosphere Monitoring (BAM): Characterizing the Coolest Atmosphere

    Science.gov (United States)

    Patience, Jennifer

    2014-10-01

    Using the G141 WFC3/IR grism, we propose a HST spectrophotometric monitoring study of the coolest variable brown dwarf (~650K) identified as part of our Brown dwarf Atmosphere Monitoring (BAM) program. The proposed observations will enable exploration of the dynamic atmospheric evolution of a benchmark T8.5 binary brown dwarf system, which we have discovered to exhibit the second-largest amplitude variation amongst all currently known brown dwarf variables. The close binarity of this system requires the exquisite stability of the HST point spread function to enable resolved monitoring of both components and to discriminate the source of the variability - the second component is a planetary mass object based on evolutionary models. This BAM follow-up study is designed to characterize both the longitudinal and vertical structure of the atmospheric properties of this system via multi-wavelength observations covering the entire spectral range of the WFC3/IR detector. Additionally, by monitoring the target over two separate epochs we will measure the evolution of atmospheric features giving rise to the flux variations. The proposed program will provide a comprehensive dataset serving as a benchmark comparison to directly imaged planets, intensely irradiated Hot Jupiters, and synthetic atmospheric models incorporating different physical processes.

  9. Surface gravity analysis of the NIRSPEC Brown Dwarf Spectroscopic Survey

    Science.gov (United States)

    Martin, Emily; McLean, Ian S.; Mace, Gregory N.; Logsdon, Sarah E.; Rice, Emily L.

    2015-01-01

    We present an analysis of J band spectra for over two hundred M, L, and T dwarfs obtained from the Brown Dwarf Spectroscopic Survey (BDSS) using NIRSPEC on the Keck II Telescope. This R~2000 sample includes spectra presented in McLean et al. (2003), as well as many new, unpublished spectra observed for the BDSS, more than doubling the size of the original survey. We determine surface gravity-sensitive spectral indices from the literature, which probe K I and FeH absorption, and we estimate uncertainties using a Monte Carlo iterative method. With these indices we characterize surface gravities of our targets in order to disentangle temperature and age of brown dwarfs and low mass stars of various masses.

  10. NTT Observations Indicate that Brown Dwarfs Form Like Stars

    Science.gov (United States)

    2001-06-01

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

  11. 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

  12. The NIRSPEC Brown Dwarf Spectroscopic Survey: A Progress Report

    Science.gov (United States)

    McGovern, M. R.; McLean, I. S.; Prato, L.; Burgasser, A.; Kirkpatrick, J. D.

    2001-12-01

    The major goal of the NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS - McLean et al. 2000, ApJ, 533, L45) is to obtain a complete sample of low resolution (R 2000) spectra spanning the M, L, and T dwarf sub-classes in order to extend spectral classification schemes to near-infrared wavebands and to investigate the spectral signatures of temperature, gravity, and composition by comparison to theoretical models. Additional goals include the acquisition of higher resolution spectra (R 25,000) of a sub-sample of the survey for detailed comparison with models and to search for radial velocity variations. Our approach is to observe two objects per sub-class at J-band at low resolution, with one object per sub-class observed from 0.9-2.5 microns to produce a complete, flux-calibrated spectrum overlapping with previously obtained Keck LRIS data from 0.5-1.0 microns. Several of the brighter sources have also been observed at high resolution at J-band. To date, over 50 objects have been studied including 7 M dwarfs, 30 L dwarfs and 15 T dwarfs. Correlations of the strength of spectral features with spectral type are shown. We also report on the probable identification of weak methane features in the K-band spectra of L7 and L8 dwarfs.

  13. The brown dwarf atmosphere monitoring (BAM) project - II. Multi-epoch monitoring of extremely cool brown dwarfs

    Science.gov (United States)

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

    2015-04-01

    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 1.0-4.5 h 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 per cent, while the second epoch light curve taken ˜2 years later did not note any variability to a 3 per cent upper limit. With an effective temperature of ˜600 K, WISE0458 is the coldest variable brown dwarf published to date, and combined with its high and variable amplitude makes it a fascinating target for detailed follow-up. The three remaining targets showed no significant variations, with a photometric precision between 0.8 and 20.0 per cent, depending on the target brightness. Combining the new results with previous multi-epoch observations of brown dwarfs with spectral types of T5 or later, the currently identified variables have locations on the colour-colour diagram better matched by theoretical models incorporating cloud opacities rather than cloud-free atmospheres. This preliminary result requires further study to determine if there is a definitive link between variability among late-T dwarfs and their location on the colour-colour diagram.

  14. Recent Results of the NIRSPEC Brown Dwarf Spectroscopic Survey

    Science.gov (United States)

    Rice, Emily L.; McLean, I. S.; Prato, L.; McGovern, M. R.; Burgasser, A. J.; Kirkpatrick, J.; Kim, S. S.

    2006-12-01

    The NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) began in 1999 with the commissioning of NIRSPEC on Keck II. In the first phase of the survey, J-band spectra of 53 objects covering all spectral types from M6 to T8 were obtained at a resolving power of R 2000 (McLean et al. 2003). This poster presents results from the second phase of the survey, which focused on high-resolution (R 20,000) J-band observations for a sample of 16 very low mass stars and brown dwarfs from M2.5 to T6 (McLean et al. 2006, submitted). By comparing opacity plots and line lists to the high-resolution spectra we identify hundreds of FeH, H2O, and atomic features and analyze how these features change with spectral type. We also begin to explore the apparently complex dependence of spectral features on the metallicity and surface gravity of brown dwarf atmospheres, which is the topic of the current phase of the BDSS. 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.

  15. Clouds and hazes in exoplanets and brown dwarfs

    Science.gov (United States)

    Morley, Caroline Victoria

    The formation of clouds significantly alters the spectra of cool substellar atmospheres from terrestrial planets to brown dwarfs. In cool planets like Earth and Jupiter, volatile species like water and ammonia condense to form ice clouds. In hot planets and brown dwarfs, iron and silicates instead condense, forming dusty clouds. Irradiated methane-rich planets may have substantial hydrocarbon hazes. During my dissertation, I have studied the impact of clouds and hazes in a variety of substellar objects. First, I present results for cool brown dwarfs including clouds previously neglected in model atmospheres. Model spectra that include sulfide and salt clouds can match the spectra of T dwarf atmospheres; water ice clouds will alter the spectra of the newest and coldest brown dwarfs, the Y dwarfs. These sulfide/salt and ice clouds potentially drive spectroscopic variability in these cool objects, and this variability should be distinguishable from variability caused by hot spots. Next, I present results for small, cool exoplanets between the size of Earth and Neptune. They likely have sulfide and salt clouds and also have photochemical hazes caused by stellar irradiation. Vast resources have been dedicated to characterizing the handful of super Earths and Neptunes accessible to current telescopes, yet of the planets smaller than Neptune studied to date, all have radii in the near-infrared consistent with being constant in wavelength, likely showing that these small planets are consistently enshrouded in thick hazes and clouds. For the super Earth GJ 1214b, very thick, lofted clouds of salts or sulfides in high metallicity (1000x solar) atmospheres create featureless transmission spectra in the near-infrared. Photochemical hazes also create featureless transmission spectra at lower metallicities. For the Neptune-sized GJ 436b, its thermal emission and transmission spectra combine indicate a high metallicity atmosphere, potentially heated by tides and affected by

  16. FINGERING CONVECTION AND CLOUDLESS MODELS FOR COOL BROWN DWARF ATMOSPHERES

    Energy Technology Data Exchange (ETDEWEB)

    Tremblin, P.; Amundsen, D. S.; Mourier, P.; Baraffe, I.; Chabrier, G.; Drummond, B. [Astrophysics Group, University of Exeter, EX4 4QL Exeter (United Kingdom); Homeier, D. [Ecole Normale Supérieure de Lyon, CRAL, UMR CNRS 5574, F-69364 Lyon Cedex 07 (France); Venot, O., E-mail: tremblin@astro.ex.ac.uk, E-mail: pascal.tremblin@cea.fr [Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

    2015-05-01

    This work aims to improve the current understanding of the atmospheres of brown dwarfs, especially cold ones with spectral types 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 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 H{sub 2}-H{sub 2}, H{sub 2}-He, H{sub 2}O, CO, CO{sub 2}, CH{sub 4}, NH{sub 3}, 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 NH{sub 3} quenching are taken into account. T dwarf spectra still have some reddening in, e.g., J–H, compared to cloudless models. This reddening can be reproduced by slightly reducing the temperature gradient in the atmosphere. We propose that this reduction of the stabilizing temperature gradient in these layers, leading to cooler structures, is due to the onset of fingering convection, triggered by the destabilizing impact of condensation of very thin dust.

  17. WISE Y dwarfs as probes of the brown dwarf-exoplanet connection

    Energy Technology Data Exchange (ETDEWEB)

    Beichman, C.; Gelino, Christopher R.; Kirkpatrick, J. Davy [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C. [Department of Physics and Astronomy, The University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606 (United States); Dodson-Robinson, Sally [Department of Astronomy, University of Delaware, Newark, DE 19716 (United States); Marley, Mark S. [NASA Ames Research Center, Mountain View, CA 94035 (United States); Morley, Caroline V. [Department of Astronomy, University of California at Santa Cruz, Santa Cruz, CA 95064 (United States); Wright, E. L., E-mail: chas@ipac.caltech.edu [Department of Astronomy, University of California Los Angeles, P.O. Box 951547, Los Angeles, CA 90095 (United States)

    2014-03-10

    We have determined astrometric positions for 15 WISE-discovered late-type brown dwarfs (six T8-9 and nine Y dwarfs) using the Keck-II telescope, the Spitzer Space Telescope, and the Hubble Space Telescope. Combining data from 8 to 20 epochs we derive parallactic and proper motions for these objects, which puts the majority within 15 pc. For ages greater than a few Gyr, as suggested from kinematic considerations, we find masses of 10-30 M {sub Jup} based on standard models for the evolution of low-mass objects with a range of mass estimates for individual objects, depending on the model in question. Three of the coolest objects have effective temperatures ∼350 K and inferred masses of 10-15 M {sub Jup}. Our parallactic distances confirm earlier photometric estimates and direct measurements and suggest that the number of objects with masses below about 15 M {sub Jup} must be flat or declining, relative to higher mass objects. The masses of the coldest Y dwarfs may be similar to those inferred for recently imaged planet-mass companions to nearby young stars. Objects in this mass range, which appear to be rare in both the interstellar and protoplanetary environments, may both have formed via gravitational fragmentation—the brown dwarfs in interstellar clouds and companion objects in a protoplanetary disk. In both cases, however, the fact that objects in this mass range are relatively infrequent suggests that this mechanism must be inefficient in both environments.

  18. Students Use VLA to Make Startling Brown-Dwarf Discovery

    Science.gov (United States)

    2001-03-01

    A group of summer students making a long-shot astronomical gamble with the National Science Foundation's (NSF) Very Large Array (VLA) have found the first radio emission ever detected from a brown dwarf, an enigmatic object that is neither a star nor a planet, but something in between. Their surprising discovery is forcing experts to re-think their theories about how brown dwarfs work. The Very Large Array "Many astronomers are surprised at this discovery, because they didn't expect such strong radio emission from this object," said Shri Kulkarni, a Caltech professor who was on the team that first discovered a brown dwarf in 1995, and advisor to one of the students. "What is so cool is that this is research that probably nobody else would have tried to do because of its low chance of success. That made it ideal for summer students -- we had almost nothing to lose," said Kate Becker, a student at Oberlin College in Ohio. "The radio emission these students discovered coming from this brown dwarf is 10,000 times stronger than anyone expected," said Dale Frail, an astronomer at the National Radio Astronomy Observatory (NRAO) in Socorro, NM. "This student project is going to open up a whole new area of research for the VLA," Frail added. The students, in addition to Becker, are: Edo Berger from Caltech; Steven Ball from New Mexico Tech in Socorro, NM; Melanie Clarke from Carleton College in Northfield, MN; Therese Fukuda from the University of Denver; Ian Hoffman from the University of New Mexico in Albuquerque; Richard Mellon from The Pennsylvania State University; Emmanuel Momjian from the University of Kentucky; Nathanial Murphy from Amherst College in Amherst, MA; Stacey Teng from the University of Maryland; Timothy Woodruff from Southwestern University in Georgetown, TX; Ashley Zauderer from Agnes Scott College in Decatur, GA; and Robert Zavala from New Mexico State University in Las Cruces, NM. Frail also is an author of the research paper, published in the March

  19. Microlensing of unresolved stars as a brown dwarf detection method

    CERN Document Server

    Bouquet, A; Melchior, A L; Giraud-Héraud, Yannick; Baillon, Paul

    1993-01-01

    We describe a project of brown dwarf detection in the dark halo of a galaxy using the microlensing effect. We argue that monitoring pixels instead of stars could provide an enhancement in the number of detectable events. We estimate the detection efficiency with a Monte-Carlo simulation. We expect a ten-fold increase with respect to current experiments. To assess the feasibility of this method we have determined the photometric precision of a pixel by comparing several pictures of a same field in the LMC. To be published in the Proceeding of the workshop 'The dark side of the universe...', Roma, Juin 1993,

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

    CERN Document Server

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

    1999-01-01

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

  1. Youngest Brown Dwarf Yet in a Multiple Stellar System

    Science.gov (United States)

    2000-07-01

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

  2. THE FIRST SPECTRUM OF THE COLDEST BROWN DWARF

    Energy Technology Data Exchange (ETDEWEB)

    Skemer, Andrew J.; Morley, Caroline V.; Fortney, Jonathan J. [University of California, Santa Cruz, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064 (United States); Allers, Katelyn N. [Bucknell University, 701 Moore Avenue, Lewisburg, PA 17837 (United States); Geballe, Thomas R. [Gemini Observatory, 670 North A’ohoku Place, Hilo, HI 96720 (United States); Marley, Mark S.; Lupu, Roxana [NASA Ames Research Center, Moffett Field, CA 94035 (United States); Faherty, Jacqueline K. [Carnegie Institute for Science, Department of Terrestrial Magnetism, 5241 Broad Branch Road, NW, Washington, DC 20015 (United States); Bjoraker, Gordon L. [NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt, MD 20771 (United States)

    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 μ 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’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.

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

    Science.gov (United States)

    Faherty, Jacqueline K.; Tinney, C. G.; Skemer, Andrew; Monson, Andrew J.

    2014-09-01

    We present a deep near-infrared image of the newly discovered brown dwarf WISE J085510.83-071442.5 (W0855) using the FourStar imager at Las Campanas Observatory. Our detection of J3 = 24.8^{+0.53}_{-0.35} (J MKO = 25.0^{+0.53}_{-0.35}) at 2.6σ—or equivalently an upper limit of J3 > 23.8 (J MKO > 24.0) at 5σ makes W0855 the reddest brown dwarf ever categorized (J MKO - W2 = 10.984^{+0.53}_{-0.35} at 2.6σ—or equivalently an upper limit of J 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. This Letter includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-11-01

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

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

    Science.gov (United States)

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

    2016-09-01

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

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

    NARCIS (Netherlands)

    Montet, B.T.; Johnson, J.A.; Fortney, J.J.; Desert, J.-M.

    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

  7. OGLE-2016-BLG-0693LB: Probing the Brown Dwarf Desert with Microlensing

    Science.gov (United States)

    Ryu, Y.-H.; Udalski, A.; Yee, J. C.; Albrow, M. D.; Chung, S.-J.; Gould, A.; Han, C.; Hwang, K.-H.; Jung, Y. K.; Shin, I.-G.; Zhu, W.; Cha, S.-M.; Kim, D.-J.; Kim, H.-W.; Kim, S.-L.; Lee, C.-U.; Lee, Y.; Park, B.-G.; Pogge, R. W.; KMTNet Collaboration; Pietrukowicz, P.; Kozłowski, S.; Poleski, R.; Skowron, J.; Mróz, P.; Szymański, M. K.; Soszyński, I.; Pawlak, M.; Ulaczyk, K.; The OGLE Collaboration

    2017-12-01

    We present an analysis of microlensing event OGLE-2016-BLG-0693, based on the survey-only microlensing observations by the OGLE and KMTNet groups. In order to analyze the light curve, we consider the effects of parallax, orbital motion, and baseline slope, and also refine the result using a Galactic model prior. From the microlensing analysis, we find that the event is a binary composed of a low-mass brown dwarf ({49}-18+20 {M}J) companion and a K- or G-dwarf host, which lies at a distance of 5.0 ± 0.6 kpc toward the Galactic bulge. The projected separation between the brown dwarf and its host star is less than ˜5 au, thus it is likely that the brown dwarf companion is located in the brown dwarf desert.

  8. 50 years of brown dwarfs from prediction to discovery to forefront of research

    CERN Document Server

    2014-01-01

    The years 2012/2013 mark the 50th anniversary of the theoretical prediction that Brown Dwarfs, i.e. degenerate objects which are just not massive enough to sustain stable hydrogen fusion, exist. Some 20 years after their discovery, how Brown Dwarfs form is still one of the main open questions in the theory of star formation. In this volume, the pioneers of Brown Dwarf research review the history of the theoretical prediction and the subsequent discovery of Brown Dwarfs. After an introduction, written by Viki Joergens, reviewing Shiv Kumar's theoretical prediction of the existence of brown dwarfs, Takenori Nakano reviews his and Hayashi's calculation of the Hydrogen Burning Minimum Mass. Both predictions happened in the early 1960s. Jill Tarter then writes on the introduction of the term 'Brown Dwarf', before Ben Oppenheimer, Rafael Rebolo and Gibor Basri describe their first discovery of Brown Dwarfs in the 1990s. Lastly, Michael Cushing and Isabelle Baraffe describe the development of the field to the curren...

  9. Brown Dwarf Binaries as Tests of Substellar Evolution

    Science.gov (United States)

    Martin, Eduardo

    2002-07-01

    We propose to obtain STIS spectroscopy of two brown dwarf binaries for which dynamical masses are being obtained by monitoring the orbital motion using ground-based telescopes with adaptive optics. The HST/STIS spectra will allow to study the LiI resonance line at 670.8 nm. The lithium depletion of the members of these binaries will be estimated with the aid of synthetic spectra. These observations will be compared to model predictions of lithium depletion as a function of age and mass, and hence will provide an observational test to the theory of substellar objects. Spin-offs will be the measurement of the strength of Halpha emission, an indicator of chromospheric activity in cool atmospheres, and comparing the shape of the optical continuum with model spectra with different dust opacities.

  10. 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.

  11. Outflows from low mass young stars and brown dwarfs

    Science.gov (United States)

    Ray, T. P.

    The phenomenon of jets from young stars has been known for over two decades. In most cases the jet is generated either by an embedded (IRAS Class I) low mass star or its more evolved, optically visible counterpart (a classical T Tauri star). In the case of the latter the flow can be traced optically right back to the star although its apparent length may be small in angular terms (typically a few arcseconds). For this reason such jets are sometimes referred to as ``micro-jets''. It is argued that brown dwarfs (BDs) outflows, when observed will almost certainly look like scaled-down versions of the micro-jet phenomenon observed in classical T Tauri stars. Not only then will we need large telescopes to detect such flows but it may also be necessary to employ special techniques, like spectro-astrometry, to resolve them.

  12. Surface Gravities for 228 M, L, and T Dwarfs in the NIRSPEC Brown Dwarf Spectroscopic Survey

    Science.gov (United States)

    Martin, Emily C.; Mace, Gregory N.; McLean, Ian S.; Logsdon, Sarah E.; Rice, Emily L.; Kirkpatrick, J. Davy; Burgasser, Adam J.; McGovern, Mark R.; Prato, Lisa

    2017-03-01

    We combine 131 new medium-resolution (R ˜ 2000) J-band spectra of M, L, and T dwarfs from the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) with 97 previously published BDSS spectra to study surface-gravity-sensitive indices for 228 low-mass stars and brown dwarfs spanning spectral types M5-T9. Specifically, we use an established set of spectral indices to determine surface gravity classifications for all of the M6-L7 objects in our sample by measuring the equivalent widths (EW) of the K I lines at 1.1692, 1.1778, and 1.2529 μm, and the 1.2 μm FeH J absorption index. Our results are consistent with previous surface gravity measurements, showing a distinct double peak—at ˜L5 and T5—in K I EW as a function of spectral type. We analyze the K I EWs of 73 objects of known ages and find a linear trend between log(Age) and EW. From this relationship, we assign age ranges to the very low gravity, intermediate gravity, and field gravity designations for spectral types M6-L0. Interestingly, the ages probed by these designations remain broad, change with spectral type, and depend on the gravity-sensitive index used. Gravity designations are useful indicators of the possibility of youth, but current data sets cannot be used to provide a precise age estimate. The data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W.M. Keck Foundation.

  13. Precise Ages for the Benchmark Brown Dwarfs HD 19467 B and HD 4747 B

    Science.gov (United States)

    Wood, Charlotte; Boyajian, Tabetha; Crepp, Justin; von Braun, Kaspar; Brewer, John; Schaefer, Gail; Adams, Arthur; White, Tim

    2018-01-01

    Large uncertainty in the age of brown dwarfs, stemming from a mass-age degeneracy, makes it difficult to constrain substellar evolutionary models. To break the degeneracy, we need ''benchmark" brown dwarfs (found in binary systems) whose ages can be determined independent of their masses. HD~19467~B and HD~4747~B are two benchmark brown dwarfs detected through the TRENDS (TaRgeting bENchmark objects with Doppler Spectroscopy) high-contrast imaging program for which we have dynamical mass measurements. To constrain their ages independently through isochronal analysis, we measured the radii of the host stars with interferometry using the Center for High Angular Resolution Astronomy (CHARA) Array. Assuming the brown dwarfs have the same ages as their host stars, we use these results to distinguish between several substellar evolutionary models. In this poster, we present new age estimates for HD~19467 and HD~4747 that are more accurate and precise and show our preliminary comparisons to cooling models.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-06-10

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

  15. 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...

  16. 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.

  17. The NIRSPEC Brown Dwarf Spectroscopic Survey Online Archive BDSSarchive.org

    Science.gov (United States)

    Mace, G.; Rice, E.; McLean, I.

    2011-12-01

    The NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) was initiated in 1999 by Ian McLean (UCLA) and Davy Kirkpatrick (IPAC) following deployment of NIRSPEC to Keck II and the discovery of brown dwarf candidates in the Two Micron All Sky Survey (2MASS). High quality near-infrared spectra for a large sample of M, L, and T dwarfs have been obtained by many members of the BDSS team since inception of the project. Moderate-resolution (R˜2,000) near-IR spectra include over 200 objects (approximately 20% field M dwarfs, 30% young M dwarfs, 10% M giants, 30% L dwarfs, and 10% T dwarfs). These medium-resolution data products include J-band (1.143-1.375 micron) coverage for every object and broader coverage (0.96-2.31 micron) for about 30 targets. High-resolution (R˜20,000) spectra consist primarily of cross-dispersed J-band (1.165-1.323 micron) observations, resulting in eight dispersion orders for ˜70 objects (approximately 15% field M dwarfs, 40% young M dwarfs, 25% L dwarfs, and 20% T dwarfs). The BDSS Online Archive (BDSSarchive.org) described in this poster is a catalog of all observed objects, with published data available as reduced and extracted ascii files. Unpublished data are also available upon request. Other database updates, including a mutable table and links to reductions for multiple observational epochs, will be implemented in the near future. The sample size, wavelength coverage, spectral resolution, and high quality data makes the BDSS Online Archive a premier library of brown dwarf medium-to-high resolution near-infrared spectra.

  18. Is this a Brown Dwarf or an Exoplanet?

    Science.gov (United States)

    2005-04-01

    Since the discovery in 1995 of the first planet orbiting a normal star other than the Sun, there are now more than 150 candidates of these so-called exoplanets known. Most of them are detected by indirect methods, based either on variations of the radial velocity or the dimming of the star as the planet passes in front of it (see ESO PR 06/03, ESO PR 11/04 and ESO PR 22/04). Astronomers would, however, prefer to obtain a direct image of an exoplanet, allowing them to better characterize the object's physical nature. This is an exceedingly difficult task, as the planet is generally hidden in the "glare" of its host star. To partly overcome this problem, astronomers study very young objects. Indeed, sub-stellar objects are much hotter and brighter when young and therefore can be more easily detected than older objects of similar mass. Based on this approach, it might well be that last year's detection of a feeble speck of light next to the young brown dwarf 2M1207 by an international team of astronomers using the ESO Very Large Telescope (ESO PR 23/04) is the long-sought bona-fide image of an exoplanet. A recent report based on data from the Hubble Space Telescope seems to confirm this result. The even more recent observations made with the Spitzer Space Telescope of the warm infrared glows of two previously detected "hot Jupiter" planets is another interesting result in this context. This wealth of new results, obtained in the time span of a few months, illustrates perfectly the dynamic of this field of research. Tiny Companion ESO PR Photo 10a/05 ESO PR Photo 10a/05 The Sub-Stellar Companion to GQ Lupi (NACO/VLT) [Preview - JPEG: 400 x 429 pix - 22k] [Normal - JPEG: 800 x 875 pix - 132k] [Full Res - JPEG: 1042 x 1116 pix - 241k] Caption: ESO PR Photo 10a/05 shows the VLT NACO image, taken in the Ks-band, of GQ Lupi. The feeble point of light to the right of the star is the newly found cold companion. It is 250 times fainter than the star itself and it located 0

  19. Exploring the brown dwarf desert: new substellar companions from the SDSS-III MARVELS survey

    Science.gov (United States)

    Grieves, Nolan; Ge, Jian; Thomas, Neil; Ma, Bo; Sithajan, Sirinrat; Ghezzi, Luan; Kimock, Ben; Willis, Kevin; De Lee, Nathan; Lee, Brian; Fleming, Scott W.; Agol, Eric; Troup, Nicholas; Paegert, Martin; Schneider, Donald P.; Stassun, Keivan; Varosi, Frank; Zhao, Bo; Jian, Liu; Li, Rui; Porto de Mello, Gustavo F.; Bizyaev, Dmitry; Pan, Kaike; Dutra-Ferreira, Letícia; Lorenzo-Oliveira, Diego; Santiago, Basílio X.; da Costa, Luiz N.; Maia, Marcio A. G.; Ogando, Ricardo L. C.; del Peloso, E. F.

    2017-06-01

    Planet searches using the radial velocity technique show a paucity of companions to solar-type stars within ˜5 au in the mass range of ˜10-80 MJup. This deficit, known as the brown dwarf desert, currently has no conclusive explanation. New substellar companions in this region help assess the reality of the desert and provide insight to the formation and evolution of these objects. Here, we present 10 new brown dwarf and 2 low-mass stellar companion candidates around solar-type stars from the Multi-object APO Radial Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III. These companions were selected from processed MARVELS data using the latest University of Florida Two Dimensional pipeline, which shows significant improvement and reduction of systematic errors over previous pipelines. The 10 brown dwarf companions range in mass from ˜13 to 76 MJup and have orbital radii of less than 1 au. The two stellar companions have minimum masses of ˜98 and 100 MJup. The host stars of the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03 ± 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence rate around solar-type stars with periods less than ˜300 d to be ˜0.56 per cent.

  20. A Data-driven Approach for Retrieving Temperatures and Abundances in Brown Dwarf Atmospheres

    Science.gov (United States)

    Line, Michael R.; Fortney, Jonathan J.; Marley, Mark S.; Sorahana, Satoko

    2014-09-01

    Brown dwarf spectra contain a wealth of information about their molecular abundances, temperature structure, and gravity. We present a new data driven retrieval approach, previously used in planetary atmosphere studies, to extract the molecular abundances and temperature structure from brown dwarf spectra. The approach makes few a priori physical assumptions about the state of the atmosphere. The feasibility of the approach is first demonstrated on a synthetic brown dwarf spectrum. Given typical spectral resolutions, wavelength coverage, and noise, property precisions of tens of percent can be obtained for the molecular abundances and tens to hundreds of K on the temperature profile. The technique is then applied to the well-studied brown dwarf, Gl 570D. From this spectral retrieval, the spectroscopic radius is constrained to be 0.75-0.83 R J, log (g) to be 5.13-5.46, and T eff to be between 804 and 849 K. Estimates for the range of abundances and allowed temperature profiles are also derived. The results from our retrieval approach are in agreement with the self-consistent grid modeling results of Saumon et al. This new approach will allow us to address issues of compositional differences between brown dwarfs and possibly their formation environments, disequilibrium chemistry, and missing physics in current grid modeling approaches as well as a many other issues.

  1. The brown dwarf atmosphere monitoring (BAM) project. I. The largest near-IR monitoring survey of L and T dwarfs

    Science.gov (United States)

    Wilson, P. A.; Rajan, A.; Patience, J.

    2014-06-01

    Using the SofI instrument on the 3.5 m New Technology Telescope, we have conducted an extensive near-infrared monitoring survey of an unbiased sample of 69 brown dwarfs spanning the L0 to T8 spectral range, with at least one example of each spectral type. Each target was observed for a 2-4 h 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 a median reference star light curve. Approximately half of the variables show pure sinusoidal amplitude variations similar to 2MASSJ2139+0220, and the remainder show multi-component variability in their light curves similar to SIMPJ0136+0933. It has been suggested that the L-T transition should 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 of both the L-T transition and non-transition brown dwarfs. The measured frequency of variables is 13+10-4% across the L7-T4 spectral range, indistinguishable from the frequency of variables of the earlier spectral types (30+11-8%), the later spectral types (13+10-4%), or the combination of all non-transition region brown dwarfs (22+7-5%). The variables are not concentrated in the transition, in a specific colour, or in binary systems. Of the brown dwarfs previously monitored for variability, only ~60% maintained the state of variability (variable or constant), with the remaining switching states. The 14 variables include 9 newly identified variables that will provide important systems for follow-up multi-wavelength monitoring to further investigate brown dwarf atmosphere physics. Based on observations made with ESO Telescopes at La Silla Observatory under programme ID 188.C-0493.Tables 1, 2, and 4 are

  2. Determining Optimal Parameters for Brown Dwarf Spectral Extraction using the aXe Pipeline

    Science.gov (United States)

    Davis, Jonathan D.; Radigan, Jacqueline

    2017-06-01

    This research seeks to find optimal extraction parameters for brown dwarf slitless spectra obtained using the Wide Field Camera 3 (WFC3), with the G141 grism on the Hubble Space Telescope. We have used the STScI aXe pipeline to extract spectral time series for three brown dwarf targets from HST program GO-13299 (PI: Radigan). These targets include two L/T transition dwarfs 2MASS-J16291840+033537 and SDSS-J075840.33+324723.4, and one L-dwarf 2MASS-J11263991-5003550. The parameters explored in this study include the spectral extraction width, the type of background subtraction, and the pixel weighting of the extraction. We also explore how target brightness effects the optimal reduction parameters. Scatter within the spectral time series are used to draw conclusions regarding the relative goodness of different sets of reduction parameters.

  3. Direct Test of the Brown Dwarf Evolutionary Models Through Secondary Eclipse Spectroscopy of LHS 6343

    Science.gov (United States)

    Albert, Loic

    2015-10-01

    As the number of field Brown Dwarfs counts in the thousands, interpreting their physical parameters (mass, temperature, radius, luminosity, age, metallicity) relies as heavily as ever on atmosphere and evolutionary models. Fortunately, models are largely successful in explaining observations (colors, spectral types, luminosity), so they appear well calibrated in a relative sense. However, an absolute model-independent calibration is still lacking. Eclipsing BDs systems are a unique laboratory in this respect but until recently only one such system was known, 2M0535-05 - a very young (Brown Dwarfs showing a peculiar temperature reversal (Stassun et al. 2006). Due to its young age, 2M0535-05 is an ill-suited test for Gyr-old field Brown Dwarfs whose population is by far the most common in the solar neighborhood. Recently, a second system - an evolved BD (>1 Gyr) - was identified (62.1+/-1.2 MJup, 0.783+/-0.011 RJup) transiting LHS6343 with a 12.7-day period. We propose to use WFC3 in drift scan mode and 5 HST orbits to determine the spectral type (a proxy for temperature) as well as the near-infrared luminosity of this brown dwarf. We conducted simulations that predict a signal-to-noise ratio ranging between 10 and 30 per resolution element in the peaks of the spectrum. These measurements, coupled with existing luminosity measurements with Spitzer at 3.6 and 4.5 microns, will allow us to trace the spectral energy distribution of the Brown Dwarf and directly calculate its blackbody temperature. It will be the first field Brown Dwarfs with simultaneous measurements of its radius, mass, luminosity and temperature all measured independently of models.

  4. First Detection of a Strong Magnetic Field on a Bursty Brown Dwarf: Puzzle Solved

    Science.gov (United States)

    Berdyugina, S. V.; Harrington, D. M.; Kuzmychov, O.; Kuhn, J. R.; Hallinan, G.; Kowalski, A. F.; Hawley, S. L.

    2017-09-01

    We report the first direct detection of a strong, 5 kG magnetic field on the surface of an active brown dwarf. LSR J1835+3259 is an M8.5 dwarf exhibiting transient radio and optical emission bursts modulated by fast rotation. We have detected the surface magnetic field as circularly polarized signatures in the 819 nm sodium lines when an active emission region faced the Earth. Modeling Stokes profiles of these lines reveals the effective temperature of 2800 K and log gravity acceleration of 4.5. These parameters place LSR J1835+3259 on evolutionary tracks as a young brown dwarf with the mass of 55+/- 4{M}{{J}} and age of 22 ± 4 Myr. Its magnetic field is at least 5.1 kG and covers at least 11% of the visible hemisphere. The active region topology recovered using line profile inversions comprises hot plasma loops with a vertical stratification of optical and radio emission sources. These loops rotate with the dwarf in and out of view causing periodic emission bursts. The magnetic field is detected at the base of the loops. This is the first time that we can quantitatively associate brown dwarf non-thermal bursts with a strong, 5 kG surface magnetic field and solve the puzzle of their driving mechanism. This is also the coolest known dwarf with such a strong surface magnetic field. The young age of LSR J1835+3259 implies that it may still maintain a disk, which may facilitate bursts via magnetospheric accretion, like in higher-mass T Tau-type stars. Our results pave a path toward magnetic studies of brown dwarfs and hot Jupiters.

  5. 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

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

    Science.gov (United States)

    Barnes, Rory; Heller, René

    2013-03-01

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

  7. Characterizing a New Candidate Benchmark Brown Dwarf Companion in the β Pic Moving Group

    Science.gov (United States)

    Phillips, Caprice; Bowler, Brendan; Liu, Michael C.; Mace, Gregory N.; Sokal, Kimberly R.

    2018-01-01

    Benchmark brown dwarfs are objects that have at least two measured fundamental quantities such as luminosity and age, and therefore can be used to test substellar atmospheric and evolutionary models. Nearby, young, loose associations such as the β Pic moving group represent some of the best regions in which to identify intermediate-age benchmark brown dwarfs due to their well-constrained ages and metallicities. We present a spectroscopic study of a new companion at the hydrogen-burning limit orbiting a low-mass star at a separation of 9″ (650 AU) in the 23 Myr old β Pic moving group. The medium-resolution near-infrared spectrum of this companion from IRTF/SpeX shows clear signs of low surface gravity and yields an index-based spectral type of M6±1 with a VL-G gravity on the Allers & Liu classification system. Currently, there are four known brown dwarf and giant planet companions in the β Pic moving group: HR 7329 B, PZ Tel B, β Pic b, and 51 Eri b. Depending on its exact age and accretion history, this new object may represent the third brown dwarf companion and fifth substellar companion in this association.

  8. The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

    Science.gov (United States)

    Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagné, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob; Mokaev, Khasan; Stajic, Tamara

    2017-06-01

    The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding nearby brown dwarfs and searching for new planets in the outer solar system, especially with the incorporation of NEOWISE and NEOWISE-Reactivation data. However, so far, searches for brown dwarfs in WISE data have yet to take advantage of the full depth of the WISE images. To efficiently search this unexplored space via visual inspection, we have launched a new citizen science project, called “Backyard Worlds: Planet 9,” which asks volunteers to examine short animations composed of difference images constructed from time-resolved WISE coadds. We report the first new substellar object discovered by this project, WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from the Sun with a total proper motion of ˜0.″7 {{yr}}-1. WISEA J110125.95+540052.8 has a WISE W2 magnitude of W2=15.37+/- 0.09; our sensitivity to this source demonstrates the ability of citizen scientists to identify moving objects via visual inspection that are 0.9 mag fainter than the W2 single-exposure sensitivity, a threshold that has limited prior motion-based brown dwarf searches with WISE.

  9. The First Brown Dwarf Discovered by the Backyard Worlds: Planet 9 Citizen Science Project

    Science.gov (United States)

    Kuchner, Marc J.; Faherty, Jacqueline K.; Schneider, Adam C.; Meisner, Aaron M.; Filippazzo, Joseph C.; Gagne, Jonathan; Trouille, Laura; Silverberg, Steven M.; Castro, Rosa; Fletcher, Bob; hide

    2017-01-01

    The Wide-field Infrared Survey Explorer (WISE) is a powerful tool for finding nearby brown dwarfs and searching for new planets in the outer solar system, especially with the incorporation of NEOWISE and NEOWISE Reactivation data. However, so far, searches for brown dwarfs in WISE data have yet to take advantage of the full depth of the WISE images. To efficiently search this unexplored space via visual inspection, we have launched anew citizen science project, called "Backyard Worlds: Planet 9," which asks volunteers to examine short animations composed of difference images constructed from time-resolved WISE co adds. We report the first new substellar object discovered by this project, WISEA J110125.95+540052.8, a T5.5 brown dwarf located approximately 34 pc from the Sun with a total proper motion of approx.0. "7/ yr. WISEA J110125.95+540052.8 has a WISE W2 magnitude of W2 = 15.37+/- 0.09; our sensitivity to this source demonstrates the ability of citizen scientists to identify moving objects via visual inspection that are 0.9 mag fainter than the W2 single-exposure sensitivity, a threshold that has limited prior motion-based brown dwarf searches with WISE.

  10. Microlensing discovery of a population of very tight, very low mass binary brown dwarfs

    DEFF Research Database (Denmark)

    Choi, J.-Y.; Han, C.; Udalski, A.

    2013-01-01

    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 disc...

  11. A spectroscopic survey of young brown dwarfs in the near-infrared

    Science.gov (United States)

    McGovern, Mark Roland

    Motivated by the discovery of numerous Jupiter-sized brown dwarfs in infrared imaging surveys, and stimulated by the advent of sensitive near-infrared (NIR) spectrometers on very large telescopes, this thesis presents the results of a unique observational survey to investigate and characterize the near-infrared spectra of low-mass stars and brown dwarfs. The project, called the NIRSPEC Brown Dwarf Spectroscopic Survey (or BDSS) was carried out with the Keck 10- m telescope on Mauna Kea, Hawaii using the facility cryogenic NIR spectrometer (NIRSPEC) developed at UCLA by Professor Ian McLean. Beginning in April 1999, immediately after NIRSPEC was delivered to the telescope, this infrared spectroscopic survey was developed in multiple phases to obtain the largest self-consistent set of high quality spectra yet obtained for the two new classes of very cool objects known as L and T dwarfs (T eff ~ 2200-750K). This work presents the results of two of the major phases of the BDSS and includes near-infrared spectra from over 150 low-mass stars and brown dwarfs. In the first phase of the project the emphasis was on the effects of decreasing effective temperature (T eff ) on the infrared spectral morphology. Observations were concentrated on the J -band region of the spectrum from 1.14- 1.36 microns. Over 50 objects spanning the spectral types from M6 to T8 were observed in this band. With the spectral resolving power of the NIRSPEC instrument (R ~ 2000) we developed nine spectral indices to classify these objects in the J -band. From this data base it was possible for the first time to create a pure infrared spectral classification system for the L dwarfs, and to confirm the existing infrared classification system for T dwarfs. This is an important development because most of the flux from L and T dwarfs is radiated in the near-infrared, where they are several magnitudes brighter than at visible wavelengths, and classification via NIR properties is not only important but

  12. Phase Curve Observations of the Irradaited Transiting Brown Dwarf KELT-1b

    Science.gov (United States)

    Beatty, Thomas; Colon, Knicole; Fortney, Jonathan; Gaudi, Scott; Marley, Mark; Rodriguez, Joseph; Showman, Adam

    2014-12-01

    We propose to observe full orbit phase curves, at 3.6um and 4.5um, of the transiting brown dwarf KELT-1b. KELT-1b is a 27MJ object on a short 1.2 day (29.2 hour) orbit around a bright (V=10.8) F5V star. This system is unique, in that it contains the only known highly irradiated brown dwarf on which it is possible to perform high precision atmospheric measurements, due to KELT-1b's short orbital period and the brightness of its host star. Future work to observationally and theoretically understand the properties of irradiated brown dwarfs will, therefore, rely on our ability to measure the properties of KELT-1b and its atmosphere. Furthermore, a comparison of KELT-1b's Spitzer phase curves to those of similarly irradiated giant planets offers the best possible test of the role of surface gravity in atmospheric circulation. Besides its one-of-a-kind status as an irradiated brown dwarf, KELT-1b is one of the best possible targets for phase curve observations. There are only seven transiting extrasolar giant planets or brown dwarfs with shorter orbital periods (11.8). Our proposed observations will therefore require a relativity low amount of Spitzer time compared to other phase curve proposals (74.5 hours for both bands), and will give very high signal-to-noise ratio (SNR) detections of the phase modulation (estimated SNR of 56 to 74). Our observations will yield one of the best defined phase curve measurements conducted by Spitzer: we estimate a SNR for the phase curve of KELT-1b similar to that achieved on WASP-18b, and a SNR 4 to 5 times higher than the next highest SNR achieved, for the phase curve of HD189733b.

  13. HUBBLE SPACE TELESCOPE SPECTROSCOPY OF BROWN DWARFS DISCOVERED WITH THE WIDE-FIELD INFRARED SURVEY EXPLORER

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Adam C.; Cushing, Michael C. [Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606 (United States); Kirkpatrick, J. Davy; Gelino, Christopher R. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Mace, Gregory N.; Wright, Edward L. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Eisenhardt, Peter R. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States); Skrutskie, M. F. [Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States); Griffith, Roger L. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Marsh, Kenneth A., E-mail: Adam.Schneider@Utoledo.edu [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom)

    2015-05-10

    We present a sample of brown dwarfs identified with the Wide-field Infrared Survey Explorer (WISE) for which we have obtained Hubble Space Telescope (HST) Wide Field Camera 3 (WFC3) near-infrared grism spectroscopy. The sample (22 in total) was observed with the G141 grism covering 1.10–1.70 μm, while 15 were also observed with the G102 grism, which covers 0.90–1.10 μm. The additional wavelength coverage provided by the G102 grism allows us to (1) search for spectroscopic features predicted to emerge at low effective temperatures (e.g.,ammonia bands) and (2) construct a smooth spectral sequence across the T/Y boundary. We find no evidence of absorption due to ammonia in the G102 spectra. Six of these brown dwarfs are new discoveries, three of which are found to have spectral types of T8 or T9. The remaining three, WISE J082507.35+280548.5 (Y0.5), WISE J120604.38+840110.6 (Y0), and WISE J235402.77+024015.0 (Y1), are the 19th, 20th, and 21st spectroscopically confirmed Y dwarfs to date. We also present HST grism spectroscopy and reevaluate the spectral types of five brown dwarfs for which spectral types have been determined previously using other instruments.

  14. Hubble Space Telescope astrometry of the closest brown dwarf binary system -- I. Overview and improved orbit

    OpenAIRE

    Bedin, L. R.; Pourbaix, D.; Apai, D.; Burgasser, A. J.; Buenzli, E.; Boffin, H.~M.~J.; Libralato, M.

    2017-01-01

    Located at ~2pc, the L7.5+T0.5 dwarfs system WISE J104915.57-531906.1 (Luhman16AB) is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity, and planet-hosting frequency. In the first study of this series -- based on a multi-cycle Hubble Space Telescope (HST) program -- we provide an overview of the project and present improved estimates of positions, proper motions, annual parallax,...

  15. A new L5 brown dwarf member of the Hyades cluster with chromospheric activity

    Science.gov (United States)

    Pérez-Garrido, A.; Lodieu, N.; Rebolo, R.

    2017-03-01

    Aims: Our aim is to identify brown dwarf members of the nearby Hyades open star cluster to determine the photometric and spectroscopic properties of brown dwarfs at moderately old ages and extend the knowledge of the substellar mass function of the cluster. Methods: We cross-matched the 2MASS and AllWISE public catalogues and measured proper motions to identify low-mass stars and brown dwarf candidates in an area of radius eight degrees around the central region of the Hyades cluster. We identified objects with photometry and proper motions consistent with cluster membership. For the faintest (J = 17.2 mag) most promising astrometric and photometric low-mass candidate 2MASS J04183483+2131275, with a membership probability of 94.5%, we obtained low-resolution (R = 300-1000) and intermediate-resolution (R = 2500) spectroscopy with the 10.4m Gran Telescopio Canarias. Results: From the low-resolution spectra we determined a L5.0 ± 0.5 spectral type, consistent with the available photometry. In the intermediate dispersion spectrum we detected Hα in emission (marginally resolved with a full width half maximum of 2.8 Å) and determined a log (LHα/Lbol) = -6.0 dex. From Hα we obtained a radial velocity of 38.0 ± 2.9 km s-1, which combined with the proper motion leads to space velocities which are fully consistent with membership in the Hyades cluster. We also report a detection in the H2 band by the UKIDSS Galactic Plane Survey. Using evolutionary models we determine from the available photometry of the object a mass in the range 0.039-0.055 M⊙. Brown dwarfs with masses below 0.055 M⊙ should fully preserve its initial lithium content, and indeed the spectrum at 6708 Å may show a feature consistent with lithium preservation; however, a higher S/N is needed to confirm this point. Conclusions: We have identified a new high-probability L5 brown dwarf member of the Hyades cluster. This is the first relatively old L5 brown dwarf with a well-determined age (500-700 Myr

  16. Identification and characterization of low mass stars and brown dwarfs using Virtual Observatory tools

    Science.gov (United States)

    Aberasturi, Miriam

    2015-11-01

    Context: Two thirds of the stars in our galactic neighborhood (d building a shortlist with the best possible candidates for exoplanet searches. Brown dwarfs (BDs) are self-gravitating objects that do not get enough mass to maintain a sufficiently high temperature in their core for stable hydrogen fusion. They represent the link between low-mass stars and giant planets. Due to their low temperatures, BDs emit significant flux at mid-infrared wavelength which makes this range very adequate to look for this type of objects. The Virtual Observatory (VO) is an international initiative designed to help the astronomical community in the exploitation of the multi-wavelength information that resides in data archives. In the last years the Spanish Virtual Observatory is conducting a number of projects focused on the study of substellar objects taking advantage of Virtual Observatory tools for an easy data access and analysis of large area surveys. This is the framework where this thesis has been carried out. This dissertation addresses three problems in the framework of low-mass stars and brown dwarfs, namely, the search for brown dwarf candidates crossmatching catalogues (Chapter 4), the search for nearby bright M dwarfs and the subsequent spectroscopic characterization (Chapter 5), and a study of binarity in mid to late-T brown dwarfs (Chapter 6); the first two topics use Virtual Observatory tools. Aims and methodology:In the first paper we carried out a search of brown dwarfs in the sky area in common to the WISE, 2MASS Point Source and SDSS catalogues. A VO-workflow with the criteria that must accomplish our candidates was built using STILTS. The workflow returned 138 sources that were visually inspected. For the six new candidates that passed the inspection, proper motions were calculated using the positions and the different observing epochs of the catalogues previously quoted. Effective temperatures were estimated using VOSA and spectral types and distances using

  17. Near-infrared spectroscopic survey of brown dwarfs using NIRSPEC on the Keck II Telescope

    Science.gov (United States)

    McLean, Ian S.

    2003-02-01

    Since commissioning the near-infrared spectrometer (NIRSPEC) on the Keck II telescope in April 1999 we have been carrying out an extensive spectroscopic survey of low-mass stars and brown dwarfs. At least two objects in every spectral sub-class from M6 to T8 have been observed in the J band at a resolution of R ~ 2,000. For a subset of these we have obtained complete near-infrared flux-calibrated spectra from 0.9 - 2.5 μm. In addition, J band spectra at even higher resolution (R ~ 20,000) have been obtained for many sub-classes. The results of the NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS) are summarized in this paper and presented as an illustration of the progress in infrared technology and the scientific productivity of the Keck telescopes.

  18. A T8.5 BROWN DWARF MEMBER OF THE {xi} URSAE MAJORIS SYSTEM

    Energy Technology Data Exchange (ETDEWEB)

    Wright, Edward L.; Mace, Gregory; McLean, Ian S. [UCLA Astronomy, P.O. Box 951547, Los Angeles, CA 90095-1547 (United States); Skrutskie, M. F.; Nelson, M. J.; Borish, H. J. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Kirkpatrick, J. Davy; Gelino, Christopher R.; Griffith, Roger L.; Jarrett, Tom [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Marsh, Kenneth A. [School of Physics and Astronomy, Cardiff University, Cardiff CF243AA (United Kingdom); Mainzer, Amanda K.; Eisenhardt, Peter R. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109-8001 (United States); Tobin, John J. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Cushing, Michael C., E-mail: wright@astro.ucla.edu [Department of Physics and Astronomy, MS 111, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606-3328 (United States)

    2013-03-15

    The Wide-field Infrared Survey Explorer has revealed a T8.5 brown dwarf (WISE J111838.70+312537.9) that exhibits common proper motion with a solar-neighborhood (8 pc) quadruple star system-{xi} Ursae Majoris. The angular separation is 8.'5, and the projected physical separation is Almost-Equal-To 4000 AU. The sub-solar metallicity and low chromospheric activity of {xi} UMa A argue that the system has an age of at least 2 Gyr. The infrared luminosity and color of the brown dwarf suggests the mass of this companion ranges between 14 and 38 M{sub J} for system ages of 2 and 8 Gyr, respectively.

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

    Science.gov (United States)

    Heller, René

    2013-01-01

    Abstract White and brown dwarfs are astrophysical objects that are bright enough to support an insolation habitable zone (IHZ). Unlike hydrogen-burning stars, they cool and become less luminous with time; hence their IHZ moves in with time. The inner edge of the IHZ is defined as the orbital radius at which a planet may enter a moist or runaway greenhouse, phenomena that can remove a planet's surface water forever. Thus, as the IHZ moves in, planets that enter it may no longer have any water and are still uninhabitable. Additionally, the close proximity of the IHZ to the primary leads to concern that tidal heating may also be strong enough to trigger a runaway greenhouse, even for orbital eccentricities as small as 10−6. Water loss occurs due to photolyzation by UV photons in the planetary stratosphere, followed by hydrogen escape. Young white dwarfs emit a large amount of these photons, as their surface temperatures are over 104 K. The situation is less clear for brown dwarfs, as observational data do not constrain their early activity and UV emission very well. Nonetheless, both types of planets are at risk of never achieving habitable conditions, but planets orbiting white dwarfs may be less likely to sustain life than those orbiting brown dwarfs. We consider the future habitability of the planet candidates KOI 55.01 and 55.02 in these terms and find they are unlikely to become habitable. Key Words: Extrasolar terrestrial planets—Habitability—Habitable zone—Tides—Exoplanets. Astrobiology 13, 279–291. PMID:23537137

  20. Sonora: A New Generation Model Atmosphere Grid for Brown Dwarfs and Young Extrasolar Giant Planets

    Science.gov (United States)

    Marley, Mark S.; Saumon, Didier; Fortney, Jonathan J.; Morley, Caroline; Lupu, Roxana Elena; Freedman, Richard; Visscher, Channon

    2017-01-01

    Brown dwarf and giant planet atmospheric structure and composition has been studied both by forward models and, increasingly so, by retrieval methods. While indisputably informative, retrieval methods are of greatest value when judged in the context of grid model predictions. Meanwhile retrieval models can test the assumptions inherent in the forward modeling procedure. In order to provide a new, systematic survey of brown dwarf atmospheric structure, emergent spectra, and evolution, we have constructed a new grid of brown dwarf model atmospheres. We ultimately aim for our grid to span substantial ranges of atmospheric metallilcity, C/O ratios, cloud properties, atmospheric mixing, and other parameters. Spectra predicted by our modeling grid can be compared to both observations and retrieval results to aid in the interpretation and planning of future telescopic observations. We thus present Sonora, a new generation of substellar atmosphere models, appropriate for application to studies of L, T, and Y-type brown dwarfs and young extrasolar giant planets. The models describe the expected temperature-pressure profile and emergent spectra of an atmosphere in radiative-convective equilibrium for ranges of effective temperatures and gravities encompassing 200 less than or equal to T(sub eff) less than or equal to 2400 K and 2.5 less than or equal to log g less than or equal to 5.5. In our poster we briefly describe our modeling methodology, enumerate various updates since our group's previous models, and present our initial tranche of models for cloudless, solar metallicity, and solar carbon-to-oxygen ratio, chemical equilibrium atmospheres. These models will be available online and will be updated as opacities and cloud modeling methods continue to improve.

  1. Brown dwarf distances and atmospheres: Spitzer Parallaxes and the Keck/NIRSPEC upgrade

    Science.gov (United States)

    Martin, Emily C.

    2018-01-01

    Advances in infrared technology have been essential towards improving our understanding of the solar neighborhood, revealing a large population of brown dwarfs, which span the mass regime between planets and stars. My thesis combines near-infrared (NIR) spectroscopic and astrometric analysis of nearby low-mass stars and brown dwarfs with instrumentation work to upgrade the NIRSPEC instrument for the Keck II Telescope. I will present results from a program using Spitzer/IRAC data to measure precise locations and distances to 22 of the coldest and closest brown dwarfs. These distances allow us to constrain absolute physical properties, such as mass, radius, and age, of free-floating planetary-mass objects through comparison to atmospheric and evolutionary models. NIR spectroscopy combined with the Spitzer photometry reveals a detailed look into the atmospheres of brown dwarfs and gaseous extrasolar planets. Additionally, I will discuss the improvements we are making to the NIRSPEC instrument at Keck. NIRSPEC is a NIR echelle spectrograph, capable of R~2000 and R~25,000 observations in the 1-5 μm range. As part of the upgrade, I performed detector characterization, optical design of a new slit-viewing camera, mechanical testing, and electronics design. NIRSPEC’s increased efficiency will allow us to obtain moderate- and high-resolution NIR spectra of objects up to a magnitude fainter than the current NIRSPEC design. Finally, I will demonstrate the utility of a NIR laser frequency comb as a high-resolution calibrator. This new technology will revolutionize precision radial velocity measurements in the coming decade.

  2. Detection of brown dwarfs by the micro-lensing of unresolved stars

    CERN Document Server

    Baillon, Paul; Giraud-Héraud, Yannick; Kaplan, J; Baillon, Paul; Bouquet, Alain; Giraud-Héraud, Yannick; Kaplan, Jean

    1993-01-01

    The presence of brown dwarfs in the dark galactic halo could be detected through their gravitational lensing effect and experiments under way monitor about one million stars to observe a few lensing events per year. We show that if the photon flux from a galaxy is measured with a good precision, it is not necessary to resolve the stars and besides more events could be observed.

  3. 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

  4. Simulating Unresolved Binary Brown Dwarfs for Cameras on the Hubble Space Telescope

    Science.gov (United States)

    Gardner, Douglas B.; Stephens, Thomas E.; Stephens, Denise C.; Salway, Elora N.

    2015-01-01

    Identification of binary brown dwarf (BD) systems with small separations can be difficult because of the inability to resolve each component according to the Rayleigh criterion and the possibility of the secondary BD being much fainter than the primary BD. Using models of the point spread function (PSF) created for several filters and cameras on the Hubble Space Telescope (HST), we have developed a technique to determine the probability that an apparently single BD observed with HST may actually be an unresolved binary. To test the detection limits of this method, we have developed code to produce simulated binary systems for several HST cameras and their filters. The simulated data cover the full range of parameter space (delta_magnitude, separation, position angle, background noise, etc.) that we might expect to encounter when searching for binary brown dwarfs in real HST data. With the simulated data, we find that we can positively identify binary brown dwarf systems in the HST archives with separations that are much smaller than the Rayleigh criterion. Our simulations also place upper limits on the separation and flux of undetected secondary companions for apparently single BD in the HST archives.

  5. VizieR Online Data Catalog: Brown dwarf surface gravities with Keck/NIRSPEC (Martin , 2017)

    Science.gov (United States)

    Martin, E. C.; Mace, G. N.; McLean, I. S.; Logsdon, S. E.; Rice, E. L.; Kirkpatrick, J. D.; Burgasser, A. J.; McGovern, M. R.; Prato, L.

    2017-10-01

    In this paper, we follow up on prior NIR spectroscopy by our group and use a modified Allers & Liu (A13, 2013ApJ...772...79A) method to determine surface gravities for 228 M, L, and T dwarfs. We present medium-resolution (R~20000) J-band spectra of 85 M dwarfs, 92 L dwarfs, and 51 T dwarfs obtained as part of the Keck NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS). Ninety-seven spectra were published previously in McLean+ (2003ApJ...596..561M), Burgasser+ (2003ApJ...592.1186B), McGovern+ (2004ApJ...600.1020M), Rice+ (2010ApJS..186...63R), Kirkpatrick+ (2010, J/ApJS/190/100), Luhman (2012ARA&A..50...65L), Thompson+ (2013PASP..125..809T), Mace+ (2013, J/ApJS/205/6), Mace+ (2013ApJ...777...36M), and Kirkpatrick+ (2014, J/ApJ/783/122), and the remaining 131 are presented here for the first time. Observation information (spanning 1999 Apr to 2015 Mar) for all of the targets in our sample is listed in Table 1. (4 data files).

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

    Science.gov (United States)

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

    2017-01-01

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

  7. Identifying Cool Brown Dwarfs and Subdwarfs in the Solar Neighborhood: Prospects for a Near-Infrared Proper Motion Survey

    Science.gov (United States)

    Burgasser, A. J.

    2003-12-01

    Low-temperature stars and brown dwarfs emit predominantly in the near-infrared, and recent wide-field surveys sampling these wavelengths (2MASS, DENIS, SDSS) have unveiled a vast repository of intrinsically faint objects, including large numbers of field brown dwarfs and members of two new spectral classes. On the other hand, proper motion surveys have been exceptionally efficient at uncovering both the nearest stars and stars with high intrinsic motions; i.e., halo/thick disk dwarfs and white dwarfs. Unfortunately, proper motion surveys are insensitive to faint stars and brown dwarfs as they have been conducted primarily at optical bands. I therefore make a case for a wide-field near-infrared proper motion survey that would detect the nearest cool stars and brown dwarfs in an efficient and photometrically unbiased manner. I demonstrate how the currently known population of field brown dwarfs are easily discernible in such a survey, and how substellar subdwarfs could potentially be found in substantial numbers. This survey could make use of existing catalog data as its first epoch. I also describe a straightforward NIR survey program using a 2Kx2K IR camera on a dedicated 1-2m class automated telescope. This somewhat more ambitious program could repeatedly scan the sky on a 6-month cycle, and would be useful for cool dwarf searches, general variability studies, searches for transits around late-type stars, and deep survey programs. This research is supported by NASA through Hubble Fellowship grant HST-HF-01137.01 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  8. Hubble Space Telescope astrometry of the closest brown dwarf binary system - I. Overview and improved orbit★

    Science.gov (United States)

    Bedin, L. R.; Pourbaix, D.; Apai, D.; Burgasser, A. J.; Buenzli, E.; Boffin, H. M. J.; Libralato, M.

    2017-09-01

    Located at 2 pc, the L7.5+T0.5 dwarfs system WISE J104915.57-531906.1 (Luhman 16 AB) is the third closest system known to Earth, making it a key benchmark for detailed investigation of brown dwarf atmospheric properties, thermal evolution, multiplicity, and planet-hosting frequency. In the first study of this series - based on a multicycle Hubble Space Telescope (HST) program - we provide an overview of the project and present improved estimates of positions, proper motions, annual parallax, mass ratio, and the current best assessment of the orbital parameters of the A-B pair. Our HST observations encompass the apparent periastron of the binary at 220.5 ± 0.2 mas at epoch 2016.402. Although our data seem to be inconsistent with recent ground-based astrometric measurements, we also exclude the presence of third bodies down to Neptune masses and periods longer than a year.

  9. Models of very-low-mass stars, brown dwarfs and exoplanets.

    Science.gov (United States)

    Allard, F; Homeier, D; Freytag, B

    2012-06-13

    Within the next few years, GAIA and several instruments aiming to image extrasolar planets will be ready. In parallel, low-mass planets are being sought around red dwarfs, which offer more favourable conditions, for both radial velocity detection and transit studies, than solar-type stars. In this paper, the authors of a model atmosphere code that has allowed the detection of water vapour in the atmosphere of hot Jupiters review recent advances in modelling the stellar to substellar transition. The revised solar oxygen abundances and cloud model allow the photometric and spectroscopic properties of this transition to be reproduced for the first time. Also presented are highlight results of a model atmosphere grid for stars, brown dwarfs and extrasolar planets.

  10. The Effect of Atmospheric Cooling on Vertical Velocity Dispersion and Density Distribution of Brown Dwarfs

    Science.gov (United States)

    Ryan, Russell E., Jr.; Thorman, Paul A.; Schmidt, Sarah J.; Cohen, Seth H.; Hathi, Nimish P.; Holwerda, Benne W.; Lunine, Jonathan I.; Pirzkal, Nor; Windhorst, Rogier A.; Young, Erick

    2017-09-01

    We present a Monte Carlo simulation designed to predict the vertical velocity dispersion of brown dwarfs in the Milky Way. We show that since these stars are constantly cooling, the velocity dispersion has a noticeable trend with the spectral type. With realistic assumptions for the initial mass function, star formation history, and the cooling models, we show that the velocity dispersion is roughly consistent with what is observed for M dwarfs, decreases to cooler spectral types, and increases again for the coolest types in our study (˜T9). We predict a minimum in the velocity dispersions for L/T transition objects, however, the detailed properties of the minimum predominately depend on the star formation history. Since this trend is due to brown dwarf cooling, we expect that the velocity dispersion as a function of spectral type should deviate from the constancy around the hydrogen-burning limit. We convert from velocity dispersion to vertical scale height using standard disk models and present similar trends in disk thickness as a function of spectral type. We suggest that future, wide-field photometric and/or spectroscopic missions may collect sizable samples of distant (˜ 1 kpc) dwarfs that span the hydrogen-burning limit. As such, we speculate that such observations may provide a unique way of constraining the average spectral type of hydrogen burning. Support for program #13266 was provided by NASA through a grant from the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under the NASA contract NAS 5-26555.

  11. GPI Spectroscopy of the Mass, Age, and Metallicity Benchmark Brown Dwarf HD 4747 B

    Science.gov (United States)

    Crepp, Justin R.; Principe, David A.; Wolff, Schuyler; Giorla Godfrey, Paige A.; Rice, Emily L.; Cieza, Lucas; Pueyo, Laurent; Bechter, Eric B.; Gonzales, Erica J.

    2018-02-01

    The physical properties of brown dwarf companions found to orbit nearby, solar-type stars can be benchmarked against independent measures of their mass, age, chemical composition, and other parameters, offering insights into the evolution of substellar objects. The TRENDS high-contrast imaging survey has recently discovered a (mass/age/metallicity) benchmark brown dwarf orbiting the nearby (d = 18.69 ± 0.19 pc), G8V/K0V star HD 4747. We have acquired follow-up spectroscopic measurements of HD 4747 B using the Gemini Planet Imager to study its spectral type, effective temperature, surface gravity, and cloud properties. Observations obtained in the H-band and K 1-band recover the companion and reveal that it is near the L/T transition (T1 ± 2). Fitting atmospheric models to the companion spectrum, we find strong evidence for the presence of clouds. However, spectral models cannot satisfactorily fit the complete data set: while the shape of the spectrum can be well-matched in individual filters, a joint fit across the full passband results in discrepancies that are a consequence of the inherent color of the brown dwarf. We also find a 2σ tension in the companion mass, age, and surface gravity when comparing to evolutionary models. These results highlight the importance of using benchmark objects to study “secondary effects” such as metallicity, non-equilibrium chemistry, cloud parameters, electron conduction, non-adiabatic cooling, and other subtleties affecting emergent spectra. As a new L/T transition benchmark, HD 4747 B warrants further investigation into the modeling of cloud physics using higher resolution spectroscopy across a broader range of wavelengths, polarimetric observations, and continued Doppler radial velocity and astrometric monitoring.

  12. Modular Spectral Inference Framework Applied to Young Stars and Brown Dwarfs

    Science.gov (United States)

    Gully-Santiago, Michael A.; Marley, Mark S.

    2017-01-01

    In practice, synthetic spectral models are imperfect, causing inaccurate estimates of stellar parameters. Using forward modeling and statistical inference, we derive accurate stellar parameters for a given observed spectrum by emulating a grid of precomputed spectra to track uncertainties. Spectral inference as applied to brown dwarfs re: Synthetic spectral models (Marley et al 1996 and 2014) via the newest grid spans a massive multi-dimensional grid applied to IGRINS spectra, improving atmospheric models for JWST. When applied to young stars(10Myr) with large starpots, they can be measured spectroscopically, especially in the near-IR with IGRINS.

  13. The Next Generation Sky Survey and the Quest for Cooler Brown Dwarfs

    OpenAIRE

    Kirkpatrick, J. Davy

    2002-01-01

    The Next Generation Sky Survey (NGSS) is a proposed NASA MIDEX mission to map the entire sky in four infrared bandpasses - 3.5, 4.7, 12, and 23 um. The seven-month mission will use a 50-cm telescope and four-channel imager to survey the sky from a circular orbit above the Earth. Expected sensitivities will be half a million times that of COBE/DIRBE at 3.5 and 4.7 um and a thousand times that of IRAS at 12 and 23 um. NGSS will be particularly sensitive to brown dwarfs cooler than those present...

  14. Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka (del Ori)

    OpenAIRE

    Caballero, J. A.; Solano, E.

    2008-01-01

    Aims: We look for new regions for the search of substellar objects. Methods: Two circular areas, 45 arcmin-radius each, centred on the young massive star systems Alnilam and Mintaka in the Orion Belt, have been explored. The regions are very young (less than 10 Ma), have low extinction, and are neighbours to sigma Orionis (~3 Ma), a young open cluster very rich in brown dwarfs and planetary-mass objects. We have used Virtual Observatory tools, the astro-photometric Tycho-2, DENIS and 2MASS ca...

  15. Very Low-mass Stars and Brown Dwarfs in Upper Scorpius Using Gaia DR1: Mass Function, Disks, and Kinematics

    Science.gov (United States)

    Cook, Neil J.; Scholz, Aleks; Jayawardhana, Ray

    2017-12-01

    Our understanding of the brown dwarf population in star-forming regions is dependent on knowing distances and proper motions and therefore will be improved through the Gaia space mission. In this paper, we select new samples of very low-mass objects (VLMOs) in Upper Scorpius using UKIDSS colors and optimized proper motions calculated using Gaia DR1. The scatter in proper motions from VLMOs in Upper Scorpius is now (for the first time) dominated by the kinematic spread of the region itself, not by the positional uncertainties. With age and mass estimates updated using Gaia parallaxes for early-type stars in the same region, we determine masses for all VLMOs. Our final most complete sample includes 453 VLMOs of which ˜125 are expected to be brown dwarfs. The cleanest sample is comprised of 131 VLMOs, with ˜105 brown dwarfs. We also compile a joint sample from the literature that includes 415 VLMOs, out of which 152 are likely brown dwarfs. The disk fraction among low-mass brown dwarfs (M< 0.05 {M}⊙ ) is substantially higher than in more massive objects, indicating that disks around low-mass brown dwarfs survive longer than in low-mass stars overall. The mass function for 0.01< M< 0.1 {M}⊙ is consistent with the Kroupa Initial Mass Function. We investigate the possibility that some “proper motion outliers” have undergone a dynamical ejection early in their evolution. Our analysis shows that the color-magnitude cuts used when selecting samples introduce strong bias into the population statistics due to varying levels of contamination and completeness.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-09-15

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

  17. Star formation in the lagoon nebula & low-mass stars and brown dwarfs

    Science.gov (United States)

    Castro, Philip J.

    Topic I of this thesis reports on star formation in the Lagoon Nebula. We report on deep Chandra X-Ray Observatory observations of the Lagoon Nebula (NGC 6530 and the Hourglass Nebula) totaling 233 ks. We find 1482 X-ray sources, 1130 associated with catalogued near-infrared or optical stars. These X-ray sources are mainly concentrated in the young Hourglass Nebula Cluster (HNC), the older NGC 6530 cluster, and the young M8E cluster in the southern rim. The clustering of X-ray sources near 850mum emission along the central ridge of NGC 6530, M8E, the southern ridge, and coincident with the Hourglass Nebula, provides evidence of triggered star formation. Chandra point-source density contours show a ridge of increased density between NGC 6530 and the HNC, 9 Sgr and the HNC, and class III/II contours stretching from 9 Sgr to the HNC, respectively, provide support for a proposed sequence of star formation in the Lagoon Nebula. Topic II of this thesis reports on low-mass stars and brown dwarfs (BDs). We report on Chandra X-Ray Observatory observations of the TW Hydrae BD 2MASSW J1139511-315921 (2M1139). In the combined 31 ks ACIS-S exposure, 2M1139 is detected at the 3sigma confidence level. This object is similar to another TW Hydrae BD member, CD-33 7795B (TWA 5B), previously detected in X-rays an order of magnitude more luminous than 2M1139. We find the discrepancy between their X-ray luminosities is consistent with BDs of similar spectral type in the Orion Nebula Cluster. 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 discover five high proper motion spectroscopically confirmed L dwarfs by comparing WISE to 2MASS. Two of these are L dwarfs at the L/T transition within 10 pc, and three are early L dwarfs within 25 pc. Of the early L dwarfs, one is a member of the class of unusually red L dwarfs whose red spectra can not be easily attributed to youth.

  18. MOA-2010-BLG-073L: AN M-DWARF WITH A SUBSTELLAR COMPANION AT THE PLANET/BROWN DWARF BOUNDARY

    Energy Technology Data Exchange (ETDEWEB)

    Street, R. A.; Tsapras, Y. [LCOGT, 6740 Cortona Drive, Suite 102, Goleta, CA 93117 (United States); Choi, J.-Y.; Han, C. [Department of Physics, Institute for Astrophysics, Chungbuk National University, Cheongju 361-763 (Korea, Republic of); Furusawa, K. [Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601 (Japan); Hundertmark, M.; Horne, K.; Dominik, M.; Browne, P.; Bajek, D. [SUPA/St Andrews, Department of Physics and Astronomy, North Haugh, St. Andrews, Fife KY16 9SS (United Kingdom); Gould, A. [Department of Astronomy, Ohio State University, McPherson Laboratory, 140 West 18th Avenue, Columbus, OH 43210-1173 (United States); Sumi, T. [Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043 (Japan); Bond, I. A. [Institute of Information and Mathematical Sciences, Massey University, Private Bag 102-904, North Shore Mail Centre, Auckland (New Zealand); Wouters, D. [UPMC-CNRS, UMR 7095, Institut d' Astrophysique de Paris, 98bis boulevard Arago, F-75014 Paris (France); Zellem, R. [Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721-0092 (United States); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland); Snodgrass, C. [Max Planck Institute for Solar System Research, Max-Planck-Str. 2, D-37191 Katlenburg-Lindau (Germany); Kains, N.; Bramich, D. M. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen (Germany); Steele, I. A., E-mail: rstreet@lcogt.net [Astrophysics Research Institute, Liverpool John Moores University, Twelve Quays House, Egerton Wharf, Birkenhead, Wirral CH41 1LD (United Kingdom); Collaboration: RoboNet Collaboration; MOA Collaboration; OGLE Collaboration; muFUN Collaboration; PLANET Collaboration; MiNDSTEp Collaboration; and others

    2013-01-20

    We present an analysis of the anomalous microlensing event, MOA-2010-BLG-073, announced by the Microlensing Observations in Astrophysics survey on 2010 March 18. This event was remarkable because the source was previously known to be photometrically variable. Analyzing the pre-event source light curve, we demonstrate that it is an irregular variable over timescales >200 days. Its dereddened color, (V - I) {sub S,0}, is 1.221 {+-} 0.051 mag, and from our lens model we derive a source radius of 14.7 {+-} 1.3 R {sub Sun }, suggesting that it is a red giant star. We initially explored a number of purely microlensing models for the event but found a residual gradient in the data taken prior to and after the event. This is likely to be due to the variability of the source rather than part of the lensing event, so we incorporated a slope parameter in our model in order to derive the true parameters of the lensing system. We find that the lensing system has a mass ratio of q = 0.0654 {+-} 0.0006. The Einstein crossing time of the event, t {sub E} = 44.3 {+-} 0.1 days, was sufficiently long that the light curve exhibited parallax effects. In addition, the source trajectory relative to the large caustic structure allowed the orbital motion of the lens system to be detected. Combining the parallax with the Einstein radius, we were able to derive the distance to the lens, D{sub L} = 2.8 {+-} 0.4 kpc, and the masses of the lensing objects. The primary of the lens is an M-dwarf with M {sub L,1} = 0.16 {+-} 0.03 M {sub Sun }, while the companion has M {sub L,2} = 11.0 {+-} 2.0 M {sub J}, putting it in the boundary zone between planets and brown dwarfs.

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

    Science.gov (United States)

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

    1992-01-01

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

  20. A HERSCHEL SEARCH FOR COLD DUST IN BROWN DWARF DISKS: FIRST RESULTS

    Energy Technology Data Exchange (ETDEWEB)

    Harvey, Paul M.; Evans, Neal J. II [Astronomy Department, University of Texas at Austin, 1 University Station C1400, Austin, TX 78712-0259 (United States); Henning, Thomas [Max-Planck-Institut for Astronomy, Koenigstuhl 17, 69117 Heidelberg (Germany); Menard, Francois; Pinte, Christophe [UJF-Grenoble 1/CNRS-INSU, Institut de Planetologie et d' Astrophysique (IPAG) UMR 5274, BP 53, 38041 Grenoble cedex 9 (France); Wolf, Sebastian; Liu Yao [Institute of Theoretical Physics and Astrophysics, University of Kiel, Leibnizstr. 15, 24098 Kiel (Germany); Cieza, Lucas A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Pascucci, Ilaria [Lunar and Planetary Laboratory, Department of Planetary Sciences, University of Arizona, 1629 East University Boulevard, Tucson, AZ 85721 (United States); Merin, Bruno, E-mail: pmh@astro.as.utexas.edu, E-mail: nje@astro.as.utexas.edu, E-mail: henning@mpia.de, E-mail: menard@obs.ujf-grenoble.fr, E-mail: christophe.pinte@obs.ujf-grenoble.fr, E-mail: wolf@astrophysik.uni-kiel.de, E-mail: yliu@pmo.ac.cn, E-mail: lcieza@ifa.hawaii.edu, E-mail: pascucci@lpl.arizona.edu, E-mail: Bruno.Merin@sciops.esa.int [Herschel Science Centre, SRE-SDH, ESA, P.O. Box 78, 28691 Villanueva de la Canada, Madrid (Spain)

    2012-01-15

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

  1. 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.

  2. A Statistical Study of Brown Dwarf Companions from the SDSS-III MARVELS Survey

    Science.gov (United States)

    Grieves, Nolan; Ge, Jian; Thomas, Neil; Ma, Bo; De Lee, Nathan M.; Lee, Brian L.; Fleming, Scott W.; Sithajan, Sirinrat; Varosi, Frank; Liu, Jian; Zhao, Bo; Li, Rui; Agol, Eric; MARVELS Team

    2016-01-01

    We present 23 new Brown Dwarf (BD) candidates from the Multi-object APO Radial-Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky Survey III (SDSS-III). The BD candidates were selected from the processed MARVELS data using the latest University of Florida 2D pipeline, which shows significant improvement and reduction of systematic errors over the 1D pipeline results included in the SDSS Data Release 12. This sample is the largest BD yield from a single radial velocity survey. Of the 23 candidates, 18 are around main sequence stars and 5 are around giant stars. Given a giant contamination rate of ~24% for the MARVELS survey, we find a BD occurrence rate around main sequence stars of ~0.7%, which agrees with previous studies and confirms the BD desert, while the BD occurrence rate around the MARVELS giant stars is ~0.6%. Preliminary results show that our new candidates around solar type stars support a two population hypothesis, where BDs are divided at a mass of ~42.5 MJup. BDs less massive than 42.5 MJup have eccentricity distributions consistent with planet-planet scattering models, where BDs more massive than 42.5 MJup have both period and eccentricity distributions similar to that of stellar binaries. Special Brown Dwarf systems such as multiple BD systems and highly eccentric BDs will also be presented.

  3. The physics of brown dwarfs and exoplanets - JWST/NIRSpec GTO program overview

    Science.gov (United States)

    Birkmann, Stephan; Alves de Oliveira, Catarina; Valenti, Jeff A.; Ferruit, Pierre; NIRSpec GTO Team

    2017-06-01

    The Near Infrared Spectrograph (NIRSpec) is one of the science instruments on the James Webb Space Telescope that is scheduled for launch in October 2018. The NIRSpec guaranteed time observer (GTO) team will use ~70 hours of NIRSpec guaranteed time to carry out spectroscopic observations of brown dwarfs as well as transiting and directly imaged exoplanets with NIRSpec. The instrument offers four distinct observing modes to proposers that will all be exercised by the GTO programs presented here: 1) multi object spectroscopy (MOS) of 10s to 100s of sources in a ~9 arcmin field of view (FOV), 2) integral field spectroscopy (IFS) with a 3” x 3” FOV, 3) high contrast slit spectroscopy of individual objects and 4) time series observations of bright sources, e.g. transiting exoplanets host stars. Seven dispersers are available in all observing modes: a prism covering the wavelength range from 0.6 to 5.3 micron with a spectral resolution R of ~30 to 300, and two sets of three gratings covering 0.7 to 5.2 micron with medium (R~1000) and high (R~2700) spectral resolution.We will present the science goals and targets for the brown dwarf and exoplanet GTO programs and discuss the planned implementation of the observations. The latter might be of particular interest to future JWST/NIRSpec proposers.

  4. 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.

  5. 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.

  6. Infrared rotational light curves on Jupiter induced by wave activities and cloud patterns andimplications on brown dwarfs

    Science.gov (United States)

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

    2017-10-01

    Many brown dwarfs exhibit infrared rotational light curves with amplitude varying from a fewpercent to twenty percent (Artigau et al. 2009, ApJ, 701, 1534; Radigan et al. 2012, ApJ, 750,105). Recently, it was claimed that weather patterns, especially planetary-scale waves in thebelts and cloud spots, are responsible for the light curves and their evolutions on brown dwarfs(Apai et al. 2017, Science, 357, 683). Here we present a clear relationship between the direct IRemission maps and light curves of Jupiter at multiple wavelengths, which might be similar withthat on cold brown dwarfs. Based on infrared disk maps from Subaru/COMICS and VLT/VISIR,we constructed full maps of Jupiter and rotational light curves at different wavelengths in thethermal infrared. We discovered a strong relationship between the light curves and weatherpatterns on Jupiter. The light curves also exhibit strong multi-bands phase shifts and temporalvariations, similar to that detected on brown dwarfs. Together with the spectra fromTEXES/IRTF, our observations further provide detailed information of the spatial variations oftemperature, ammonia clouds and aerosols in the troposphere of Jupiter (Fletcher et al. 2016,Icarus, 2016 128) and their influences on the shapes of the light curves. We conclude that waveactivities in Jupiter’s belts (Fletcher et al. 2017, GRL, 44, 7140), cloud holes, and long-livedvortices such as the Great Red Spot and ovals control the shapes of IR light curves and multi-wavelength phase shifts on Jupiter. Our finding supports the hypothesis that observed lightcurves on brown dwarfs are induced by planetary-scale waves and cloud spots.

  7. A search for J-band variability from late-L and T brown dwarfs

    Science.gov (United States)

    Clarke, F. J.; Hodgkin, S. T.; Oppenheimer, B. R.; Robertson, J.; Haubois, X.

    2008-06-01

    We present J-band photometric observations of eight late-L and T type brown dwarfs designed to search for variability. We detect small amplitude periodic variability from three of the objects on time-scales of several hours, probably indicating the rotation period of the objects. The other targets do not show any variability down to the level of 0.5-5 per cent This work is based on observations obtained at the European Southern Observatory, La Silla, Chile (ESO Programme 72.C-0006). E-mail: fclarke@astro.ox.ac.uk (FJC); sth@ast.cam.ac.uk (STH); bro@amnh.org (BRO); xavier.haubois@obspm.fr (XH)

  8. Measuring the wind speed on a radio-emitting brown dwarf

    Science.gov (United States)

    Allers, Katelyn; Vos, Johanna; Williams, Peter; Biller, Beth

    2017-10-01

    We propose for photometric monitoring observations of 2MASS J10475385+2124234 using Spitzer/IRAC. 2MASS J1047+21 is a late spectral type (T6.5) radio emitter with a measured radio period of 1.77 hrs. As a part of our successful Cycle 13 program, we detected photometric variability for 2MASS J1047+21. Our proposed observations will not only characterize this variability of the coolest known radio emitter, but also provide a unique opportunity to measure the wind speed of this brown dwarf. Spitzer is currently the only facility capable of the photometric stability, continuous observations and 4.5 micron sensitivity necessary for the success of our program.

  9. 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.

  10. Young stars and brown dwarfs surrounding Alnilam (ɛ Orionis) and Mintaka (δ Orionis)

    Science.gov (United States)

    Caballero, J. A.; Solano, E.

    2008-07-01

    Aims: We look for new regions to search for substellar objects. Methods: Two circular areas, 45 arcmin-radius each, centred on the young massive star systems Alnilam and Mintaka in the Orion Belt, were explored. The regions are very young (less than 10 Ma), have low extinction, and are neighbours to σ Orionis (~3 Ma), a young open cluster very rich in brown dwarfs and planetary-mass objects. We used Virtual Observatory tools, the astro-photometric Tycho-2, DENIS and 2MASS catalogues, 10 control fields at similar galactic latitudes, as well as X-ray, mid-infrared, and spectroscopic data from the literature. Results: We compiled exhaustive lists of known young stars and new candidate members in the Ori OB1b association and of fore- and background sources. A total of 136 stars display features of extreme youth, like early spectral types, lithium in absorption, or mid-infrared flux excess. Other two young brown dwarf and 289 star candidates have been identified from an optical/near-infrared colour-magnitude diagram. We list another 74 known objects that might belong to the association. This catalogue can serve as input for characterising the stellar and high-mass substellar populations in the Orion Belt. Finally, we investigated the surface densities and radial distributions of young objects surrounding Alnilam and Mintaka and compared them with those in the σ Orionis cluster. We report on a new open cluster centred on Mintaka. Conclusions: Both regions can be analogues to the σ Orionis cluster, but more massive, more extended, slightly older, and less radially concentrated. Tables A.1 to A.18 are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/485/931

  11. 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

    Science.gov (United States)

    Cushing, Michael C.; Kirkpatrick, J. Davy; Gelino, Christopher R.; Mace, Gregory N.; Skrutskie, Michael F.; Gould, Andrew

    2014-05-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2014-05-01

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

  13. Giant Planet Candidates, Brown Dwarfs, and Binaries from the SDSS-III MARVELS Planet Survey.

    Science.gov (United States)

    Thomas, Neil; Ge, Jian; Li, Rui; de Lee, Nathan M.; Heslar, Michael; Ma, Bo; SDSS-Iii Marvels Team

    2015-01-01

    We report the discoveries of giant planet candidates, brown dwarfs, and binaries from the SDSS-III MARVELS survey. The finalized 1D pipeline has provided 18 giant planet candidates, 16 brown dwarfs, and over 500 binaries. An additional 96 targets having RV variability indicative of a giant planet companion are also reported for future investigation. These candidates are found using the advanced MARVELS 1D data pipeline developed at UF from scratch over the past three years. This pipeline carefully corrects most of the instrument effects (such as trace, slant, distortion, drifts and dispersion) and observation condition effects (such as illumination profile, fiber degradation, and tracking variations). The result is long-term RV precisions that approach the photon limits in many cases for the ~89,000 individual stellar observations. A 2D version of the pipeline that uses interferometric information is nearing completion and is demonstrating a reduction of errors to half the current levels. The 2D processing will be used to increase the robustness of the detections presented here and to find new candidates in RV regions not confidently detectable with the 1D pipeline. The MARVELS survey has produced the largest homogeneous RV measurements of 3300 V=7.6-12 FGK stars with a well defined cadence of 27 RV measurements over 2 years. The MARVELS RV data and other follow-up data (photometry, high contrast imaging, high resolution spectroscopy and RV measurements) will explore the diversity of giant planet companion formation and evolution around stars with a broad range in metallicity (Fe/H -1.5-0.5), mass ( 0.6-2.5M(sun)), and environment (thin disk and thick disk), and will help to address the key scientific questions identified for the MARVELS survey including, but not limited to: Do metal poor stars obey the same trends for planet occurrence as metal rich stars? What is the distribution of giant planets around intermediate-mass stars and binaries? Is the 'planet desert

  14. Determining the Physical Properties of Very-Low-Mass Stars and Brown Dwarfs in the Near-Infrared

    Science.gov (United States)

    Rice, Emily L.; Barman, Travis S.; McLean, Ian S.; Prato, L.; Kirkpatrick, J. Davy

    2009-02-01

    Accurate measurements of the fundamental physical properties of very-low-mass stars and brown dwarfs are crucial for calibrating evolutionary models. Photometry and low-resolution spectroscopy effectively average over absorption features that sample different layers in complex cool atmospheres. By studying a large sample of objects bright enough for high-resolution spectroscopy, we can develop methods for determining physical properties as accurately and efficiently as possible. As part of the Brown Dwarf Spectroscopic Survey (BDSS [1, 2]), we are conducting a detailed comparison of observed and synthetic spectra for a sample of young M and L dwarfs and field M, L, and T dwarfs (~50 objects in total). High-resolution near-infrared spectra from NIRSPEC on Keck II provide an unequaled combination of resolving power and wavelength coverage. Synthetic spectra were created from PHOENIX atmosphere models calculated exclusively for this project with updated line lists and solar abundances. Combined with spectral types from photometric studies and low-resolution spectra and surface gravity estimates from age determination, the high-resolution spectra enable precise measurements of effective temperature and surface gravity, as well as accurate determination of radial velocity and projected rotational velocity. Our preliminary observation-model comparisons distinguish between wavelength regimes for which the models reproduce observed high-resolution spectra and regimes in which model data (line lists, oscillator strengths, etc.) are lacking.

  15. Extremely Low Mass: The Circumstellar Envelope of a Potential Proto-Brown Dwarf

    Science.gov (United States)

    Wiseman, Jennifer

    2011-01-01

    What is the environment for planet formation around extremely low mass stars? Is the environment around brown dwarfs and extremely low mass stars conducive and sufficiently massive for planet production? The determining conditions may be set very early in the process of the host object's formation. IRAS 16253-2429, the source of the Wasp-Waist Nebula seen in Spitzer IRAC images, is an isolated, very low luminosity ("VeLLO") Class 0 protostar in the nearby rho Ophiuchi cloud. We present VLA ammonia mapping observations of the dense gas envelope feeding the central core accreting system. We find a flattened envelope perpendicular to the outflow axis, and gas cavities that appear to cradle the outflow lobes as though carved out by the flow and associated (apparently precessing) jet, indicating environmental disruption. Based on the NH3 (1,1) and (2,2) emission distribution, we derive the mass, velocity fields and temperature distribution for the envelope. We discuss the combined evidence for this source to be one of the youngest and lowest mass sources in formation yet known, and discuss the ramifications for planet formation potential in this extremely low mass system.

  16. 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.

  17. Molecular Outflows Driven by Young Brown Dwarfs And VLMs. New Clues from IRAM Interferometer Observations

    Science.gov (United States)

    Monin, J.-L.; Whelan, E.; Lefloch, B.; Dougados, C.

    2015-01-01

    The outflow phenomenon is ubiquitous in star forming regions and is now known to play an important role in the formation of both young stellar objects (YSOs) and brown dwarfs (BDs) (Whelan et al., 2012). Observations of outflows from both stars and BDs are thus essential to our understanding of the overall star & planet formation process. In 2011 and 2012 we conducted a survey with the IRAM 30 m telescope of the CO emission in the vicinity of a large sample of BDs and VLMSs to check for molecular outflows. We followed up three of the most remarkable sources namely MHO 5, BD Tau 6 and FU Tau A with high angular resolution observations with the Plateau de Bure Interferometer (PdBI). These sources were chosen because their associated CO emission showed clear evidence of an outflow and / or their spectral energy distributions (SEDs) showed strong evidence of a massive accretion disk, that we postulate to be associated with an outflow. In this paper, we present the first results of our CO(1-0) PdBI investigations of the molecular outflows of 2 of these sources, MHO5 and BD Tau 6. The signal to noise ratio on FU Tau is 3 times less than on the other sources and the results need more investigation.

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

    Science.gov (United States)

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

    2013-09-01

    Context. Although many new brown dwarf (BD) neighbours have recently been discovered thanks to new sky surveys in the mid- and near-infrared (MIR, NIR), their numbers are still more than five times lower than those of stars in the same volume. Aims: Our aim is to detect and classify new BDs to eventually complete their census in the immediate solar neighbourhood. Methods: We combined multi-epoch data from sky surveys at different wavelengths to detect BD neighbours of the Sun by their high proper motion (HPM). We concentrated on relatively bright MIR (w2 new BDs and estimated their distances and velocities. Results: We have discovered the HPM (μ ~ 470 mas/yr) T7.5 dwarf, WISE J0521+1025, which is at d = 5.0 ± 1.3 pc from the Sun the nearest known T dwarf in the northern sky, and two early T dwarfs, WISE J0457-0207 (T2) and WISE J2030+0749 (T1.5), with proper motions of ~120 and ~670 mas/yr and distances of 12.5 ± 3.1 pc and 10.5 ± 2.6 pc, respectively. The last one was independently discovered and also classified as a T1.5 dwarf by Mace and coworkers. All three show thin disc kinematics. They may have been overlooked in the past owing to overlapping images and because of problems with matching objects between different surveys and measuring their proper motions. Based on observations with the Large Binocular Telescope (LBT).

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

    Science.gov (United States)

    Marley, Mark Scott

    2016-01-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2016-01-20

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

  1. Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes

    Science.gov (United States)

    Marks, M.; Martín, E. L.; Béjar, V. J. S.; Lodieu, N.; Kroupa, P.; Manjavacas, E.; Thies, I.; Rebolo López, R.; Velasco, S.

    2017-08-01

    Context. One of the key questions of the star formation problem is whether brown dwarfs (BDs) form in the manner of stars directly from the gravitational collapse of a molecular cloud core (star-like) or whether BDs and some very low-mass stars (VLMSs) constitute a separate population that forms alongside stars comparable to the population of planets, for example through circumstellar disk (peripheral) fragmentation. Aims: For young stars in Taurus-Auriga the binary fraction has been shown to be large with little dependence on primary mass above ≈ 0.2 M⊙, while for BDs the binary fraction is universal with a large binary fraction close to unity. Peripheral objects form separately in circumstellar disks with a distinctive initial mass function (IMF), their own orbital parameter distributions for binaries, and small binary fractions, according to observations and expectations from smoothed particle hydrodynamics (SPH) and grid-based computations. A small amount of dynamical processing of the stellar component was accounted for as appropriate for the low-density Taurus-Auriga embedded clusters. Results: The binary fraction declines strongly in the transition region between star-like and peripheral formation, exhibiting characteristic features. The location of these features and the steepness of this trend depend on the mass limits for star-like and peripheral formation. Such a trend might be unique to low density regions, such as Taurus, which host binary populations that are largely unprocessed dynamically in which the binary fraction is large for stars down to M-dwarfs and small for BDs. Conclusions: The existence of a strong decline in the binary fraction - primary mass diagram will become verifiable in future surveys on BD and VLMS binarity in the Taurus-Auriga star-forming region. The binary fraction - primary mass diagram is a diagnostic of the (non-)continuity of star formation along the mass scale, the separateness of the stellar and BD populations, and

  2. A Search for Water Maser Emission from Brown Dwarfs and Low-luminosity Young Stellar Objects

    Energy Technology Data Exchange (ETDEWEB)

    Gómez, José F.; Manjarrez, Guillermo [Instituto de Astrofísica de Andalucía, CSIC, Glorieta de la Astronomía s/n, E-18008 Granada (Spain); Palau, Aina [Instituto de Radioastronomía y Astrofísica, UNAM, P.O. Box 3-72, 58090, Morelia, Michoacán, México (Mexico); Uscanga, Lucero [Departamento de Astronomía, Universidad de Guanajuato, A.P. 144, 36000 Guanajuato, Gto., México (Mexico); Barrado, David, E-mail: jfg@iaa.es [Centro de Astrobiología, INTA-CSIC, PO BOX 28692, ESAC Campus, E-208691 Villanueva de la Cañada, Madrid (Spain)

    2017-05-01

    We present a survey for water maser emission toward a sample of 44 low-luminosity young objects, comprising (proto-)brown dwarfs, first hydrostatic cores (FHCs), and other young stellar objects (YSOs) with bolometric luminosities lower than 0.4 L {sub ⊙}. Water maser emission is a good tracer of energetic processes, such as mass-loss and/or accretion, and is a useful tool to study these processes with very high angular resolution. This type of emission has been confirmed in objects with L {sub bol} ≳ 1 L {sub ⊙}. Objects with lower luminosities also undergo mass-loss and accretion, and thus, are prospective sites of maser emission. Our sensitive single-dish observations provided a single detection when pointing toward the FHC L1448 IRS 2E. However, follow-up interferometric observations showed water maser emission associated with the nearby YSO L1448 IRS 2 (a Class 0 protostar of L {sub bol} ≃ 3.6–5.3 L {sub ⊙}) and did not find any emission toward L1448 IRS 2E. The upper limits for water maser emission determined by our observations are one order of magnitude lower than expected from the correlation between water maser luminosities and bolometric luminosities found for YSOs. This suggests that this correlation does not hold at the lower end of the (sub)stellar mass spectrum. Possible reasons are that the slope of this correlation is steeper at L {sub bol} ≤ 1 L {sub ⊙} or that there is an absolute luminosity threshold below which water maser emission cannot be produced. Alternatively, if the correlation still stands at low luminosity, the detection rates of masers would be significantly lower than the values obtained in higher-luminosity Class 0 protostars.

  3. First Large-scale Herbig-Haro Jet Driven by a Proto-brown Dwarf

    Science.gov (United States)

    Riaz, B.; Briceño, C.; Whelan, E. T.; Heathcote, S.

    2017-07-01

    We report the discovery of a new Herbig-Haro jet, HH 1165, in SOAR narrow-band imaging of the vicinity of the σ Orionis cluster. HH 1165 shows a spectacular extended and collimated spatial structure, with a projected length of 0.26 pc, a bent C-shaped morphology, multiple knots, and fragmented bow shocks at the apparent ends of the flow. The Hα image shows a bright halo with a clumpy distribution of material seen around the driving source, and curved reflection nebulosity tracing the outflow cavities. The driving source of HH 1165 is a Class I proto-brown dwarf, Mayrit 1701117 (M1701117), with a total (dust+gas) mass of ˜36 M Jup and a bolometric luminosity of ˜0.1 L ⊙. High-resolution VLT/UVES spectra of M1701117 show a wealth of emission lines indicative of strong outflow and accretion activity. SOAR/Goodman low-resolution spectra along the jet axis show an asymmetrical morphology for HH 1165. We find a puzzling picture wherein the northwest part exhibits a classical HH jet running into a pre-dominantly neutral medium, while the southern part resembles an externally irradiated jet. The C-shaped bending in HH 1165 may be produced by the combined effects from the massive stars in the ionization front to the east, the σ Orionis core to the west, and the close proximity to the B2-type star HR 1950. HH 1165 shows all of the signatures to be considered as a scaled-down version of parsec-length HH jets, and can be termed as the first sub-stellar analog of a protostellar HH jet system.

  4. Hints for Small Disks around Very Low Mass Stars and Brown Dwarfs

    Science.gov (United States)

    Hendler, Nathanial P.; Mulders, Gijs D.; Pascucci, Ilaria; Greenwood, Aaron; Kamp, Inga; Henning, Thomas; Ménard, François; Dent, William R. F.; Evans, Neal J., II

    2017-06-01

    The properties of disks around brown dwarfs and very low mass stars (hereafter VLMOs) provide important boundary conditions on the process of planet formation and inform us about the numbers and masses of planets than can form in this regime. We use the Herschel Space Observatory PACS spectrometer to measure the continuum and [O I] 63 μm line emission toward 11 VLMOs with known disks in the Taurus and Chamaeleon I star-forming regions. We fit radiative transfer models to the spectral energy distributions of these sources. Additionally, we carry out a grid of radiative transfer models run in a regime that connects the luminosity of our sources with brighter T Tauri stars. We find that VLMO disks with sizes 1.3-78 au, smaller than typical T Tauri disks, fit well the spectral energy distributions assuming that disk geometry and dust properties are stellar mass independent. Reducing the disk size increases the disk temperature, and we show that VLMOs do not follow previously derived disk temperature-stellar luminosity relationships if the disk outer radius scales with stellar mass. Only 2 out of 11 sources are detected in [O I] despite a better sensitivity than was achieved for T Tauri stars, suggesting that VLMO disks are underluminous. Using thermochemical models, we show that smaller disks can lead to the unexpected [O I] 63 μm nondetections in our sample. The disk outer radius is an important factor in determining the gas and dust observables. Hence, spatially resolved observations with ALMA—to establish if and how disk radii scale with stellar mass—should be pursued further. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2015-07-01

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

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

    Energy Technology Data Exchange (ETDEWEB)

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

    2012-07-10

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

  7. Effect of accretion on the pre-main-sequence evolution of low-mass stars and brown dwarfs

    Science.gov (United States)

    Vorobyov, Eduard I.; Elbakyan, Vardan; Hosokawa, Takashi; Sakurai, Yuya; Guedel, Manuel; Yorke, Harold

    2017-09-01

    Aims: The pre-main-sequence evolution of low-mass stars and brown dwarfs is studied numerically starting from the formation of a protostellar or proto-brown dwarf seed and taking into account the mass accretion onto the central object during the initial several Myr of evolution. Methods: The stellar evolution was computed using the STELLAR evolution code with recent modifications. The mass accretion rates were taken from numerical hydrodynamics models by computing the circumstellar disk evolution starting from the gravitational collapse of prestellar cloud cores of various mass and angular momentum. The resulting stellar evolution tracks were compared with the isochrones and isomasses calculated using non-accreting models. Results: We find that mass accretion in the initial several Myr of protostellar evolution can have a strong effect on the subsequent evolution of young stars and brown dwarfs. The disagreement between accreting and non-accreting models in terms of the total stellar luminosity L∗, stellar radius R∗, and effective temperature Teff depends on the thermal efficiency of accretion, that is, on the fraction of accretion energy that is absorbed by the central object. The largest mismatch is found for the cold accretion case, in which essentially all accretion energy is radiated away. The relative deviations in L∗ and R∗ in this case can reach 50% for objects 1.0 Myr old, and they remain notable even for objects 10 Myr old. In the hot and hybrid accretion cases, in which a constant fraction of accretion energy is absorbed, the disagreement between accreting and non-accreting models becomes less pronounced, but still remains notable for objects 1.0 Myr old. These disagreements may lead to an incorrect age estimate for objects of (sub-)solar mass when using the isochrones that are based on non-accreting models, as has also been noted previously. We find that objects with strong luminosity bursts exhibit notable excursions in the L∗-Teff diagram

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

    Science.gov (United States)

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

    2013-05-01

    We report the discovery of a highly eccentric, double-lined spectroscopic binary star system (TYC 3010-1494-1), comprising two solar-type stars that we had initially identified as a single star with a brown dwarf companion. At the moderate resolving power of the MARVELS spectrograph and the spectrographs used for subsequent radial-velocity (RV) measurements (R 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.

  9. Transmission of Rice Black-Streaked Dwarf Virus from Frozen Infected Leaves to Healthy Rice Plants by Small Brown Planthopper (Laodelphax striatellus)

    OpenAIRE

    Zhou, Tong; Wu, Li-juan; Wang, Ying; Cheng, Zhao-Bang; Ji, Ying-Hua; Yong-jian FAN; Zhou, Yi-Jun

    2011-01-01

    In order to preserve virus for identifying the resistance of rice varieties against rice black-streaked dwarf disease, a simple and reliable method was developed, through which virus-free small brown planthopper (SBPH) acquired rice black-streaked dwarf virus (RBSDV) from frozen infected leaves and the virus was transmitted to healthy rice plants. The experimental results showed that SBPH could obtain RBSDV from frozen infected rice leaves and the virus could be transmitted to a susceptible r...

  10. A search for companions to brown dwarfs in the Taurus and Chamaeleon star-forming regions

    Energy Technology Data Exchange (ETDEWEB)

    Todorov, K. O.; Luhman, K. L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Konopacky, Q. M. [Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550 (United States); McLeod, K. K. [Whitin Observatory, Wellesley College, Wellesley, MA 02481 (United States); Apai, D.; Pascucci, I. [Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Ghez, A. M. [Division of Astronomy and Astrophysics, University of California, Los Angeles, CA 90095 (United States); Robberto, M., E-mail: todorovk@phys.ethz.ch [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2014-06-10

    We have used WFPC2 on board the Hubble Space Telescope to obtain images of 47 members of the Taurus and Chamaeleon I star-forming regions that have spectral types of M6-L0 (M ∼ 0.01-0.1 M {sub ☉}). An additional late-type member of Taurus, FU Tau (M7.25+M9.25), was also observed with adaptive optics at Keck Observatory. In these images, we have identified promising candidate companions to 2MASS J04414489+2301513 (ρ = 0.''105/15 AU), 2MASS J04221332+1934392 (ρ = 0.''05/7 AU), and ISO 217 (ρ = 0.''03/5 AU). We reported the first candidate in a previous study, showing that it has a similar proper motion as the primary in images from WFPC2 and Gemini adaptive optics. We have collected an additional epoch of data with Gemini that further supports that result. By combining our survey with previous high-resolution imaging in Taurus, Chamaeleon I, and Upper Sco (τ ∼ 10 Myr), we measure binary fractions of 14/93 = 0.15{sub −0.03}{sup +0.05} for M4-M6 (M ∼ 0.1-0.3 M {sub ☉}) and 4/108 = 0.04{sub −0.01}{sup +0.03} for >M6 (M ≲ 0.1 M {sub ☉}) at separations of >10 AU. Given the youth and low density of these regions, the lower binary fraction at later types is probably primordial rather than due to dynamical interactions among association members. The widest low-mass binaries (>100 AU) also appear to be more common in Taurus and Chamaeleon I than in the field, which suggests that the widest low-mass binaries are disrupted by dynamical interactions at >10 Myr, or that field brown dwarfs have been born predominantly in denser clusters where wide systems are disrupted or inhibited from forming.

  11. 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

  12. Emission line diagnostics for accretion and outflows in young very low-mass stars and brown dwarfs

    Science.gov (United States)

    Stelzer, B.; Alcalá, J. M.; Whelan, E.; Scholz, A.

    2014-01-01

    We discuss accretion and outflow properties of three very low-mass young stellar objects based on broad-band mid-resolution X-Shooter/VLT spectra. Our targets (FU Tau A, 2M1207-39, and Par-Lup3-4) have spectral types between M5 and M8, ages between 1Myr and ~ 10Myr, and are known to be accreting from previous studies. The final objective of our project is the determination of mass outflow to accretion rate for objects near or within the substellar regime as a probe for the T Tauri phase of brown dwarfs and the investigation of variability in the accretion and outflow processes.

  13. Emission line diagnostics for accretion and outflows in young very low-mass stars and brown dwarfs

    Directory of Open Access Journals (Sweden)

    Stelzer B.

    2014-01-01

    Full Text Available We discuss accretion and outflow properties of three very low-mass young stellar objects based on broad-band mid-resolution X-Shooter/VLT spectra. Our targets (FU Tau A, 2M1207-39, and Par-Lup3-4 have spectral types between M5 and M8, ages between 1Myr and ~ 10Myr, and are known to be accreting from previous studies. The final objective of our project is the determination of mass outflow to accretion rate for objects near or within the substellar regime as a probe for the T Tauri phase of brown dwarfs and the investigation of variability in the accretion and outflow processes.

  14. VizieR Online Data Catalog: Young stars and brown dwarfs in Ori OB1b (Caballero+, 2008)

    Science.gov (United States)

    Caballero, J. A.; Solano, E.

    2008-06-01

    We present here exhaustive lists of known young stars and new candidate members around Alnilam and Mintaka in the Ori OB1b association as well as of fore- and background sources. A total of 133 stars display features of extreme youth, including early spectral types, lithium in absorption, or mid-infrared flux excess. Other two young brown dwarf and 289 star candidates have been identified from an optical/near-infrared colour-magnitude diagram. We list additional 74 known objects that might belong to the association. This compilation of tables can serve as an input for characterisation of the stellar and high-mass substellar populations in the Orion Belt. (20 data files).

  15. Transmission of Rice Black-Streaked Dwarf Virus from Frozen Infected Leaves to Healthy Rice Plants by Small Brown Planthopper (Laodelphax striatellus

    Directory of Open Access Journals (Sweden)

    Tong ZHOU

    2011-06-01

    Full Text Available In order to preserve virus for identifying the resistance of rice varieties against rice black-streaked dwarf disease, a simple and reliable method was developed, through which virus-free small brown planthopper (SBPH acquired rice black-streaked dwarf virus (RBSDV from frozen infected leaves and the virus was transmitted to healthy rice plants. The experimental results showed that SBPH could obtain RBSDV from frozen infected rice leaves and the virus could be transmitted to a susceptible rice variety. For the ability to acquire RBSDV and transmit the virus to healthy plants by SBPH, there was no significant difference between frozen infected leaves and in vitro infected leaves. The novel method could be applied to identification of rice variety resistance to rice black-streaked dwarf disease, facilitating the breeding process for rice black-streaked dwarf disease resistance.

  16. Modeling the Cloudy Atmospheres of Cool Stars, Brown Dwarfs and Hot Exoplanets

    DEFF Research Database (Denmark)

    Juncher, Diana

    M-dwarfs are very attractive targets when searching for new exoplanets. Unfortunately, they are also very difficult to model since their temperatures are low enough for dust clouds to form in their atmospheres. Because the properties of an exoplanet cannot be determined without knowing the proper......M-dwarfs are very attractive targets when searching for new exoplanets. Unfortunately, they are also very difficult to model since their temperatures are low enough for dust clouds to form in their atmospheres. Because the properties of an exoplanet cannot be determined without knowing......-consistent cloudy atmosphere models that can be used to properly determine the stellar parameters of cool stars. With this enhanced model atmosphere code I have created a grid of cool, dusty atmosphere models ranging in effective temperatures from Teff = 2000 − 3000 K. I have studied the formation and structure...... of their clouds and found that their synthetic spectra fit the observed spectra of mid to late type M-dwarfs and early type L-dwarfs well. With additional development into even cooler regimes, they could be used to characterize the atmospheres of exoplanets and aid us in our search for the kind of chemical...

  17. HS 2231+2441: an HW Vir system composed of a low-mass white dwarf and a brown dwarf★

    Science.gov (United States)

    Almeida, L. A.; Damineli, A.; Rodrigues, C. V.; Pereira, M. G.; Jablonski, F.

    2017-12-01

    HW Vir systems are rare evolved eclipsing binaries composed of a hot compact star and a low-mass main sequence star in a close orbit. These systems provide a direct way to measure the fundamental properties, e.g. masses and radii, of their components, hence they are crucial in studying the formation of subdwarf B stars and low-mass white dwarfs, the common-envelope phase and the pre-phase of cataclysmic variables. Here, we present a detailed study of HS 2231+2441, an HW Vir type system, by analysing BVRCIC photometry and phase-resolved optical spectroscopy. The spectra of this system, which are dominated by the primary component features, were fitted using non-local thermodynamic equilibrium models providing an effective temperature Teff = 28 500 ± 500 K, surface gravity log g = 5.40 ± 0.05 cm s-2 and helium abundance log (n(He)/n(H)) = -2.52 ± 0.07. The geometrical orbit and physical parameters were derived by simultaneously modelling the photometric and spectroscopic data using the Wilson-Devinney code. We derive two possible solutions for HS 2231+2441 that provide the component masses: M1 = 0.19 M⊙ and M2 = 0.036 M⊙ or M1 = 0.288 M⊙ and M2 = 0.046 M⊙. Considering the possible evolutionary channels for forming a compact hot star, the primary of HS 2231+2441 probably evolved through the red-giant branch scenario and does not have a helium-burning core, which is consistent with a low-mass white dwarf. Both solutions are consistent with a brown dwarf as the secondary.

  18. A Pan-STARRS1 Proper-Motion Survey for Young Brown Dwarfs in the Nearest Star-Forming Regions and a Reddening-Free Classification Method for Ultracool Dwarfs

    Science.gov (United States)

    Zhang, Zhoujian; Liu, Michael C.; Best, William M. J.; Magnier, Eugene; Aller, Kimberly

    2018-01-01

    Young brown dwarfs are of prime importance to investigate the universality of the initial mass function (IMF). Based on photometry and proper motions from the Pan-STARRS1 (PS1) 3π survey, we are conducting the widest and deepest brown dwarf survey in the nearby star-forming regions, Taurus–Auriga (Taurus) and Upper Scorpius (USco). Our work is the first to measure proper motions, a robust proxy of membership, for brown dwarf candidates in Taurus and USco over such a large area and long time baseline (≈ 15 year) with such high precision (≈ 4 mas yr-1). Since extinction complicates spectral classification, we have developed a new approach to quantitatively determine reddening-free spectral types, extinctions, and gravity classifications for mid-M to late-L ultracool dwarfs (≈ 100–5 MJup), using low-resolution near-infrared spectra. So far, our IRTF/SpeX spectroscopic follow-up has increased the substellar and planetary-mass census of Taurus by ≈ 50% and almost doubled the substellar census of USco, constituting the largest single increases of brown dwarfs and free-floating planets found in both regions to date. Most notably, our new discoveries reveal an older (> 10 Myr) low-mass population in Taurus, in accord with recent studies of the higher-mass stellar members. In addition, the mass function appears to differ between the younger and older Taurus populations, possibly due to incompleteness of the older stellar members or different star formation processes. Upon completion, our survey will establish the most complete substellar and planetary-mass census in both Taurus and USco associations, make a significant addition to the low-mass IMF in both regions, and deliver more comprehensive pictures of star formation histories.

  19. 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.

  20. The T Tauri Phase Down to Nearly Planetary Masses: Echelle Spectra of 82 Very Low Mass Stars and Brown Dwarfs

    Science.gov (United States)

    Mohanty, Subhanjoy; Jayawardhana, Ray; Basri, Gibor

    2005-06-01

    Using the largest high-resolution spectroscopic sample to date of young, very low mass stars and brown dwarfs, we investigate disk accretion in objects ranging from just above the hydrogen-burning limit all the way to nearly planetary masses. Our 82 targets span spectral types from M5 to M9.5, or masses from 0.15 Msolar down to about 15 jupiters. They are confirmed members of the ρ Ophiuchus, Taurus, Chamaeleon I, IC 348, R Coronae Australis, Upper Scorpius, and TW Hydrae star-forming regions and young clusters, with ages from =M6.5). We have previously presented high-resolution optical spectra for roughly half the sample; the rest are new. This is a close to complete survey of all confirmed brown dwarfs known so far in the regions examined, except in ρ Oph and IC 348 (where we are limited by a combination of extinction and distance). We find that (1) classical T Tauri-like disk accretion persists in the substellar domain down to nearly the deuterium-burning limit; (2) while an Hα 10% width >~200 km s-1 is our prime accretion diagnostic (following our previous work), permitted emission lines of Ca II, O I, and He I are also good accretion indicators, just as in classical T Tauri stars (we caution against a blind use of Hα width alone, since inclination and rotation effects on the line are especially important at the low accretion rates in very low mass objects); (3) the Ca II λ8662 line flux is an excellent quantitative measure of the accretion rate in very low mass stars and brown dwarfs (as in higher mass classical T Tauri Stars), correlating remarkably well with the M˙ obtained from veiling and Hα modeling; (4) the accretion rate diminishes rapidly with mass-our measurements support previous suggestions that M˙~M2* (albeit with considerable scatter) and extend this correlation to the entire range of substellar masses; (5) the fraction of very low mass stellar and substellar accretors decreases substantially with age, as in higher mass stars; (6) at any

  1. OGLE-2016-BLG-1190Lb: The First Spitzer Bulge Planet Lies Near the Planet/Brown-dwarf Boundary

    Science.gov (United States)

    Ryu, Y.-H.; Yee, J. C.; Udalski, A.; Bond, I. A.; Shvartzvald, Y.; Zang, W.; Figuera Jaimes, R.; Jørgensen, U. G.; Zhu, W.; Huang, C. X.; Jung, Y. K.; Albrow, M. D.; Chung, S.-J.; Gould, A.; Han, C.; Hwang, K.-H.; Shin, I.-G.; Cha, S.-M.; Kim, D.-J.; Kim, H.-W.; Kim, S.-L.; Lee, C.-U.; Lee, D.-J.; Lee, Y.; Park, B.-G.; Pogge, R. W.; KMTNet Collaboration; Calchi Novati, S.; Carey, S.; Henderson, C. B.; Beichman, C.; Gaudi, B. S.; Spitzer team; Mróz, P.; Poleski, R.; Skowron, J.; Szymański, M. K.; Soszyński, I.; Kozłowski, S.; Pietrukowicz, P.; Ulaczyk, K.; Pawlak, M.; OGLE Collaboration; Abe, F.; Asakura, Y.; Barry, R.; Bennett, D. P.; Bhattacharya, A.; Donachie, M.; Evans, P.; Fukui, A.; Hirao, Y.; Itow, Y.; Kawasaki, K.; Koshimoto, N.; Li, M. C. A.; Ling, C. H.; Masuda, K.; Matsubara, Y.; Miyazaki, S.; Muraki, Y.; Nagakane, M.; Ohnishi, K.; Ranc, C.; Rattenbury, N. J.; Saito, To.; Sharan, A.; Sullivan, D. J.; Sumi, T.; Suzuki, D.; Tristram, P. J.; Yamada, T.; Yamada, T.; Yonehara, A.; MOA Collaboration; Bryden, G.; Howell, S. B.; Jacklin, S.; UKIRT Microlensing Team; Penny, M. T.; Mao, S.; Fouqué, Pascal; Wang, T.; CFHT-K2C9 Microlensing Survey group; Street, R. A.; Tsapras, Y.; Hundertmark, M.; Bachelet, E.; Dominik, M.; Li, Z.; Cross, S.; Cassan, A.; Horne, K.; Schmidt, R.; Wambsganss, J.; Ment, S. K.; Maoz, D.; Snodgrass, C.; Steele, I. A.; RoboNet Team; Bozza, V.; Burgdorf, M. J.; Ciceri, S.; D’Ago, G.; Evans, D. F.; Hinse, T. C.; Kerins, E.; Kokotanekova, R.; Longa, P.; MacKenzie, J.; Popovas, A.; Rabus, M.; Rahvar, S.; Sajadian, S.; Skottfelt, J.; Southworth, J.; von Essen, C.; MiNDSTEp Team

    2018-01-01

    We report the discovery of OGLE-2016-BLG-1190Lb, which is likely to be the first Spitzer microlensing planet in the Galactic bulge/bar, an assignation that can be confirmed by two epochs of high-resolution imaging of the combined source–lens baseline object. The planet’s mass, M p = 13.4 ± 0.9 M J , places it right at the deuterium-burning limit, i.e., the conventional boundary between “planets” and “brown dwarfs.” Its existence raises the question of whether such objects are really “planets” (formed within the disks of their hosts) or “failed stars” (low-mass objects formed by gas fragmentation). This question may ultimately be addressed by comparing disk and bulge/bar planets, which is a goal of the Spitzer microlens program. The host is a G dwarf, M host = 0.89 ± 0.07 M ⊙, and the planet has a semimajor axis a ∼ 2.0 au. We use Kepler K2 Campaign 9 microlensing data to break the lens-mass degeneracy that generically impacts parallax solutions from Earth–Spitzer observations alone, which is the first successful application of this approach. The microlensing data, derived primarily from near-continuous, ultradense survey observations from OGLE, MOA, and three KMTNet telescopes, contain more orbital information than for any previous microlensing planet, but not quite enough to accurately specify the full orbit. However, these data do permit the first rigorous test of microlensing orbital-motion measurements, which are typically derived from data taken over <1% of an orbital period.

  2. The possible false-detection of a transiting brown dwarf candidate in the overlapping fields of Kepler and MARVELS

    Science.gov (United States)

    Reyes, Alan; Ge, Jian; Thomas, Neil; Ma, Bo; Heslar, Michael Francis; SDSS-III MARVELS Team

    2016-01-01

    While searching for exoplanets via the transit method, it has been documented that the periodicity of an unresolved background eclipsing binary (BEB) can be misinterpreted as the orbital companion of a target star. We explore the possibility that this false-positive contamination method can also occur in Doppler surveys if the angular separation between a BEB and a selected primary is under a certain threshold, dependent on the fiber diameter of the spectrometer instrument. The case example of this investigation is a K2 giant in the constellation Cygnus, in the region of overlap of the Kepler and MARVELS surveys. This star was originally flagged for potentially having a 5.56d period companion as per the Kepler transit photometry. It was also imbricated with radial velocity (RV) observations performed by the SDSS-III MARVELS survey, in which Doppler information was extracted from along the dispersion direction of the fiducially-calibrated, post-pipeline-rendered spectra. The 5.56d period was corroborated after testing its probability against that of others via a Lomb-Scargle periodogram analysis. The pipeline mass determination yielded a ~17 MJupiter companion, within the characteristic mass-range of brown dwarfs. The MARVELS results seem to constitute an independent discovery, and hence confirmation, of the brown dwarf candidate. However, a later investigation conducted by EXPERT, intent upon refining the system's physical parameters, failed to identify the RV signal of any companion whatsoever. EXPERT, with its superior resolving power (R=30,000 vs R=11,000 in MARVELS), finer fiber width (1.2 vs 1.9 arcsec), and higher degree of precision (~10 m/s), was expected to finalize the confirmation, but now offers a major challenge to previous models of the system. Additionally, high-resolution adaptive optics imaging reveals the presence of a distinct, close-in object. The object may itself be an unbound BEB, and thus the source of the period signals reported by Kepler

  3. CFBDSIR 2149-0403: young isolated planetary-mass object or high-metallicity low-mass brown dwarf?

    Science.gov (United States)

    Delorme, P.; Dupuy, T.; Gagné, J.; Reylé, C.; Forveille, T.; Liu, M. C.; Artigau, E.; Albert, L.; Delfosse, X.; Allard, F.; Homeier, D.; Malo, L.; Morley, C.; Naud, M. E.; Bonnefoy, M.

    2017-06-01

    Aims: We conducted a multi-wavelength, multi-instrument observational characterisation of the candidate free-floating planet CFBDSIR J214947.2-040308.9, a late T-dwarf with possible low-gravity features, in order to constrain its physical properties. Methods: We analysed nine hours of X-shooter spectroscopy with signal detectable from 0.8 to 2.3 μm, as well as additional photometry in the mid-infrared using the Spitzer Space Telescope. Combined with a VLT/HAWK-I astrometric parallax, this enabled a full characterisation of the absolute flux from the visible to 5 μm, encompassing more than 90% of the expected energy emitted by such a cool late T-type object. Our analysis of the spectrum also provided the radial velocity and therefore the determination of its full 3D kinematics. Results: While our new spectrum confirms the low gravity and/or high metallicity of CFBDSIR 2149, the parallax and kinematics safely rule out membership to any known young moving group, including AB Doradus. We use the equivalent width of the K I doublet at 1.25 μm as a promising tool to discriminate the effects of low-gravity from the effects of high-metallicity on the emission spectra of cool atmospheres. In the case of CFBDSIR 2149, the observed K I doublet clearly favours the low-gravity solution. Conclusions: CFBDSIR 2149 is therefore a peculiar late-T dwarf that is probably a young, planetary-mass object (2-13 MJup, <500 Myr) possibly similar to the exoplanet 51 Eri b, or perhaps a 2-40 MJup brown dwarf with super-solar metallicity. Based on observations obtained with X-shooter on VLT-UT2 at ESO-Paranal (run 091.D-0723). Based on observations obtained with HAWKI on VLT-UT4 (run 089.C-0952, 090.C-0483, 091.C-0543,092.C-0548,293.C-5019(A) and run 086.C-0655(A)). Based on observations obtained with ISAAC on VLT-UT3 at ESO-Paranal (run 290.C-5083). Based on observation obtained with WIRCam at CFHT (program 2012BF12). Based on Spitzer Space telescope DDT observation (program 10166).

  4. Cloud Atlas: Discovery of Rotational Spectral Modulations in a Low-mass, L-type Brown Dwarf Companion to a Star

    Science.gov (United States)

    Manjavacas, Elena; Apai, Dániel; Zhou, Yifan; Karalidi, Theodora; Lew, Ben W. P.; Schneider, Glenn; Cowan, Nicolas; Metchev, Stan; Miles-Páez, Paulo A.; Burgasser, Adam J.; Radigan, Jacqueline; Bedin, Luigi R.; Lowrance, Patrick J.; Marley, Mark S.

    2018-01-01

    Observations of rotational modulations of brown dwarfs and giant exoplanets allow the characterization of condensate cloud properties. As of now, rotational spectral modulations have only been seen in three L-type brown dwarfs. We report here the discovery of rotational spectral modulations in LP261-75B, an L6-type intermediate surface gravity companion to an M4.5 star. As a part of the Cloud Atlas Treasury program, we acquired time-resolved Wide Field Camera 3 grism spectroscopy (1.1–1.69 μm) of LP261-75B. We find gray spectral variations with the relative amplitude displaying only a weak wavelength dependence and no evidence for lower-amplitude modulations in the 1.4 μm water band than in the adjacent continuum. The likely rotational modulation period is 4.78 ± 0.95 hr, although the rotational phase is not well sampled. The minimum relative amplitude in the white light curve measured over the whole wavelength range is 2.41% ± 0.14%. We report an unusual light curve, which seems to have three peaks approximately evenly distributed in rotational phase. The spectral modulations suggests that the upper atmosphere cloud properties in LP261-75B are similar to two other mid-L dwarfs of typical infrared colors, but differ from that of the extremely red L-dwarf WISE0047.

  5. An Independent Analysis of the Brown Dwarf Atmosphere Monitoring (BAM) Data: Large-amplitude Variability is Rare Outside the L/T Transition

    Science.gov (United States)

    Radigan, Jacqueline

    2014-12-01

    Observations of variability can provide valuable information about the processes of cloud formation and dissipation in brown dwarf atmospheres. Here we report the results of an independent analysis of archival data from the Brown dwarf Atmosphere Monitoring (BAM) program. Time series data for 14 L and T dwarfs reported to be significantly variable over timescales of hours were analyzed. We confirm large-amplitude variability (amplitudes >2%) for 4 out of 13 targets and place upper limits of 0.7%-1.6% on variability in the remaining sample. For two targets we find evidence of weak variability at amplitudes of 1.3% and 1.6%. Based on our revised classification of variable objects in the BAM study, we find strong variability outside the L/T transition to be rare at near infrared wavelengths. From a combined sample of 81 L0-T9 dwarfs from the revised BAM sample and the variability survey of Radigan et al., we infer an overall observed frequency for large-amplitude variability outside the L/T transition of 3.2-1.8+2.8%, in contrast to 24+11-9% for L9-T3.5 spectral types. We conclude that while strong variability is not limited to the L/T transition, it occurs more frequently in this spectral type range, indicative of larger or more highly contrasting cloud features at these spectral types.

  6. NEPTUNE’S DYNAMIC ATMOSPHERE FROM KEPLER K2 OBSERVATIONS: IMPLICATIONS FOR BROWN DWARF LIGHT CURVE ANALYSES

    Science.gov (United States)

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

    2017-01-01

    Observations of Neptune with the Kepler Space Telescope yield a 49 day light curve with 98% coverage at a 1 minute cadence. A significant signature in the light curve comes from discrete cloud features. We compare results extracted from the light curve data with contemporaneous disk-resolved imaging of Neptune from the Keck 10-m telescope at 1.65 microns and Hubble Space Telescope visible imaging acquired nine months later. This direct comparison validates the feature latitudes assigned to the K2 light curve periods based on Neptune’s zonal wind profile, and confirms observed cloud feature variability. Although Neptune’s clouds vary in location and intensity on short and long timescales, a single large discrete storm seen in Keck imaging dominates the K2 and Hubble light curves; smaller or fainter clouds likely contribute to short-term brightness variability. The K2 Neptune light curve, in conjunction with our imaging data, provides context for the interpretation of current and future brown dwarf and extrasolar planet variability measurements. In particular we suggest that the balance between large, relatively stable, atmospheric features and smaller, more transient, clouds controls the character of substellar atmospheric variability. Atmospheres dominated by a few large spots may show inherently greater light curve stability than those which exhibit a greater number of smaller features. PMID:28127087

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

    Science.gov (United States)

    Song, Inseok; Schneider, G.; Zuckerman, B.; Farihi, J.; Becklin, E. E.; Bessell, M. S.; Lowrance, P.; Macintosh, B. A.

    2006-11-01

    Multiband (0.9-1.6 μm) images of the TW Hydrae association (TWA) brown dwarf 2MASSW J1207334-393254 (also known as 2M 1207) and its candidate planetary-mass companion (2M 1207b) were obtained on 2004 August 28 and 2005 April 26 with HST NICMOS. The images from these two epochs unequivocally confirm the two objects as a common proper motion pair (16.0 σ confidence). A new measurement of the proper motion of 2M 1207 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 2M 1207b, extending overall from 0.9 to 3.8 μm, 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 2M 1207b 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.

  8. 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.

  9. 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.

  10. Project 1640 Observations of Brown Dwarf GJ 758 B: Near-infrared Spectrum and Atmospheric Modeling

    Science.gov (United States)

    Nilsson, R.; Veicht, A.; Giorla Godfrey, P. A.; Rice, E. L.; Aguilar, J.; Pueyo, L.; Roberts, L. C., Jr.; Oppenheimer, R.; Brenner, D.; Luszcz-Cook, S. H.; Bacchus, E.; Beichman, C.; Burruss, R.; Cady, E.; Dekany, R.; Fergus, R.; Hillenbrand, L.; Hinkley, S.; King, D.; Lockhart, T.; Parry, I. R.; Sivaramakrishnan, A.; Soummer, R.; Vasisht, G.; Zhai, C.; Zimmerman, N. T.

    2017-03-01

    The nearby Sun-like star GJ 758 hosts a cold substellar companion, GJ 758 B, at a projected separation of ≲30 au, previously detected in high-contrast multi-band photometric observations. In order to better constrain the companion’s physical characteristics, we acquired the first low-resolution (R ˜ 50) near-infrared spectrum of it using the high-contrast hyperspectral imaging instrument Project 1640 on Palomar Observatory’s 5 m Hale telescope. We obtained simultaneous images in 32 wavelength channels covering the Y, J, and H bands (˜952-1770 nm), and used data processing techniques based on principal component analysis to efficiently subtract chromatic background speckle-noise. GJ 758 B was detected in four epochs during 2013 and 2014. Basic astrometric measurements confirm its apparent northwest trajectory relative to the primary star, with no clear signs of orbital curvature. Spectra of SpeX/IRTF observed T dwarfs were compared to the combined spectrum of GJ 758 B, with χ 2 minimization suggesting a best fit for spectral type T7.0 ± 1.0, but with a shallow minimum over T5-T8. Fitting of synthetic spectra from the BT-Settl13 model atmospheres gives an effective temperature T eff = 741 ± 25 K and surface gravity {log}g=4.3+/- 0.5 dex (cgs). Our derived best-fit spectral type and effective temperature from modeling of the low-resolution spectrum suggest a slightly earlier and hotter companion than previous findings from photometric data, but do not rule out current results, and confirm GJ 758 B as one of the coolest sub-stellar companions to a Sun-like star to date.

  11. Using brown midrib 6 dwarf forage sorghum silage and fall-grown oat silage in lactating dairy cow rations.

    Science.gov (United States)

    Harper, M T; Oh, J; Giallongo, F; Lopes, J C; Roth, G W; Hristov, A N

    2017-07-01

    Double cropping and increasing crop diversity could improve dairy farm economic and environmental sustainability. In this experiment, corn silage was partially replaced with 2 alternative forages, brown midrib-6 brachytic dwarf forage sorghum (Sorghum bicolor) or fall-grown oat (Avena sativa) silage, in the diet of lactating dairy cows. We investigated the effect on dry matter (DM) intake, milk yield (MY), milk components and fatty acid profile, apparent total-tract nutrient digestibility, N utilization, enteric methane emissions, and income over feed cost. We analyzed the in situ DM and neutral detergent fiber disappearance of the alternative forages versus corn silage and alfalfa haylage. Sorghum was grown in the summer and harvested in the milk stage. Oats were grown in the fall and harvested in the boot stage. Compared with corn silage, neutral detergent fiber and acid detergent fiber concentrations were higher in the alternative forages. Lignin content was highest for sorghum silage and similar for corn silage and oat silage. The alternative forages had less than 1% starch compared with the approximately 35% starch in the corn silage. Ruminal in situ DM effective degradability was similar, although statistically different, for corn silage and oat silage, but lower for sorghum silage. Diets with the alternative forages were fed in a replicated 3 × 3 Latin square design experiment with three 28-d periods and 12 Holstein cows. The control diet contained 44% (DM basis) corn silage. In the other 2 diets, sorghum or oat silages were included at 10% of dietary DM, replacing corn silage. Sorghum silage inclusion decreased DM intake, MY, and milk protein content but increased milk fat and maintained energy-corrected MY similar to the control. Oat silage had no effect on DM intake, MY, or milk components compared to the control. The oat silage diet increased apparent total-tract digestibility of dietary nutrients, except starch, whereas the sorghum diet slightly

  12. Kepler and L Dwarfs

    OpenAIRE

    Gizis, John

    2014-01-01

    I presented results from the original Kepler and new K2 missions on L dwarfs. The L1 dwarf star WISE 1906 was monitored with both Spitzer and Kepler, revealing variability and evidence of both clouds and flares. The L8 brown dwarf WISE 0607 was recently monitored with both Kepler K2 and Spitzer, but did not vary. I discussed challenges for the K2 analysis, which is ongoing, but many L dwarfs should be monitored in the future.

  13. Dust in brown dwarfs and extrasolar planets. V. Cloud formation in carbon- and oxygen-rich environments

    Science.gov (United States)

    Helling, Ch.; Tootill, D.; Woitke, P.; Lee, G.

    2017-07-01

    Context. Recent observations indicate potentially carbon-rich (C/O > 1) exoplanet atmospheres. Spectral fitting methods for brown dwarfs and exoplanets have invoked the C/O ratio as additional parameter but carbon-rich cloud formation modeling is a challenge for the models applied. The determination of the habitable zone for exoplanets requires the treatment of cloud formation in chemically different regimes. Aims: We aim to model cloud formation processes for carbon-rich exoplanetary atmospheres. Disk models show that carbon-rich or near-carbon-rich niches may emerge and cool carbon planets may trace these particular stages of planetary evolution. Methods: We extended our kinetic cloud formation model by including carbon seed formation and the formation of C[s], TiC[s], SiC[s], KCl[s], and MgS[s] by gas-surface reactions. We solved a system of dust moment equations and element conservation for a prescribed Drift-Phoenixatmosphere structure to study how a cloud structure would change with changing initial C/O0 = 0.43...10.0. Results: The seed formation efficiency is lower in carbon-rich atmospheres than in oxygen-rich gases because carbon is a very effective growth species. The consequence is that fewer particles make up a cloud if C/O0 > 1. The cloud particles are smaller in size than in an oxygen-rich atmosphere. An increasing initial C/O ratio does not revert this trend because a much greater abundance of condensible gas species exists in a carbon-rich environment. Cloud particles are generally made of a mix of materials: carbon dominates if C/O0 > 1 and silicates dominate if C/O0 < 1. A carbon content of 80-90% carbon is reached only in extreme cases where C/O0 = 3.0 or 10.0. Conclusions: Carbon-rich atmospheres form clouds that are made of particles of height-dependent mixed compositions, sizes and numbers. The remaining gas phase is far less depleted than in an oxygen-rich atmosphere. Typical tracer molecules are HCN and C2H2 in combination with a featureless

  14. Deep search for companions to probable young brown dwarfs. VLT/NACO adaptive optics imaging using IR wavefront sensing

    Science.gov (United States)

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

    2012-12-01

    Aims: We have obtained high contrast images of four nearby, faint, and very low mass objects 2MASS J04351455-1414468, SDSS J044337.61+000205.1, 2MASS J06085283-2753583 and 2MASS J06524851-5741376 (hereafter 2MASS0435-14, SDSS0443+00, 2MASS0608-27 and 2MASS0652-57), identified in the field as probable isolated young brown dwarfs. Our goal was to search for binary companions down to the planetary mass regime. Methods: We used the NAOS-CONICA adaptive optics instrument (NACO) and its unique capability to sense the wavefront in the near-infrared to acquire sharp images of the four systems in Ks, with a field of view of 28'' × 28''. Additional J and L' imaging and follow-up observations at a second epoch were obtained for 2MASS0652-57. Results: With a typical contrast ΔKs = 4.0-7.0 mag, our observations are sensitive down to the planetary mass regime considering a minimum age of 10 to 120 Myr for these systems. No additional point sources are detected in the environment of 2MASS0435-14, SDSS0443+00 and 2MASS0608-27 between 0.1-12'' (i.e. about 2 to 250 AU at 20 pc). 2MASS0652-57 is resolved as a ~230 mas binary. Follow-up observations reject a background contaminate, resolve the orbital motion of the pair, and confirm with high confidence that the system is physically bound. The J, Ks and L' photometry suggest a q ~ 0.7-0.8 mass ratio binary with a probable semi-major axis of 5-6 AU. Among the four systems, 2MASS0652-57 is probably the less constrained in terms of age determination. Further analysis would be necessary to confirm its youth. It would then be interesting to determine its orbital and physical properties to derive the system's dynamical mass and to test evolutionary model predictions. Based on observations collected at the European Southern Observatory, Chile (ESO programmes 076.C-0554(A), 076.C-0554(B) and 085.C-0257(A).

  15. UlaR activates expression of the ula operon in Streptococcus pneumoniae in the presence of ascorbic acid

    NARCIS (Netherlands)

    Afzal, Muhammad; Shafeeq, Sulman; Henriques-Normark, Birgitta; Kuipers, Oscar P

    In this study, the regulatory mechanism of the ula (utilization of l-ascorbic acid) operon, putatively responsible for transport and utilization of ascorbic acid in Streptococcus pneumoniae strain D39, is studied. β-Galactosidase assay data demonstrate that expression of the ula operon is increased

  16. SCExAO and GPI Y JHBand Photometry and Integral Field Spectroscopy of the Young Brown Dwarf Companion to HD 1160

    Science.gov (United States)

    Garcia, E. Victor; Currie, Thayne; Guyon, Olivier; Stassun, Keivan G.; Jovanovic, Nemanja; Lozi, Julien; Kudo, Tomoyuki; Doughty, Danielle; Schlieder, Josh; Kwon, J.; Uyama, T.; Kuzuhara, M.; Carson, J. C.; Nakagawa, T.; Hashimoto, J.; Kusakabe, N.; Abe, L.; Brandner, W.; Brandt, T. D.; Feldt, M.; Goto, M.; Grady, C. A.; Hayano, Y.; Hayashi, M.; Hayashi, S. S.; Henning, T.; Hodapp, K. W.; Ishii, M.; Iye, M.; Janson, M.; Kandori, R.; Knapp, G. R.; Matsuo, T.; McElwain, M. W.; Miyama, S.; Morino, J.-I.; Moro-Martin, A.; Nishimura, T.; Pyo, T.-S.; Serabyn, E.; Suenaga, T.; Suto, H.; Suzuki, R.; Takahashi, Y. H.; Takami, H.; Takami, M.; Takato, N.; Terada, H.; Thalmann, C.; Turner, E. L.; Watanabe, M.; Wisniewski, J.; Yamada, T.; Usuda, T.; Tamura, M.

    2017-01-01

    We present high signal-to-noise ratio, precise Y JH photometry and Y band (0.957-1.120 μm) spectroscopy of HD 1160 B, a young substellar companion discovered from the Gemini NICI Planet Finding Campaign using the Subaru Coronagraphic Extreme Adaptive Optics instrument and the Gemini Planet Imager. HD 1160 B has typical mid-M dwarf-like infrared colors and a spectral type of M5.5{}-0.5+1.0, where the blue edge of our Y band spectrum rules out earlier spectral types. Atmospheric modeling suggests HD 1160 B has an effective temperature of 3000-3100 K, a surface gravity of log g = 4-4.5, a radius of 1.55 ± 0.10 R J, and a luminosity of log L/L ⊙ = -2.76 ± 0.05. Neither the primary’s Hertzspring-Russell diagram position nor atmospheric modeling of HD 1160 B show evidence for a subsolar metallicity. Interpretation of the HD 1160 B spectroscopy depends on which stellar system components are used to estimate the age. Considering HD 1160 A, B and C jointly, we derive an age of 80-125 Myr, implying that HD 1160 B straddles the hydrogen-burning limit (70-90 M J). If we consider HD 1160 A alone, younger ages (20-125 Myr) and a brown dwarf-like mass (35-90 M J) are possible. Interferometric measurements of the primary, a precise Gaia parallax, and moderate-resolution spectroscopy can better constrain the system’s age and how HD 1160 B fits within the context of (sub)stellar evolution.

  17. CLOUD STRUCTURE OF THE NEAREST BROWN DWARFS. II. HIGH-AMPLITUDE VARIABILITY FOR LUHMAN 16 A AND B IN AND OUT OF THE 0.99 μm FeH FEATURE

    Energy Technology Data Exchange (ETDEWEB)

    Buenzli, Esther [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Marley, Mark S. [NASA Ames Research Center, MS-245-3, Moffett Field, CA 94035 (United States); Apai, Dániel [Department of Astronomy, University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721 (United States); Saumon, Didier [Los Alamos National Laboratory, Mail Stop F663, Los Alamos, NM 87545 (United States); Biller, Beth A. [Institute for Astronomy, University of Edinburgh, Blackford Hill, Edinburgh EH9 3HJ (United Kingdom); Crossfield, Ian J. M. [Department of Planetary Sciences, University of Arizona, 1629 E. University Blvd, Tucson, AZ 85721 (United States); Radigan, Jacqueline, E-mail: buenzli@mpia.de [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2015-10-20

    The re-emergence of the 0.99 μm FeH feature in brown dwarfs of early- to mid-T spectral type has been suggested as evidence for cloud disruption where flux from deep, hot regions below the Fe cloud deck can emerge. The same mechanism could account for color changes at the L/T transition and photometric variability. We present the first observations of spectroscopic variability of brown dwarfs covering the 0.99 μm FeH feature. We observed the spatially resolved very nearby brown dwarf binary WISE J104915.57–531906.1 (Luhman 16AB), a late-L and early-T dwarf, with Hubble Space Telescope/WFC3 in the G102 grism at 0.8–1.15 μm. We find significant variability at all wavelengths for both brown dwarfs, with peak-to-valley amplitudes of 9.3% for Luhman 16B and 4.5% for Luhman 16A. This represents the first unambiguous detection of variability in Luhman 16A. We estimate a rotational period between 4.5 and 5.5 hr, very similar to Luhman 16B. Variability in both components complicates the interpretation of spatially unresolved observations. The probability for finding large amplitude variability in any two brown dwarfs is less than 10%. Our finding may suggest that a common but yet unknown feature of the binary is important for the occurrence of variability. For both objects, the amplitude is nearly constant at all wavelengths except in the deep K i feature below 0.84 μm. No variations are seen across the 0.99 μm FeH feature. The observations lend strong further support to cloud height variations rather than holes in the silicate clouds, but cannot fully rule out holes in the iron clouds. We re-evaluate the diagnostic potential of the FeH feature as a tracer of cloud patchiness.

  18. An eccentric companion at the edge of the brown dwarf desert orbiting the 2.4 M⊙ giant star HIP 67537

    Science.gov (United States)

    Jones, M. I.; Brahm, R.; Wittenmyer, R. A.; Drass, H.; Jenkins, J. S.; Melo, C. H. F.; Vos, J.; Rojo, P.

    2017-06-01

    We report the discovery of a substellar companion around the giant star HIP 67537. Based on precision radial velocity measurements from CHIRON and FEROS high-resolution spectroscopic data, we derived the following orbital elements for HIP 67537 b: mb sin I = 11.1+0.4-1.1Mjup, a =4.9+0.14-0.13 AU and e = 0.59+0.05-0.02 . Considering random inclination angles, this object has ≳65% probability to be above the theoretical deuterium-burning limit, thus it is one of the few known objects in the planet to brown-dwarf (BD) transition region. In addition, we analyzed the Hipparcos astrometric data of this star, from which we derived a minimum inclination angle for the companion of 2 deg. This value corresponds to an upper mass limit of 0.3 M⊙, therefore the probability that HIP 67537 b is stellar in nature is ≲7%. The large mass of the host star and the high orbital eccentricity makes HIP 67537 b a very interesting and rare substellar object. This is the second candidate companion in the brown dwarf desert detected in the sample of intermediate-mass stars targeted by the EXoPlanets aRound Evolved StarS (EXPRESS) radial velocity program, which corresponds to a detection fraction of f = +2.0-0.5 %. This value is larger than the fraction observed in solar-type stars, providing new observational evidence of an enhanced formation efficiency of massive substellar companions in massive disks. Finally, we speculate about different formation channels for this object. Based on observations collected at La Silla - Paranal Observatory under programs ID's 085.C-0557, 087.C.0476, 089.C-0524, 090.C-0345 and through the Chilean Telescope Time under programs ID's CN-12A-073, CN-12B-047, CN-13A-111, CN-2013B-51, CN-2014A-52, CN-15A-48, CN-15B-25 and CN-16A-13.

  19. 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

    Science.gov (United States)

    Jiang, Peng; Ge, Jian; Cargile, Phillip; Crepp, Justin R.; De Lee, Nathan; Porto de Mello, Gustavo F.; Esposito, Massimiliano; Ferreira, Letícia D.; Femenia, Bruno; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; González Hernández, Jonay I.; Hebb, Leslie; Lee, Brian L.; Ma, Bo; Stassun, Keivan G.; Wang, Ji; Wisniewski, John P.; Agol, Eric; Bizyaev, Dmitry; Brewington, Howard; Chang, Liang; Nicolaci da Costa, Luiz; Eastman, Jason D.; Ebelke, Garrett; Gary, Bruce; Kane, Stephen R.; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A. G.; Malanushenko, Viktor; Malanushenko, Elena; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Audrey; Oravetz, Daniel; Pan, Kaike; Pepper, Joshua; Paegert, Martin; Allende Prieto, Carlos; Rebolo, Rafael; Santiago, Basilio X.; Schneider, Donald P.; Shelden Bradley, Alaina C.; Sivarani, Thirupathi; Snedden, Stephanie; van Eyken, J. C.; Wan, Xiaoke; Weaver, Benjamin A.; Zhao, Bo

    2013-09-01

    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 T 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 ⊙ and 0.92 ± 0.19 R ⊙. The minimum mass of MARVELS-5b is 65.0 ± 2.9M 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 ⊙ at a separation larger than 40 AU.

  20. 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.

  1. Comparative study of the banana pulp browning process of 'Giant Dwarf' and FHIA-23 during fruit ripening based on image analysis and the polyphenol oxidase and peroxidase biochemical properties.

    Science.gov (United States)

    Escalante-Minakata, Pilar; Ibarra-Junquera, Vrani; Ornelas-Paz, José de Jesús; García-Ibáñez, Victoria; Virgen-Ortíz, José J; González-Potes, Apolinar; Pérez-Martínez, Jaime D; Orozco-Santos, Mario

    2018-01-01

    This work presents a novel method to associate the polyphenol oxidase (PPO) and the peroxidase (POD) activities with the ripening-mediated color changes in banana peel and pulp by computational image analysis. The method was used to follow up the de-greening of peel and browning of homogenized pulp from 'Giant Dwarf' (GD: Musa AAA, subgroup Cavendish) and FHIA-23 (tetraploid hybrid, AAAA) banana cultivars. In both cultivars, the color changes of peel during the ripening process clearly showed four stages, which were used to group the fruit into ripening stages. The PPO and POD were extracted from pulp of fruit at these ripening stages, precipitated, and partially purified by gel filtration chromatography. Moreover, the pulp browning was digitally monitored after homogenization for a span time of up to 120 min. The browning level was higher for GD than FHIA-23 tissues. This fact correlated with an 11.7-fold higher PPO activity in the GD cultivar, as compared with that of FHIA-23. POD activity was 8.1 times higher for GD as compared that that of FHIA-23.

  2. The complete plastome sequence of Gnetum ula (Gnetales: Gnetaceae).

    Science.gov (United States)

    Hsu, Chih-Yao; Wu, Chung-Shien; Surveswaran, Siddharthan; Chaw, Shu-Miaw

    2016-09-01

    This study reports the complete plastome sequence of Gnetum ula, a gymnosperm species of Gnetaceae (Gnetophyta). The plastome is 113 249 bp long. It has a quadripartite structure containing a pair of large inverted repeat regions of 19 772 bp each, a large single-copy region of 64 914 bp, and a small single-copy region of 8791 bp. One hundred sixteen genes were predicted in the plastome, including 68 protein-coding genes, eight ribosomal RNA genes, and 40 transfer RNA genes. The gene density is 1.024 (genes/kb). Similar to other known Gnetum plastomes, the G.ula plastome has lost 20 protein-coding genes commonly present in other seed plant plastomes. Our phylogenetic analyses indicate that the four sampled Gnetum species are monophyletic and that G. ula is close to the two other lianas rather than the only small tree species, G. gnemon. Our phylogenetic trees also indicate that gnetophytes have the fastest evolutionary rates among gymnosperms.

  3. TWO EXTRAORDINARY SUBSTELLAR BINARIES AT THE T/Y TRANSITION AND THE Y-BAND FLUXES OF THE COOLEST BROWN DWARFS {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Michael C.; Bowler, Brendan P.; Best, William M. J. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Dupuy, Trent J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Leggett, S. K. [Gemini Observatory, 670 North A' ohoku Place, Hilo, HI 96720 (United States)

    2012-10-10

    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 ( Almost-Equal-To 0.''8, 8-15 AU), large near-IR flux ratios ( Almost-Equal-To 2-3 mag), and small mass ratios ( Almost-Equal-To 0.5) compared to previously known field ultracool binaries. 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 Almost-Equal-To 400 K and being planetary-mass binaries if their ages are {approx}<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 the color drop arises from a change in temperature, not surface gravity or metallicity variations among the field population. Thus, the T/Y transition established by near-IR spectra coincides with a significant change in the Almost-Equal-To 1 {mu}m fluxes of ultracool photospheres. One explanation is the depletion of potassium, whose broad absorption wings dominate the far-red optical spectra of T dwarfs. This large color change suggests that far-red data may be valuable for classifying objects of {approx}<500 K.

  4. A Physical Model-based Correction for Charge Traps in the Hubble Space Telescope’s Wide Field Camera 3 Near-IR Detector and Its Applications to Transiting Exoplanets and Brown Dwarfs

    Science.gov (United States)

    Zhou, Yifan; Apai, Dániel; Lew, Ben W. P.; Schneider, Glenn

    2017-06-01

    The Hubble Space Telescope Wide Field Camera 3 (WFC3) near-IR channel is extensively used in time-resolved observations, especially for transiting exoplanet spectroscopy as well as brown dwarf and directly imaged exoplanet rotational phase mapping. The ramp effect is the dominant source of systematics in the WFC3 for time-resolved observations, which limits its photometric precision. Current mitigation strategies are based on empirical fits and require additional orbits to help the telescope reach a thermal equilibrium. We show that the ramp-effect profiles can be explained and corrected with high fidelity using charge trapping theories. We also present a model for this process that can be used to predict and to correct charge trap systematics. Our model is based on a very small number of parameters that are intrinsic to the detector. We find that these parameters are very stable between the different data sets, and we provide best-fit values. Our model is tested with more than 120 orbits (∼40 visits) of WFC3 observations and is proved to be able to provide near photon noise limited corrections for observations made with both staring and scanning modes of transiting exoplanets as well as for starting-mode observations of brown dwarfs. After our model correction, the light curve of the first orbit in each visit has the same photometric precision as subsequent orbits, so data from the first orbit no longer need to be discarded. Near-IR arrays with the same physical characteristics (e.g., JWST/NIRCam) may also benefit from the extension of this model if similar systematic profiles are observed.

  5. HIAD on ULA (HULA) Orbital Reentry Flight Experiment Concept

    Science.gov (United States)

    Dinonno, J. M.; Cheatwood, F. M.; Hughes, S. J.; Ragab, M. M.; Dillman, R. A.; Bodkin, R. J.; Zumwalt, C. H.; Johnson, R. K.

    2016-01-01

    This paper describes a proposed orbital velocity reentry flight test of a Hypersonic Inflatable Aerodynamic Decelerator (HIAD). The flight test builds upon ground development activities that continue to advance the materials, design, and manufacturing techniques for the inflatable structure and flexible thermal protection system (F-TPS) that comprise the inflatable heat shield. While certain aspects of material and system performance can be assessed using a variety of ground testing capabilities, only orbital velocity energy on a trajectory through the gradient density of the atmosphere can impart the combined aerodynamic and aeroheating design environments in real time. To achieve this at limited cost, the HIAD would be delivered to a spin-stabilized entry trajectory as a secondary payload on the Centaur stage of a United Launch Alliance (ULA) Atlas V launch vehicle. Initial trajectory studies indicate that the combination of launch vehicle capability and achievable reentry vehicle ballistic numbers make this a strategic opportunity for technology development. This 4 to 6 meter diameter scale aeroshell flight, referred to as HIAD on ULA (HULA), would also contribute to ULA asset recovery development. ULA has proposed that a HIAD be utilized as part of the Sensible, Modular, Autonomous Return Technology (SMART) initiative to enable recovery of the Vulcan launch vehicle booster main engines [1], including a Mid-Air Recovery (MAR) to gently return these assets for reuse. Whereas HULA will attain valuable aerothermal and structural response data toward advancing HIAD technology, it may also provide a largest-to-date scaled flight test of the MAR operation, which in turn would allow the examination of a nearly pristine post-entry aeroshell. By utilizing infrared camera imaging, HULA will also attain aft-side thermal response data, enhancing understanding of the aft side aerothermal environment, an area of high uncertainty. The aeroshell inflation will utilize a

  6. Transcriptional profiling of UlaR-regulated genes in Streptococcus pneumoniae

    NARCIS (Netherlands)

    Shafeeq, Sulman; Afzal, Muhammad; Henriques-Normark, Birgitta; Kuipers, Oscar P

    The transcriptional regulator UlaR belongs to the family of PRD-containing transcriptional regulators, which are mostly involved in the regulation of carbohydrate metabolism. The role of the transcriptional regulator UlaR in Streptococcus pneumoniae has recently been described [1]. Here, we report

  7. Forest structures retrieval from LiDAR onboard ULA

    Science.gov (United States)

    Shang, Xiaoxia; Chazette, Patrick; Totems, Julien; Marnas, Fabien; Sanak, Joseph

    2013-04-01

    Following the United Nations Framework Convention on Climate Change, the assessment of forest carbon stock is one of the main elements for a better understanding of the carbon cycle and its evolution following the climate change. The forests sequester 80% of the continental biospheric carbon and this efficiency is a function of the tree species and the tree health. The airborne backscatter LiDAR onboard the ultra light aircraft (ULA) can provide the key information on the forest vertical structures and evolution in the time. The most important structural parameter is the tree top height, which is directly linked to the above-ground biomass using non-linear relationships. In order to test the LiDAR capability for retrieving the tree top height, the LiDAR ULICE (Ultraviolet LIdar for Canopy Experiment) has been used over different forest types, from coniferous (maritime pins) to deciduous (oaks, hornbeams ...) trees. ULICE works at the wavelength of 355 nm with a sampling along the line-of-sight between 15 and 75 cm. According to the LiDAR signal to noise ratio (SNR), two different algorithms have been used in our study. The first algorithm is a threshold method directly based on the comparison between the LiDAR signal and the noise distributions, while the second one used a low pass filter by fitting a Gaussian curve family. In this paper, we will present these two algorithms and their evolution as a function of the SNR. The main error sources will be also discussed and assessed for each algorithm. The results show that these algorithms have great potential for ground-segment of future space borne LiDAR missions dedicated to the forest survey at the global scale. Acknowledgements: the canopy LiDAR system ULICE has been developed by CEA (Commissariat à l'Energie Atomique). It has been deployed with the support of CNES (Centre National d'Etude Spariales) and ANR (Agence Nationale de la Recherche). We acknowledge the ULA pilots Franck Toussaint for logistical help

  8. Institutional Repository saber.ula.ve: A testimonial perspective

    CERN Document Server

    Briceno, Y; Nunez, L A; Salager-Meyer, F; Rojas, A; Torrens, R

    2009-01-01

    In this paper, we describe our decade-long experience of building and operating one of the most active Institutional Repository in the world: www.saber.ula.ve (University of the Andes, Merida-Venezuela). In order to share our experience with other institutions, we firstly explain the steps we followed to preserve and disseminate the scientific production of the University of Los Andes' researchers. We then present some recent quantitative results about our repository activities and we outline some methodological guidelines that could be applied in order to replicate similar experiences. These guidelines list the ingredients or building blocks as well as the processes followed for developing and maintaining the services of an Institutional Repository. These include technological infrastructure; institutional policies on preservation, publication and dissemination of knowledge; recommendations on incentives for open access publication; the process of selection, testing and adaptation of technological tools; th...

  9. Encounters with Science at ULA, Venezuela: An Incentive for Learning

    Science.gov (United States)

    Rosenzweig, P.

    2006-08-01

    In the School of Science of the Universidad de Los Andes (ULA), in Mérida, Venezuela, a very successful event focused on high school students and primary school students, was founded in 2000. The name of this event is "Encounters with Physics, Chemistry, Mathematics, and Biology" (hereinafter "Encounters with Science"), and it integrates these disciplines as well as Astronomy. Its main purpose is that young minds can become familiar with the methods of science inquiry and reasoning, and can understand the concepts and processes of the sciences through thoroughly prepared experiences. This flourishing program is continuing to grow and to become strong. As a matter of fact, in its sixth edition (2005), the number of high and elementary school students coming from all over the country, has reached the outstanding number of nine thousand. Among all the experiences that the students could be engaged in were many involving Astronomy. These experiences were prepared by professors, together with graduate and undergraduate students, who are pursuing their degrees in all branches of science including astronomy. Although there is this incredible team of faculties and graduate and undergraduate students working together; the target is the students of the high and elementary schools. We certainly focus on the engaging and encouraging of students to experience scientific work first hand. Additionally, our professors have prepared an excellent didactic material that can, together with the hour/class teaching, prepare high school and elementary school students for a better understanding of science; particularly, helping in this way for a better education in Astronomy. The main event of the Encounters lasts five days in the School of Science of ULA, but subsidiary events are spread all over the year and around the country. As a successful program, it can be interesting to see if other countries can adopt this method to recruit or to trigger the interest of students to pursue their

  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

    Science.gov (United States)

    De Lee, Nathan; Ge, Jian; Crepp, Justin R.; Eastman, Jason; Esposito, Massimiliano; Femenía, Bruno; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; González Hernández, Jonay I.; Lee, Brian L.; Stassun, Keivan G.; Wisniewski, John P.; Wood-Vasey, W. Michael; Agol, Eric; Allende Prieto, Carlos; Barnes, Rory; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Da Costa, Luiz N.; Porto De Mello, G. F.; Ferreira, Leticia D.; Gary, Bruce; Hebb, Leslie; Holtzman, Jon; Liu, Jian; Ma, Bo; Mack, Claude E., III; 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.; Shelden Bradley, Alaina C.; Wan, Xiaoke; Wang, Ji; Zhao, Bo

    2013-06-01

    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 ⊙, 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: 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 * = 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. 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

    Science.gov (United States)

    Ma, Bo; Ge, Jian; Wolszczan, Alex; Muterspaugh, Matthew W.; Lee, Brian; Henry, Gregory W.; Schneider, Donald P.; Martín, Eduardo L.; Niedzielski, Andrzej; Xie, Jiwei; Fleming, Scott W.; Thomas, Neil; Williamson, Michael; Zhu, Zhaohuan; Agol, Eric; Bizyaev, Dmitry; Nicolaci da Costa, Luiz; Jiang, Peng; Martinez Fiorenzano, A. F.; González Hernández, Jonay I.; 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

    2016-11-01

    We report the detections of a giant planet (MARVELS-7b) and a brown dwarf (BD) candidate (MARVELS-7c) around the primary star in the close binary system, HD 87646. To the best of our knowledge, it is the first close binary system with more than one substellar circumprimary companion that has been discovered. 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 the Exoplanet Tracker at the Kitt Peak National Observatory, the High Resolution Spectrograph at the Hobby Eberley telescope, the “Classic” spectrograph at the Automatic Spectroscopic Telescope at the Fairborn Observatory, and MARVELS from SDSS-III confirmed this giant planet discovery and revealed the existence of a long-period BD in this binary. HD 87646 is a close binary with a separation of ˜22 au between the two stars, estimated using the Hipparcos catalog and our newly acquired AO image from PALAO on the 200 inch Hale Telescope at Palomar. The primary star in the binary, HD 87646A, has {T}{eff} = 5770 ± 80 K, log g = 4.1 ± 0.1, and [Fe/H] = -0.17 ± 0.08. The derived minimum masses of the two substellar companions of HD 87646A are 12.4 ± 0.7 {M}{Jup} and 57.0 ± 3.7 {M}{Jup}. The periods are 13.481 ± 0.001 days and 674 ± 4 days and the measured eccentricities are 0.05 ± 0.02 and 0.50 ± 0.02 respectively. Our dynamical simulations show that the system is stable if the binary orbit has a large semimajor axis and a low eccentricity, which can be verified with future astrometry observations.

  12. Very-low-mass Stellar and Substellar Companions to Solar-like Stars from Marvels. III. A Short-period Brown Dwarf Candidate around an Active G0IV Subgiant

    Science.gov (United States)

    Ma, Bo; Ge, Jian; Barnes, Rory; Crepp, Justin R.; De Lee, Nathan; Dutra-Ferreira, Leticia; Esposito, Massimiliano; Femenia, Bruno; Fleming, Scott W.; Gaudi, B. Scott; Ghezzi, Luan; Hebb, Leslie; Gonzalez Hernandez, Jonay I.; Lee, Brian L.; Porto de Mello, G. F.; Stassun, Keivan G.; Wang, Ji; Wisniewski, John P.; Agol, Eric; Bizyaev, Dmitry; Cargile, Phillip; Chang, Liang; Nicolaci da Costa, Luiz; Eastman, Jason D.; Gary, Bruce; Jiang, Peng; Kane, Stephen R.; Li, Rui; Liu, Jian; Mahadevan, Suvrath; Maia, Marcio A. G.; Muna, Demitri; Nguyen, Duy Cuong; Ogando, Ricardo L. C.; Oravetz, Daniel; Pepper, Joshua; Paegert, Martin; Allende Prieto, Carlos; Rebolo, Rafael; Santiago, Basilio X.; Schneider, Donald P.; Shelden, Alaina; Simmons, Audrey; Sivarani, Thirupathi; van Eyken, J. C.; Wan, Xiaoke; Weaver, Benjamin A.; Zhao, Bo

    2013-01-01

    We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T eff = 5903 ± 42 K, surface gravity log (g) = 4.07 ± 0.16 (cgs), and metallicity [Fe/H] = -0.23 ± 0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey, which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 3.571 ± 0.041 km s-1, period P = 9.0090 ± 0.0004 days, and eccentricity e = 0.226 ± 0.011. Adopting a mass of 1.16 ± 0.11 M ⊙ for the subgiant host star, we infer that the companion has a minimum mass of 40.0 ± 2.5 M Jup. Assuming an edge-on orbit, the semimajor axis is 0.090 ± 0.003 AU. The host star is photometrically variable at the ~1% level with a period of ~13.16 ± 0.01 days, indicating that the host star spin and companion orbit are not synchronized. Through adaptive optics imaging we also found a point source 643 ± 10 mas away from TYC 2087-00255-1, which would have a mass of 0.13 M ⊙ if it is physically associated with TYC 2087-00255-1 and has the same age. Future proper motion observation should be able to resolve if this tertiary object is physically associated with TYC 2087-00255-1 and make TYC 2087-00255-1 a triple body system. Core Ca II H and K line emission indicate that the host is chromospherically active, at a level that is consistent with the inferred spin period and measured v rotsin i, but unusual for a subgiant of this T eff. This activity could be explained by ongoing tidal spin-up of the host star by the companion.

  13. VERY-LOW-MASS STELLAR AND SUBSTELLAR COMPANIONS TO SOLAR-LIKE STARS FROM MARVELS. III. A SHORT-PERIOD BROWN DWARF CANDIDATE AROUND AN ACTIVE G0IV SUBGIANT

    Energy Technology Data Exchange (ETDEWEB)

    Ma Bo; Ge Jian; De Lee, Nathan; Fleming, Scott W.; Lee, Brian L.; Wang Ji [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, Gainesville, FL 32611-2055 (United States); Barnes, Rory; Agol, Eric [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195-1580 (United States); Crepp, Justin R. [Department of Physics, University of Notre Dame, 225 Nieuwland Science Hall, Notre Dame, IN 46556 (United States); Dutra-Ferreira, Leticia; Porto de Mello, G. F. [Observatorio do Valongo, Universidade Federal do Rio de Janeiro, Ladeira do Pedro Antonio, 43, CEP: 20080-090, Rio de Janeiro, RJ (Brazil); Esposito, Massimiliano; Femenia, Bruno; Gonzalez Hernandez, Jonay I. [Instituto de Astrofisica de Canarias, C/Via Lctea S/N, E-38200 La Laguna (Spain); Gaudi, B. Scott [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Ghezzi, Luan [Laboratorio Interinstitucional de e-Astronomia (LIneA), Rio de Janeiro, RJ 20921-400 (Brazil); Hebb, Leslie; Stassun, Keivan G. [Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235 (United States); Wisniewski, John P. [Homer L Dodge Department of Physics and Astronomy, University of Oklahoma, 440 W Brooks St, Norman, OK 73019 (United States); Bizyaev, Dmitry, E-mail: boma@astro.ufl.edu [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); and others

    2013-01-01

    We present an eccentric, short-period brown dwarf candidate orbiting the active, slightly evolved subgiant star TYC 2087-00255-1, which has effective temperature T{sub eff} = 5903 {+-} 42 K, surface gravity log (g) = 4.07 {+-} 0.16 (cgs), and metallicity [Fe/H] = -0.23 {+-} 0.07. This candidate was discovered using data from the first two years of the Multi-object APO Radial Velocity Exoplanets Large-area Survey, which is part of the third phase of Sloan Digital Sky Survey. From our 38 radial velocity measurements spread over a two-year time baseline, we derive a Keplerian orbital fit with semi-amplitude K = 3.571 {+-} 0.041 km s{sup -1}, period P = 9.0090 {+-} 0.0004 days, and eccentricity e = 0.226 {+-} 0.011. Adopting a mass of 1.16 {+-} 0.11 M{sub Sun} for the subgiant host star, we infer that the companion has a minimum mass of 40.0 {+-} 2.5 M{sub Jup}. Assuming an edge-on orbit, the semimajor axis is 0.090 {+-} 0.003 AU. The host star is photometrically variable at the {approx}1% level with a period of {approx}13.16 {+-} 0.01 days, indicating that the host star spin and companion orbit are not synchronized. Through adaptive optics imaging we also found a point source 643 {+-} 10 mas away from TYC 2087-00255-1, which would have a mass of 0.13 M{sub Sun} if it is physically associated with TYC 2087-00255-1 and has the same age. Future proper motion observation should be able to resolve if this tertiary object is physically associated with TYC 2087-00255-1 and make TYC 2087-00255-1 a triple body system. Core Ca II H and K line emission indicate that the host is chromospherically active, at a level that is consistent with the inferred spin period and measured v{sub rot}sin i, but unusual for a subgiant of this T{sub eff}. This activity could be explained by ongoing tidal spin-up of the host star by the companion.

  14. The UlaG protein family defines novel structural and functional motifs grafted on an ancient RNase fold

    Directory of Open Access Journals (Sweden)

    Coll Miquel

    2011-09-01

    Full Text Available Abstract Background Bacterial populations are highly successful at colonizing new habitats and adapting to changing environmental conditions, partly due to their capacity to evolve novel virulence and metabolic pathways in response to stress conditions and to shuffle them by horizontal gene transfer (HGT. A common theme in the evolution of new functions consists of gene duplication followed by functional divergence. UlaG, a unique manganese-dependent metallo-β-lactamase (MBL enzyme involved in L-ascorbate metabolism by commensal and symbiotic enterobacteria, provides a model for the study of the emergence of new catalytic activities from the modification of an ancient fold. Furthermore, UlaG is the founding member of the so-called UlaG-like (UlaGL protein family, a recently established and poorly characterized family comprising divalent (and perhaps trivalent metal-binding MBLs that catalyze transformations on phosphorylated sugars and nucleotides. Results Here we combined protein structure-guided and sequence-only molecular phylogenetic analyses to dissect the molecular evolution of UlaG and to study its phylogenomic distribution, its relatedness with present-day UlaGL protein sequences and functional conservation. Phylogenetic analyses indicate that UlaGL sequences are present in Bacteria and Archaea, with bona fide orthologs found mainly in mammalian and plant-associated Gram-negative and Gram-positive bacteria. The incongruence between the UlaGL tree and known species trees indicates exchange by HGT and suggests that the UlaGL-encoding genes provided a growth advantage under changing conditions. Our search for more distantly related protein sequences aided by structural homology has uncovered that UlaGL sequences have a common evolutionary origin with present-day RNA processing and metabolizing MBL enzymes widespread in Bacteria, Archaea, and Eukarya. This observation suggests an ancient origin for the UlaGL family within the broader trunk

  15. 67 additional L dwarfs discovered by the Two Micron All Sky Survey

    Science.gov (United States)

    Kirkpatrick, J.; Reid, I.; Liebert, J.; Gizis, J.; Burgasser, A.; Monet, D.; Dahn, C.; Nelson, B.; Williams, R.

    2000-01-01

    One of the goals of this new search was to locate more examples of the latest L dwarfs. Of the 67 new discoveries, 17 have types of L6 or later. Analysis of these new discoveries shows that 16 (and possibly four more) of the new L dwarfs are lithium brown dwarfs and that the average line strength for those L dwarfs showing lithium increases until type L6.5 V, then declines for later types.

  16. Modernist searches of Ulas Samchuk in the book “Rediscovered Paradise”

    Directory of Open Access Journals (Sweden)

    Tkachenko Tetiana

    2016-03-01

    Full Text Available The article deals with the peculiarities of the small prose by Ulas Samchuk. The research investigates the role and the sense of the titles and image’s symbolism in his short stories, the formal and substantive, conceptual levels of the text’s organization. The study pays particular attention to author’s individual style.

  17. Water clouds in Y dwarfs and exoplanets

    Energy Technology Data Exchange (ETDEWEB)

    Morley, Caroline V.; Fortney, Jonathan J. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Marley, Mark S.; Lupu, Roxana; Greene, Tom [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); Lodders, Katharina, E-mail: cmorley@ucolick.org [Washington University in St Louis, 1 Brookings Drive, St Louis, MO 63130 (United States)

    2014-05-20

    The formation of clouds affects brown dwarf and planetary atmospheres of nearly all effective temperatures. Iron and silicate condense in L dwarf atmospheres and dissipate at the L/T transition. Minor species such as sulfides and salts condense in mid- to late T dwarfs. For brown dwarfs below T {sub eff} ∼ 450 K, water condenses in the upper atmosphere to form ice clouds. Currently, over a dozen objects in this temperature range have been discovered, and few previous theoretical studies have addressed the effect of water clouds on brown dwarf or exoplanetary spectra. Here we present a new grid of models that include the effect of water cloud opacity. We find that they become optically thick in objects below T {sub eff} ∼ 350-375 K. Unlike refractory cloud materials, water-ice particles are significantly nongray absorbers; they predominantly scatter at optical wavelengths through the J band and absorb in the infrared with prominent features, the strongest of which is at 2.8 μm. H{sub 2}O, NH{sub 3}, CH{sub 4}, and H{sub 2} CIA are dominant opacity sources; less abundant species may also be detectable, including the alkalis, H{sub 2}S, and PH{sub 3}. PH{sub 3}, which has been detected in Jupiter, is expected to have a strong signature in the mid-infrared at 4.3 μm in Y dwarfs around T {sub eff} = 450 K; if disequilibrium chemistry increases the abundance of PH{sub 3}, it may be detectable over a wider effective temperature range than models predict. We show results incorporating disequilibrium nitrogen and carbon chemistry and predict signatures of low gravity in planetary mass objects. Finally, we make predictions for the observability of Y dwarfs and planets with existing and future instruments, including the James Webb Space Telescope and Gemini Planet Imager.

  18. White dwarf-red dwarf binaries in the Galaxy

    NARCIS (Netherlands)

    Besselaar, E.J.M. van den

    2007-01-01

    This PhD thesis shows several studies on white dwarf - red dwarf binaries. White dwarfs are the end products of most stars and red dwarfs are normal hydrogen burning low-mass stars. White dwarf - red dwarf binaries are both blue (white dwarf) and red (red dwarf). Together with the fact that they are

  19. Brown Syndrome

    Science.gov (United States)

    ... extraction) have also been linked to acquired Brown syndrome. Inflammation of the tendon-trochlea complex (from adult and juvenile rheumatoid arthritis, systemic lupus erythematosus and sinusitis) can be ... syndrome hereditary? Hereditary cases of Brown syndrome are rare. ...

  20. Brief activity performance measure for upper limb amputees: BAM-ULA.

    Science.gov (United States)

    Resnik, Linda; Borgia, Matthew; Acluche, Frantzy

    2017-01-01

    Measures of activity performance for adults with upper limb amputation are needed. The purposes of this study were to evaluate the measurement properties of a new measure of activity performance for adults with upper limb amputation, which we call the Brief Activity Measure for Upper Limb Amputees (BAM-ULA) and to compare BAM-ULA scores for users of different types of prostheses. In all, 35 persons with upper limb amputation were administered the BAM-ULA, twice within 1 week. Internal consistency and test-retest reliability were evaluated. Construct validity was examined by comparing scores by amputation level. Concurrent validity was evaluated by examining correlations with other measures. Exploratory analyses using linear regression compared sub-group scores for users of myoelectric and body-powered devices, and for users of single-degree-of-freedom and multi-articulating devices, controlling for amputation level. The scale alpha was 0.83; intraclass correlation coefficient was 0.91. Item scores differed by amputation level and device type. Persons with transradial amputation completed more items than those with amputations at the transhumeral or shoulder level ( p BAM-ULA strongly correlated with the Activities Measure for Upper Limb Amputees; R = 0.86) and three modified Jebsen-Taylor Hand Function Tests ( R = 0.62-0.68) and moderately correlated with one Jebsen-Taylor Hand Function Test ( R = 0.46) as well as with the Wong-Baker FACES Pain Rating Scale. No differences in scores were found by degree of freedom of the terminal device after controlling for amputation level. Analyses support reliability, construct validity, and concurrent validity of the Brief Activity Measure for Upper Limb Amputees. This new briefer measure is easier to score than the Activities Measure for Upper Limb Amputees. Clinical relevance This article reported on the development and evaluation of a brief 10-item measure of activity performance for persons with upper limb

  1. Naming Disney's Dwarfs.

    Science.gov (United States)

    Sidwell, Robert T.

    1980-01-01

    Discusses Disney's version of the folkloric dwarfs in his production of "Snow White" and weighs the Disney rendition of the dwarf figure against the corpus of traits and behaviors pertaining to dwarfs in traditional folklore. Concludes that Disney's dwarfs are "anthropologically true." (HOD)

  2. Computational study on transfer of L-ascorbic acid by UlaA through Escherichia coli membrane.

    Science.gov (United States)

    Faghih-Mirzaee, Ehsan; Dehestani, Maryam; Zeidabadinejad, Leila

    2017-06-01

    In this study, the transfer of L-ascorbic acid by UlaA through Escherichia coli (E. coli) membrane was evaluated using density functional theory (DFT), molecular docking, and molecular dynamics (MD) simulation methods. DFT calculations at the B3lyp/6[Formula: see text]311[Formula: see text]G(p,d) level were performed to investigate the interaction properties and molecular descriptors. The physical properties, such as chemical potential, chemical hardness, and chemical electrophilicity of all studied molecules, were investigated. Natural population analysis was employed to describe the state of charge transfer between interactions using the natural bond orbital (NBO). The atoms in molecules (AIM) theory was used to examine the properties of the bond critical points such as their electron densities and Laplacians. Molecular docking studies showed that L-ascorbic acid was bounded to the internal cavity of UlaA. It was found that there were some hydrogen bond interactions between L-ascorbic acid and active sites of UlaA. The results of the MD simulation showed that the root mean square deviation (RMSD) of UlaA and L-ascorbic acid bound-UlaA reached equilibrium after 3.7[Formula: see text]ns. An evaluation of the radius of gyration ([Formula: see text]) revealed that UlaA and L-ascorbic acid bound-UlaA were stabilized around 10,000[Formula: see text]ns. Finally, analysis of the RMS fluctuations suggested that the structure of the L-ascorbic acid binding site remained approximately rigid during simulation. All obtained results shed light on the special manner of L-ascorbic acid transfer through E. coli membrane, and confirmed the results of previous studies on this issue.

  3. Strain characterization of West African Dwarf goats of Ogun State II ...

    African Journals Online (AJOL)

    The West African Dwarf (WAD) goat presents variable coat colours, ranging from black, brown, gray, red and white and sometimes combinations of these variety of patterns. In this study, strains of West African Dwarf (WAD) goat were characterized using linear body measurement. The WAD goat included the chocolate, white ...

  4. SEARCHING FOR BINARY Y DWARFS WITH THE GEMINI MULTI-CONJUGATE ADAPTIVE OPTICS SYSTEM (GeMS)

    Energy Technology Data Exchange (ETDEWEB)

    Opitz, Daniela; Tinney, C. G. [School of Physics, University of New South Wales, NSW 2052 (Australia); Faherty, Jacqueline K. [Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 (United States); Sweet, Sarah [Research School of Astronomy and Astrophysics, Australian National University, Canberra, ACT 2611 (Australia); Gelino, Christopher R.; Kirkpatrick, J. Davy, E-mail: daniela.opitz@student.unsw.edu.au [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States)

    2016-03-01

    The NASA Wide-field Infrared Survey Explorer (WISE) has discovered almost all the known members of the new class of Y-type brown dwarfs. Most of these Y dwarfs have been identified as isolated objects in the field. It is known that binaries with L- and T-type brown dwarf primaries are less prevalent than either M-dwarf or solar-type primaries, they tend to have smaller separations and are more frequently detected in near-equal mass configurations. The binary statistics for Y-type brown dwarfs, however, are sparse, and so it is unclear if the same trends that hold for L- and T-type brown dwarfs also hold for Y-type ones. In addition, the detection of binary companions to very cool Y dwarfs may well be the best means available for discovering even colder objects. We present results for binary properties of a sample of five WISE Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System. We find no evidence for binary companions in these data, which suggests these systems are not equal-luminosity (or equal-mass) binaries with separations larger than ∼0.5–1.9 AU. For equal-mass binaries at an age of 5 Gyr, we find that the binary binding energies ruled out by our observations (i.e., 10{sup 42} erg) are consistent with those observed in previous studies of hotter ultra-cool dwarfs.

  5. The Late-Type Extension to MoVeRS (LaTE-MoVeRS): Proper Motion Verified Low-mass Stars and Brown Dwarfs from SDSS, 2MASS, and WISE

    Science.gov (United States)

    Theissen, Christopher A.; West, Andrew A.; Shippee, Guillaume; Burgasser, Adam J.; Schmidt, Sarah J.

    2017-03-01

    We present the Late-Type Extension to the Motion Verified Red Stars (LaTE-MoVeRS) catalog, containing 46,463 photometric late-type (>M5) dwarfs within the Sloan Digital Sky Survey (SDSS) footprint. Proper motions were computed for objects combining astrometry from the SDSS Data Release 12 (DR12), the Two-micron All-Sky Survey (2MASS) Point Source Catalog, and the Wide-field Infrared Survey Explorer (WISE) AllWISE data sets. LaTE-MoVeRS objects were required to have significant proper motion ({μ }{tot}≥slant 2{σ }{μ {tot}}). Using the LaTE-MoVeRS sample and Gaia Data Release 1, we estimate Gaia will be ˜64% complete for very low-mass objects (>M5) in comparison to the combined SDSS+2MASS+WISE data set (i< 21.3). We computed photometric distances and estimated stellar effective temperatures for the LaTE-MoVeRS catalog. The majority of the dwarfs in the sample have distances < 150 pc and {T}{eff}< 3000 K. Thirteen objects that have not been previously identified as nearby objects were identified within LaTE-MoVeRS with estimated photometric distances within 25 pc. We also identified one new object that has not been previously identified with a large amount of excess mid-infrared flux (2MASS J11151597+1937266). This object appears to be an L2γ at ˜50 pc showing spectroscopic signs of a flaring event (e.g., strong hydrogen Balmer emission lines). This object does not exhibit kinematics similar to any known kinematic association. The LaTE-MoVeRS catalog is available through SDSS CasJobs and VizieR.

  6. Haematological and physiological parameters of West African dwarf ...

    African Journals Online (AJOL)

    Twenty four West African Dwarf (WAD) goats of both sexes (12 bucks and 12 does) raised under intensive system and weighing between 5 and 11 kg with different coat colours (Black, Brown, Tan and White) were used for this study to evaluate the effects of sex and coat colour on their haematological and physiological ...

  7. Ascorbic acid-dependent gene expression in Streptococcus pneumoniae and the activator function of the transcriptional regulator UlaR2

    Science.gov (United States)

    Afzal, Muhammad; Shafeeq, Sulman; Kuipers, Oscar P.

    2015-01-01

    In this study, we have explored the impact of ascorbic acid on the transcriptome of Streptococcus pneumoniae D39. The expression of several genes and operons, including the ula operon (which has been previously shown to be involved in ascorbic acid utilization), the AdcR regulon (which has been previously shown to be involved in zinc transport and virulence) and a PTS operon (which we denote here as ula2 operon) were altered in the presence of ascorbic acid. The ula2 operon consists of five genes, including the transcriptional activator ulaR2. Our β-galactosidase assay data and transcriptome comparison of the ulaR2 mutant with the wild-type demonstrated that the transcriptional activator UlaR2 in the presence of ascorbic acid activates the expression of the ula2 operon. We further predict a 16-bp regulatory site (5′-ATATTGTGCTCAAATA-3′) for UlaR2 in the Pula2. Furthermore, we have explored the effect of ascorbic acid on the expression of the AdcR regulon. Our ICP-MS analysis showed that addition of ascorbic acid to the medium causes zinc starvation in the cell which leads to the activation of the AdcR regulon. PMID:25717320

  8. Unmaking Brown

    Science.gov (United States)

    Lockette, Tim

    2010-01-01

    America's schools are more segregated now than they were in the late 1960s. More than 50 years after "Brown v. Board of Education," educators need to radically rethink the meaning of "school choice." For decades at Wake County, buses would pick up public school students in largely minority communities along the Raleigh…

  9. Difference distance map data of alternative crystal forms of UlaA

    Directory of Open Access Journals (Sweden)

    Ake Vastermark

    2017-02-01

    Full Text Available We introduce the value of information obtained by comparing alternative crystal forms of the same sub-state (of outward open UlaA, our example protein, which is found in the same lattice configuration but different space groups. We compare instability estimates obtained using this new method (alternative crystal forms with temperature factors. Using a transport assay result, we correlate observations for two homologous secondary structure elements, and show that the alternative states method for obtaining instability estimates provide differentiating information about an important and immobilized mid-TMS region. The data presented in this article are related to the article entitled “The V-motifs facilitate the substrate capturing step of the PTS elevator mechanism” (A. Vastermark, A. Driker, J. Weng, X. Li, J. Wang, M.H. Saier Jr., 2016.

  10. Difference distance map data of alternative crystal forms of UlaA.

    Science.gov (United States)

    Vastermark, Ake; Driker, Adelle; Weng, Jingwei; Li, Xiaochun; Wang, Jiawei; Saier, Milton H

    2017-02-01

    We introduce the value of information obtained by comparing alternative crystal forms of the same sub-state (of outward open UlaA, our example protein), which is found in the same lattice configuration but different space groups. We compare instability estimates obtained using this new method (alternative crystal forms) with temperature factors. Using a transport assay result, we correlate observations for two homologous secondary structure elements, and show that the alternative states method for obtaining instability estimates provide differentiating information about an important and immobilized mid-TMS region. The data presented in this article are related to the article entitled "The V-motifs facilitate the substrate capturing step of the PTS elevator mechanism" (A. Vastermark, A. Driker, J. Weng, X. Li, J. Wang, M.H. Saier Jr., 2016).

  11. A N2-Raman lidar on board ULA for Arctic atmospheric studies

    Science.gov (United States)

    de Cacqueray, Victor; Chazette, Patrick; Totems, Julien; Raut, Jean-Christophe; Shang, Xiaoxia; Marpillat, Alexandre

    2016-04-01

    A key scientific question relative to atmospheric studies in the Arctic is the quantification and the vertical distribution of aerosols and their interactions with clouds in the lower troposphere. In May 2016, as part of the PARCS (Pollution in the ARCtic System) project, we will conduct an experiment in order to assess the optical properties and concentrations of aerosols near the North-Cape in Norway. This campaign will involve a new airborne N2-Raman lidar (355 nm) on board an Ultra Light Aircraft (ULA) and an original instrumental synergy between ground-based radar (95 GHz) and N2-H2O Raman lidar. The airborne experimental preparation for this campaign was divided in two weeks: the first week of experiments above the Rhône valley in June 2015 and the second in the Maurienne valley in the French Alps in December 2015. The capability of the N2-Raman lidar to perform measurements from the ULA during daytime has been checked. After the first campaign of tests, the laser emitted energy per pulse has been upgraded to improve the signal to noise ratio. Both the strategies and the main results of the two field campaigns will be presented. We will focus on the error budget for the retrieval of the aerosol optical thickness in the first atmospheric kilometer. We will present in addition the potential of such a lidar to monitor industrial pollution plumes in the planetary boundary layer. The airborne lidar measurements will be analysed taking into account the synergy with an in situ particle sizer (FIDAS) provided by the ADDAIR Company.

  12. A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE

    Energy Technology Data Exchange (ETDEWEB)

    Mace, Gregory N.; Wright, Edward L.; McLean, Ian S. [Department of Physics and Astronomy, UCLA, 430 Portola Plaza, Box 951547, Los Angeles, CA 90095-1547 (United States); Davy Kirkpatrick, J.; Gelino, Christopher R.; Griffith, Roger L.; Mix, Katholeen; Beichman, Charles A.; Lowrance, Patrick J. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C. [Department of Physics and Astronomy, MS 111, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606-3328 (United States); Skrutskie, Michael F. [Department of Astronomy, University of Virginia, Charlottesville, VA 22904 (United States); Marsh, Kenneth A. [School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA (United Kingdom); Eisenhardt, Peter R. [NASA Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Thompson, Maggie A. [Department of Astrophysical Sciences, Princeton University, Peyton Hall, 4 Ivy Lane, Princeton, NJ 08544-1001 (United States); Bailey, Vanessa; Hinz, Philip M.; Knox, Russell P. [Steward Observatory, The University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721 (United States); Bloom, Joshua S. [Department of Astronomy, University of California, Berkeley, CA 94720 (United States); Burgasser, Adam J. [Department of Physics, University of California, San Diego, CA 92093 (United States); Fortney, Jonathan J., E-mail: gmace@astro.ucla.edu [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); and others

    2013-03-01

    We report the discovery of 87 new T dwarfs uncovered with the Wide-field Infrared Survey Explorer (WISE) and 3 brown dwarfs with extremely red near-infrared colors that exhibit characteristics of both L and T dwarfs. Two of the new T dwarfs are likely binaries with L7 {+-} 1 primaries and mid-type T secondaries. In addition, our follow-up program has confirmed 10 previously identified T dwarfs and 4 photometrically selected L and T dwarf candidates in the literature. This sample, along with the previous WISE discoveries, triples the number of known brown dwarfs with spectral types later than T5. Using the WISE All-Sky Source Catalog we present updated color-color and color-type diagrams for all the WISE-discovered T and Y dwarfs. Near-infrared spectra of the new discoveries are presented along with spectral classifications. To accommodate later T dwarfs we have modified the integrated flux method of determining spectral indices to instead use the median flux. Furthermore, a newly defined J-narrow index differentiates the early-type Y dwarfs from late-type T dwarfs based on the J-band continuum slope. The K/J indices for this expanded sample show that 32% of late-type T dwarfs have suppressed K-band flux and are blue relative to the spectral standards, while only 11% are redder than the standards. Comparison of the Y/J and K/J index to models suggests diverse atmospheric conditions and supports the possible re-emergence of clouds after the L/T transition. We also discuss peculiar brown dwarfs and candidates that were found not to be substellar, including two young stellar objects and two active galactic nuclei. The substantial increase in the number of known late-type T dwarfs provides a population that will be used to test models of cold atmospheres and star formation. The coolest WISE-discovered brown dwarfs are the closest of their type and will remain the only sample of their kind for many years to come.

  13. Individual Dynamical Masses of Ultracool Dwarfs

    Science.gov (United States)

    Dupuy, Trent J.; Liu, Michael C.

    2017-08-01

    We present the full results of our decade-long astrometric monitoring programs targeting 31 ultracool binaries with component spectral types M7-T5. Joint analysis of resolved imaging from Keck Observatory and Hubble Space Telescope and unresolved astrometry from CFHT/WIRCam yields parallactic distances for all systems, robust orbit determinations for 23 systems, and photocenter orbits for 19 systems. As a result, we measure 38 precise individual masses spanning 30-115 {M}{Jup}. We determine a model-independent substellar boundary that is ≈70 {M}{Jup} in mass (≈L4 in spectral type), and we validate Baraffe et al. evolutionary model predictions for the lithium-depletion boundary (60 {M}{Jup} at field ages). Assuming each binary is coeval, we test models of the substellar mass-luminosity relation and find that in the L/T transition, only the Saumon & Marley “hybrid” models accounting for cloud clearing match our data. We derive a precise, mass-calibrated spectral type-effective temperature relation covering 1100-2800 K. Our masses enable a novel direct determination of the age distribution of field brown dwarfs spanning L4-T5 and 30-70 {M}{Jup}. We determine a median age of 1.3 Gyr, and our population synthesis modeling indicates our sample is consistent with a constant star formation history modulated by dynamical heating in the Galactic disk. We discover two triple-brown-dwarf systems, the first with directly measured masses and eccentricities. We examine the eccentricity distribution, carefully considering biases and completeness, and find that low-eccentricity orbits are significantly more common among ultracool binaries than solar-type binaries, possibly indicating the early influence of long-lived dissipative gas disks. Overall, this work represents a major advance in the empirical view of very low-mass stars and brown dwarfs.

  14. 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

  15. Brown recluse spider (image)

    Science.gov (United States)

    The brown recluse is a venomous spider most commonly found in midwestern and southern states of the United States. It ... inch overall and has long skinny legs. The brown recluse is brown with a characteristic dark violin-shaped ...

  16. Astrometric Binaries: White Dwarfs?

    Science.gov (United States)

    Oliversen, Nancy A.

    We propose to observe a selection of astrometric or spectroscopicastrometric binaries nearer than about 20 pc with unseen low mass companions. Systems of this type are important for determining the luminosity function of low mass stars (white dwarfs and very late main sequence M stars), and their contribution to the total mass of the galaxy. Systems of this type are also important because the low mass, invisible companions are potential candidates in the search for planets. Our target list is selected primarily from the list of 31 astrometric binaries near the sun by Lippincott (1978, Space Sci. Rev., 22, 153), with additional candidates from recent observations by Kamper. The elimination of stars with previous IUE observations, red companions resolved by infrared speckle interferometry, or primaries later than M1 (because if white dwarf companions are present they should have been detected in the visible region) reduces the list to 5 targets which need further information. IUE SWP low dispersion observations of these targets will show clearly whether the remaining unseen companions are white dwarfs, thus eliminating very cool main sequence stars or planets. This is also important in providing complete statistical information about the nearest stars. The discovery of a white dwarf in such a nearby system would provide important additional information about the masses of white dwarfs. Recent results by Greenstein (1986, A. J., 92, 859) from binary systems containing white dwarfs imply that 80% of such systems are as yet undetected. The preference of binaries for companions of approximately equal mass makes the Lippincott-Kamper list of A through K primaries with unseen companions a good one to use to search for white dwarfs. The mass and light dominance of the current primary over the white dwarf in the visible makes ultraviolet observations essential to obtain an accurate census of white dwarf binaries.

  17. Dwarfs in ancient Egypt.

    Science.gov (United States)

    Kozma, Chahira

    2006-02-15

    Ancient Egypt was one of the most advanced and productive civilizations in antiquity, spanning 3000 years before the "Christian" era. Ancient Egyptians built colossal temples and magnificent tombs to honor their gods and religious leaders. Their hieroglyphic language, system of organization, and recording of events give contemporary researchers insights into their daily activities. Based on the record left by their art, the ancient Egyptians documented the presence of dwarfs in almost every facet of life. Due to the hot dry climate and natural and artificial mummification, Egypt is a major source of information on achondroplasia in the old world. The remains of dwarfs are abundant and include complete and partial skeletons. Dwarfs were employed as personal attendants, animal tenders, jewelers, and entertainers. Several high-ranking dwarfs especially from the Old Kingdom (2700-2190 BCE) achieved important status and had lavish burial places close to the pyramids. Their costly tombs in the royal cemeteries and the inscriptions on their statutes indicate their high-ranking position in Egyptian society and their close relation to the king. Some of them were Seneb, Pereniankh, Khnumhotpe, and Djeder. There were at least two dwarf gods, Ptah and Bes. The god Ptah was associated with regeneration and rejuvenation. The god Bes was a protector of sexuality, childbirth, women, and children. He was a favored deity particularly during the Greco-Roman period. His temple was recently excavated in the Baharia oasis in the middle of Egypt. The burial sites and artistic sources provide glimpses of the positions of dwarfs in daily life in ancient Egypt. Dwarfs were accepted in ancient Egypt; their recorded daily activities suggest assimilation into daily life, and their disorder was not shown as a physical handicap. Wisdom writings and moral teachings in ancient Egypt commanded respect for dwarfs and other individuals with disabilities. Copyright (c) 2005 Wiley-Liss, Inc.

  18. A Dark Spot on a Massive White Dwarf

    Science.gov (United States)

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

    2015-12-01

    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 minutes 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 Tecnologia e Inovação (Brazil) and Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina).

  19. Periodic optical variability of radio-detected ultracool dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Harding, L. K.; Golden, A.; Singh, Navtej; Sheehan, B.; Butler, R. F. [Centre for Astronomy, National University of Ireland, Galway, University Road, Galway (Ireland); Hallinan, G. [Cahill Center for Astrophysics, California Institute of Technology, 1200 East California Boulevard, MC 249-17, Pasadena, CA 91125 (United States); Boyle, R. P. [Vatican Observatory Research Group, Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Zavala, R. T., E-mail: lkh@astro.caltech.edu [United States Naval Observatory, Flagstaff Station, Flagstaff, AZ 86001 (United States)

    2013-12-20

    A fraction of very low mass stars and brown dwarfs are known to be radio active, in some cases producing periodic pulses. Extensive studies of two such objects have also revealed optical periodic variability, and the nature of this variability remains unclear. Here, we report on multi-epoch optical photometric monitoring of six radio-detected dwarfs, spanning the ∼M8-L3.5 spectral range, conducted to investigate the ubiquity of periodic optical variability in radio-detected ultracool dwarfs. This survey is the most sensitive ground-based study carried out to date in search of periodic optical variability from late-type dwarfs, where we obtained 250 hr of monitoring, delivering photometric precision as low as ∼0.15%. Five of the six targets exhibit clear periodicity, in all cases likely associated with the rotation period of the dwarf, with a marginal detection found for the sixth. Our data points to a likely association between radio and optical periodic variability in late-M/early-L dwarfs, although the underlying physical cause of this correlation remains unclear. In one case, we have multiple epochs of monitoring of the archetype of pulsing radio dwarfs, the M9 TVLM 513–46546, spanning a period of 5 yr, which is sufficiently stable in phase to allow us to establish a period of 1.95958 ± 0.00005 hr. This phase stability may be associated with a large-scale stable magnetic field, further strengthening the correlation between radio activity and periodic optical variability. Finally, we find a tentative spin-orbit alignment of one component of the very low mass binary, LP 349–25.

  20. Brown Dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS)

    Science.gov (United States)

    Hambly, Nigel; UKIDSS Consortium

    2003-06-01

    During the final quarter of 2003, UKIRT will take delivery of WFCAM. This new wide--field camera will have a FOV of 0.2 square degrees, and is therefore well suited to large--scale survey work. A consortium of more than 60 astronomers has successfully bid for a large fraction of all UKIRT time over the next 5 years to undertake several public surveys using this new facility. These surveys are collectively known as the UKIRT Infrared Deep Sky Survey (UKIDSS). In this short paper I will describe the project and review the prospects for BD research using UKIDSS data, highlighting some of the major science goals related to BDs that we hope will be achieved.

  1. Brown Recluse Spider

    Science.gov (United States)

    ... 6.4-19.1mm) • Color: Golden brown • A dark violin/fiddle shape (see top photo) is located ... Habitat The Brown Recluse Spider builds small retreat webs behind objects of any type. Symptoms • The severity ...

  2. Strain characterization of West African Dwarf Goats of Ogun State I ...

    African Journals Online (AJOL)

    Characterization of West African Dwarf goat is an approach to a sustainable use of its great potentials. In this study, strains of WAD goat were characterized using linear body measurement. The WAD goat included the gold (brown), black, buckskin and chaimose of ages 1, 2, 3 and 4 years,raised under extensive system of ...

  3. Uniform Atmospheric Retrieval Analysis of Ultracool Dwarfs. II. Properties of 11 T dwarfs

    Science.gov (United States)

    Line, Michael R.; Marley, Mark S.; Liu, Michael C.; Burningham, Ben; Morley, Caroline V.; Hinkel, Natalie R.; Teske, Johanna; Fortney, Jonathan J.; Freedman, Richard; Lupu, Roxana

    2017-10-01

    Brown dwarf spectra are rich in information revealing of the chemical and physical processes operating in their atmospheres. We apply a recently developed atmospheric retrieval tool to an ensemble of late-T dwarf (600-800 K) near-infrared (1-2.5 μm) spectra. With these spectra we are able to directly constrain the molecular abundances for the first time of H2O, CH4, CO, CO2, NH3, H2S, and Na+K, surface gravity, effective temperature, thermal structure, photometric radius, and cloud optical depths. We find that ammonia, water, methane, and the alkali metals are present and that their abundances are well constrained in all 11 objects. We find no significant trend in the water, methane, or ammonia abundances with temperature, but find a very strong (>25σ) decreasing trend in the alkali metal abundances with decreasing effective temperature, indicative of alkali rainout. As expected from previous work, we also find little evidence for optically thick clouds. With the methane and water abundances, we derive the intrinsic atmospheric metallicity and carbon-to-oxygen ratios. We find in our sample that metallicities are typically subsolar (-0.4 , different than expectations from the local stellar population. We also find that the retrieved vertical thermal profiles are consistent with radiative equilibrium over the photospheric regions. Finally, we find that our retrieved effective temperatures are lower than previous inferences for some objects and that some of our radii are larger than expectations from evolutionary models, possibly indicative of unresolved binaries. This investigation and method represent a new and powerful paradigm for using spectra to determine the fundamental chemical and physical processes governing cool brown dwarf atmospheres.

  4. A Volume-Limited Sample of L and T Dwarfs Defined by Parallaxes

    Science.gov (United States)

    Best, William M. J.; Liu, Michael C.; Magnier, Eugene; Dupuy, Trent

    2018-01-01

    Volume-limited samples are the gold standard for stellar population studies, as they enable unbiased measurements of space densities and luminosity functions. Parallaxes are the most direct measures of distance and are therefore essential for defining high-confidence volume limited samples. Previous efforts to model the local brown dwarf population were hampered by samples based on a small number of parallaxes. We are using UKIRT/WFCAM to conduct the largest near-infrared program to date to measure parallaxes and proper motions of L and T dwarfs. For the past 3+ years we have monitored over 350 targets, ≈90% of which are too faint to be observed by Gaia. We present preliminary results from our observations. Our program more than doubles the number of known L and T dwarf parallaxes, defining a volume-limited sample of ≈400 L0-T6 dwarfs out to 25 parsecs, the first L and T dwarf sample of this size and depth based entirely on parallaxes. Our sample will combine with the upcoming stellar census from Gaia DR2 parallaxes to form a complete volume-limited sample of nearby stars and brown dwarfs.

  5. [Human brown adipose tissue].

    Science.gov (United States)

    Virtanen, Kirsi A; Nuutila, Pirjo

    2015-01-01

    Adult humans have heat-producing and energy-consuming brown adipose tissue in the clavicular region of the neck. There are two types of brown adipose cells, the so-called classic and beige adipose cells. Brown adipose cells produce heat by means of uncoupler protein 1 (UCP1) from fatty acids and sugar. By applying positron emission tomography (PET) measuring the utilization of sugar, the metabolism of brown fat has been shown to multiply in the cold, presumably influencing energy consumption. Active brown fat is most likely present in young adults, persons of normal weight and women, least likely in obese persons.

  6. Atmospheric Habitable Zones in Y Dwarf Atmospheres

    Energy Technology Data Exchange (ETDEWEB)

    Yates, Jack S.; Palmer, Paul I. [School of GeoSciences, University of Edinburgh (United Kingdom); Biller, Beth; Cockell, Charles S., E-mail: j.s.yates@ed.ac.uk [Centre for Exoplanet Science, University of Edinburgh (United Kingdom)

    2017-02-20

    We use a simple organism lifecycle model to explore the viability of an atmospheric habitable zone (AHZ), with temperatures that could support Earth-centric life, which sits above an environment that does not support life. To illustrate our model, we use a cool Y dwarf atmosphere, such as WISE J085510.83–0714442.5, whose 4.5–5.2 μ m spectrum shows absorption features consistent with water vapor and clouds. We allow organisms to adapt to their atmospheric environment (described by temperature, convection, and gravity) by adopting different growth strategies that maximize their chance of survival and proliferation. We assume a constant upward vertical velocity through the AHZ. We found that the organism growth strategy is most sensitive to the magnitude of the atmospheric convection. Stronger convection supports the evolution of more massive organisms. For a purely radiative environment, we find that evolved organisms have a mass that is an order of magnitude smaller than terrestrial microbes, thereby defining a dynamical constraint on the dimensions of life that an AHZ can support. Based on a previously defined statistical approach, we infer that there are of the order of 10{sup 9} cool Y brown dwarfs in the Milky Way, and likely a few tens of these objects are within 10 pc from Earth. Our work also has implications for exploring life in the atmospheres of temperate gas giants. Consideration of the habitable volumes in planetary atmospheres significantly increases the volume of habitable space in the galaxy.

  7. Photometry, Astrometry, and Discoveries of Ultracool Dwarfs in the Pan-STARRS 3π Survey

    Science.gov (United States)

    Best, William M. J.; Magnier, Eugene A.; Liu, Michael C.; Deacon, Niall; Aller, Kimberly; Zhang, Zhoujian; Pan-STARRS1 Builders

    2018-01-01

    The Pan-STARRS1 3π Survey (PS1)'s far-red optical sensitivity makes it an exceptional new resource for discovering and characterizing ultracool dwarfs. We present a PS1-based catalog of photometry and proper motions of nearly 10,000 M, L, and T dwarfs, along with our analysis of the kinematics of nearby M6-T9 dwarfs, building a comprehensive picture of the local ultracool population. We highlight some especially interesting ultracool discoveries made with PS1, including brown dwarfs with spectral types in the enigmatic L/T transition, wide companions to main sequence stars that serve as age and metallicity bechmarks for substellar models, and free-floating members of the nearby young moving groups and star-forming regions with masses down to ≈5 MJup. With its public release, PS1 will continue to be a vital tool for studying the ultracool population.

  8. REVITALISATION OF THE AGRICULTURAL LANDSCAPE, ON THE ISLAND OF KORČULA – Cay study municipality Blato

    Directory of Open Access Journals (Sweden)

    Branka Aničić

    2001-09-01

    Full Text Available Cultural landscapes of the Mediterranean should become one among the bearers of the regional and national identity and in this way give their contribution to tourism and economic progress because of their recognizability and rarity. Since the importance of these landscapes is not currently recognized and designated the aim of this paper, containing the Blato example, on the island of Korčula, is to defi ne a procedure and a possibility of their protection and revitalization. This site is selected due to its natural, cultural and structural diversity, the revitalization of which one can realize, i.e. restore the landscape of an outstanding value. Apart from revitalization of the landscape and the landscape diversity, agriculture can manifest itself as something visually attractive what is positively refl ected in the potential of further tourism development on the island.

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

    Science.gov (United States)

    2012-06-10

    2006; (78) Reid et al. 1995; (79) Rice et al. 2010; (80) Jao et al. 2005; (81) Cruz et al. 2009; (82) Scholz et al. 2004b; (83) Chauvin et al. 2005...G239-25 (Forveille et al. 2004), and 2MASS J0619−5803 which is a companion (∼260 AU) to the young K2 star AB Pic ( Chauvin et al. 2005). The independent...al. 2010; Chauvin et al. 2005; Dupuy et al. 2008; Wahhaj et al. 2011). Figure 11 shows the near-IR absolute magnitude versus spectral type diagrams

  10. White dwarf planets

    Directory of Open Access Journals (Sweden)

    Bonsor Amy

    2013-04-01

    Full Text Available The recognition that planets may survive the late stages of stellar evolution, and the prospects for finding them around White Dwarfs, are growing. We discuss two aspects governing planetary survival through stellar evolution to the White Dwarf stage. First we discuss the case of a single planet, and its survival under the effects of stellar mass loss, radius expansion, and tidal orbital decay as the star evolves along the Asymptotic Giant Branch. We show that, for stars initially of 1 − 5 M⊙, any planets within about 1 − 5 AU will be engulfed, this distance depending on the stellar and planet masses and the planet's eccentricity. Planets engulfed by the star's envelope are unlikely to survive. Hence, planets surviving the Asymptotic Giant Branch phase will probably be found beyond ∼ 2 AU for a 1  M⊙ progenitor and ∼ 10 AU for a 5 M⊙ progenitor. We then discuss the evolution of two-planet systems around evolving stars. As stars lose mass, planet–planet interactions become stronger, and many systems stable on the Main Sequence become destabilised following evolution of the primary. The outcome of such instabilities is typically the ejection of one planet, with the survivor being left on an eccentric orbit. These eccentric planets could in turn be responsible for feeding planetesimals into the neighbourhood of White Dwarfs, causing observed pollution and circumstellar discs.

  11. Ascorbic acid-dependent gene expression in Streptococcus pneumoniae and the activator function of the transcriptional regulator UlaR2

    NARCIS (Netherlands)

    Afzal, Muhammad; Shafeeq, Sulman; Kuipers, Oscar P

    2015-01-01

    In this study, we have explored the impact of ascorbic acid on the transcriptome of Streptococcus pneumoniae D39. The expression of several genes and operons, including the ula operon (which has been previously shown to be involved in ascorbic acid utilization), the AdcR regulon (which has been

  12. Throwing Icebergs at White Dwarfs

    OpenAIRE

    Stephan, Alexander P.; Naoz, Smadar; Zuckerman, B.

    2017-01-01

    White dwarfs have atmospheres that are expected to consist nearly entirely of hydrogen and helium, since heavier elements will sink out of sight on short timescales. However, observations have revealed atmospheric pollution by heavier elements in about a quarter to a half of all white dwarfs. While most of the pollution can be accounted for with asteroidal or dwarf planetary material, recent observations indicate that larger planetary bodies, as well as icy and volatile material from Kuiper b...

  13. Understanding the Population of Distant Ultracool-Dwarfs from WISPS and 3d-HST

    Science.gov (United States)

    Ryan, Russell

    2013-10-01

    We are the proposing largest, most comprehensive archival campaign with HST to identify and characterize distant brown dwarfs to date. By exploiting the unprecedented sensitivity and excellent field-of-view of the WFC3/IR detector, we expect to find 110 M- and 30 L-dwarfs out to heliocentric distances of >1000 pc {for an L8-dwarf}, whereas current surveys are limited to 90% complete to J 24 and nearly 100% free of contaminating objects {such as giants, subdwarfs, or high-redshift quasars}. We have four main science goals for these ultracool dwarfs:{1} Identify ultracool dwarfs from water absorption;{2} Measure the vertical scale height as a function of spectral type;{3} Characterize the atmospheric properties of distant ultracool-dwarfs; and {4} Search for rare T/Y transition dwarfs by complete water/methane and enhanced ammonia absorption.We plan to mine 0.5 square degrees of archival grism data in G141 taken by the pure-parallel {WISPS} and the Legacy {3d-HST} surveys. Our approach represents the most efficient means of surveying these low luminosity objects at kiloparsec distances with robust spectral types.

  14. Brown recluse spider envenomation.

    Science.gov (United States)

    Furbee, R Brent; Kao, Louise W; Ibrahim, Danyal

    2006-03-01

    Brown recluse spider bite is a common diagnosis in almost every state in America. In fact, cases have been reported in areas where the spider has never been seen. A review of medical literature reveals that most current concepts regarding brown recluse spider envenomation are based on supposition. In this article, we attempt to review critically our present understanding of brown recluse bites with a focus on the published evidence.

  15. Brown Fat Cell Isolation

    OpenAIRE

    sprotocols

    2014-01-01

    Author: C.R. Kahn ### 1.) ISOLATION AND PRIMARY CULTURE OF BROWN FAT PREADIPOCYTES ### Rationale: To prepare primary brown preadipocytes for immortalization: useful for metabolic studies from knockout mice. This consists of the following five protocols. References: Fasshauer, M., J. Klein, K M. Kriauciunas, K. Ueki, M.Benito, and C.R. Kahn. 2001. Essential role of insulin substrate 1 in differentiation of brown adipocytes. *Mol Cell Biol* 21: 319-329. Fasshauer, M....

  16. Plasmodesmata of brown algae

    OpenAIRE

    Terauchi, Makoto; Nagasato, Chikako; Motomura, Taizo

    2014-01-01

    Plasmodesmata (PD) are intercellular connections in plants which play roles in various developmental processes. They are also found in brown algae, a group of eukaryotes possessing complex multicellularity, as well as green plants. Recently, we conducted an ultrastructural study of PD in several species of brown algae. PD in brown algae are commonly straight plasma membrane-lined channels with a diameter of 10?20?nm and they lack desmotubule in contrast to green plants. Moreover, branched PD ...

  17. Slowly Spinning Southern M Dwarfs

    Science.gov (United States)

    Newton, Elisabeth; Mondrik, Nicholas; Irwin, Jonathan; Charbonneau, David

    2018-01-01

    M dwarf stars are the most common type of star in the galaxy, but their ages are challenging to determine due to their trillion-year lifetimes on the main sequence. Consequently, the evolution of rotation and magnetism at field ages is difficult to investigate observationally. M dwarfs in the Solar Neighborhood provide a unique opportunity to make progress in this area due to the availability of parallaxes and the accessibility of spectroscopy. We have used new rotation period measurements and our compilation of H-alpha emission for nearby M dwarfs to explore two questions: 1) What is the longest rotation period an M dwarf can have? And 2) Do M dwarfs undergo an era of rapid angular momentum evolution? Here, we focus on the view from the Southern hemisphere, presenting approximately 200 new rotation periods for fully convective M dwarfs. Amongst the highest-quality datasets, we identify rotation periods in three-quarters of all stars; of these, half have rotation periods longer than 70 days. The longest rotation period we detect is 148 days, which is for a 0.15 solar-mass star. The lack of M dwarfs with intermediate rotation periods that we previously identified persists, supporting our hypothesis that M dwarfs rapidly spin down from 10-day to 100-day periods.ERN is supported by the National Science Foundation Astronomy & Astrophysics Postdoctoral Fellowship. We gratefully acknowledge support from the David and Lucille Packard Foundation, the National Science Foundation, and the John Templeton Foundation.

  18. Axion cooling of white dwarfs

    OpenAIRE

    Isern, J.; Catalan, S.; Garcia--Berro, E.; Salaris, M.; Torres, S.

    2013-01-01

    The evolution of white dwarfs is a simple gravothermal process. This process can be tested in two ways, through the luminosity function of these stars and through the secular variation of the period of pulsation of those stars that are variable. Here we show how the mass of the axion can be constrained using the white dwarf luminosity function.

  19. Astrophysics of white dwarf binaries

    NARCIS (Netherlands)

    Nelemans, G.A.

    2006-01-01

    White dwarf binaries are the most common compact binaries in the Universe and are especially important for low-frequency gravitational wave detectors such as LISA. There are a number of open questions about binary evolution and the Galactic population of white dwarf binaries that can be solved using

  20. Seeing Baby Dwarf Galaxies

    Science.gov (United States)

    2009-01-01

    [figure removed for brevity, see original site] [figure removed for brevity, see original site] [figure removed for brevity, see original site] Visible/DSS Click on image for larger version Ultraviolet/GALEX Click on image for larger version Poster Version Click on image for larger version The unique ultraviolet vision of NASA's Galaxy Evolution Explorer reveals, for the first time, dwarf galaxies forming out of nothing more than pristine gas likely leftover from the early universe. Dwarf galaxies are relatively small collections of stars that often orbit around larger galaxies like our Milky Way. The forming dwarf galaxies shine in the far ultraviolet spectrum, rendered as blue in the call-out on the right hand side of this image. Near ultraviolet light, also obtained by the Galaxy Evolution Explorer, is displayed in green, and visible light from the blue part of the spectrum here is represented by red. The clumps (in circles) are distinctively blue, indicating they are primarily detected in far ultraviolet light. The faint blue overlay traces the outline of the Leo Ring, a huge cloud of hydrogen and helium that orbits around two massive galaxies in the constellation Leo (left panel). The cloud is thought likely to be a primordial object, an ancient remnant of material that has remained relatively unchanged since the very earliest days of the universe. Identified about 25 years ago by radio waves, the ring cannot be seen in visible light. Only a portion of the Leo Ring has been imaged in the ultraviolet, but this section contains the telltale ultraviolet signature of recent massive star formation within this ring of pristine gas. Astronomers have previously only seen dwarf galaxies form out of gas that has already been cycled through a galaxy and enriched with metals elements heavier than helium produced as stars evolve. The visible data come from the Digitized Sky Survey of the Space Telescope Science Institute in Baltimore, Md. The Leo Ring visible image (left

  1. White dwarf dynamical interactions

    OpenAIRE

    Aznar Siguan, Gabriela

    2015-01-01

    Premi Extraordinari de Doctorat, promoció 2014-2015. Àmbit de Ciències Merging white dwarfs is a promising channel to trigger Type Ia supernovae, known as the double degenerate scenario. Supernovae are stellar explosions that radiate as much energy as any ordinary star is expected to emit over its entire life span, outshining briefly the whole hosting galaxy. They enrich the interstellar medium with higher mass elements and trigger the formation of new stars by the produced expanding shock...

  2. Father Brown, Selected sories

    NARCIS (Netherlands)

    Chesterton, G.K.

    2005-01-01

    Father Brown, a small, round Catholic priest with a remarkable understanding of the criminal mind, is one of literature's most unusual and endearing detectives, able to solve the strangest crimes in a most fascinating manner. This collection draws from all five Father Brown books, and within their

  3. Brown adipocyte function

    DEFF Research Database (Denmark)

    Winther, Sally

    . The first part of this thesis explores this by identifying and investigating two novel kinase regulators of brown adipocyte function. Study 1 demonstrates that spleen tyrosine kinase is a hitherto undescribed regulator of brown adipocyte differentiation and activation. Study 2 identifies glycogen synthase...... kinase 3 as a negative regulator of the canonical p38 mitogen-activated protein kinase signaling cascade. Thus both studies add novel regulatory layers to the growing understanding of brown adipocyte signal transduction. Activated BAT also exerts great influence on whole body glucose homeostasis......, of great interest for diabetes treatment. The second part of this thesis explores this by investigating glycolytic flux in activated brown adipocytes. Study 3 identifies hypoxia-inducible factor 1α as an important regulator of glycolytic gene expression in brown adipocytes. Study 4 establishes...

  4. Robust detection of quasi-periodic variability: a HAWK-I mini survey of late-T dwarfs

    Science.gov (United States)

    Littlefair, S. P.; Burningham, B.; Helling, Ch.

    2017-04-01

    We present HAWK-I J-band light curves of five late-type T dwarfs (T6.5-T7.5) with a typical duration of 4 h and investigate the evidence for quasi-periodic photometric variability on intra-night time-scales. Our photometry reaches precisions in the range 7-20 mmag, after removing instrumental systematics that correlate with sky background, seeing and airmass. Based upon a Lomb-Scargle periodogram analysis, the latest object in the sample - ULAS J2321 (T7.5) - appears to show quasi-periodic variability with a period of 1.64 h and an amplitude of 3 mmag. Given the low amplitude of variability and presence of systematics in our light curves, we discuss a Bayesian approach to robustly determine if quasi-periodic variability is present in a light curve affected by red noise. Using this approach, we conclude that the evidence for quasi-periodic variability in ULAS J2321 is not significant. As a result, we suggest that studies which identify quasi-periodic variables using the false alarm probability from a Lomb-Scargle periodogram are likely to overestimate the number of variable objects, even if field stars are used to set a higher false alarm probability threshold. Instead we argue that a hybrid approach combining a false alarm probability cut, followed by Bayesian model selection, is necessary for robust identification of quasi-periodic variability in light curves with red noise.

  5. Throwing Icebergs at White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-08-01

    Where do the metals come from that pollute the atmospheres of many white dwarfs? Close-in asteroids may not be the only culprits! A new study shows that distant planet-size and icy objects could share some of the blame.Pollution ProblemsArtists impression of rocky debris lying close around a white dwarf star. [NASA/ESA/STScI/G. Bacon]When a low- to intermediate-mass star reaches the end of its life, its outer layers are blown off, leaving behind its compact core. The strong gravity of this white dwarf causes elements heavier than hydrogen and helium to rapidly sink to its center in a process known as sedimentation, leaving an atmosphere that should be free of metallic elements.Therefore its perhaps surprising that roughly 2550% of all white dwarfs are observed to have atmospheric pollution by heavy elements. The short timescales for sedimentation suggest that these elements were added to the white dwarf recently but how did they get there?Bringing Ice InwardIn the generally accepted theory, pre-existing rocky bodies or an orbiting asteroid belt survive the stars evolution, later accreting onto the final white dwarf. But this scenario doesnt explain a few observations that suggest white dwarfs might be accreting larger planetary-size bodies and bodies with ices and volatile materials.Dynamical evolution of a Neptune-like planet (a) and a Kuiper belt analog object (b) in wide binary star systems. Both have large eccentricity excitations during the white dwarf phase. [Stephan et al. 2017]How might you get large or icy objects which would begin on very wide orbits close enough to a white dwarf to become disrupted and accrete? Led by Alexander Stephan, a team of scientists at UCLA now suggest that the key is for the white dwarf to be in a binary system.Influence of a CompanionIn the authors model, the white-dwarf progenitor is orbited by both a distant stellar companion (a common occurrence) and a number of large potential polluters, which could have masses between that

  6. Analisis On-Bottom Stability dan Local Buckling: Studi Kasus Pipa Bawah Laut dari Platform Ula Menuju Platform Uw

    Directory of Open Access Journals (Sweden)

    Clinton Sibuea

    2017-01-01

    Full Text Available Pipa bawah laut merupakan suatu teknologi transportasi yang digunakan untuk mengangkut produk hidrokarbon. Industri minyak dan gas telah membuktikan bahwa penggunakan pipa bawah laut merupakan cara yang paling ekonomis untuk memindahkan fluida dalam skala besar. Pada penelitian ini, dilakukan analisis on-bottom stability dan local buckling pada pipa bawah laut dari platform ULA menuju platform UW milik PT.PHE ONWJ. Analisis on-bottom stability bertujuan untuk mengetahui apakah pipa bawah laut stabil secara vertikal dan lateral di dasar laut pada saat terkena beban hidrodinamis. Analisis local buckling bertujuan untuk menentukan panjang maksimum free span yang diijinkan agar pipa tidak mengalami buckling. Besar gaya horizontal pada kondisi instalasi dan operasi masing-masing adalah 405 N/m dan 1119 N/m. Besar gaya vertikal pada kondisi instalasi dan operasi masing-masing adalah 138 N/m dan 1058 N/m. Besar gaya tahanan tanah pada kondisi instalasi dan operasi masing-masing adalah  111 N/m dan 121 N/m.  Hasil analisis absolute lateral static menunjukkan pipa bawah laut tidak stabil secara lateral pada kondisi instalasi dan operasi karena berat terendam aktual lebih kecil dari berat terendam minimum yang harus dipenuhi agar stabil. Hasil analisis generalized parameter menunjukkan pipa bawah laut tidak stabil secara lateral pada kondisi operasi, namun stabil secara lateral pada kondisi instalasi. Panjang free span pipa bawah laut maksimum yang diijinkan agar tidak terjadi local buckling adalah 50 m.

  7. Low-complexity DOA estimation from short data snapshots for ULA systems using the annihilating filter technique

    Science.gov (United States)

    Bellili, Faouzi; Amor, Souheib Ben; Affes, Sofiène; Ghrayeb, Ali

    2017-12-01

    This paper addresses the problem of DOA estimation using uniform linear array (ULA) antenna configurations. We propose a new low-cost method of multiple DOA estimation from very short data snapshots. The new estimator is based on the annihilating filter (AF) technique. It is non-data-aided (NDA) and does not impinge therefore on the whole throughput of the system. The noise components are assumed temporally and spatially white across the receiving antenna elements. The transmitted signals are also temporally and spatially white across the transmitting sources. The new method is compared in performance to the Cramér-Rao lower bound (CRLB), the root-MUSIC algorithm, the deterministic maximum likelihood estimator and another Bayesian method developed precisely for the single snapshot case. Simulations show that the new estimator performs well over a wide SNR range. Prominently, the main advantage of the new AF-based method is that it succeeds in accurately estimating the DOAs from short data snapshots and even from a single snapshot outperforming by far the state-of-the-art techniques both in DOA estimation accuracy and computational cost.

  8. Ultracool dwarf benchmarks with Gaia primaries

    Science.gov (United States)

    Marocco, F.; Pinfield, D. J.; Cook, N. J.; Zapatero Osorio, M. R.; Montes, D.; Caballero, J. A.; Gálvez-Ortiz, M. C.; Gromadzki, M.; Jones, H. R. A.; Kurtev, R.; Smart, R. L.; Zhang, Z.; Cabrera Lavers, A. L.; García Álvarez, D.; Qi, Z. X.; Rickard, M. J.; Dover, L.

    2017-10-01

    We explore the potential of Gaia for the field of benchmark ultracool/brown dwarf companions, and present the results of an initial search for metal-rich/metal-poor systems. A simulated population of resolved ultracool dwarf companions to Gaia primary stars is generated and assessed. Of the order of ˜24 000 companions should be identifiable outside of the Galactic plane (|b| > 10 deg) with large-scale ground- and space-based surveys including late M, L, T and Y types. Our simulated companion parameter space covers 0.02 ≤ M/M⊙ ≤ 0.1, 0.1 ≤ age/Gyr ≤ 14 and -2.5 ≤ [Fe/H] ≤ 0.5, with systems required to have a false alarm probability Gaia benchmarks. As a test of the veracity of our methodology and simulations, our initial search uses UKIRT Infrared Deep Sky Survey and Sloan Digital Sky Survey to select secondaries, with the parameters of primaries taken from Tycho-2, Radial Velocity Experiment, Large sky Area Multi-Object fibre Spectroscopic Telescope and Tycho-Gaia Astrometric Solution. We identify and follow up 13 new benchmarks. These include M8-L2 companions, with metallicity constraints ranging in quality, but robust in the range -0.39 ≤ [Fe/H] ≤ +0.36, and with projected physical separation in the range 0.6 Gaia offers a very high yield of benchmark systems, from which diverse subsamples may be able to calibrate a range of foundational ultracool/sub-stellar theory and observation.

  9. Satellite Dwarf Galaxies in a Hierarchical Universe: The Prevalence of Dwarf-Dwarf Major Mergers

    OpenAIRE

    Deason, Alis; Wetzel, Andrew; Garrison-Kimmel, Shea

    2014-01-01

    Mergers are a common phenomenon in hierarchical structure formation, especially for massive galaxies and clusters, but their importance for dwarf galaxies in the Local Group remains poorly understood. We investigate the frequency of major mergers between dwarf galaxies in the Local Group using the ELVIS suite of cosmological zoom-in dissipationless simulations of Milky Way- and M31-like host halos. We find that ~10% of satellite dwarf galaxies with M_star > 10^6 M_sun that are within the host...

  10. Study of Dwarf Novae Outbursts

    Science.gov (United States)

    Otulakowska-Hypka, Magdalena; Olech, Arkadiusz

    2015-06-01

    Based on all accessible data for the whole sample of dwarf novae, we performed an extensive study of all photometric features which are possible to measure during their outburst and superoutbursts. For all of them we looked for possible correlations. We confirmed a few of the known relations, questioned the existence of others, found new ones, as well as failed to find another presumed relation. In particular, in the context of white dwarfs, we present one of the most interesting correlations among them. Based on vast amount of up-to-date measurements, we were able to enhance the Stolz and Schoembs relation and make accurate estimates on the mass ratio and thus on masses of white dwarfs in such systems. We hope that results of this study will impact our knowledge on the physical phenomena which take place in dwarf novae and help to direct theoretical work to the areas where there is still a discrepancy between observations and theory.

  11. Singing and dancing white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Mukadam, Anjum S; Szkody, Paula [Department of Astronomy, University of Washington, Seattle, WA 98195 (United States); Gaensicke, Boris T [Department of Physics, University of Warwick, Coventry, CV4 7AL (United Kingdom); Nitta, Atsuko, E-mail: anjum@astro.washington.ed [Gemini Observatory, Hilo, HI 96720 (United States)

    2009-06-01

    Accreting white dwarfs have recently been shown to exhibit non-radial pulsations similar to their non-interacting counterparts. This allows us to probe the interior of the accreting white dwarf using seismology, and may be the only way to determine masses for non-eclipsing cataclysmic variables. Improving our understanding of accreting white dwarfs will have implications for models of supernovae Type Ia. Pulsating white dwarfs in cataclysmic variables are also useful in establishing the effects of accretion on pulsations. A search for nonradial pulsations among suitable candidates has led to the discovery of twelve such systems known to date. With the goal of establishing an instability strip (or strips) for these pulsating accretors, we acquired HST ultra-violet time-series spectroscopy of six pulsating white dwarfs in cataclysmic variables in 2007 and 2008. This approach enables us to measure the effective temperature of the white dwarf using the co-added spectrum, and to simultaneously characterize the pulsations. We also intended to constrain the pulsation mode identification by comparing the ultra-violet amplitudes to those from near-simultaneous ground-based photometry. Our preliminary results indicate a broad instability strip in the temperature range of 10500-15400 K.

  12. DISCOVERY OF THE Y1 DWARF WISE J064723.23–623235.5

    Energy Technology Data Exchange (ETDEWEB)

    Kirkpatrick, J. Davy; Gelino, Christopher R.; Beichman, Charles A.; Mace, Gregory N. [Infrared Processing and Analysis Center, MS 100-22, California Institute of Technology, Pasadena, CA 91125 (United States); Cushing, Michael C.; Schneider, Adam [Department of Physics and Astronomy, MS 111, University of Toledo, 2801 West Bancroft Street, Toledo, OH 43606-3328 (United States); Tinney, C. G. [School of Physics, University of New South Wales, Sydney, NSW 2052 (Australia); Faherty, Jacqueline K., E-mail: davy@ipac.caltech.edu [Department of Astronomy, University of Chile, Camino El Observatorio 1515, Casilla 36-D Santiago (Chile)

    2013-10-20

    We present the discovery of a very cold, very low mass, nearby brown dwarf using data from the NASA Wide-field Infrared Survey Explorer (WISE). The object, WISE J064723.23–623235.5, has a very red WISE color of W1–W2 > 3.77 mag and a very red Spitzer Space Telescope color of ch1–ch2 = 2.82 ± 0.09 mag. In J{sub MKO} –ch2 color (7.58 ± 0.27 mag) it is one of the two or three reddest brown dwarfs known. Our grism spectrum from the Hubble Space Telescope (HST) confirms it to be the seventeenth Y dwarf discovered, and its spectral type of Y1 ± 0.5 makes it one of the four latest-type Y dwarfs classified. Astrometric imaging from Spitzer and HST, combined with data from WISE, provides a preliminary parallax of π = 115 ± 12 mas (d = 8.7 ± 0.9 pc) and proper motion of μ = 387 ± 25 mas yr{sup –1} based on 2.5 yr of monitoring. The spectrum implies a blue J–H color, for which model atmosphere calculations suggest a relatively low surface gravity. The best fit to these models indicates an effective temperature of 350-400 K and a mass of ∼5-30 M{sub Jup}. Kinematic analysis hints that this object may belong to the Columba moving group, which would support an age of ∼30 Myr and thus an even lower mass of <2 M{sub Jup}, but verification would require a radial velocity measurement not currently possible for a J = 22.7 mag brown dwarf.

  13. Plasmodesmata of brown algae.

    Science.gov (United States)

    Terauchi, Makoto; Nagasato, Chikako; Motomura, Taizo

    2015-01-01

    Plasmodesmata (PD) are intercellular connections in plants which play roles in various developmental processes. They are also found in brown algae, a group of eukaryotes possessing complex multicellularity, as well as green plants. Recently, we conducted an ultrastructural study of PD in several species of brown algae. PD in brown algae are commonly straight plasma membrane-lined channels with a diameter of 10-20 nm and they lack desmotubule in contrast to green plants. Moreover, branched PD could not be observed in brown algae. In the brown alga, Dictyota dichotoma, PD are produced during cytokinesis through the formation of their precursor structures (pre-plasmodesmata, PPD). Clustering of PD in a structure termed "pit field" was recognized in several species having a complex multicellular thallus structure but not in those having uniseriate filamentous or multiseriate one. The pit fields might control cell-to-cell communication and contribute to the establishment of the complex multicellular thallus. In this review, we discuss fundamental morphological aspects of brown algal PD and present questions that remain open.

  14. Dwarf elliptical galaxies

    Science.gov (United States)

    Ferguson, Henry C.; Binggeli, Bruno

    1994-01-01

    Dwarf elliptical (dE) galaxies, with blue absolute magnitudes typically fainter than M(sub B) = -16, are the most numerous type of galaxy in the nearby universe. Tremendous advances have been made over the past several years in delineating the properties of both Local Group satellite dE's and the large dE populations of nearby clusters. We review some of these advances, with particular attention to how well currently availiable data can constrain (a) models for the formation of dE's, (b) the physical and evolutionary connections between different types of galaxies that overlap in the same portion of the mass-spectrum of galaxies, (c) the contribution of dE's to the galaxy luminosity functions in clusters and the field, (d) the star-forming histories of dE's and their possible contribution to faint galaxy counts, and (e) the clustering properties of dE's. In addressing these issues, we highlight the extent to which selection effects temper these constraints, and outline areas where new data would be particularly valuable.

  15. Retrieval of atmospheric properties of cloudy L dwarfs

    Science.gov (United States)

    Burningham, Ben; Marley, M. S.; Line, M. R.; Lupu, R.; Visscher, C.; Morley, C. V.; Saumon, D.; Freedman, R.

    2017-09-01

    We present the first results from applying the spectral inversion technique in the cloudy L dwarf regime. Our new framework provides a flexible approach to modelling cloud opacity which can be built incrementally as the data require and improves upon previous retrieval experiments in the brown dwarf regime by allowing for scattering in two-stream radiative transfer. Our first application of the tool to two mid-L dwarfs is able to reproduce their near-infrared spectra far more closely than grid models. Our retrieved thermal, chemical and cloud profiles allow us to estimate T_eff = 1796^{+23}_{-25} K and log g = 5.21^{+0.05}_{-0.08} for 2MASS J05002100+0330501, and for 2MASSW J2224438-015852 we find T_eff = 1723^{+18}_{-19} K and log g = 5.31^{+0.04}_{-0.08}, in close agreement with previous empirical estimates. Our best model for both objects includes an optically thick cloud deck which passes τcloud ≥ 1 (looking down) at a pressure of around 5 bar. The temperature at this pressure is too high for silicate species to condense, and we argue that corundum and/or iron clouds are responsible for this cloud opacity. Our retrieved profiles are cooler at depth and warmer at altitude than the forward grid models that we compare, and we argue that some form of heating mechanism may be at work in the upper atmospheres of these L dwarfs. We also identify anomalously high CO abundance in both targets, which does not correlate with the warmth of our upper atmospheres or our choice of cloud model, and find similarly anomalous alkali abundance for one of our targets. These anomalies may reflect unrecognized shortcomings in our retrieval model or inaccuracies in our gas phase opacities.

  16. Star Formation Histories of Nearby Dwarf Galaxies

    OpenAIRE

    Grebel, Eva K.

    2000-01-01

    Properties of nearby dwarf galaxies are briefly discussed. Dwarf galaxies vary widely in their star formation histories, the ages of their subpopulations, and in their enrichment history. Furthermore, many dwarf galaxies show evidence for spatial variations in their star formation history; often in the form of very extended old populations and radial gradients in age and metallicity. Determining factors in dwarf galaxy evolution appear to be both galaxy mass and environment. We may be observi...

  17. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    García-Aspeitia, Miguel A., E-mail: aspeitia@fisica.uaz.edu.mx [Consejo Nacional de Ciencia y Tecnología, Av, Insurgentes Sur 1582, Colonia Crédito Constructor, Del. Benito Juárez, C.P. 03940, Mexico, D.F. (Mexico); Unidad Académica de Física, Universidad Autónoma de Zacatecas, Calzada Solidaridad esquina con Paseo a la Bufa S/N, C.P. 98060, Zacatecas (Mexico)

    2015-11-06

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane–Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of <λ>≳84.818 MeV{sup 4}, with a standard deviation σ≃82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others.

  18. Branes constrictions with White Dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Garcia-Aspeitia, Miguel A. [Consejo Nacional de Ciencia y Tecnologia, Mexico (Mexico); Unidad Academica de Fisica, Universidad Autonoma de Zacatecas (Mexico)

    2015-11-15

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane-Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of left angle λ right angle >or similar 84.818 MeV{sup 4}, with a standard deviation σ ≅ 82.021 MeV{sup 4}, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others. (orig.)

  19. Branes constrictions with White Dwarfs

    Science.gov (United States)

    García-Aspeitia, Miguel A.

    2015-11-01

    We consider here a robust study of stellar dynamics for white dwarf stars with polytropic matter in the weak-field approximation using the Lane-Emden equation from the brane-world scenario. We also derive an analytical solution to the nonlocal energy density and show the behavior and sensitivity of these stars to the presence of extra dimensions. Similarly, we analyze stability and compactness, in order to show whether it is possible to agree with the conventional wisdom of white dwarfs dynamics. Our results predict an average value of the brane tension of < λ rangle ≳ 84.818MeV^4, with a standard deviation σ ˜eq 82.021MeV^4, which comes from a sample of dwarf stars, being weaker than other astrophysical observations but remaining higher than cosmological results provided by nucleosynthesis among others.

  20. The Dusty Accretion of Polluted White Dwarfs

    Science.gov (United States)

    Bonsor, A.; Farihi, J.; Wyatt, M. C.; van Lieshout, R.

    2017-03-01

    Infrared observations of polluted white dwarfs provide key insights into the accretion processes in action. The standard model for the observed infrared excesses is a flat, opaque, dust disc. The infrared observations are inconsistent with the presence of such a disc around all polluted white dwarfs. We discuss potential explanations for the absence of an infrared excess for many polluted white dwarfs.

  1. A Statistical Survey of Peculiar L and T Dwarfs in SDSS, 2MASS, and WISE

    Science.gov (United States)

    Kellogg, Kendra; Metchev, Stanimir; Miles-Páez, Paulo A.; Tannock, Megan E.

    2017-09-01

    We present the final results from a targeted search for brown dwarfs with unusual near-infrared colors. From a positional cross-match of the Sloan Digital Sky Survey (SDSS), 2-Micron All-Sky Survey (2MASS), and Wide-Field Infrared Survey Explorer (WISE) catalogs, we have identified 144 candidate peculiar L and T dwarfs. Spectroscopy confirms that 20 of the objects are peculiar or are candidate binaries. Of the 420 objects in our full sample 9 are young (≲ 200 {Myr}; 2.1%) and another 8 (1.9%) are unusually red, with no signatures of youth. With a spectroscopic J-{K}s color of 2.58 ± 0.11 mag, one of the new objects, the L6 dwarf 2MASS J03530419+0418193, is among the reddest field dwarfs currently known and is one of the reddest objects with no signatures of youth known to date. We have also discovered another potentially very-low-gravity object, the L1 dwarf 2MASS J00133470+1109403, and independently identified the young L7 dwarf 2MASS J00440332+0228112, which was first reported by Schneider and collaborators. Our results confirm that signatures of low gravity are no longer discernible in low to moderate resolution spectra of objects older than ˜200 Myr. The 1.9% of unusually red L dwarfs that do not show other signatures of youth could be slightly older, up to ˜400 Myr. In this case a red J-{K}s color may be more diagnostic of moderate youth than individual spectral features. However, its is also possible that these objects are relatively metal-rich, and thus have enhanced atmospheric dust content.

  2. Tune Your Brown Clustering, Please

    DEFF Research Database (Denmark)

    Derczynski, Leon; Chester, Sean; Bøgh, Kenneth Sejdenfaden

    2015-01-01

    Brown clustering, an unsupervised hierarchical clustering technique based on ngram mutual information, has proven useful in many NLP applications. However, most uses of Brown clustering employ the same default configuration; the appropriateness of this configuration has gone predominantly...

  3. VAMPIRES IN DALMATIA: THE EXAMPLE OF THE VILLAGE OF ŽRNOVO ON THE ISLAND OF KORČULA IN THE EIGHTEENTH CENTURY

    OpenAIRE

    Čoralić, Lovorka; Dugac, Željko; Sardelić, Sani

    2014-01-01

    The principal area of interest of this essay is the analysis of a document from the State Archive of Venice (the archival series Capi del Consiglio dei Dieci: Lettere di Rettori e di altre cariche) connected to an episode from 1748, when the inhabitants of the village of Žrnovo on the island of Korčula in Croatia (Dalmatia) opened several tombs in the local cemetery, because they feared the malicious activity of vampires. This essay tries to discuss the social circumstances of this event and ...

  4. Dwarfs and Giants: Massive Stars in Little Dwarf Galaxies

    Science.gov (United States)

    Andrews, Jennifer

    2017-08-01

    Dwarf galaxies are sensitive laboratories for testing theories of star formation and for investigating possible variations of the stellar Initial Mass Function (IMF). Establishing whether the IMF, in particular the upper end of the IMF (uIMF), is invariant or dependent upon the conditions of star formation is key for interpreting the vast majority of observations on galaxy evolution, and for understanding cosmic reionization. Low-metallicity dwarf galaxies are fairly isolated systems that are ideal locales to test the uIMF. We propose to obtain STIS UV/optical spectroscopy of 8 H-alpha bright stellar clusters in 4 dwarf galaxies within 3 Mpc to accurately determine their ages, masses, extinction, metallicity, and stellar content. We will use state of the art stellar synthesis models that include massive star specific evolutionary tracks, massive star rotation, and stochasticity to test whether dwarf galaxies really do have a top-light IMF. The success of this project relies on the spectroscopic UV capability of HST/STIS to isolate young compact star clusters and break the degeneracies between reddening and age.

  5. Natural Inhibitors of Maillard Browning

    Science.gov (United States)

    2013-12-01

    incorporated into pre-selected candidate ration components for evaluation via storage, sensory and chemical analysis. The concentration of inhibitor was...inhibiting Maillard browning, also known as non-enzymatic browning, a complex reaction which can lead to darkening of color, off- odors , off-flavors...nutritional intake, and decrease waste due to non-consumption of sensory degraded ration components. 1.1 Maillard Browning Maillard browning, also

  6. Fucoidans from brown seaweeds

    DEFF Research Database (Denmark)

    Ale, Marcel Tutor; Meyer, Anne S.

    2013-01-01

    structural details of fucoidans. Mild extraction techniques coupled with the use of new tools such as enzymes can provide the much needed knowledge about structural characteristics of different fucoidan molecules and thus pave the way for a better understanding of the structural chemistry and bioactivities......-proliferative effects on cancer cells. Recent work has revealed distinct structural features of fucoidans obtained from different brown seaweed sources. Fucoidans are classically obtained from brown seaweeds by multi-step, hot acid extraction, but the structural and compositional traits, and possibly the bioactivity......, of the fucoidan polysaccharides are significantly influenced by the extraction parameters. This review discusses the structural features of fucoidans, the significance of different extraction technologies, and reviews enzymatic degradation of fucoidans and the use of fucoidan-modifying enzymes for elucidating...

  7. Formation of dwarf ellipticals and dwarf irregular galaxies by interaction of giant galaxies under environmental influence

    OpenAIRE

    Chattopadhyay, Tanuka; Debsarma, Suma; Karmakar, Pradip; Davoust, Emmanuel

    2014-01-01

    A model is proposed for the formation of gas-rich dwarf irregular galaxies and gas-poor, rotating dwarf elliptical galaxies following the interaction between two giant galaxies as a function of space density. The formation of dwarf galaxies is considered to depend on a random variable, the tidal index theta, an environmental parameter defined by Karachentsev et al. (2004), such that for theta less than zero, the formation of dwarf irregular galaxy is assured whereas for theta greater than zer...

  8. AGN feedback in dwarf galaxies?

    Science.gov (United States)

    Dashyan, Gohar; Silk, Joseph; Mamon, Gary A.; Dubois, Yohan; Hartwig, Tilman

    2018-02-01

    Dwarf galaxy anomalies, such as their abundance and cusp-core problems, remain a prime challenge in our understanding of galaxy formation. The inclusion of baryonic physics could potentially solve these issues, but the efficiency of stellar feedback is still controversial. We analytically explore the possibility of feedback from active galactic nuclei (AGNs) in dwarf galaxies and compare AGN and supernova (SN) feedback. We assume the presence of an intermediate-mass black hole within low-mass galaxies and standard scaling relations between the relevant physical quantities. We model the propagation and properties of the outflow and explore the critical condition for global gas ejection. Performing the same calculation for SNe, we compare the ability of AGNs and SNe to drive gas out of galaxies. We find that a critical halo mass exists below which AGN feedback can remove gas from the host halo and that the critical halo mass for an AGN is greater than the equivalent for SNe in a significant part of the parameter space, suggesting that an AGN could provide an alternative and more successful source of negative feedback than SNe, even in the most massive dwarf galaxies.

  9. Probing the Long Timescale Evolution of Magnetic Activity of Ultracool Dwarfs

    Science.gov (United States)

    Cid, Aurora; Schmidt, Sarah J.; Rice, Emily; Cruz, Kelle; Ventura, Jean-Paul

    2018-01-01

    The chromospheric variability, as measured by H-alpha emission, of ultracool dwarfs (M7-L3) is still not completely understood. Objects of these spectral types encompass the transition between stars and brown dwarfs. We want to compare these objects to the Sun and Jupiter to understand the dynamo causing magnetic activity. Using spectra from the Sloan Digital Sky Survey (SDSS), we measure equivalent widths of the H-alpha emission lines of ultracool dwarfs over multi-year timescales. More specifically, we are utilizing spectra from Data Release 7, composed of data from 2000-2008, and the Few Epoch Spectroscopy (FES) component of the Time Domain Spectroscopic Survey (TDSS), which is composed of data from 2014-2018. By the end of this project we will have 2-3 spectra for about 1000 objects. We will obtain H-alpha equivalent width measurements of these objects over time spans of 6-18 years. By studying the chromospheres of ultracool dwarfs on these timescales, we can make comparisons to the solar magnetic cycle and try to understand the process causing their H-alpha variability. Additionally, we can investigate any relationship between variability and stellar age by combining our measurements with age tracers like galactic height and UVW kinematics. We will present preliminary results of this work.

  10. Physical Properties of T Dwarfs Inferred from High-Resolution Near-Infrared Spectra

    Science.gov (United States)

    Rice, Emily L.; Barman, T. S.; McLean, I. S.; Kirkpatrick, J. D.

    2010-01-01

    T dwarfs are ideal laboratories for understanding cool, complex atmospheres and calibrating low-mass evolutionary models in preparation for spectral studies of exoplanetary atmospheres. We present the expanded sample of T dwarfs from the NIRSPEC Brown Dwarf Spectroscopic Survey (BDSS). High-resolution near-infrared spectra from the cross-dispersed echelle spectrometer NIRSPEC on Keck II provide an unequaled combination of resolving power and wavelength coverage for detailed study of these intrinsically faint objects. The sample of 14 objects covers spectral types from T0 to T7.5, including two unresolved binaries and two peculiar objects. Physical properties of the T dwarfs are inferred from comparison of the observed spectra with synthetic spectra from PHOENIX "cond" model atmospheres, in which dust opacity is removed. We estimate effective temperature, surface gravity, radial and projected rotational velocity for the targets and compare to previously derived quantities. Furthermore we identify successes and deficiencies in the synthetic spectra, particularly in the reproduction of T0-T4 spectra.

  11. Transit detection limits for sub-stellar and terrestrial companions to white dwarfs

    Science.gov (United States)

    Faedi, F.; West, R.; Burleigh, M. R.; Goad, M. R.; Hebb, L.

    2009-06-01

    The SuperWASP project is a ground-based ultra wide angle search for extra-solar planetary transits that has successfully detected 15 previously unknown planets in the last two years. We have used SuperWASP photometric data to investigate the transit characteristics of and detection limits for brown dwarfs, gas giants and terrestrial companions in orbit around white dwarfs. The relatively small size of a white dwarf host star (approximately 1 Earth radius), implies that any sub-stellar or gas giant companion will completely eclipse it, while terrestrial bodies smaller than the Moon will produce relatively large (> 1%) transits, detectable in good S/N light-curves. We performed extensive simulations using SuperWASP photometric data and we found that for Gaussian random noise we are sensitive to companions as small as the Moon. Our sensitivity drops in the presence of co-variant noise structure, nevertheless Earth-size bodies remain readily detectable in relatively low S/N data. We searched for eclipses and transit signals in a sample of 174 WASP targets, resulting from a cross-correlation of the McCook & Sion catalogue and the SuperWASP data archive. This study found no evidence for sub-stellar or planetary companions in close orbits around our sample of white dwarfs.

  12. Calibrating Detailed Chemical Analysis of M dwarfs

    Science.gov (United States)

    Veyette, Mark; Muirhead, Philip Steven; Mann, Andrew; Brewer, John; Allard, France; Homeier, Derek

    2018-01-01

    The ability to perform detailed chemical analysis of Sun-like F-, G-, and K-type stars is a powerful tool with many applications including studying the chemical evolution of the Galaxy, assessing membership in stellar kinematic groups, and constraining planet formation theories. Unfortunately, complications in modeling cooler stellar atmospheres has hindered similar analysis of M-dwarf stars. Large surveys of FGK abundances play an important role in developing methods to measure the compositions of M dwarfs by providing benchmark FGK stars that have widely-separated M dwarf companions. These systems allow us to empirically calibrate metallicity-sensitive features in M dwarf spectra. However, current methods to measure metallicity in M dwarfs from moderate-resolution spectra are limited to measuring overall metallicity and largely rely on astrophysical abundance correlations in stellar populations. In this talk, I will discuss how large, homogeneous catalogs of precise FGK abundances are crucial to advancing chemical analysis of M dwarfs beyond overall metallicity to direct measurements of individual elemental abundances. I will present a new method to analyze high-resolution, NIR spectra of M dwarfs that employs an empirical calibration of synthetic M dwarf spectra to infer effective temperature, Fe abundance, and Ti abundance. This work is a step toward detailed chemical analysis of M dwarfs at a similar precision achieved for FGK stars.

  13. White dwarf cooling sequences and cosmochronology

    Science.gov (United States)

    Isern, J.; Artigas, A.; García-Berro, E.

    2013-03-01

    The evolution of white dwarfs is a simple gravothermal process. This means that their luminosity function, i.e. the number of white dwarfs per unit bolometric magnitude and unit volume as a function of bolometric magnitude, is a monotonically increasing function that decreases abruptly as a consequence of the finite age of the Galaxy. The precision and the accuracy of the white dwarf luminosity functions obtained with the recent large surveys together with the improved quality of the theoretical models of evolution of white dwarfs allow to feed the hope that in a near future it will be possible to reconstruct the history of the different Galactic populations.

  14. [Brown recluse bite].

    Science.gov (United States)

    Nehemya, Moshe

    2008-01-01

    Spider bites are not uncommon in our warm climate. The most prevalent species of venomous spiders in Israel are the brown recluse and the black widow. Although the black widow is more notorious than the recluse, for every bite by a black widow there are hundreds of recluse bites reported. Despite the numerous bites, there is little awareness amongst physicians with regard to the clinical signs of recluse bites, and very often the wrong diagnosis is made, resulting in complex and unnecessary treatments. The basis of this error stems from the numerous clinical diagnoses which closely imitate a recluse bite, the relative scarceness of documented recluse bites and the fact that in most cases the spider is not witnessed by the victim. The following article describes three cases of children admitted to our department, presenting with high fever, a necrotic lesion and an extensive maculopapular rash. The children were eventually diagnosed with brown recluse bites. Furthermore, the article summarizes the literature regarding the clinical signs of recluse bites, possible complications and treatment options. The objective of this review is to increase awareness towards recluse bites, thereby preventing misdiagnoses and unnecessary treatments.

  15. [Gene analysis of Chinese barley dwarf germplasm resources. I. Inheritance and allelism test of the dwarf genes] [In Process Citation

    Science.gov (United States)

    Zhang

    1999-01-01

    The plant height inheritance of 24 Chinese barley dwarf germplasms and the allelic relationships between the dwarf genes in them and the known dwarf genes uz, sdw, br and denso were studied. It was found that most Chinese barley dwarfs were controlled by 1 pair, a few by 2 pairs of recessive genes, only one by 1 pair recessive and 1 pair incomplete dominant genes. Allele frequence at the known dwarf gene uz locus was very high in Chinese barley dwarfs. Most monogenic and 2 digenic barley dwarfs had allelic relationships with uz. A monogenic barley dwarf 11012.2 from India and a digenic dwarf Yan 66 were found allelic to the known dwarf gene sdw. But no dwarfs had allelic relationship with the known dwarf genes br and denso. Monogenic dwarf mutants 91G318, 91D27 and 93-597 carried 1 pair of new recessive dwarf genes respectively. Digenic dwarf mutant 1974E possessed 1 pair of new incomplete dominant dwarf genes. Besides, 4 pairs of new recessive dwarf genes were indentified in 6 Tibetan barley dwarfs.

  16. What fraction of white dwarfs are members of binary systems?

    Science.gov (United States)

    Holberg, J. B.

    2009-06-01

    White dwarfs were originally discovered as the subordinate faint companions of bright nearby stars (i.e. Sirius B and 40 Eri B). Several general categories of binary systems involving white dwarfs are recognized: Sirius-like systems, where the white dwarf may be difficult to detect, binary systems containing white dwarfs and low mass stars, where the white dwarf is often readily discerned; and double degenerate systems. Different modes of white dwarf discovery influence our perception of both the overall binary fraction and the nature of these systems; proper motion surveys emphasize resolved systems, while photometric surveys emphasize unresolved systems containing relatively hot white dwarfs. Recent studies of the local white dwarf population offer some hope of achieving realistic estimates of the relative number of binary systems containing white dwarfs. A sample of 132 white dwarfs within 20 pc indicates that an individual white dwarf has a probability of 32 ± 8% of occurring within a binary or multiple star system.

  17. SIM's Search for Planets Orbiting White Dwarfs

    Science.gov (United States)

    Subasavage, John P., Jr.

    2009-01-01

    Once launched, The Space Interferometry Mission (SIM) will be the most precise astrometric instrument ever developed. These capabilities are vital to exoplanetary studies, in particular, for low-mass, Earthlike planets. I propose to use SIM to observe a sample ( 25-50) of nearby white dwarfs in hopes of detecting planetary companions with masses in the 10 Earth mass range on average. Because of the nature of white dwarfs' spectral signatures (a few broad, if any, absorption lines), current radial velocity planet hunting techniques are not viable. Astrometry is currently the only technique capable of detecting low mass planets around white dwarfs and SIM would be the best suited astrometric instrument to do so. Planetary detections around white dwarfs would better enable us to probe planetary formation theory as well as planetary evolution theory in conjunction with stellar evolution. Because astrometric signatures are inversely related to distance, the closer the system, the larger the signature (all else being equal). Because most stars will eventually end their lives as white dwarfs, these objects are plentiful and on average, closer to the Sun than more rare objects. Thus, a number of white dwarfs are close enough to the Sun to permit low mass planetary signature detections. Given that white dwarfs are the remnants of main-sequence dwarfs with spectral classes from B to K (thus far), we could better understand planetary formation over a broader range of objects than those currently investigated using radial velocity techniques (F, G, and K stars primarily).

  18. Dwarf mistletoes: Biology, pathology, and systematics

    Science.gov (United States)

    Frank G. Hawksworth; Delbert Wiens

    1996-01-01

    Arceuthobium (dwarf mistletoes), a well defined but morphologically reduced genus of the family Viscaceae, is parasitic on Pinaceae in the Old and New Worlds and on Cupressaceae in the Old World. Although conifer forests in many parts of the Northern Hemisphere are infested with dwarf mistletoes, those most commonly infested are in western North...

  19. Do dwarf chameleons ( Bradypodion ) show developmental plasticity?

    African Journals Online (AJOL)

    The phenomenon of phenotype–genotype uncoupling (plasticity) causes problems in species delineations, and has been suggested as a cause underlying a mismatch between morphology and genetics between the Natal Midlands dwarf chameleon (Bradypodion thamnobates) and the KwaZulu dwarf chameleon ...

  20. Stars at Low Metallicity in Dwarf Galaxies

    NARCIS (Netherlands)

    Tolstoy, Eline; Battaglia, Giuseppina; Cole, Andrew; Hunt, LK; Madden, S; Schneider, R

    2008-01-01

    Dwarf galaxies offer an opportunity to understand the properties of low metallicity star formation both today and at the earliest times at the, epoch of the formation of the first stars. Here we concentrate on two galaxies in the Local Group: the dwarf irregular galaxy Leo A, which has been the

  1. Metals and ionizing photons from dwarf galaxies

    NARCIS (Netherlands)

    Salvadori, S.; Tolstoy, E.; Ferrara, A.; Zaroubi, S.

    We estimate the potential contribution of M <10(9)M(circle dot) dwarf galaxies to the reionization and early metal enrichment of the Milky Way environment, or circum-Galactic medium. Our approach is to use the observed properties of ancient stars ()under tilde>12 Gyr old) measured in nearby dwarf

  2. Kinematically Decoupled Cores in Dwarf (Elliptical) Galaxies

    NARCIS (Netherlands)

    Toloba, E.; Peletier, R. F.; Guhathakurta, P.; van de Ven, G.; Boissier, S.; Boselli, A.; Brok, M. d.; Falcón-Barroso, J.; Hensler, G.; Janz, J.; Laurikainen, E.; Lisker, T.; Paudel, S.; Ryś, A.; Salo, H.

    An overview is given of what we know about the frequency of kinematically decoupled cores in dwarf elliptical galaxies. New observations show that kinematically decoupled cores happen just as often in dwarf elliptical as in ordinary early-type galaxies. This has important consequences for the

  3. Double White Dwarf Merger Rates

    Science.gov (United States)

    Toonen, Silvia; Nelemans, Gijs; Portegies Zwart, Simon

    2013-01-01

    Type Ia supernovae (SNe Ia) are very successfully used as standard candles on cosmological distance scales, but so far the nature of the progenitor(s) is unclear. A possible scenario for SNe Ia are merging carbon/oxygen white dwarfs with a combined mass exceeding the Chandrasekhar mass. We determine the theoretical rates and delay time distribution of these mergers for two different common envelope prescriptions and metallicities. The shape of the delay time distributions is rather insensitive to the assumptions. The normalization is a factor ~3-13 too low compared to observations.

  4. White Dwarfs Cosmological and Galactic Probes

    CERN Document Server

    Sion, Edward M; Vennes, Stéphane

    2005-01-01

    The emphasis on white dwarf stars and cosmology arises from the most recent advances in cosmological and galactic structure research in which white dwarf stars are playing a very prominent role. Examples are Type Ia supernovae (i.e. white dwarf supernovae), the origin and evolution of the universe, the age of the galactic disk, cosmochronology using white dwarfs in globular clusters and galactic clusters, and the physics of accretion onto compact (very dense) stars. As an assisting guide to the reader, we have included, by invitation, comprehensive review articles in each of the four major areas of the book, white dwarf supernovae, cosmology, accretion physics and galactic structure. The reviews include introductory material that they build upon. The book is suitable and most useful to advanced undergraduates, graduate students and scientific professionals (e.g. astronomers, astrophysicists, cosmologists, physicists).

  5. PREFACE: 16th European White Dwarfs Workshop

    Science.gov (United States)

    Garcia-Berro, Enrique; Hernanz, Margarita; Isern, Jordi; Torres, Santiago

    2009-07-01

    The 16th European Workshop on White Dwarfs was held in Barcelona, Spain, from 30 June to 4 July 2008 at the premises of the UPC. Almost 120 participants from Europe (France, Germany, United Kingdom, Italy, and several others), America (USA, Canada, Argentina, Brazil, and Chile), and other continents (Australia, South Africa, . . . ) attended the workshop. Among these participants were the most relevant specialists in the field. The topics covered by the conference were: White dwarf structure and evolution Progenitors and Planetary Nebulae White dwarfs in binaries: cataclysmic variables, double degenerates and other binaries White dwarfs, dust disks and planetary systems Atmospheres, chemical composition, magnetic fields Variable white dwarfs White dwarfs in stellar clusters and the halo White Dwarfs as SNIa progenitors The programme included 54 talks, and 45 posters. The oral presentations were distributed into the following sessions: Luminosity function, mass function and populations White dwarf structure and evolution White dwarf ages White dwarf catalogs and surveys Central stars of planetary nebulae Supernovae progenitors White dwarfs in novae and CVs Physical processes in white dwarfs and magnetic white dwarfs Disks, dust and planets around white dwarfs Pulsating white dwarfs Additionally we had a special open session about Spitzer and white dwarfs. The Proceedings of the 16th European Workshop on White Dwarfs are representative of the current state-of-the-art of the research field and include new and exciting results. We acknowledge the very positive attitude of the attendants to the workshop, which stimulated very fruitful discussions that took place in all the sessions and after the official schedule. Also, the meeting allowed new collaborations tp start that will undoubtedly result in significant advances in the research field. We also acknowledge the willingness of the participants to deliver their contributions before the final deadline. We sincerely

  6. Angular Momentum of Dwarf Galaxies

    Science.gov (United States)

    Butler, Kirsty M.; Obreschkow, Danail; Oh, Se-Heon

    2017-01-01

    We present measurements of baryonic mass {M}{{b}} and specific angular momentum (sAM) {j}{{b}} in 14 rotating dwarf Irregular (dIrr) galaxies from the LITTLE THINGS sample. These measurements, based on 21 cm kinematic data from the Very Large Array and stellar mass maps from the Spitzer Space Telescope, extend previous AM measurements by more than two orders of magnitude in {M}{{b}}. The dwarf galaxies show systematically higher {j}{{b}} values than expected from the {j}{{b}}\\propto {M}{{b}}2/3 scaling of spiral galaxies, representative of a scale-free galaxy formation scenario. This offset can be explained by decreasing baryon mass fractions {f}{{M}}={M}{{b}}/{M}{dyn} (where {M}{dyn} is the dynamical mass) with decreasing {M}{{b}} (for {M}{{b}}< {10}11 {M}⊙ ). We find that the sAM of neutral atomic hydrogen (H I) alone is about 2.5 times higher than that of the stars. The M-j relation of H I is significantly steeper than that of the stars, as a direct consequence of the systematic variation of the H I fraction with {M}{{b}}.

  7. A SEARCH FOR L/T TRANSITION DWARFS WITH Pan-STARRS1 AND WISE: DISCOVERY OF SEVEN NEARBY OBJECTS INCLUDING TWO CANDIDATE SPECTROSCOPIC VARIABLES

    Energy Technology Data Exchange (ETDEWEB)

    Best, William M. J.; Liu, Michael C.; Magnier, Eugene A.; Aller, Kimberly M.; Burgett, W. S.; Chambers, K. C.; Hodapp, K. W.; Kaiser, N.; Kudritzki, R.-P.; Morgan, J. S.; Tonry, J. L.; Wainscoat, R. J. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Deacon, Niall R. [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Dupuy, Trent J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Redstone, Joshua [Facebook, 335 Madison Ave, New York, NY 10017-4677 (United States); Price, P. A., E-mail: wbest@ifa.hawaii.edu [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States)

    2013-11-10

    We present initial results from a wide-field (30,000 deg{sup 2}) search for L/T transition brown dwarfs within 25 pc using the Pan-STARRS1 and Wide-field Infrared Survey Explorer (WISE) surveys. Previous large-area searches have been incomplete for L/T transition dwarfs, because these objects are faint in optical bands and have near-infrared (near-IR) colors that are difficult to distinguish from background stars. To overcome these obstacles, we have cross-matched the Pan-STARRS1 (optical) and WISE (mid-IR) catalogs to produce a unique multi-wavelength database for finding ultracool dwarfs. As part of our initial discoveries, we have identified seven brown dwarfs in the L/T transition within 9-15 pc of the Sun. The L9.5 dwarf PSO J140.2308+45.6487 and the T1.5 dwarf PSO J307.6784+07.8263 (both independently discovered by Mace et al.) show possible spectroscopic variability at the Y and J bands. Two more objects in our sample show evidence of photometric J-band variability, and two others are candidate unresolved binaries based on their spectra. We expect our full search to yield a well-defined, volume-limited sample of L/T transition dwarfs that will include many new targets for study of this complex regime. PSO J307.6784+07.8263 in particular may be an excellent candidate for in-depth study of variability, given its brightness (J = 14.2 mag) and proximity (11 pc)

  8. Consideraciones económicas sobre el oppidum de La Ulaña (Humada, Burgos: la explotación ganadera

    Directory of Open Access Journals (Sweden)

    Ana Belén MARÍN ARROYO

    2009-08-01

    Full Text Available RESUMEN: El oppidum de La Ulaña, que tiene una extensión de 285 ha, es el mayor de los asentamientos de la Península Ibérica durante la Segunda Edad del Hierro. Los trabajos arqueológicos han puesto en evidencia un sistema defensivo que combina elementos naturales, como un gran foso de 301 ha, que rodea el yacimiento y que tiene una serie de muros que lo compartimentaban, limitando la circulación y el acceso a los recursos hídricos, y estructuras antrópicas, como una muralla en su lado Norte, el más accesible, y otra que corta el asentamiento en dos partes desiguales. Una serie de caminos entraban en él a través de portillas naturales, dejando expuestos a los visitantes frente a los pobladores. Las viviendas excavadas y los materiales exhumados lo relacionan, fundamentalmente, con la Meseta Norte y el Valle del Ebro. Asimismo, los datos arqueológicos indican un abandono, no necesariamente voluntario, en la segunda mitad del siglo I a. e. El estudio de los restos de macromamíferos encontrados en él muestra una economía basada, principalmente, en la explotación de ganado vacuno, seguida del aprovechamiento de ovicaprinos y suidos. Destaca, a pesar de la escasez de restos hallados, el consumo alimenticio de caballo. Las evidencias de caza han resultado mínimas, sólo representadas por jabalí. Esta información se contextualiza con el resto de los datos arqueológicos que, hasta la fecha, ha proporcionado el oppidum, con objeto de establecer un panorama de las actividades económicas realizadas en él durante la Segunda Edad del Hierro, haciéndose hincapié en los problemas de conservación de los materiales alterados por diversos procesos post-depósito.ABSTRACT: La Ulaña oppidum occupies an area of 285 hectareas. It is the biggest of the settlements of the Iberian Peninsula for the Second Iron Age. The archaeological works have shown a defensive system in which natural elements are combined, like a great moat that surrounds the

  9. Dwarf spheroidal galaxies: Keystones of galaxy evolution

    Science.gov (United States)

    Gallagher, John S., III; Wyse, Rosemary F. G.

    1994-01-01

    Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

  10. Activity and Kinematics of White Dwarf-M Dwarf Binaries from the SUPERBLINK Proper Motion Survey

    Energy Technology Data Exchange (ETDEWEB)

    Skinner, Julie N. [Institute for Astrophysical Research, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Morgan, Dylan P.; West, Andrew A. [Department of Astronomy, Boston University, 725 Commonwealth Avenue, Boston, MA 02215 (United States); Lépine, Sébastien [Department of Physics and Astronomy, Georgia State University, 25 Park Place NE, Atlanta, GA, 30303 (United States); Thorstensen, John R., E-mail: jskinner@bu.edu [Department of Physics and Astronomy, 6127 Wilder Laboratory, Dartmouth College, Hanover, NH 03755 (United States)

    2017-09-01

    We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV–optical–IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use H α chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population.

  11. White Dwarf/M Dwarf Binaries as Single Degenerate Progenitors of Type Ia Supernovae

    Science.gov (United States)

    Wheeler, J. Craig

    2012-10-01

    Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, MV >~ 8.4 on the SN Ia in SNR 0509-67.5 and MV >~ 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a "magnetic bottle" connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the "nova limit" and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

  12. WHITE DWARF/M DWARF BINARIES AS SINGLE DEGENERATE PROGENITORS OF TYPE Ia SUPERNOVAE

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, J. Craig, E-mail: wheel@astro.as.utexas.edu [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)

    2012-10-20

    Limits on the companions of white dwarfs in the single-degenerate scenario for the origin of Type Ia supernovae (SNe Ia) have gotten increasingly tight, yet igniting a nearly Chandrasekhar mass C/O white dwarf from a condition of near hydrostatic equilibrium provides compelling agreement with observed spectral evolution. The only type of non-degenerate stars that survive the tight limits, M{sub V} {approx}> 8.4 on the SN Ia in SNR 0509-67.5 and M{sub V} {approx}> 9.5 in the remnant of SN 1572, are M dwarfs. While M dwarfs are observed in cataclysmic variables, they have special properties that have not been considered in most work on the progenitors of SNe Ia: they have small but finite magnetic fields and they flare frequently. These properties are explored in the context of SN Ia progenitors. White dwarf/M dwarf pairs may be sufficiently plentiful to provide, in principle, an adequate rate of explosions even with slow orbital evolution due to magnetic braking or gravitational radiation. Even modest magnetic fields on the white dwarf and M dwarf will yield adequate torques to lock the two stars together, resulting in a slowly rotating white dwarf, with the magnetic poles pointing at one another in the orbital plane. The mass loss will be channeled by a 'magnetic bottle' connecting the two stars, landing on a concentrated polar area on the white dwarf. This enhances the effective rate of accretion compared to spherical accretion. Luminosity from accretion and hydrogen burning on the surface of the white dwarf may induce self-excited mass transfer. The combined effects of self-excited mass loss, polar accretion, and magnetic inhibition of mixing of accretion layers give possible means to beat the 'nova limit' and grow the white dwarf to the Chandrasekhar mass even at rather moderate mass accretion rates.

  13. Activity and Kinematics of White Dwarf-M Dwarf Binaries from the SUPERBLINK Proper Motion Survey

    Science.gov (United States)

    Skinner, Julie N.; Morgan, Dylan P.; West, Andrew A.; Lépine, Sébastien; Thorstensen, John R.

    2017-09-01

    We present an activity and kinematic analysis of high proper motion white dwarf-M dwarf binaries (WD+dMs) found in the SUPERBLINK survey, 178 of which are new identifications. To identify WD+dMs, we developed a UV-optical-IR color criterion and conducted a spectroscopic survey to confirm each candidate binary. For the newly identified systems, we fit the two components using model white dwarf spectra and M dwarf template spectra to determine physical parameters. We use Hα chromospheric emission to examine the magnetic activity of the M dwarf in each system, and investigate how its activity is affected by the presence of a white dwarf companion. We find that the fraction of WD+dM binaries with active M dwarfs is significantly higher than their single M dwarf counterparts at early and mid-spectral types. We corroborate previous studies that find high activity fractions at both close and intermediate separations. At more distant separations, the binary fraction appears to approach the activity fraction for single M dwarfs. Using derived radial velocities and the proper motions, we calculate 3D space velocities for the WD+dMs in SUPERBLINK. For the entire SUPERBLINK WD+dMs, we find a large vertical velocity dispersion, indicating a dynamically hotter population compared to high proper motion samples of single M dwarfs. We compare the kinematics for systems with active M dwarfs and those with inactive M dwarfs, and find signatures of asymmetric drift in the inactive sample, indicating that they are drawn from an older population. Based on observations obtained at the MDM Observatory operated by Dartmouth College, Columbia University, The Ohio State University, and the University of Michigan.

  14. Pluto: Planet or "Dwarf Planet"?

    Science.gov (United States)

    Voelzke, M. R.; de Araújo, M. S. T.

    2010-09-01

    In August 2006 during the XXVI General Assembly of the International Astronomical Union (IAU), taken place in Prague, Czech Republic, new parameters to define a planet were established. According to this new definition Pluto will be no more the ninth planet of the Solar System but it will be changed to be a "dwarf planet". This reclassification of Pluto by the academic community clearly illustrates how dynamic science is and how knowledge of different areas can be changed and evolves through the time, allowing to perceive Science as a human construction in a constant transformation, subject to political, social and historical contexts. These epistemological characteristics of Science and, in this case, of Astronomy, constitute important elements to be discussed in the lessons, so that this work contributes to enable Science and Physics teachers who perform a basic education to be always up to date on this important astronomical fact and, thereby, carry useful information to their teaching.

  15. Transit probabilities for debris around white dwarfs

    Science.gov (United States)

    Lewis, John Arban; Johnson, John A.

    2017-01-01

    The discovery of WD 1145+017 (Vanderburg et al. 2015), a metal-polluted white dwarf with an infrared-excess and transits confirmed the long held theory that at least some metal-polluted white dwarfs are actively accreting material from crushed up planetesimals. A statistical understanding of WD 1145-like systems would inform us on the various pathways for metal-pollution and the end states of planetary systems around medium- to high-mass stars. However, we only have one example and there are presently no published studies of transit detection/discovery probabilities for white dwarfs within this interesting regime. We present a preliminary look at the transit probabilities for metal-polluted white dwarfs and their projected space density in the Solar Neighborhood, which will inform future searches for analogs to WD 1145+017.

  16. Building Magnetic Fields in White Dwarfs

    Science.gov (United States)

    Kohler, Susanna

    2017-03-01

    White dwarfs, the compact remnants left over at the end of low- and medium-mass stars lifetimes, are often found to have magnetic fields with strengths ranging from thousands to billions of times that of Earth. But how do these fields form?MultiplePossibilitiesAround 1020% of white dwarfs have been observed to have measurable magnetic fields with a wide range of strengths. There are several theories as to how these fields might be generated:The fields are fossil.The original weak magnetic fields of the progenitor stars were amplified as the stars cores evolved into white dwarfs.The fields are caused by binary interactions.White dwarfs that formed in the merger of a binary pair might have had a magnetic field amplified as a result of a dynamo that was generated during the merger.The fields were produced by some other internal physical mechanism during the cooling of the white dwarf itself.In a recent publication, a team of authors led by Jordi Isern (Institute of Space Sciences, CSIC, and Institute for Space Studies of Catalonia, Spain) explored this third possibility.Dynamos from CrystallizationThe inner and outer boundaries of the convective mantle of carbon/oxygen white dwarfs of two different masses (top vs. bottom panel) as a function of luminosity. As the white dwarf cools (toward the right), the mantle grows thinner due to the crystallization and settling of material. [Isern et al. 2017]As white dwarfs have no nuclear fusion at their centers, they simply radiate heat and gradually cool over time. The structure of the white dwarf undergoes an interesting change as it cools, however: though the object begins as a fluid composed primarily of an ionized mixture of carbon and oxygen (and a few minor species like nickel and iron), it gradually crystallizes as its temperature drops.The crystallized phase of the white dwarf is oxygen-rich which is denser than the liquid, so the crystallized material sinks to the center of the dwarf as it solidifies. As a result, the

  17. Astronomy: Ring detected around a dwarf planet

    Science.gov (United States)

    Sickafoose, Amanda A.

    2017-10-01

    Observations of the distant dwarf planet Haumea constrain its size, shape and density, and reveal an encircling planetary ring. The discovery suggests that rings are not as rare in the Solar System as previously thought. See Letter p.219

  18. DWARF BUNT: politics, identification, and biology.

    Science.gov (United States)

    Mathre, D E

    1996-01-01

    Dwarf bunt is a disease of wheat caused by the smut fungus Tilletia controversa Kuhn. Winter wheat (Triticum aestivum L.) is the primary host of economic significance. Although the total acreage affected by dwarf bunt is small relative to total wheat production worldwide, the disease has assumed attention disproportionate to its economic impact because it has become a matter of contention in world trade in cereals. This review describes the political and economic issues underlying the study and identification of T. controversa.

  19. Temperate Earth-sized planets transiting a nearby ultracool dwarf star

    Science.gov (United States)

    Gillon, Michaël; Jehin, Emmanuël; Lederer, Susan M.; Delrez, Laetitia; de Wit, Julien; Burdanov, Artem; Van Grootel, Valérie; Burgasser, Adam; Triaud, Amaury H. M. J.; Opitom, Cyrielle; Demory, Brice-Olivier; Sahu, Devendra K.; Bardalez Gagliuffi, Daniella; Magain, Pierre; Queloz, Didier

    2017-01-01

    Stellar-like objects with effective temperatures of 2700K and below are referred to as “ultracool dwarfs”1. This heterogeneous group includes both extremely low-mass stars and brown dwarfs (substellar objects not massive enough to sustain hydrogen fusion), and represents about 15% of the stellar-like objects in the vicinity of the Sun2. Based on the small masses and sizes of their protoplanetary disks3,4, core-accretion theory for ultracool dwarfs predicts a large, but heretofore undetected population of close-in terrestrial planets5, ranging from metal-rich Mercury-sized planets6 to more hospitable volatile-rich Earth-sized planets7. Here we report the discovery of three short-period Earth-sized planets transiting an ultracool dwarf star 12 parsecs away using data collected by the TRAPPIST8 telescope as part of an ongoing prototype transit survey9. The inner two planets receive four and two times the irradiation of Earth, respectively, placing them close to the inner edge of the habitable zone of the star10. Eleven orbits remain possible for the third planet based on our data, the most likely resulting in an irradiation significantly smaller than Earth's. The infrared brightness of the host star combined with its Jupiter-like size offer the possibility of thoroughly characterizing the components of this nearby planetary system. PMID:27135924

  20. ON THE EVOLUTION OF MAGNETIC WHITE DWARFS

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, P.-E. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Fontaine, G.; Brassard, P. [Département de Physique, Université de Montréal, C. P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7 (Canada); Freytag, B. [Department of Physics and Astronomy at Uppsala University, Regementsvägen 1, Box 516, SE-75120 Uppsala (Sweden); Steiner, O. [Kiepenheuer-Institut für Sonnenphysik, Schöneckstr. 6, D-79104 Freiburg (Germany); Ludwig, H.-G. [Zentrum für Astronomie der Universität Heidelberg, Landessternwarte, Königstuhl 12, D-69117 Heidelberg (Germany); Steffen, M. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Wedemeyer, S., E-mail: tremblay@stsci.edu [Institute of Theoretical Astrophysics, University of Oslo, P.O. Box 1029 Blindern, NO-0315 Oslo (Norway)

    2015-10-10

    We present the first radiation magnetohydrodynamic simulations of the atmosphere of white dwarf stars. We demonstrate that convective energy transfer is seriously impeded by magnetic fields when the plasma-β parameter, the thermal-to-magnetic-pressure ratio, becomes smaller than unity. The critical field strength that inhibits convection in the photosphere of white dwarfs is in the range B = 1–50 kG, which is much smaller than the typical 1–1000 MG field strengths observed in magnetic white dwarfs, implying that these objects have radiative atmospheres. We have employed evolutionary models to study the cooling process of high-field magnetic white dwarfs, where convection is entirely suppressed during the full evolution (B ≳ 10 MG). We find that the inhibition of convection has no effect on cooling rates until the effective temperature (T{sub eff}) reaches a value of around 5500 K. In this regime, the standard convective sequences start to deviate from the ones without convection due to the convective coupling between the outer layers and the degenerate reservoir of thermal energy. Since no magnetic white dwarfs are currently known at the low temperatures where this coupling significantly changes the evolution, the effects of magnetism on cooling rates are not expected to be observed. This result contrasts with a recent suggestion that magnetic white dwarfs with T{sub eff} ≲ 10,000 K cool significantly slower than non-magnetic degenerates.

  1. Cloudless Atmospheres for L/T Dwarfs and Extrasolar Giant Planets

    Science.gov (United States)

    Tremblin, P.; Amundsen, D. S.; Chabrier, G.; Baraffe, I.; Drummond, B.; Hinkley, S.; Mourier, P.; Venot, O.

    2016-01-01

    The admitted, conventional scenario to explain the complex spectral evolution of brown dwarfs (BDs) since their first detection 20 years ago has always been the key role played by micron-size condensates, called "dust" or "clouds," in their atmosphere. This scenario, however, faces major problems, in particular the J-band brightening and the resurgence of FeH absorption at the L to T transition, and a physical first-principle understanding of this transition is lacking. In this Letter, we propose a new, completely different explanation for BD and extrasolar giant planet (EGP) spectral evolution, without the need to invoke clouds. We show that, due to the slowness of the CO/ CH4 and N2/NH3 chemical reactions, brown dwarf (L and T, respectively) and EGP atmospheres are subject to a thermo-chemical instability similar in nature to the fingering or chemical convective instability present in Earth oceans and at the Earth core/mantle boundary. The induced small-scale turbulent energy transport reduces the temperature gradient in the atmosphere, explaining the observed increase in near-infrared J-H and J-K colors of L dwarfs and hot EGPs, while a warming up of the deep atmosphere along the L to T transition, as the CO/CH4 instability vanishes, naturally solves the two aforementioned puzzles, and provides a physical explanation of the L to T transition. This new picture leads to a drastic revision of our understanding of BD and EGP atmospheres and their evolution.

  2. An observer's guide to the (Local Group) dwarf galaxies: predictions for their own dwarf satellite populations

    Science.gov (United States)

    Dooley, Gregory A.; Peter, Annika H. G.; Yang, Tianyi; Willman, Beth; Griffen, Brendan F.; Frebel, Anna

    2017-11-01

    A recent surge in the discovery of new ultrafaint dwarf satellites of the Milky Way has inspired the idea of searching for faint satellites, 103 M⊙ field galaxies in the Local Group. Such satellites would be subject to weaker environmental influences than Milky Way satellites, and could lead to new insights on low-mass galaxy formation. In this paper, we predict the number of luminous satellites expected around field dwarf galaxies by applying several abundance-matching models and a reionization model to the dark-matter only Caterpillar simulation suite. For three of the four abundance-matching models used, we find a >99 per cent chance that at least one satellite with stellar mass M* > 105 M⊙ exists around the combined five Local Group field dwarf galaxies with the largest stellar mass. When considering satellites with M* > 104 M⊙, we predict a combined 5-25 satellites for the five largest field dwarfs, and 10-50 for the whole Local Group field dwarf population. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Group dwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellites in a given field of view of specific Local Group galaxies, as a function of minimum satellite luminosity, and explicitly obtain such values for the Solitary Local dwarfs survey. Uncertainties in abundance-matching and reionization models are large, implying that comprehensive searches could lead to refinements of both models.

  3. An observer's guide to the (Local Group) dwarf galaxies: predictions for their own dwarf satellite populations

    Science.gov (United States)

    Dooley, Gregory A.; Peter, Annika H. G.; Yang, Tianyi; Willman, Beth; Griffen, Brendan F.; Frebel, Anna

    2017-11-01

    A recent surge in the discovery of new ultrafaint dwarf satellites of the Milky Way has inspired the idea of searching for faint satellites, 103 M⊙ satellites would be subject to weaker environmental influences than Milky Way satellites, and could lead to new insights on low-mass galaxy formation. In this paper, we predict the number of luminous satellites expected around field dwarf galaxies by applying several abundance-matching models and a reionization model to the dark-matter only Caterpillar simulation suite. For three of the four abundance-matching models used, we find a >99 per cent chance that at least one satellite with stellar mass M* > 105 M⊙ exists around the combined five Local Group field dwarf galaxies with the largest stellar mass. When considering satellites with M* > 104 M⊙, we predict a combined 5-25 satellites for the five largest field dwarfs, and 10-50 for the whole Local Group field dwarf population. Because of the relatively small number of predicted dwarfs, and their extended spatial distribution, a large fraction each Local Group dwarf's virial volume will need to be surveyed to guarantee discoveries. We compute the predicted number of satellites in a given field of view of specific Local Group galaxies, as a function of minimum satellite luminosity, and explicitly obtain such values for the Solitary Local dwarfs survey. Uncertainties in abundance-matching and reionization models are large, implying that comprehensive searches could lead to refinements of both models.

  4. Response of dwarf mistletoe-infested ponderosa pine to thinning: 2. Dwarf mistletoe propagation.

    Science.gov (United States)

    Lewis F. Roth; James W. Barrett

    1985-01-01

    Propagation of dwarf mistletoe in ponderosa pine saplings is little influenced by thinning overly dense stands to 250 trees per acre. Numerous plants that appear soon after thinning develop from formerly latent plants in the suppressed under-story. Subsequently, dwarf mistletoe propagates nearly as fast as tree crowns enlarge but the rate differs widely among trees....

  5. Tracking an Exodus: Lost Children of the Dwarf Planet Haumea

    Science.gov (United States)

    Maggard, Steven; Ragozzine, Darin

    2017-10-01

    The orbital properties of Kuiper Belt Objects (KBOs) refine our understanding of the formation of the solar system. One object of particular interest is the dwarf planet Haumea which experienced a collision in the early stages of our solar system that ejected shards form its surface and spread them over a localized part of the Kuiper Belt. Detailed orbital integrations are required to determine the dynamical distances between family members, in the form of "Delta v" as measured from conserved proper orbital elements (Ragozzine & Brown 2007). In the past 10 years, the number of known KBOs has tripled; here, we perform dynamical integrations to triple the number of candidate Haumea family members. The resulting improved understanding of Haumea's family will bring us closer to understanding its formation. In order to place more secure estimates on the dynamical classification of Haumea family members (and KBOs generally), we use OpenOrb to perform rigorous Bayesian uncertainty propagation from observational uncertainty into orbital elements and then into dynamical classifications. We will discuss our methodology, the new Haumea family members, and some implications for the Haumea family.

  6. Metallic Winds in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Robles-Valdez, F.; Rodríguez-González, A.; Hernández-Martínez, L.; Esquivel, A., E-mail: fatima.robles@correo.nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, A.P. 70-543, 04510, Mexico City (Mexico)

    2017-02-01

    We present results from models of galactic winds driven by energy injected from nuclear (at the galactic center) and non-nuclear starbursts. The total energy of the starburst is provided by very massive young stellar clusters, which can push the galactic interstellar medium and produce an important outflow. Such outflow can be a well or partially mixed wind, or a highly metallic wind. We have performed adiabatic 3D N -Body/Smooth Particle Hydrodynamics simulations of galactic winds using the gadget-2 code. The numerical models cover a wide range of parameters, varying the galaxy concentration index, gas fraction of the galactic disk, and radial distance of the starburst. We show that an off-center starburst in dwarf galaxies is the most effective mechanism to produce a significant loss of metals (material from the starburst itself). At the same time, a non-nuclear starburst produces a high efficiency of metal loss, in spite of having a moderate to low mass loss rate.

  7. 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.; hide

    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.

  8. How brown is brown fat that we can see?

    Science.gov (United States)

    Kolonin, Mikhail G

    2014-04-01

    There are many unanswered questions related to the heterogeneity of adipose tissue depots and the paucity of their function, development, and organization at the cellular level. Much effort has been directed at studying white adipose tissue (WAT), the driver of obesity and the associated metabolic disease. In recent years, the importance of brown adipose tissue (BAT) has also been appreciated. While BAT depots are prominent in many small mammal species, their detection in adult humans has been technically challenging and the identity of brown human adipocytes found within depots of WAT has remained controversial. We recently reported a peptide probe that binds to BAT vasculature and, when coupled with a near-infrared fluorophore, can be used to detect BAT in whole body imaging. This probe reliably discriminates between endothelium associated with brown or brown-like (beige/brite) adipocytes and endothelium of visceral WAT. Improved probes based on this approach could aid in assessing human adipose tissue body distribution and remodeling, which is a process underlying various pathologies. This commentary aims at discussing open questions that need to be addressed before full clinical advantage can be taken from adipose tissue imaging, as well as its metabolic activation strategies.

  9. Rapid Rotation of a Heavy White Dwarf

    Science.gov (United States)

    Kohler, Susanna

    2017-05-01

    New Kepler observations of a pulsating white dwarf have revealed clues about the rotation of intermediate-mass stars.Learning About ProgenitorsStars weighing in at under 8 solar masses generally end their lives as slowly cooling white dwarfs. By studying the rotation of white dwarfs, therefore, we are able to learn about the final stages of angular momentum evolution in these progenitor stars.Most isolated field white dwarfs cluster in mass around 0.62 solar masses, which corresponds to a progenitor mass of around 2.2 solar masses. This abundance means that weve already learned a good deal about the final rotation of low-mass (13 solar-mass) stars. Our knowledge about the angular momentum of intermediate-mass (38 solar-mass) stars, on the other hand, remains fairly limited.Fourier transform of the pulsations from SDSSJ0837+1856. The six frequencies of stellar variability, marked with red dots, reveal a rotation period of 1.13 hours. [Hermes et al. 2017]Record-Breaking FindA newly discovered white dwarf, SDSSJ0837+1856, is now helping to shed light on this mass range. SDSSJ0837+1856 appears to be unusually massive: its measured at 0.87 solar masses, which corresponds to a progenitor mass of roughly 4.0 solar masses. Determining the rotation of this white dwarf would therefore tell us about the final stages of angular momentum in an intermediate-mass star.In a new study led by J.J. Hermes (Hubble Fellow at University of North Carolina, Chapel Hill), a team of scientists presents a series of measurements of SDSSJ0837+1856 that suggest its the highest-mass and fastest-rotating isolated pulsating white dwarf known.Histogram of rotation rates determined from the asteroseismology of pulsating white dwarfs (marked in red). SDSSJ0837+1856 (indicated in black) is more massive and rotates faster than any other known pulsating white dwarf. [Hermes et al. 2017]Rotation from PulsationsWhy pulsating? In the absence of measurable spots and other surface features, the way we

  10. Tidal Dwarf Galaxies and Missing Baryons

    Directory of Open Access Journals (Sweden)

    Frederic Bournaud

    2010-01-01

    Full Text Available Tidal dwarf galaxies form during the interaction, collision, or merger of massive spiral galaxies. They can resemble “normal” dwarf galaxies in terms of mass, size, and become dwarf satellites orbiting around their massive progenitor. They nevertheless keep some signatures from their origin, making them interesting targets for cosmological studies. In particular, they should be free from dark matter from a spheroidal halo. Flat rotation curves and high dynamical masses may then indicate the presence of an unseen component, and constrain the properties of the “missing baryons,” known to exist but not directly observed. The number of dwarf galaxies in the Universe is another cosmological problem for which it is important to ascertain if tidal dwarf galaxies formed frequently at high redshift, when the merger rate was high, and many of them survived until today. In this paper, “dark matter” is used to refer to the nonbaryonic matter, mostly located in large dark halos, that is, CDM in the standard paradigm, and “missing baryons” or “dark baryons” is used to refer to the baryons known to exist but hardly observed at redshift zero, and are a baryonic dark component that is additional to “dark matter”.

  11. Live-trapping and handling brown bear

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This paper reports techniques developed to live trap and handle brown bears on the Kodiak National Wildlife Refuge. The brown bears (Ursus middendorffi) on the...

  12. Brown Adipose Tissue: Function and Physiological Significance

    National Research Council Canada - National Science Library

    CANNON, BARBARA; NEDERGAARD, JAN

    2004-01-01

    .... Brown Adipose Tissue: Function and Physiological Significance. Physiol Rev 84: 277–359, 2004; 10.1152/physrev.00015.2003.—The function of brown adipose tissue is to transfer energy from food into heat...

  13. Hydrothermal-mechanical dewatering of brown coal

    OpenAIRE

    Guo, Jian

    2017-01-01

    There are enormous reserves of brown coal in the world. In Australia, brown coal is used to generate most of electricity in the states of Victoria and South Australia. Brown coal is characterised by very high moisture content (around 60 wt% on a wet basis). Therefore, boilers used in the power station are very large and have low thermal efficiency, leading to high cost and large emissions of green house gas. High moisture content also makes brown coal uneconomical for transport...

  14. A wide binary trigger for white dwarf pollution

    OpenAIRE

    Bonsor, Amy; Veras, Dimitri

    2015-01-01

    Metal pollution in white dwarf atmospheres is likely to be a signature of remnant planetary systems. Most explanations for this pollution predict a sharp decrease in the number of polluted systems with white dwarf cooling age. Observations do not confirm this trend, and metal pollution in old (1-5 Gyr) white dwarfs is difficult to explain. We propose an alternative, time-independent mechanism to produce the white dwarf pollution. The orbit of a wide binary companion can be perturbed by Galact...

  15. Harassment Origin for Kinematic Substructures in Dwarf Elliptical Galaxies?

    OpenAIRE

    Gonzalez-Garcia, A. C.; Aguerri, J. A. L.; Balcells, M.

    2005-01-01

    [EN]We have run high resolution N-body models simulating the encounter of a dwarf galaxy with a bright elliptical galaxy. The dwarf absorbs orbital angular momentum and shows counter-rotating features in the external regions of the galaxy. To explain the core-envelope kinematic decoupling observed in some dwarf galaxies in high-density environments requires nearly head-on collisions and very little dark matter bound to the dwarf. These kinematic structures appear under rather restrictive cond...

  16. DISCOVERY OF A BINARY BROWN DWARF AT 2 pc FROM THE SUN

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-04-10

    I am using multi-epoch astrometry from the Wide-field Infrared Survey Explorer (WISE) to search for new members of the solar neighborhood via their high proper motions. Through this work, I have identified WISE J104915.57-531906.1 as a high proper motion object and have found additional detections in images from the Digitized Sky Survey, the Two Micron All-Sky Survey, and the Deep Near-Infrared Survey of the Southern Sky. I have measured a parallax of 0.''496 {+-} 0.''037 (2.0 {+-} 0.15 pc) from the astrometry in these surveys, making WISE J104915.57-531906.1 the third closest system to the Sun. During spectroscopic observations with the Gemini Multi-Object Spectrograph at Gemini Observatory, an i-band acquisition image resolved it as a 1.''5 (3 AU) binary. A spectrum was collected for the primary, which I classify as L8 {+-} 1. The secondary is probably near the L/T transition as well given that it is only modestly fainter than the primary ({Delta}i = 0.45 mag).

  17. Opportunities for Laboratory Opacity Chemistry Studies to Facilitate Characterization of Young Giant Planets and Brown Dwarfs

    Science.gov (United States)

    Marley, Mark; Freedman, Richard S.

    2015-01-01

    The thermal emission spectra of young giant planets is shaped by the opacity of atoms and molecules residing in their atmospheres. While great strides have been made in improving the opacities of important molecules, particularly NH3 and CH4, at high temperatures, much more work is needed to understand the opacity and chemistry of atomic Na and K. The highly pressure broadened fundamental band of Na and K in the optical stretches into the near-infrared, strongly influencing the shape of the Y and K spectral bands. Since young giant planets are bright in these bands it is important to understand the influences on the spectral shape. Discerning gravity and atmospheric composition is difficult, if not impossible, without both good atomic opacities as well as an excellent understanding of the relevant atmospheric chemistry. Since Na and K condense at temperatures near 500 to 600 K, the chemistry of the condensation process must be well understood as well, particularly any disequilibrium chemical pathways. Comparisons of the current generation of sophisticated atmospheric models and available data, however, reveal important shortcomings in the models. We will review the current state of observations and theory of young giant planets and will discuss these and other specific examples where improved laboratory measurements for alkali compounds have the potential of substantially improving our understanding of these atmospheres.

  18. Deuterium burning in objects forming via the core accretion scenario - Brown dwarfs or planets?

    OpenAIRE

    Mollière, Paul; Mordasini, Christoph

    2012-01-01

    Aims. Our aim is to study deuterium burning in objects forming according to the core accretion scenario in the hot and cold start assumption and what minimum deuterium burning mass limit is found for these objects. We also study how the burning process influences the structure and luminosity of the objects. Furthermore we want to test and verify our results by comparing them to already existing hot start simulations which did not consider, however, the formation process. Methods. We present a...

  19. Convective Dynamics and Disequilibrium Chemistry in the Atmospheres of Giant Planets and Brown Dwarfs

    Science.gov (United States)

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

    2018-02-01

    Disequilibrium chemical processes significantly affect the spectra of substellar objects. To study these effects, dynamical disequilibrium has been parameterized using the quench and eddy diffusion approximations, but little work has been done to explore how these approximations perform under realistic planetary conditions in different dynamical regimes. As a first step toward addressing this problem, we study the localized, small-scale convective dynamics of planetary atmospheres by direct numerical simulation of fully compressible hydrodynamics with reactive tracers using the Dedalus code. Using polytropically stratified, plane-parallel atmospheres in 2D and 3D, we explore the quenching behavior of different abstract chemical species as a function of the dynamical conditions of the atmosphere as parameterized by the Rayleigh number. We find that in both 2D and 3D, chemical species quench deeper than would be predicted based on simple mixing-length arguments. Instead, it is necessary to employ length scales based on the chemical equilibrium profile of the reacting species in order to predict quench points and perform chemical kinetics modeling in 1D. Based on the results of our simulations, we provide a new length scale, derived from the chemical scale height, that can be used to perform these calculations. This length scale is simple to calculate from known chemical data and makes reasonable predictions for our dynamical simulations.

  20. Sleep in spontaneous dwarf rats.

    Science.gov (United States)

    Peterfi, Zoltan; Obal, Ferenc; Taishi, Ping; Gardi, Janos; Kacsoh, Balint; Unterman, Terry; Krueger, James M

    2006-09-07

    Spontaneous dwarf rats (SDRs) display growth hormone (GH) deficiency due to a mutation in the GH gene. This study investigated sleep in SDRs and their somatotropic axis and compared to Sprague-Dawley rats. SDRs had almost undetectable levels of plasma GH. Hypothalamic GH-releasing hormone (GHRH) mRNA was increased, whereas GHRH-receptor (GHRH-R) and somatostatin mRNAs were decreased in SDRs. Hypothalamic GHRH and somatostatin peptide content decreased in SDRs. Quantitative immunohistochemistry for GHRH and GHRH-R corroborated and extended these findings. In the arcuate nucleus, the number of GHRH-positive cells was significantly higher, whereas GHRH-R-positive perikarya were diminished in SDRs. Cortical GHRH and GHRH-R measurements showed similar expression characteristics as those found in the hypothalamus. SDRs had less rapid eye movement sleep (REMS) and more non-REMS (NREMS) than the control rats during the light period. The electroencephalogram (EEG) delta and theta power decreased during NREMS in the SDRs. After 4-h of sleep deprivation, SDRs had a significantly reduced REMS rebound compared to the controls, whereas NREMS rebound was normal in SDRs. The enhancement in delta power was significantly less than in the control group during recovery sleep. Intracerebroventricular (icv) administration of GHRH promoted NREMS in both strains of rats; however, increased REMS and EEG delta activity was observed only in control rats. Icv injection of insulin-like growth factor 1 increased NREMS in control rats, but not in the SDRs. These results support the ideas that GHRH is involved in NREMS regulation and that GH is involved in the regulation of REMS and in EEG slow wave activity regulation during NREMS.

  1. Fulfilling the Promise of Brown.

    Science.gov (United States)

    Winston, Judith A.

    1995-01-01

    Summarizes the U.S. Department of Education's efforts to implement the mandate of "Brown v. Board of Education of Topeka, Kansas" and the Civil Rights Act of 1964, examining traditional tools used in enforcing civil rights laws and reviewing new strategies to promote high quality education, equal educational opportunity, and diversity.…

  2. White Dwarfs in Gaia Data Release 1

    Science.gov (United States)

    Jordan, S.

    2017-03-01

    On September 14, the Gaia archives opened for access to the Gaia DR1. The catalogue with more than one billion star positions and more than two million parallaxes and proper motions will have enormous influence on many topics in astronomy. However, due to their extremely blue colour, parallaxes and proper motions of only six white dwarfs were directly measured. Tremblay et al. used these data and those for 46 white dwarfs in binaries in order to construct an empirical mass-radius relation. As it was the case for Hipparcos, the precision of the data does not allow for the characterisation of hydrogen envelope masses. With Gaia DR2 coming in late 2017 the prospects for white dwarf research are much better.

  3. Youth Indicators of Late-M Dwarfs

    Science.gov (United States)

    Feldman, Daniel; Cruz, K.; Lépine, S.; Alpert, N.

    2011-01-01

    We present a study in which we searched for a correlation between weak Na absorption doublet (8183Å, 8194Å) and strong H-Alpha emission (6563Å) in late-M dwarf stars (M6-M9), as both are indicative of youth. Our sample consists of late-M Dwarfs from the LSPM Survey (Lépine and Shara, 2005), which contain stars with measured proper motions of mu > 40 mas/yr. Measurements for emission and absorption strength were made using spectral indices. Our preliminary results are presented; future work will include a similar analysis of early type M Dwarfs, as well as kinematics. This work was funded by the CUNY Summer Undergraduate Research Program, as well as the CUNY Macaulay Honors College, and we acknowledge the hospitality of the American Museum of Natural History.

  4. Actively Disintegrating Astroids around a White Dwarf

    Science.gov (United States)

    Xu, Siyi

    2017-08-01

    Recent studies show that planetary systems can be widespread around white dwarfs. It has been proposed that planetary systems are responsible for the pollution observed in a white dwarf's atmosphere and the excess infrared radiation. This scenario is greatly strengthened by the recent discovery of actively disintegrating bodies orbiting around the white dwarf WD 1145+017. In addition, this system has a heavily polluted atmosphere, a dust disk, and circumstellar gas. Our team has been monitoring this system since its discovery and our recent COS data have revealed many new surprises. We propose to continue studying this system for the next two cycles and further constrain the evolution of the disintegrating bodies: what are the main mechanisms responsible for its destruction? How is circumstellar gas produced and maintained?

  5. The benefit of amateur observations for research in dwarf novae

    Science.gov (United States)

    La Dous, Constanze

    1992-01-01

    Contributions of amateur astronomers to research on dwarf novae, which are based on carefully monitoring the outburst behavior of these objects, are reviewed. These contributions range from scheduling of observations to the observational basis for research on the dwarf nova outburst mechanism. It is suggested, that, with better equipment, observations of orbital light variations in dwarf novae might be performed by amateur astronomers.

  6. The origin of the strongest magnetic fields in dwarfs

    Indian Academy of Sciences (India)

    Abstract. White dwarfs have frozen in magnetic fields ranging from below the measurable limit of about 3 × 103 to 109 G. White dwarfs with surface magnetic fields in excess of 1 MG are found as isolated single stars and relatively more often in magnetic cataclysmic variables. Some 1253 white dwarfs with a detached ...

  7. A dwarf wheat mutant is associated with increased drought ...

    African Journals Online (AJOL)

    ... was significantly higher than Jingdong 6. Most of the s-dwarf seedlings survived in recovering experiement after water loss. The stalk of s-dwarf seedling also showed reduced gravitropism. This is the first report about a new dwarf wheat mutant associated with increased drought resistance and altered stalk gravitropism.

  8. White Dwarf/M Dwarf Binaries as Single Degenerate Progenitors of Type Ia Supernovae

    OpenAIRE

    Wheeler, J. Craig

    2012-01-01

    Limits on the companions of white dwarfs in the single degenerate scenario for the origin of Type Ia supernovae (SNIa) have gotten increasingly tight. The only type of non-degenerate stars that survive the limits on the companions of SNIa in SNR 0509-67.5 and SN1572 are M dwarfs. M dwarfs have special properties that have not been considered in most work on the progenitors of SNIa: they have small but finite magnetic fields, and they flare frequently. These properties are explored in the cont...

  9. 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.

  10. ROBO-AO M DWARF MULTIPLICITY SURVEY

    Science.gov (United States)

    Lamman, Claire; Berta-Thompson, Zachory; Baranec, Christoph; Law, Nicholas; Schonhut, Jessica

    2018-01-01

    We analyzed over 7,000 observations from Robo-AO’s field M dwarf survey taken on the 2.1m Kitt Peak telescope. Results will help determine the multiplicity fraction of M dwarfs as a function of primary mass, which is a crucial step towards understanding their evolution and formation mechanics. Through its robotic, laser-guided, and automated system, the Robo-AO instrument has yielded the largest adaptive-optics M dwarf survey to date. I developed a graphical user interface to quickly analyze this data. Initial data analysis included assessing data quality, checking the result from Robo-AO’s automatic reduction pipeline, and determining existence as well as the relative position of companions through a visual inspection. This program can be applied to other datasets and was successfully tested by re-analyzing observations from a separate Robo-AO survey. Following the preliminary results from this data analysis tool, further observations were done with the Keck II telescope by using its NIRC2 imager to follow up on ten select targets for the existence and physical association of companions. After a conservative initial cut for quality, 356 companions were found within 4” of a primary star out of 2,746 high quality Robo-AO M dwarf observations, including four triple systems. We will present a preliminary estimate for the multiplicity rate of wide M dwarf companions after accounting for observation limitations and the completeness of our search. Future research will yield insights into low-mass stellar formation and provide a database of nearby M dwarf multiples that will potentially assist ongoing and future surveys for planets around these stars, such as the NASA TESS mission.

  11. White Dwarf Mergers on Adaptive Meshes

    Science.gov (United States)

    Katz, Maximilian Peter

    The mergers of binary white dwarf systems are potential progenitors of astrophysical explosions such as Type Ia supernovae. These white dwarfs can merge either by orbital decay through the emission of gravitational waves or by direct collisions as a result of orbital perturbations. The coalescence of the stars may ignite nuclear fusion, resulting in the destruction of both stars through a thermonuclear runaway and ensuing detonation. The goal of this dissertation is to simulate binary white dwarf systems using the techniques of computational fluid dynamics and therefore to understand what numerical techniques are necessary to obtain accurate dynamical evolution of the system, as well as to learn what conditions are necessary to enable a realistic detonation. For this purpose I have used software that solves the relevant fluid equations, the Poisson equation for self-gravity, and the systems governing nuclear reactions between atomic species. These equations are modeled on a computational domain that uses the technique of adaptive mesh refinement to have the highest spatial resolution in the areas of the domain that are most sensitive to the need for accurate numerical evolution. I have identified that the most important obstacles to accurate evolution are the numerical violation of conservation of energy and angular momentum in the system, and the development of numerically seeded thermonuclear detonations that do not bear resemblance to physically correct detonations. I then developed methods for ameliorating these problems, and determined what metrics can be used for judging whether a given white dwarf merger simulation is trustworthy. This involved the development of a number of algorithmic improvements to the simulation software, which I describe. Finally, I performed high-resolution simulations of typical cases of white dwarf mergers and head-on collisions to demonstrate the impacts of these choices. The results of these simulations and the corresponding

  12. White dwarf atmospheres and circumstellar environments

    CERN Document Server

    Hoard, Donald W

    2012-01-01

    Written by selected astronomers at the forefront of their fields, this timely and novel book compiles the latest results from research on white dwarf stars, complementing existing literature by focusing on fascinating new developments in our understanding of the atmospheric and circumstellar environments of these stellar remnants. Complete with a thorough refresher on the observational characteristics and physical basis for white dwarf classification, this is a must-have resource for researchers interested in the late stages of stellar evolution, circumstellar dust and nebulae, and the future

  13. The angular momentum of isolated white dwarfs

    Directory of Open Access Journals (Sweden)

    Brassard P.

    2013-03-01

    Full Text Available This is a very brief report on an ongoing program aimed at mapping the internal rotation profiles of stars through asteroseismology. Three years ago, we developed and applied successfully a new technique to the pulsating GW Vir white dwarf PG 1159−035, and were able to infer that it rotates very slowly and rigidly over some 99% of its mass. We applied the same approach to the three other GW Vir pulsators with available rotational splitting data, and found similar results. We discuss the implications of these findings on the question of the angular momentum of white dwarfs resulting from single star evolution.

  14. Dwarf mistletoe (Arceuthobium oxycedri) and damage caused by dwarf mistletoe to family Cupressaceae

    National Research Council Canada - National Science Library

    Humaira Abdul Wahid; Muhammad Younas Khan Barozai; Muhammad Din

    2015-01-01

    .... Their damaging effects are growth reduction, branch distortions, and decreased longevity. All mistletoes take water and nutrients by tapping the host xylem but differ in their dependence on the host for carbon. Dwarf mistletoes (Arceuthobium spp...

  15. TIDAL STIRRING OF DISKY DWARFS WITH SHALLOW DARK MATTER DENSITY PROFILES: ENHANCED TRANSFORMATION INTO DWARF SPHEROIDALS

    Energy Technology Data Exchange (ETDEWEB)

    Kazantzidis, Stelios [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Lokas, Ewa L. [Nicolaus Copernicus Astronomical Center, 00-716 Warsaw (Poland); Mayer, Lucio, E-mail: stelios@mps.ohio-state.edu [Institute for Theoretical Physics, University of Zuerich, CH-8057 Zuerich (Switzerland)

    2013-02-20

    According to the tidal stirring model, late type, rotationally supported dwarfs resembling present day dwarf irregular (dIrr) galaxies can transform into dwarf spheroidals (dSphs) via interactions with Milky-Way-sized hosts. We perform collisionless N-body simulations to investigate for the first time how tidal stirring depends on the dark matter (DM) density distribution in the central stellar region of the progenitor disky dwarf. Specifically, we explore various asymptotic inner slopes {gamma} of the dwarf DM density profiles ({rho}{proportional_to}r {sup -{gamma}}). For a given orbit inside the primary galaxy, rotationally supported dwarfs embedded in DM halos with core-like distributions ({gamma} = 0.2) and mild density cusps ({gamma} = 0.6) demonstrate a substantially enhanced likelihood and efficiency of transformation into dSphs compared to their counterparts with steeper DM density profiles ({gamma} = 1). Such shallow DM distributions are akin to those of observed dIrrs highlighting tidal stirring as a plausible model for the Local Group (LG) morphology-density relation. When {gamma} < 1, a single pericentric passage can induce dSph formation and disky dwarfs on low-eccentricity or large-pericenter orbits are able to transform; these new results allow tidal stirring to explain virtually all known dSphs across a wide range of distances from their hosts. A subset of disky dwarfs initially embedded in DM halos with shallow density profiles are eventually disrupted by the primary; those that survive as dSphs are generally on orbits with lower eccentricities and/or larger pericenters compared to those of typical cold dark matter satellites. The latter could explain the peculiar orbits of several LG dSphs such as Fornax, Leo I, Tucana, and Cetus.

  16. Marvel-ous Dwarfs: Results from Four Heroically Large Simulated Volumes of Dwarf Galaxies

    Science.gov (United States)

    Munshi, Ferah; Brooks, Alyson; Weisz, Daniel; Bellovary, Jillian; Christensen, Charlotte

    2018-01-01

    We present results from high resolution, fully cosmological simulations of cosmic sheets that contain many dwarf galaxies. Together, they create the largest collection of simulated dwarf galaxies to date, with z=0 stellar masses comparable to the LMC or smaller. In total, we have simulated almost 100 luminous dwarf galaxies, forming a sample of simulated dwarfs which span a wide range of physical (stellar and halo mass) and evolutionary properties (merger history). We show how they can be calibrated against a wealth of observations of nearby galaxies including star formation histories, HI masses and kinematics, as well as stellar metallicities. We present preliminary results answering the following key questions: What is the slope of the stellar mass function at extremely low masses? Do halos with HI and no stars exist? What is the scatter in the stellar to halo mass relationship as a function of dwarf mass? What drives the scatter? With this large suite, we are beginning to statistically characterize dwarf galaxies and identify the types and numbers of outliers to expect.

  17. Theoretical Study of White Dwarf Double Stars

    Science.gov (United States)

    Hira, Ajit; Koetter, Ted; Rivera, Ruben; Diaz, Juan

    2015-04-01

    We continue our interest in the computational simulation of the astrophysical phenomena with a study of gravitationally-bound binary stars, composed of at least one white dwarf star. Of particular interest to astrophysicists are the conditions inside a white dwarf star in the time frame leading up to its explosive end as a Type Ia supernova, for an understanding of the massive stellar explosions. In addition, the studies of the evolution of white dwarfs could serve as promising probes of theories of gravitation. We developed FORTRAN computer programs to implement our models for white dwarfs and other stars. These codes allow for different sizes and masses of stars. Simulations were done in the mass interval from 0.1 to 2.0 solar masses. Our goal was to obtain both atmospheric and orbital parameters. The computational results thus obtained are compared with relevant observational data. The data are further analyzed to identify trends in terms of sizes and masses of stars. We hope to extend our computational studies to blue giant stars in the future. Research Supported by National Science Foundation.

  18. Computational Study of White Dwarf Stars

    Science.gov (United States)

    Pacheco, Jose; Hira, Ajit; Jaramillo, Danelle

    2014-03-01

    We begin our interest in the computational simulation of the astrophysical phenomena with a study of white dwarf stars. Of particular interest to astrophysicists are the conditions inside a white dwarf star in the time frame leading up to its explosive end as a Type Ia supernova, for an understanding of the massive stellar explosions. In addition, the studies of the evolution of white dwarfs could serve as promising probes of theories of gravitation. First, we set up the equations of equilibrium for the star of interest. Then we derived the appropriate equation of state. Next, a FORTRAN computer program was developed to implement our model for white dwarfs. This code allows for different sizes and masses of stars. Simulations were done in the mass interval from 0.4 to 0.8 solar masses. Our goal was to obtain both atmospheric and orbital parameters. The computational results thus obtained are compared with relevant observational data. The data are further analyzed to identify trends in terms of sizes and masses of stars. We hope to extend our computational studies to red giant stars in the future.

  19. Detailed analysis of carbon atmosphere white dwarfs

    Science.gov (United States)

    Dufour, Patrick

    2009-07-01

    We propose to obtain UV spectra for the newly discovered white dwarf stars with a carbon-dominated atmosphere. Model calculations show that these stars emit most of their light in the UV part of the electromagnetic spectrum and that an accurate determination of the flux in this region is crucial for an accurate determination of the atmospheric parameters. It will also provide a unique opportunity to test the atomic data and broadening theory in stellar conditions never met before. This will play a primordial role in our path to understand the origin of these objects as well to obtain a better understanding of the evolution of stars in general. The principal objective we hope to achieve with these observations are 1} obtain accurate surface gravity/mass for these stars, 2} constrain/determine the abundance of other elements {O, He, Mg, Ne etc.}, especially oxygen, 3} verify the accuracy of the various theoretical atomic data used in the model calculations, 4} understand the origin and evolution of carbon atmosphere white dwarfs, in particular whether progenitor stars as massive as 10.5 solar masses can produce white dwarfs, rather than supernovae. We propose to observe 5 objects chosen carefully to cover the range of observed properties among carbon atmosphere white dwarfs {effective temperature, surface gravity, abundance of hydrogen/helium and magnetic field}.

  20. Lessons for Asteroseismology from White Dwarf Stars

    Indian Academy of Sciences (India)

    The interpretation of pulsation data for sun-like stars is currently facing challenges quite similar to those faced by white dwarf modelers ten years ago. The observational requirements for uninterrupted long-term monitoring are beginning to be satisfied by successful multi-site campaigns and dedicated satellite missions.

  1. Modelling the formation of double white dwarfs

    NARCIS (Netherlands)

    van der Sluijs, M.V.; Verbunt, F.W.M.|info:eu-repo/dai/nl/068970374; Pols, O.|info:eu-repo/dai/nl/111811155

    2006-01-01

    We investigate the formation of the ten double-lined double white dwarfs that have been observed so far. A detailed stellar evolution code is used to calculate grids of single-star and binary models and we use these to reconstruct possible evolutionary scenarios. We apply various criteria to select

  2. anaesthesia in west-african dwarf goat

    African Journals Online (AJOL)

    0.05/10mg/kg) intramuscularly (1M), xylazine/lignocaine (0.05/10mg/kg) IM lsubcutaneously (SC) and Lignocaine. (lOmg/kg) SC were evaluated in mature, non-fasted West- African Dwarf (WAD) goats for a period of 80 minutes during ...

  3. Period changes in ultracompact double white dwarfs

    NARCIS (Netherlands)

    Marsh, T.R.; Nelemans, G.A.

    2005-01-01

    In recent years there has been much interest in the nature of two stars, V407 Vul and RX J0806+1527, which are widely thought to be binary white dwarfs of very short orbital period, 570 and 321s, respectively. As such they should be strong sources of gravitational waves and possible ancestors of the

  4. Giant Broad Line Regions in Dwarf Seyferts

    Indian Academy of Sciences (India)

    High angular resolution spectroscopy obtained with the Hubble Space Telescope (HST) has revealed a remarkable population of galaxies hosting dwarf Seyfert nuclei with an unusually large broad-line region (BLR). These objects are remarkable for two reasons. Firstly, the size of the BLR can, in some cases, rival those ...

  5. Nutrient relations of dwarf Rhizophora mangle L

    Science.gov (United States)

    Ernesto Medina; Elvira Cuevas; Ariel E. Lugo

    2010-01-01

    Dwarf mangroves on peat substrate growing in eastern Puerto Rico (Los Machos, Ceiba State Forest) were analyzed for element concentration, leaf sap osmolality, and isotopic signatures of C and N in leaves and substrate. Mangrove communities behind the fringe presented poor structural development with maximum height below 1.5 m, lacked a main stem, and produced...

  6. Efficiency of Metal Mixing in Dwarf Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Hirai, Yutaka [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); Saitoh, Takayuki R., E-mail: yutaka.hirai@nao.ac.jp [Earth-Life Science Institute, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8551 (Japan)

    2017-04-01

    Metal mixing plays a critical role in the enrichment of metals in galaxies. The abundance of elements such as Mg, Fe, and Ba in metal-poor stars helps us understand the metal mixing in galaxies. However, the efficiency of metal mixing in galaxies is not yet understood. Here we report a series of N -body/smoothed particle hydrodynamics simulations of dwarf galaxies with different efficiencies of metal mixing using a turbulence-induced mixing model. We show that metal mixing apparently occurs in dwarf galaxies from Mg and Ba abundances. We find that a scaling factor for metal diffusion larger than 0.01 is necessary to reproduce the measured abundances of Ba in dwarf galaxies. This value is consistent with the value expected from turbulence theory and experiments. We also find that the timescale of metal mixing is less than 40 Myr. This timescale is shorter than the typical dynamical times of dwarf galaxies. We demonstrate that the determination of a degree of scatters of Ba abundance by the observation will help us to better constrain the efficiency of metal mixing.

  7. Dwarf galaxies : Important clues to galaxy formation

    NARCIS (Netherlands)

    Tolstoy, E

    2003-01-01

    The smallest dwarf galaxies are the most straight forward objects in which to study star formation processes on a galactic scale. They are typically single cell star forming entities, and as small potentials in orbit around a much larger one they are unlikely to accrete much (if any) extraneous

  8. The White Dwarf Companions of Recycled Pulsars

    OpenAIRE

    van Kerkwijk, M. H.

    1996-01-01

    I review what properties of the white-dwarf companions of recycled pulsars can be inferred from optical observations, and discuss how these can help us understand the characteristics and evolution of these binaries. I focus on spectroscopic observations, describing results obtained recently, and looking forward to what may come.

  9. Line Broadening in White Dwarf Photospheres

    Science.gov (United States)

    Winget, D. E.

    2012-06-01

    White dwarfs are the simplest stars with the simplest surface chemical compositions known. Spectroscopically we detect only hydrogen in surfaces of the vast majority of these stars. The remainders are of various types, including stars with surfaces of nearly pure helium and some apparently massive stars with carbon and oxygen at the photosphere. We will examine the potential offered by the white dwarf stars in the context of both astrophysics and physics. This potential includes studying cosmochronology--establishing the age and evolutionary history of our galaxy and an independent lower limit on the age of the universe, constraining the properties of axions and WIMPS in the context of dark matter models, constraining dark energy by establishing the properties of the massive progenitors of type Ia supernovae, studying nucleosynthesis from their internal composition structure, and crystallization in dense Coulomb plasmas, among many others. Realizing this tremendous scientific potential depends on the determination of two boundary conditions for each star: the surface gravity and effective temperature. To do this, we must establish the photospheric plasma conditions, density and temperature, using observations of the stellar absorption spectra. Our understanding of line broadening appears to be an obstacle, at present. We will discuss the evidence for past theoretical inadequacies in line broadening theory and the hope for recent and future calculations. We will discuss how the experiments underway on the Z-facility at Sandia National Laboratories --where we can create macroscopic uniform plasmas under white dwarf photospheric conditions--will provide the benchmarks for improving our understanding of line broadening under white dwarf photospheric plasma conditions. These experiments will guide future theory and improve our understanding of the white dwarf stars and, through them, the contents and evolution of the cosmos.

  10. Resonant stripping as the origin of dwarf spheroidal galaxies

    Science.gov (United States)

    D'Onghia, Elena; Besla, Gurtina; Cox, Thomas J.; Hernquist, Lars

    2009-07-01

    Dwarf spheroidal galaxies are the most dark-matter-dominated systems in the nearby Universe and their origin is one of the outstanding puzzles of how galaxies form. Dwarf spheroidals are poor in gas and stars, making them unusually faint, and those known as ultra-faint dwarfs have by far the lowest measured stellar content of any galaxy. Previous theories require that dwarf spheroidals orbit near giant galaxies like the Milky Way, but some dwarfs have been observed in the outskirts of the Local Group. Here we report simulations of encounters between dwarf disk galaxies and somewhat larger objects. We find that the encounters excite a process, which we term `resonant stripping', that transforms them into dwarf spheroidals. This effect is distinct from other mechanisms proposed to form dwarf spheroidals, including mergers, galaxy-galaxy harassment, or tidal and ram pressure stripping, because it is driven by gravitational resonances. It may account for some of the observed properties of dwarf spheroidals in the Local Group. Within this framework, dwarf spheroidals should form and interact in pairs, leaving detectable long stellar streams and tails.

  11. CSS 41177: an eclipsing double white dwarf binary

    Science.gov (United States)

    Bours, Madelon

    2013-10-01

    The overwhelming majority of stellar remnants are white dwarfs. Despite their abundance and importance to, amongst others, Galactic age determinations and our understanding of type Ia supernovae fewer than a dozen white dwarfs have model-independent measurements of fundamental parameters like mass and radius. A major limitation on the observational side is that such parameters are extremely difficult to determine in a model-independant way for single white dwarfs. Close white dwarf binaries can provide these important tests.The largest class of white dwarf binaries in the Galaxy are the detached double white dwarfs, which are becoming increasingly popular as the progenitor systems of Type Ia supernovae. In recent years four eclipsing double white dwarfs have been found, creating the opportunity for precision mass and radius measurements of two white dwarfs at once. Our target, CSS 41177, contains two extremely low-gravity white dwarfs with very different temperatures, presenting us with a unique chance to test the existing mass-radius relation at its extremes.Here we propose a 2 orbit HST/COS FUV observation of CSS 41177, to accurately determine the temperature and surface gravity of the hot white dwarf. Through the flux ratio from the light curve this will at the same time constrain those of the cool white dwarf. Therefore it will allow us to add two more white dwarfs with accurate parameters to the short list of white dwarfs for which precise masses and radii are known.Note: The proposed observations are part of the doctoral thesis of Ms. Madelon C.P. Bours.

  12. A tale of seven narrow spikes and a long trough: constraining the timing of the percolation of H II bubbles at the tail end of reionization with ULAS J1120+0641

    Science.gov (United States)

    Chardin, Jonathan; Haehnelt, Martin G.; Bosman, Sarah E. I.; Puchwein, Ewald

    2018-01-01

    High signal-to-noise observations of the Ly α forest transmissivity in the z = 7.085 quasi-stellar object (QSO) ULAS J1120+0641 show seven narrow transmission spikes followed by a long 240 cMpc h-1 trough. Here, we use radiative transfer simulations of cosmic reionization previously calibrated to match a wider range of Ly α forest data to show that the occurrence of seven transmission spikes in the narrow redshift range z = 5.85-6.1 is very sensitive to the exact timing of reionization. Occurrence of the spikes requires the most underdense regions of the intergalactic medium to be already fully ionized. The rapid onset of a long trough at z = 6.12 requires a strong decrease of the photoionization rate Γ at z ≳ 6.1 in this line of sight, consistent with the end of percolation at this redshift. The narrow range of reionization histories that we previously found to be consistent with a wider range of Ly α forest data have a reasonable probability of showing seven spikes and the mock absorption spectra provide an excellent match to the spikes and the trough in the observed spectrum of ULAS J1120+0641. Larger samples of high signal-to-noise searches for rare Ly α transmission spikes at z > 5.8 should therefore provide important further insights into the exact timing of the percolation of H II bubbles at the tail end of reionization.

  13. The K Dwarf Advantage for Biosignatures

    Science.gov (United States)

    Arney, Giada; Domagal-Goldman, Shawn David; Meadows, Victoria

    2018-01-01

    Biosignature detection is typically studied in the context of an atmosphere in chemical disequilibrium. Oxygen (O2) and methane (CH4) are generally considered the “canonical” biosignature disequilibrium pair. However, the modern CH4 concentration poses a major detection challenge to future direct imaging telescopes, and it has been difficult for Earth to accumulate spectrally detectable quantities of O2 and CH4 over its history (Olson et al 2016, Reinhard et al 2017). Even the lower atmospheric levels of O2 typical of the Earth’s Proterozoic eon (0.01-1% of the modern O2 amount) may have resulted in a reduced photochemical lifetime of CH4 due to decreased UV shielding of CH4 (Claire et al 2006, Goldblatt et al 2006). However, while the above is true for an Earthlike planet orbiting a sunlike star, the situation changes for other stars. For instance, Segura et al (2005) found longer photochemical lifetimes for CH4 in the atmospheres of Earthlike planets orbiting M dwarfs. M dwarfs, however, present several barriers to planetary habitability including desiccation during the stellar super-luminous pre-main sequence phase (Lugar and Barnes 2015) and tidal locking. K dwarfs, which comprise about 12% of all main sequence stars, avoid these M dwarf hazards, and will be important targets for future exoplanet direct imaging missions. Using a photochemical model, we find CH4 and O2 are simultaneously detectable in the atmospheres of K dwarf planets with various O2 concentrations ranging between Proterozoic levels and modern O2 amounts. For instance, for a planet with an Earth-like CH4 surface flux (1 x 1011 molecules/cm2/s) and a Proterozoic-like O2 level (1% of modern), the planet generates a CH4 surface mixing ratio of 1x10-5 for a planet orbiting the sun, and 1.5x10-4 – an order of magnitude more CH4 – for a planet orbiting a K6V star. This is enough to produce detectable CH4 and O2 for the planet orbiting the K6V star. We discuss the implications of this

  14. TRIGONOMETRIC PARALLAXES AND PROPER MOTIONS OF 134 SOUTHERN LATE M, L, AND T DWARFS FROM THE CARNEGIE ASTROMETRIC PLANET SEARCH PROGRAM

    Energy Technology Data Exchange (ETDEWEB)

    Weinberger, Alycia J.; Boss, Alan P.; Keiser, Sandra A. [Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Road, NW, Washington, DC 20015-1305 (United States); Anglada-Escudé, Guillem [School of Physics and Astronomy, Queen Mary University of London, 327 Mile End Road, London, E1 4NS (United Kingdom); Thompson, Ian B. [Carnegie Observatories, Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101-1292 (United States); Burley, Gregory [National Research Council of Canada, 5071 West Saanich Road, Victoria, BC V9E 2E7 (Canada)

    2016-07-01

    We report trigonometric parallaxes for 134 low-mass stars and brown dwarfs, of which 38 have no previously published measurement and 79 more have improved uncertainties. Our survey focused on nearby targets, so 119 are closer than 30 pc. Of the 38 stars with new parallaxes, 14 are within 20 pc and seven are likely brown dwarfs (spectral types later than L0). These parallaxes are useful for studies of kinematics, multiplicity, and spectrophotometric calibration. Two objects with new parallaxes are confirmed as young stars with membership in nearby young moving groups: LP 870-65 in AB Doradus and G 161-71 in Argus. We also report the first parallax for the planet-hosting star GJ 3470; this allows us to refine the density of its Neptune-mass planet. T-dwarf 2MASS J12590470-4336243, previously thought to lie within 4 pc, is found to be at 7.8 pc, and the M-type star 2MASS J01392170-3936088 joins the ranks of nearby stars as it is found to be within 10 pc. Five stars that are overluminous and/or too red for their spectral types are identified and deserve further study as possible young stars.

  15. 21 CFR 184.1120 - Brown algae.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Brown algae. 184.1120 Section 184.1120 Food and... Substances Affirmed as GRAS § 184.1120 Brown algae. (a) Brown algae are seaweeds of the species Analipus.../code_of_federal_regulations/ibr_locations.html. (c) In accordance with § 184.1(b)(2), the ingredient is...

  16. Loss of the tumour suppressor gene AIP mediates the browning of human brown fat tumours.

    Science.gov (United States)

    Magnusson, Linda; Hansen, Nils; Saba, Karim H; Nilsson, Jenny; Fioretos, Thoas; Rissler, Pehr; Nord, Karolin H

    2017-10-01

    Human brown fat tumours (hibernomas) show concomitant loss of the tumour suppressor genes MEN1 and AIP. We hypothesized that the brown fat phenotype is attributable to these mutations. Accordingly, in this study, we demonstrate that silencing of AIP in human brown preadipocytic and white fat cell lines results in the induction of the brown fat marker UCP1. In human adipocytic tumours, loss of MEN1 was found both in white (one of 51 lipomas) and in brown fat tumours. In contrast, concurrent loss of AIP was always accompanied by a brown fat morphology. We conclude that this white-to-brown phenotype switch in brown fat tumours is mediated by the loss of AIP. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

  17. Surprising Legacies of Brown v. Board

    OpenAIRE

    Minow, Martha Louise

    2014-01-01

    Perhaps the most powerful legacy of Brown v. Board is this: opponents in varied political battles fifty years later each claim ties to the decision and its meaning. So although the analogy between Brown and same-sex marriage has divided Black clergy, each side vies to inherit the civil rights heritage. President George W. Bush invoked Brown in opposing race-conscious college admission practices. The success of Brown in reshaping the moral landscape has been so profound that I fear we do not f...

  18. Seasonality of brown recluse populations is reflected by numbers of brown recluse envenomations

    OpenAIRE

    Rader, RK; Stoecker, WV; Malters, JM; Marr, MT; Dyer, JA

    2012-01-01

    A significant seasonal correlation was recently shown for brown recluse spider activity. Vetter (2011) observed brown recluse spiders were submitted by the general public predominantly during April–October. For patients with suspected brown recluse spider bites (BRSB), we have observed the same seasonality. Among 45 cases with features consistent of a BRSB, 43 (95.6%) occurred during April–October. Both the Vetter study and our study serve to demonstrate seasonal activity for brown recluse sp...

  19. Enzymatic Browning: a practical class

    Directory of Open Access Journals (Sweden)

    Maria Teresa Pedrosa Silva Clerici

    2014-10-01

    Full Text Available This paper presents a practical class about the enzymes polyphenol oxidases, which have been shown to be responsible for the enzymatic browning of fruits and vegetables. Vegetables samples were submitted to enzymatic inactivation process with chemical reagents, as well as by bleaching methods of applying heat by conventional oven and microwave oven. Process efficiency was assessed qualitatively by both observing the guaiacol peroxidase activity and after the storage period under refrigeration or freezing. The practical results obtained in this class allow exploring multidisciplinary knowledge in food science, with practical applications in everyday life.

  20. Electron capture in carbon dwarf supernovae

    Science.gov (United States)

    Mazurek, T. J.; Truran, J. W.; Cameron, A. G. W.

    1974-01-01

    The rates of electron capture on heavier elements under the extreme conditions predicted for dwarf star supernovae have been computed, incorporating modifications that seem to be indicated by present experimental results. An estimate of the maximum possible value of such rates is also given. The distribution of nuclei in nuclear statistical equilibrium has been calculated for the range of expected supernovae conditions, including the effects of the temperature dependence of nuclear partition functions. These nuclide abundance distributions are then used to compute nuclear equilibrium thermodynamic properties. The effects of the electron capture on such equilibrium matter are discussed. In the context of the 'carbon detonation' supernova model, the dwarf central density required to ensure core collapse to a neutron star configuration is found to be slightly higher than that obtained by Bruenn (1972) with the electron capture rates of Hansen (1966).-

  1. Brown Fat and Browning for the Treatment of Obesity and Related Metabolic Disorders

    Directory of Open Access Journals (Sweden)

    So Hun Kim

    2016-02-01

    Full Text Available Brown fat is a specialized fat depot that can increase energy expenditure and produce heat. After the recent discovery of the presence of active brown fat in human adults and novel transcription factors controlling brown adipocyte differentiation, the field of the study of brown fat has gained great interest and is rapidly growing. Brown fat expansion and/or activation results in increased energy expenditure and a negative energy balance in mice and limits weight gain. Brown fat is also able to utilize blood glucose and lipid and results in improved glucose metabolism and blood lipid independent of weight loss. Prolonged cold exposure and beta adrenergic agonists can induce browning of white adipose tissue. The inducible brown adipocyte, beige adipocyte evolving by thermogenic activation of white adipose tissue have different origin and molecular signature from classical brown adipocytes but share the characteristics of high mitochondria content, UCP1 expression and thermogenic capacity when activated. Increasing browning may also be an efficient way to increase whole brown fat activity. Recent human studies have shown possibilities that findings in mice can be reproduced in human, making brown fat a good candidate organ to treat obesity and its related disorders.

  2. SIM's Search for Planets Orbiting Nearby White Dwarfs - Update

    Science.gov (United States)

    Subasavage, John P., Jr.

    2009-05-01

    I propose to use the Space Interferometry Mission (SIM) to observe a sample ( 25-50) of nearby white dwarfs in hopes of detecting planetary companions with masses in the 10 Earth mass range on average. Because of the nature of white dwarfs' spectral signatures (a few broad, if any, absorption lines), current radial velocity planet hunting techniques are not viable. Astrometry is currently the only technique capable of detecting low mass planets around white dwarfs and SIM would be the best suited astrometric instrument to do so once launched. As part of a SIM Science Study, I present a detailed evaluation of the star fields in the vicinity of nearby white dwarfs within 20 pc and with V white dwarfs with accuate trigonometric parallaxes and photometry. This effort will aid in the selection of white dwarfs to be targeted for planet searches using SIM by maximizing planetary sensitivities while minimizing total mission time spent on these observations.

  3. Activity-induced radial velocity variation of M dwarf stars

    DEFF Research Database (Denmark)

    Andersen, Jan Marie; Korhonen, Heidi Helena

    2012-01-01

    that can drown out a planetary signature. Cool, low-mass M dwarf stars can be highly active, which can make detection of potentially habitable planets around these stars difficult. We investigate radial velocity variations caused by different activity (spot) patterns on M dwarf stars in order to determine......Stellar magnetic activity manifests itself in a variety of ways including starspots-cool, dark regions on the stellar surface. Starspots can cause variations ('jitter') in spectral line-profiles which can mimic the radial velocity (RV) variations caused by an orbiting planet, or create RV noise...... the limits of detectability for small planets orbiting active M dwarfs. We report on our progress toward the aim of answering the following questions: What types of spot patterns are realistic for M dwarf stars? What effect will spots have on M dwarf RV measurements? Can jitter from M dwarf spots mimic...

  4. Identifying Likely Disk-hosting M dwarfs with Disk Detective

    Science.gov (United States)

    Silverberg, Steven; Wisniewski, John; Kuchner, Marc J.; Disk Detective Collaboration

    2018-01-01

    M dwarfs are critical targets for exoplanet searches. Debris disks often provide key information as to the formation and evolution of planetary systems around higher-mass stars, alongside the planet themselves. However, less than 300 M dwarf debris disks are known, despite M dwarfs making up 70% of the local neighborhood. The Disk Detective citizen science project has identified over 6000 new potential disk host stars from the AllWISE catalog over the past three years. Here, we present preliminary results of our search for new disk-hosting M dwarfs in the survey. Based on near-infrared color cuts and fitting stellar models to photometry, we have identified over 500 potential new M dwarf disk hosts, nearly doubling the known number of such systems. In this talk, we present our methodology, and outline our ongoing work to confirm systems as M dwarf disks.

  5. Anderson and Stoner Published White Dwarf Mass Limits Before Chandrasekhar

    CERN Document Server

    Blackman, Eric G

    2011-01-01

    In their engaging recountals of Chandrasekhar's extraordinary career (Physics Today, vol 63, Issue 12, Dec 2010), neither Dyson nor Wali mention that Chandrasekhar was the third person not the first, to publish a white dwarf mass limit incorporating a relativistic treatment of degenerate electrons. As it has become a common misconception that Chandrasekhar was the first, a clarifying reminder on this historical point is warranted. In short, the white dwarf mass limit widely attributed to Chandrasekhar (1931) should be the specific white dwarf mass limit calculated for a polytrope. The insight that a relativistic treatment of degeneracy leads to the existence of a white dwarf mass limit first appeared in papers of W. Anderson (1929) and E.C. Stoner (1930) for a uniform density star. Accordingly, Chandrasekhar (1931) cites Stoner (1930) and points out that the polytrope white dwarf mass limit is less than Stoner's uniform density white dwarf mass limit by about 20%.

  6. Workshop on the Magellanic Clouds and other Dwarf Galaxies

    CERN Document Server

    Richtler, T; Richtler, Tom; Braun, Jochen M.

    1998-01-01

    The Workshop 'The Magellanic Clouds and Other Dwarf Galaxies' was held at the Physikzentrum Bad Honnef in January 1998. The proceedings comprise 79 contributions. About 1/3 of the 352 pages contain the following Reviews: The Violent Interstellar Medium in Dwarf Galaxies: Atomic Gas (Elias Brinks and Fabian Walter), Hot Gas in the Large Magellanic Cloud (You-Hua Chu), Astrophysics of Dwarf Galaxies: Structures and Stellar Populations (John S. Gallagher), Star-forming regions and ionized gas in irregular galaxies (Deidre A. Hunter), The Law of Star Formation in Disk Galaxies (Joachim Koeppen), Strange Dark Matters in Nearby Dwarf Galaxies (Mario Mateo), Holes and Shells in Galaxies: Observations versus Theoretical Concepts (Jan Palous), Detailed Recent Star Formation Histories of Dwarf Irregular Galaxies and Their Many Uses (Evan D. Skillman et al.), and Nearby Young Dwarf Galaxies (Trinh X. Thuan and Yuri I. Izotov). See the complete electronic version for further details.

  7. Surface photometry of new nearby dwarf galaxies

    OpenAIRE

    Makarova, L. N.; Karachentsev, I. D.; Grebel, E. K.; Barsunova, O. Yu.

    2002-01-01

    We present CCD surface photometry of 16 nearby dwarf galaxies, many of which were only recently discovered. Our sample comprises both isolated galaxies and galaxies that are members of nearby galaxy groups. The observations were obtained in the Johnson B and V bands (and in some cases in Kron-Cousins I). We derive surface brightness profiles, total magnitudes, and integrated colors. For the 11 galaxies in our sample with distance estimates the absolute B magnitudes lie in the range of -10>Mb>...

  8. The white dwarf population of NGC 6397

    Science.gov (United States)

    Torres, Santiago; García-Berro, Enrique; Althaus, Leandro G.; Camisassa, María E.

    2015-09-01

    Context. NGC 6397 is one of the most interesting, well-observed, and most thoroughly theoretically studied globular clusters. The existing wealth of observations allows us to study the reliability of the theoretical white dwarf cooling sequences of low-metallicity progenitors, to determine the age of NGC 6397 and the percentage of unresolved binaries. We also assess other important characteristics of the cluster, such as the slope of the initial mass function or the fraction of white dwarfs with hydrogen-deficient atmospheres. Aims: We present a population synthesis study of the white dwarf population of NGC 6397. In particular, we study the shape of the color-magnitude diagram and the corresponding magnitude and color distributions. Methods: To do this, we used an advanced Monte Carlo code that incorporates the most recent and reliable cooling sequences and an accurate modeling of the observational biases. Results: Our theoretical models and the observed data agree well. In particular, we find that this agreement is best for those cooling sequences that take into account residual hydrogen burning. This result has important consequences for the evolution of progenitor stars during the thermally pulsing asymptotic giant branch phase, since it implies that appreciable third dredge-up in low-mass, low-metallicity progenitors is not expected to occur. Using a standard burst duration of 1.0 Gyr, we obtain that the age of the cluster is 12.8+0.50-0.75 Gyr. Greater ages are also compatible with the observed data, but then unrealistic longer durations of the initial burst of star formation are needed to fit the luminosity function. Conclusions: We conclude that a correct modeling of the white dwarf population of globular clusters, used in combination with the number counts of main-sequence stars, provides a unique tool for modeling the properties of globular clusters.

  9. Dwarf Galaxies Swimming in Tidal Tails

    Science.gov (United States)

    2005-01-01

    This false-color infrared image from NASA's Spitzer Space Telescope shows little 'dwarf galaxies' forming in the 'tails' of two larger galaxies that are colliding together. The big galaxies are at the center of the picture, while the dwarfs can be seen as red dots in the red streamers, or tidal tails. The two blue dots above the big galaxies are stars in the foreground. Galaxy mergers are common occurrences in the universe; for example, our own Milky Way galaxy will eventually smash into the nearby Andromeda galaxy. When two galaxies meet, they tend to rip each other apart, leaving a trail, called a tidal tail, of gas and dust in their wake. It is out of this galactic debris that new dwarf galaxies are born. The new Spitzer picture demonstrates that these particular dwarfs are actively forming stars. The red color indicates the presence of dust produced in star-forming regions, including organic molecules called polycyclic aromatic hydrocarbons. These carbon-containing molecules are also found on Earth, in car exhaust and on burnt toast, among other places. Here, the molecules are being heated up by the young stars, and, as a result, shine in infrared light. This image was taken by the infrared array camera on Spitzer. It is a 4-color composite of infrared light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0 microns (red). Starlight has been subtracted from the orange and red channels in order to enhance the dust features.

  10. Formation of dwarf galaxies in tidal tails

    Science.gov (United States)

    Barnes, Joshua E.; Hernquist, Lars

    1992-01-01

    The results are reported of numerical simulations of encounters between disk galaxies, each modeled with a central bulge, an exponential disk, and a spheroidal dark-matter halo. It is found that dwarf systems form in material drawn out during the encounter; these objects can capture large amounts of moderately enriched gas but retain little dark matter from their parents' haloes. They should therefore have lower mass-to-light ratios than galaxies formed directly by the collapse of primordial matter.

  11. Local Thermonuclear Runaways in Dwarf Novae?

    Science.gov (United States)

    Shara, Michael

    2012-10-01

    We have no hope of understanding the structure and evolution of a class of astrophysical objects if we cannot identify the dominant energy source of those objects.The Disk Instability Model {DIM} postulates that Dwarf Nova {DN} outbursts are powered by runaway accretion from an accretion disk onto a White Dwarf {WD} in a red dwarf-WD mass transferring binary. Ominously, HST observations {e.g. Sion et al. 2001} of WD surface abundances hint at a significant shortcoming of the DIM. The data from the present proposal will be able to unequivocally demonstrate if the observed highly Carbon-depleted and Nitrogen-enhanced abundances on WD surfaces {NOT predicted by DIM} vary with binary orbital phase, or throughout a DN quiescence cycle, or from cycle to cycle. These same data will test if predicted {but never observed} Local Thermonuclear Runaways {"Nuclear-powered mini-novas"} occur on the WDs of DN. Such events could trigger or even power DN, providing the long-sought physical mechanism of DN eruptions that DIM lacks. As a "free" bonus, the same data may also directly detect the diffusion of accreted metals in a WD atmosphere for the first time, or provide significant limits on the diffusion rate.

  12. White dwarf cosmochronology in the solar neighborhood

    Energy Technology Data Exchange (ETDEWEB)

    Tremblay, P.-E.; Kalirai, J. S.; Soderblom, D. R.; Cignoni, M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Cummings, J., E-mail: tremblay@stsci.edu [Center for Astrophysical Sciences, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States)

    2014-08-20

    The study of the stellar formation history in the solar neighborhood is a powerful technique to recover information about the early stages and evolution of the Milky Way. We present a new method that consists of directly probing the formation history from the nearby stellar remnants. We rely on the volume complete sample of white dwarfs within 20 pc, where accurate cooling ages and masses have been determined. The well characterized initial-final mass relation is employed in order to recover the initial masses (1 ≲ M {sub initial}/M {sub ☉} ≲ 8) and total ages for the local degenerate sample. We correct for moderate biases that are necessary to transform our results to a global stellar formation rate, which can be compared to similar studies based on the properties of main-sequence stars in the solar neighborhood. Our method provides precise formation rates for all ages except in very recent times, and the results suggest an enhanced formation rate for the solar neighborhood in the last 5 Gyr compared to the range 5 < Age (Gyr) < 10. Furthermore, the observed total age of ∼10 Gyr for the oldest white dwarfs in the local sample is consistent with the early seminal studies that have determined the age of the Galactic disk from stellar remnants. The main shortcoming of our study is the small size of the local white dwarf sample. However, the presented technique can be applied to larger samples in the future.

  13. A minimum mass nebula for M dwarfs

    Science.gov (United States)

    Gaidos, E.

    2017-09-01

    Recently revealed differences in planets around M dwarf versus solar-type stars could arise from differences in their primordial discs and surveys of T Tauri stars find a correlation between stellar mass and disc mass. 'Minimum' discs have been reconstructed for the Solar system and solar-type stars and here this exercise is performed for M dwarfs using Kepler-detected planets. Distribution of planet mass between current orbits produces a disc with total mass of ≈0.009 M⊙ and a power-law profile with index α = 2.2. Disc reconstruction from the output of a forward model of planet formation indicates that the effect of detection bias on disc profile is slight and that the observed scatter in planet masses and semimajor axes are consistent with a universal disc profile. This nominal M dwarf disc is more centrally concentrated than those inferred around the solar-type stars observed by Kepler, and the mass surface density beyond 0.02 au is sufficient for in situ accretion of planets as single embryos. The mass of refractory solids within 0.5 au is 5.6 M⊕ compared to 4 M⊕ for solar-type stars in contrast with the trend with total disc mass. The total solid beyond 0.5 au is sufficient for the core of at least one giant planet.

  14. White Dwarf Cosmochronology in the Solar Neighborhood

    Science.gov (United States)

    Tremblay, P.-E.; Kalirai, J. S.; Soderblom, D. R.; Cignoni, M.; Cummings, J.

    2014-08-01

    The study of the stellar formation history in the solar neighborhood is a powerful technique to recover information about the early stages and evolution of the Milky Way. We present a new method that consists of directly probing the formation history from the nearby stellar remnants. We rely on the volume complete sample of white dwarfs within 20 pc, where accurate cooling ages and masses have been determined. The well characterized initial-final mass relation is employed in order to recover the initial masses (1 ages for the local degenerate sample. We correct for moderate biases that are necessary to transform our results to a global stellar formation rate, which can be compared to similar studies based on the properties of main-sequence stars in the solar neighborhood. Our method provides precise formation rates for all ages except in very recent times, and the results suggest an enhanced formation rate for the solar neighborhood in the last 5 Gyr compared to the range 5 Age (Gyr) age of ~10 Gyr for the oldest white dwarfs in the local sample is consistent with the early seminal studies that have determined the age of the Galactic disk from stellar remnants. The main shortcoming of our study is the small size of the local white dwarf sample. However, the presented technique can be applied to larger samples in the future.

  15. Unlocking the secrets of white dwarf stars

    CERN Document Server

    Van Horn, Hugh M

    2015-01-01

    White dwarfs, each containing about as much mass as our Sun but packed into a volume about the size of Earth, are the endpoints of evolution for most stars. Thousands of these faint objects have now been discovered, though only a century ago only three were known. They are among the most common stars in the Milky Way Galaxy, and they have become important tools in understanding the universe. Yet a century ago only three white dwarfs were known.   The existence of these stars completely baffled the scientists of the day, and solving the mysteries of these strange objects required revolutionary advances in science and technology, including the development of quantum physics, the construction and utilization of large telescopes, the invention of the digital computer, and the ability to make astronomical observations from space.   This book tells the story of the growth in our understanding of white dwarf stars, set within the context of the relevant scientific and technological advances. Part popular science, ...

  16. Reading the Chemical Evolution of Stellar Populations in Dwarf Galaxies

    OpenAIRE

    Hendricks, Benjamin Thomas

    2015-01-01

    In this thesis I present observations and analyses addressed to understand the individual evolution of dwarf galaxies and the interdependency with their local environment. My study focuses on the Fornax dwarf spheroidal galaxy, which is the most massive galaxy of its type in the Local Group, hosting stars with a broad range in age and metallicity. Additionally, it is the only intact dwarf spheroidal with an own globular cluster system. Therefore, it provides a superb laboratory to...

  17. Optical and EUV light curves of dwarf nova outbursts

    Energy Technology Data Exchange (ETDEWEB)

    Mauche, C W; Mattei, J A; Bateson, F M

    2000-11-15

    We combine AAVSO and VSS/RASNZ optical and Extreme Ultraviolet Explorer EUV light curves of dwarf novae in outburst to place constraints on the nature of dwarf nova outbursts. From the observed optical-EUV time delays of {approx} 0.75-1.5 days, we show that the propagation velocity of the dwarf nova instability heating wave is {approx} 3 km s{sup -1}.

  18. The brain and brown fat.

    Science.gov (United States)

    Contreras, Cristina; Gonzalez, Francisco; Fernø, Johan; Diéguez, Carlos; Rahmouni, Kamal; Nogueiras, Rubén; López, Miguel

    2015-03-01

    Brown adipose tissue (BAT) is a specialized organ responsible for thermogenesis, a process required for maintaining body temperature. BAT is regulated by the sympathetic nervous system (SNS), which activates lipolysis and mitochondrial uncoupling in brown adipocytes. For many years, BAT was considered to be important only in small mammals and newborn humans, but recent data have shown that BAT is also functional in adult humans. On the basis of this evidence, extensive research has been focused on BAT function, where new molecules, such as irisin and bone morphogenetic proteins, particularly BMP7 and BMP8B, as well as novel central factors and new regulatory mechanisms, such as orexins and the canonical ventomedial nucleus of the hypothalamus (VMH) AMP- activated protein kinase (AMPK)-SNS-BAT axis, have been discovered and emerged as potential drug targets to combat obesity. In this review we provide an overview of the complex central regulation of BAT and how different neuronal cell populations co-ordinately work to maintain energy homeostasis.

  19. The fate of exomoons in white dwarf planetary systems

    Science.gov (United States)

    Payne, Matthew J.; Veras, Dimitri; Gänsicke, Boris T.; Holman, Matthew J.

    2017-01-01

    Roughly 1000 white dwarfs are known to be polluted with planetary material, and the progenitors of this material are typically assumed to be asteroids. The dynamical architectures which perturb asteroids into white dwarfs are still unknown, but may be crucially dependent on moons liberated from parent planets during post-main-sequence gravitational scattering. Here, we trace the fate of these exomoons, and show that they more easily achieve deep radial incursions towards the white dwarf than do scattered planets. Consequently, moons are likely to play a significant role in white dwarf pollution, and in some cases may be the progenitors of the pollution itself.

  20. Hey! A Brown Recluse Spider Bit Me!

    Science.gov (United States)

    ... System Taking Care of Your Teeth Bad Breath Hey! A Brown Recluse Spider Bit Me! KidsHealth > For Kids > Hey! A Brown Recluse Spider Bit Me! Print A ... For Kids For Parents MORE ON THIS TOPIC Hey! A Fire Ant Stung Me! Hey! A Tarantula ...

  1. Remembering "Brown": Silence, Loss, Rage, and Hope

    Science.gov (United States)

    Banks, James A.

    2004-01-01

    The author was in the seventh grade at the Newsome Training School in Aubrey, Arkansas when the Supreme Court handed down "Brown v. Board of Education" on May 17, 1954. His most powerful memory of the "Brown" decision is that he has no memory of it being rendered or mentioned by his parents, teachers, or preachers. In his rural…

  2. Isolation of glycoproteins from brown algae

    DEFF Research Database (Denmark)

    2015-01-01

    The present invention relates to a novel process for the isolation of unique anti-oxidative glycoproteins from the pH precipitated fractions of enzymatic extracts of brown algae. Two brown seaweeds viz, Fucus serratus and Fucus vesiculosus were hydrolysed by using 3 enzymes viz, Alcalase, Viscozyme...

  3. Brown vs. Board of Education Booklet

    OpenAIRE

    IDEA, UCLA

    2004-01-01

    This booklet was designed for K-12 classrooms and community groups examining the legacy of Brown v Board for California. The booklet chronicles the national battle for equal schooling up to and since the Brown decision. It also highlights the history of school segregation in California and the ongoing struggle for equal schooling.

  4. "Brown" and Black-White Achievement

    Science.gov (United States)

    Armor, David J.

    2006-01-01

    "Brown v. Board of Education" only presumed to eliminate the "de jure" apartheid that existed in 1954. It was never intended to resolve the "de facto" gap in minority achievement that still faces education policymakers today. Sociologist David J. Armor goes beyond "Brown" to identify a set of definite risk…

  5. Brown recluse spider bite on the breast.

    Science.gov (United States)

    Norris, Kori; Misra, Subhasis

    2014-05-01

    Brown recluse spiders are one of two types of spiders in the United States that can cause significant tissue damage and, in rare cases, death. Brown recluse spider bites are most often benign and self-limiting, but in a few cases can cause severe necrotic skin lesions.

  6. Some Aspects of Enzymatic Browning in Apples

    Science.gov (United States)

    Liffen, C. L.; Cleeve, H. N.

    1975-01-01

    Describes material modified from the Nuffield advanced chemistry course to make it meaningful and relevant to pupils in the middle school. Discusses a series of simple experiments on apple browning and summarizes the browning process and its control. (Author/GS)

  7. Traumatic Brown-Séquard-plus syndrome.

    Science.gov (United States)

    McCarron, M O; Flynn, P A; Pang, K A; Hawkins, S A

    2001-09-01

    In the 1840s Brown-Séquard described the motor and sensory effects of sectioning half of the spinal cord. Penetrating injuries can cause Brown-Séquard or, more frequently, Brown-Séquard-plus syndromes. To report the case of a 25-year-old man who developed left-sided Brown-Séquard syndrome at the C8 level and left-sided Horner syndrome plus urinary retention and bilateral extensor responses following a stab wound in the right side of the neck. Magnetic resonance imaging demonstrated a low cervical lesion and somatosensory evoked potentials confirmed the clinical finding of left-side dorsal column disturbance. At follow-up, the patient's mobility and bladder function had returned to normal. This patient recovered well after a penetrating neck injury that disturbed function in more than half the lower cervical spinal cord (Brown-Séquard-plus syndrome).

  8. K-KIDS: The Imaging Survey for Stellar Companions at Solar System Scales Around More than 1000 K Dwarfs

    Science.gov (United States)

    Nusdeo, Daniel A.

    2018-01-01

    An initial sample of 1048 K dwarfs, hereafter known as the “K-KIDS” targets, was built from the Hipparcos and 2MASS catalogs in order to construct a robust list for a multiplicity survey. There have been two recent comprehensive stellar multiplicity surveys of low mass stars: Raghavan et. al. (2010) searched 454 solar-type stars and found a stellar multiplicity rate of 50%, and Winters et. al. (2017) surveyed 1121 M dwarfs and found a rate of 27%. A gap still remains in our understanding of the multiplicity rate of K dwarfs.For observational purposes, K-KIDS is confined equatorally to -30 stars are observable from either hemisphere, thereby creating a legacy sample that can be investigated for decades for stellar, brown dwarf, and planetary companions of various types. The RECONS team is conducting four companion surveys of these 1048 stars, including imaging surveys at various separations --- large (10+ arcseconds), medium (2–10 arcseconds), and small (0.02–2 arcseconds) --- and a radial velocity survey for the closest companions. Here we report on the small separation survey that targets scales similar to our Solar System, 0.1-100 AU, carried out using the Differential Speckle Survey Instrument on the Gemini and WIYN telescopes. To date, we have observed 964 out of 1048 systems, already finding 135 companions. We present a sample of K dwarf double stars with separations less than 100 AU, of which the vast majority are new discoveries. Further progress on the medium and large separation regimes ensures that a statistically significant stellar multiplicity rate for K dwarfs will soon be in achieved, which can then be investigated for dependences on, for example, stellar age and metallicity.This effort has been supported by the NSF through grant AST-1517413 and via observations obtained at the Gemini Observatory (North and South telescopes), which is operated by AURA under a cooperative agreement with the NSF on behalf of the Gemini partnership, and at the

  9. Kepler monitoring of an L dwarf I. The photometric period and white light flares

    Energy Technology Data Exchange (ETDEWEB)

    Gizis, John E. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Burgasser, Adam J. [Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093 (United States); Berger, Edo; Williams, Peter K. G. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Vrba, Frederick J. [US Naval Observatory, Flagstaff Station, 10391 West Naval Observatory Road, Flagstaff, AZ 86001 (United States); Cruz, Kelle L. [Department of Physics and Astronomy, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10065 (United States); Metchev, Stanimir [Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794 (United States)

    2013-12-20

    We report on the results of 15 months of monitoring the nearby field L1 dwarf WISEP J190648.47+401106.8 (W1906+40) with the Kepler mission. Supporting observations with the Karl G. Jansky Very Large Array and Gemini North Telescope reveal that the L dwarf is magnetically active, with quiescent radio and variable Hα emission. A preliminary trigonometric parallax shows that W1906+40 is at a distance of 16.35{sub −0.34}{sup +0.36} pc, and all observations are consistent with W1906+40 being an old disk star just above the hydrogen-burning limit. The star shows photometric variability with a period of 8.9 hr and an amplitude of 1.5%, with a consistent phase throughout the year. We infer a radius of 0.92 ± 0.07R{sub J} and sin i > 0.57 from the observed period, luminosity (10{sup –3.67} {sup ±} {sup 0.03} L {sub ☉}), effective temperature (2300 ± 75 K), and vsin i (11.2 ± 2.2 km s{sup –1}). The light curve may be modeled with a single large, high latitude dark spot. Unlike many L-type brown dwarfs, there is no evidence of other variations at the ≳ 2% level, either non-periodic or transient periodic, that mask the underlying rotation period. We suggest that the long-lived surface features may be due to starspots, but the possibility of cloud variations cannot be ruled out without further multi-wavelength observations. During the Gemini spectroscopy, we observed the most powerful flare ever seen on an L dwarf, with an estimated energy of ∼1.6 × 10{sup 32} erg in white light emission. Using the Kepler data, we identify similar flares and estimate that white light flares with optical/ultraviolet energies of 10{sup 31} erg or more occur on W1906+40 as often as 1-2 times per month.

  10. Brown Swiss cattle cytogenetic analysis

    Directory of Open Access Journals (Sweden)

    Rita Maria Ladeira Pires

    2010-02-01

    Full Text Available At 1985, a Brown Swiss herd from the Institute of Animal Science and Pastures, APTA/ SAA was cytogenetically analyzed and 1/29 Robertsonian translocation was observed. Such anomaly is related to fertility reduction. Quimeric abnormality such as 60,XX/60,XY in freemartin females. This study aimed to evaluate the incidence of cromossomic abnormalities in Brown Swiss animals, descending form herd karyotyped earlier. After 25 years, 127 animals (97 females and 30 males from this herd were karyotyped by metaphases obtained from blood lymphocyte cultures. The typical diploid number 2n=60, 58 acrocentric and two X submetacentric chromosomes were confirmed in 94 females and in 27 males the sexual complement X and Y, both submetacentric, although from different sizes. Four females from gemelar parturition whit males were karyotyped. Three of them presented quimerism 60,XX/60,XY (one with 25.8% of female cells (XX and 74.2% male cells (XY; one another with 10% of cells XX e 90% of XY and the third with 50% of each type showing genital masculinization, diagnosed as freemartism and discarded from herd. Two hundred and five cells were analyzed from another female twins and only 60,XX cells were found, diagnosed as normal. His sister also were normal (60,XY. The another three males were also analyzed from gemelar heterosexual parturition, with karyotype 60,XX/60,XY. Cytogenetic analysis are a safe methodology for freemartin abnormalities identification in female bovine twins with male bovine, giving the opportunity of selecting fertile animals, avoiding loses in the management of sterile animals. Robertsonian’s translocation was not observed in any of the animals analyzed.

  11. The RSA survey of dwarf galaxies, 1: Optical photometry

    Science.gov (United States)

    Vader, J. Patricia; Chaboyer, Brian

    1994-01-01

    We present detailed surface photometry, based on broad B-band charge coupled device (CCD) images, of about 80 dwarf galaxies. Our sample represents approximately 10% of all dwarf galaxies identified in the vicinity of Revised Shapley-Ames (RSA) galaxies on high resolution blue photographic plates, referred to as the RSA survey of dwarf galaxies. We derive global properties and radial surface brightness profiles, and examine the morphologies. The radial surface brightness profiles of dwarf galaxies, whether early or late type, display the same varieties in shape and complexity as those of classical giant galaxies. Only a few are well described by a pure r(exp 1/4) law. Exponential profiles prevail. Features typical of giant disk galaxies, such as exponential profiles with a central depression, lenses, and even, in one case (IC 2041), a relatively prominent bulge are also found in dwarf galaxies. Our data suggest that the central region evolves from being bulge-like, with an r(exp 1/4) law profile, in bright galaxies to a lens-like structure in dwarf galaxies. We prove detailed surface photometry to be a helpful if not always sufficient tool in investigating the structure of dwarf galaxies. In many cases kinematic information is needed to complete the picture. We find the shapes of the surface brightness profiles to be loosely associated with morphological type. Our sample contains several new galaxies with properties intermediate between those of giant and dwarf ellipticals (but no M32-like objects). This shows that such intermediate galaxies exist so that at least a fraction of early-type dwarf ellipticals is structurally related to early-type giants instead of belonging to a totally unrelated, disjunct family. This supports an origin of early-type dwarf galaxies as originally more massive systems that acquired their current morphology as a result of substantial, presumable supernova-driven, mass loss. On the other hand, several early-type dwarfs in our sample are

  12. Distinguishing cold dark matter dwarfs from self-interacting dark matter dwarfs in baryonic simulations

    Science.gov (United States)

    Strickland, Emily; Fitts, Alex; Boylan-Kolchin, Michael

    2018-01-01

    Our collaboration has simulated several high-resolution (mbaryon = 500Mo, mdm = 2500Mo) cosmological zoom-in simulations of isolated dwarf galaxies. We simulate each galaxy in standard cold dark matter (ΛCDM) as well as a self-interacting dark matter (SIDM) (with a cross section of σ/m ~ 1 cm2/g), both with and without baryons, to identify distinguishing characteristics between the two. The simulations are run using GIZMO, a meshless-finite-mass (MFM) hydrodynamical code, and are part of the Feedback in Realistic Environments (FIRE) project. By analyzing both the global properties and inner structure of the dwarfs in varying dark matter prescriptions, we provide a side-by-side comparison of isolated, dark matter dominated galaxies at the mass scale where differences in the two models of dark matter are thought to be the most obvious. We find that the edge of classical dwarfs and ultra-faint dwarfs (UFDs) (at ~105 Mo) provides the clearest window for distinguishing between the two theories. Here our SIDM galaxies continue to display a cored inner profile unlike their CDM counterparts. The SIDM versions of each galaxy also have measurably lower stellar velocity dispersions than their CDM counterparts.

  13. Serendipitous discovery of a faint dwarf galaxy near a Local Volume dwarf

    Science.gov (United States)

    Makarova, L. N.; Makarov, D. I.; Antipova, A. V.; Karachentsev, I. D.; Tully, R. B.

    2018-03-01

    A faint dwarf irregular galaxy has been discovered in the HST/ACS field of LV J1157+5638. The galaxy is resolved into individual stars, including the brightest magnitude of the red giant branch. The dwarf is very likely a physical satellite of LV J1157+5638. The distance modulus of LV J1157+5638 using the tip of the red giant branch (TRGB) distance indicator is 29.82 ± 0.09 mag (D = 9.22 ± 0.38 Mpc). The TRGB distance modulus of LV J1157+5638 sat is 29.76 ± 0.11 mag (D = 8.95 ± 0.42 Mpc). The distances to the two galaxies are consistent within the uncertainties. The projected separation between them is only 3.9 kpc. LV J1157+5638 has a total absolute V magnitude of -13.26 ± 0.10 and linear Holmberg diameter of 1.36 kpc, whereas its faint satellite LV J1157+5638 sat has MV = -9.38 ± 0.13 mag and Holmberg diameter of 0.37 kpc. Such a faint dwarf was discovered for the first time beyond the nearest 4 Mpc from us. The presence of main-sequence stars in both galaxies unambiguously indicates the classification of the objects as dwarf irregulars with recent or ongoing star formation events in both galaxies.

  14. A Spectral Analysis of a Rare "Dwarf Eat Dwarf" Cannibalism Event

    Science.gov (United States)

    Theakanath, Kuriakose; Toloba, E.; Guhathakurta, P.; Romanowsky, A. J.; Ramachandran, N.; Arnold, J.

    2014-01-01

    We have used Keck/DEIMOS to conduct the first detailed spectroscopic study of the recently discovered stellar stream in the Large Magellanic Cloud analog NGC 4449. Martinez-Delgado et al. (2012), using the tip of the red giant branch (TRGB), found that both objects, the stream and NGC 4449, are at the same distance, which suggests that this stream is the remnant of the first ongoing dwarf-dwarf cannibalism event known so far. Learning about the orbital properties of this event is a powerful tool to constrain the physical conditions involved in dwarf-dwarf merger events. The low surface-brightness of this structure makes impossible to obtain integrated light spectroscopic measurements, and its distance (3.8 Mpc) is too large as to observe stars individually. In the color-magnitude diagram of the stellar stream there is an excess of objects brighter than the TRGB which are potential star blends. We designed our DEIMOS mask to contain as many of these objects as possible and, while some of them turned out to be background galaxies, a handful happened to be star blends in the stream. Our velocity measurements along the stream prove that it is gravitationally bound to NGC 4449 and put strong constraints on the orbital properties of the infall. This research was carried out under the auspices of UCSC's Science Internship Program. We thank the National Science Foundation for funding support. ET was supported by a Fulbright fellowship.

  15. Probing LSST's Ability to Detect Planets Around White Dwarfs

    Science.gov (United States)

    Cortes, Jorge; Kipping, David

    2018-01-01

    Over the last four years more than 2,000 planets outside our solar system have been discovered, motivating us to search for and characterize potentially habitable worlds. Most planets orbit Sun-like stars, but more exotic stars can also host planets. Debris disks and disintegrating planetary bodies have been detected around white dwarf stars, the inert, Earth-sized cores of once-thriving stars like our Sun. These detections are clues that planets may exist around white dwarfs. Due to the faintness of white dwarfs and the potential rarity of planets around them, a vast survey is required to have a chance at detecting these planetary systems. The Large Synoptic Survey Telescope (LSST), scheduled to commence operations in 2023, will image the entire southern sky every few nights for 10 years, providing our first real opportunity to detect planets around white dwarfs. We characterized LSST’s ability to detect planets around white dwarfs through simulations that incorporate realistic models for LSST’s observing strategy and the white dwarf distribution within the Milky Way galaxy. This was done through the use of LSST's Operations Simulator (OpSim) and Catalog Simulator (CatSim). Our preliminary results indicate that, if all white dwarfs were to possess a planet, LSST would yield a detection for every 100 observed white dwarfs. In the future, a larger set of ongoing simulations will help us quantify the number of planets LSST could potentially find.

  16. [The bodies of dwarfs in Italian art during the Renaissance].

    Science.gov (United States)

    Portmann, Maria

    2014-01-01

    Agnolo Bronzino's painting of Nano Morgante depicts for the first time the anatomy of a dwarf. This image testifies Cosimo's special interest for this dwarf. In Antonio Francesco Grazzini's poem written in Nano Morgante's honor, we underline some interesting aspects of his physical deformities and his small height, which are highly praised as we can see them on the painting.

  17. Evolution of dwarf galaxies in the Centaurus A group

    OpenAIRE

    Makarova, L.; Makarov, D.

    2007-01-01

    We consider star formation properties of dwarf galaxies in Cen A group observed within our HST/ACS projects number 9771 and 10235. We model color-magnitude diagrams of the galaxies under consideration and measure star formation rate and metallicity dependence on time. We study environmental dependence of the galaxy evolution and probable origin of the dwarf galaxies in the group.

  18. Chemical Abundances of Metal-poor stars in Dwarf Galaxies

    NARCIS (Netherlands)

    Venn, Kim A.; Jablonka, Pascale; Hill, Vanessa; Starkenburg, Else; Lemasle, Bertrand; Shetrone, Matthew; Irwin, Mike; Norris, John; Yong, David; Gilmore, Gerry; Salvadori, Stephania; Skuladottir, Asa; Tolstoy, Eline; Bragaglia, A.; Arnaboldi, M.; Rejkuba, M.; Romano, D.

    2016-01-01

    Stars in low-mass dwarf galaxies show a larger range in their chemical properties than those in the Milky Way halo. The slower star formation efficiency make dwarf galaxies ideal systems for testing nucleosynthetic yields. Not only are alpha-poor stars found at lower metallicities, and a higher

  19. Dissecting Early-type Dwarf Galaxies into Their Multiple Components

    NARCIS (Netherlands)

    Janz, J.; Laurikainen, E.; Lisker, T.; Salo, H.; Peletier, R. F.; Niemi, S. -M.; den Brok, M.; Toloba, E.; Falcon-Barroso, J.; Boselli, A.; Hensler, G.

    2012-01-01

    Early-type dwarf galaxies, once believed to be simple systems, have recently been shown to exhibit an intriguing diversity in structure and stellar content. To analyze this further, we started the SMAKCED project (Stellar content, MAss and Kinematics of Cluster Early-type Dwarfs,

  20. A search for LSB dwarf galaxies in various environments

    OpenAIRE

    Roberts, Sarah; Davies, Jonathan; Sabatini, Sabina

    2003-01-01

    The varying dwarf galaxy populations in different environments poses a problem for Cold Dark Matter (CDM) hierarchical clustering models. In this paper we present results from a survey conducted in different environments to search for low surface brightness (LSB) dwarf galaxies.

  1. The dwarf spheroidal galaxies around the milky way

    NARCIS (Netherlands)

    Tolstoy, E.; Battaglia, G.; Helmi, A.; Irwin, M. J.; Hill, V.; Vallenari, A; Tantalo, R; Portinari, L; Moretti, A

    2007-01-01

    We review the progress of ESO/WFI Imaging and VLT/FLAMES spectroscopy of large numbers of individual stars in nearby dwarf spheroidal galaxies by the Dwarf Abundances and Radial-velocities Team (DART). These observations have allowed us to show that neither the kinematics nor the abundance nor the

  2. Carbon-enhanced metal-poor stars in dwarf galaxies

    NARCIS (Netherlands)

    Salvadori, Stefania; Skúladóttir, Ása; Tolstoy, Eline

    2015-01-01

    We investigate the frequency and origin of carbon-enhanced metal-poor (CEMP) stars in Local Group dwarf galaxies by means of a statistical, data-calibrated cosmological model for the hierarchical build-up of the Milky Way and its dwarf satellites. The model self-consistently explains the variation

  3. Performance Of West African Dwarf Sheep Fed Diets Supplemented ...

    African Journals Online (AJOL)

    An experiment to investigate the possible growth promoting effect of rare earth elements (REE) in growing West African dwarf sheep as well as their influence on the haematological and blood serum biochemical changes was conducted for 12 weeks. Forty West African dwarf sheep were allotted to four dietary treatments: a ...

  4. Dwarf mutations in grass pea (Lathyrus sativus L.): origin ...

    Indian Academy of Sciences (India)

    advanced generations and characterized as dwarf mutant 1. (dwf1), dwarf ... types were recorded and statistically analysed in advanced ...... valuable multiple marker stock in genetics and breeding re- search in grass pea. Downes and Marshall (1983) described colchicine as a powerful mutagen in at least some genotypes.

  5. Dwarf elliptical galaxies with kinematically decoupled cores

    Science.gov (United States)

    De Rijcke, S.; Dejonghe, H.; Zeilinger, W. W.; Hau, G. K. T.

    2004-10-01

    We present, for the first time, photometric and kinematical evidence, obtained with FORS2 on the VLT, for the existence of kinematically decoupled cores (KDCs) in two dwarf elliptical galaxies; FS76 in the NGC 5044 group and FS373 in the NGC 3258 group. Both kinematically peculiar subcomponents rotate in the same sense as the main body of their host galaxy but betray their presence by a pronounced bump in the rotation velocity profiles at a radius of about 1''. The KDC in FS76 rotates at 10 ± 3 km s-1, with the host galaxy rotating at 15 ± 6 km s-1; the KDC in FS373 has a rotation velocity of 6 ± 2 km s-1 while the galaxy itself rotates at 20 ± 5 km s-1. FS373 has a very complex rotation velocity profile with the velocity changing sign at 1.5 Re. The velocity and velocity dispersion profiles of FS76 are asymmetric at larger radii. This could be caused by a past gravitational interaction with the giant elliptical NGC 5044, which is at a projected distance of 50 kpc. We argue that these decoupled cores are most likely not produced by mergers in a group or cluster environment because of the prohibitively large relative velocities. A plausible alternative is offered by flyby interactions between a dwarf elliptical or its disky progenitor and a massive galaxy. The tidal forces during an interaction at the relative velocities and impact parameters typical for a group environment exert a torque on the dwarf galaxy that, according to analytical estimates, transfers enough angular momentum to its stellar envelope to explain the observed peculiar kinematics.

  6. Dwarf galaxy mass estimators versus cosmological simulations

    Science.gov (United States)

    González-Samaniego, Alejandro; Bullock, James S.; Boylan-Kolchin, Michael; Fitts, Alex; Elbert, Oliver D.; Hopkins, Philip F.; Kereš, Dušan; Faucher-Giguère, Claude-André

    2017-12-01

    We use a suite of high-resolution cosmological dwarf galaxy simulations to test the accuracy of commonly used mass estimators from Walker et al. (2009) and Wolf et al. (2010), both of which depend on the observed line-of-sight velocity dispersion and the 2D half-light radius of the galaxy, Re. The simulations are part of the Feedback in Realistic Environments (FIRE) project and include 12 systems with stellar masses spanning 105-107 M⊙ that have structural and kinematic properties similar to those of observed dispersion-supported dwarfs. Both estimators are found to be quite accurate: M_Wolf/M_true = 0.98^{+0.19}_{-0.12} and M_Walker/M_true =1.07^{+0.21}_{-0.15}, with errors reflecting the 68 per cent range over all simulations. The excellent performance of these estimators is remarkable given that they each assume spherical symmetry, a supposition that is broken in our simulated galaxies. Though our dwarfs have negligible rotation support, their 3D stellar distributions are flattened, with short-to-long axis ratios c/a ≃ 0.4-0.7. The median accuracy of the estimators shows no trend with asphericity. Our simulated galaxies have sphericalized stellar profiles in 3D that follow a nearly universal form, one that transitions from a core at small radius to a steep fall-off ∝r-4.2 at large r; they are well fit by Sérsic profiles in projection. We find that the most important empirical quantity affecting mass estimator accuracy is Re. Determining Re by an analytic fit to the surface density profile produces a better estimated mass than if the half-light radius is determined via direct summation.

  7. Search for Higgs shifts in white dwarfs

    Energy Technology Data Exchange (ETDEWEB)

    Onofrio, Roberto [Dipartimento di Fisica e Astronomia " Galileo Galilei," Università di Padova, Via Marzolo 8, I-35131 Padova (Italy); Wegner, Gary A., E-mail: onofrior@gmail.com, E-mail: gary.a.wegner@dartmouth.edu [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States)

    2014-08-20

    We report on a search for differential shifts between electronic and vibronic transitions in carbon-rich white dwarfs BPM 27606 and Procyon B. The absence of differential shifts within the spectral resolution and taking into account systematic effects such as space motion and pressure shifts allows us to set the first upper bound of astrophysical origin on the coupling between the Higgs field and the Kreschmann curvature invariant. Our analysis provides the basis for a more general methodology to derive bounds to the coupling of long-range scalar fields to curvature invariants in an astrophysical setting complementary to the ones available from high-energy physics or table-top experiments.

  8. Ordered framboids in dwarfed biotic molds

    Science.gov (United States)

    El-Dahhar, M. A.

    Abundant framboids of an ordered nature are encountered in some dwarfed biotic molds which were collected from an integral part of the Eocene sedimentary succession exposed at Garret Gehannan area, Fayoum Province, Egypt. These framboids are either clustered in polyframboids or occur as discrete individuals. Pyrite and/or limonite microaggregates constitute the internal makeup of both types. Morphology and other characteristics of the framboids and a genetic appraisal is further discussed. The invoked mechanism strongly suggests the necessity of a precursor in developing the framboid texture.

  9. A SEARCH FOR L/T TRANSITION DWARFS WITH PAN-STARRS1 AND WISE. II. L/T TRANSITION ATMOSPHERES AND YOUNG DISCOVERIES

    Energy Technology Data Exchange (ETDEWEB)

    Best, William M. J.; Liu, Michael C.; Magnier, Eugene A.; Aller, Kimberly M.; Chambers, K. C.; Flewelling, H.; Hodapp, K. W.; Kaiser, N.; Tonry, J. L.; Wainscoat, R. J.; Waters, C. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Deacon, Niall R. [Centre for Astrophysics Research, University of Hertfordshire, College Lane Campus, Hatfield AL10 9AB (United Kingdom); Redstone, Joshua [Equatine Labs, 89 Antrim Street, #2, Cambridge, MA 02139 (United States); Burgett, W. S. [GMTO Corporation, 251 S. Lake Ave., Suite 300, Pasadena, CA 91101 (United States); Draper, P.; Metcalfe, N., E-mail: wbest@ifa.hawaii.edu [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

    2015-12-01

    The evolution of brown dwarfs from L to T spectral types is one of the least understood aspects of the ultracool population, partly for lack of a large, well-defined, and well-characterized sample in the L/T transition. To improve the existing census, we have searched ≈28,000 deg{sup 2} using the Pan-STARRS1 and Wide-field Infrared Survey Explorer surveys for L/T transition dwarfs within 25 pc. We present 130 ultracool dwarf discoveries with estimated distances ≈9–130 pc, including 21 that were independently discovered by other authors and 3 that were previously identified as photometric candidates. Seventy-nine of our objects have near-IR spectral types of L6–T4.5, the most L/T transition dwarfs from any search to date, and we have increased the census of L9–T1.5 objects within 25 pc by over 50%. The color distribution of our discoveries provides further evidence for the “L/T gap,” a deficit of objects with (J − K){sub MKO} ≈ 0.0–0.5 mag in the L/T transition, and thus reinforces the idea that the transition from cloudy to clear photospheres occurs rapidly. Among our discoveries are 31 candidate binaries based on their low-resolution spectral features. Two of these candidates are common proper motion companions to nearby main sequence stars; if confirmed as binaries, these would be rare benchmark systems with the potential to stringently test ultracool evolutionary models. Our search also serendipitously identified 23 late-M and L dwarfs with spectroscopic signs of low gravity implying youth, including 10 with vl-g or int-g gravity classifications and another 13 with indications of low gravity whose spectral types or modest spectral signal-to-noise ratio do not allow us to assign formal classifications. Finally, we identify 10 candidate members of nearby young moving groups (YMG) with spectral types L7–T4.5, including three showing spectroscopic signs of low gravity. If confirmed, any of these would be among the coolest known YMG members

  10. Brown recluse spider bite to the eyelid.

    Science.gov (United States)

    Jarvis, R M; Neufeld, M V; Westfall, C T

    2000-08-01

    To present a photographically documented case of a known brown recluse spider bite to the eyelid. Interventional case report. The wound was photographed daily during an 11-day hospitalization and at 1 month and 6 months after the injury. Treatment included canthotomy and cantholysis; administration of dapsone, antibiotics, and steroids; and hyperbaric oxygen therapy. Clinical presentation and course of a known brown recluse spider bite. Complete recovery with cicatrization at the site of the bite. We present a case of a brown recluse spider bite to the left lower eyelid with a discussion of management and outcome of this rarely reported injury.

  11. Molecular characterization of barley 3H semi-dwarf genes.

    Directory of Open Access Journals (Sweden)

    Haobing Li

    Full Text Available The barley chromosome 3H accommodates many semi-dwarfing genes. To characterize these genes, the two-rowed semi-dwarf Chinese barley landrace 'TX9425' was crossed with the Australian barley variety 'Franklin' to generate a doubled haploid (DH population, and major QTLs controlling plant height have been identified in our previous study. The major QTL derived from 'TX9425' was targeted to investigate the allelism of the semi-dwarf gene uzu in barley. Twelve sets of near-isogenic lines and a large NILF2 fine mapping population segregating only for the dwarfing gene from 'TX9425' were developed. The semi-dwarfing gene in 'TX9425' was located within a 2.8 cM region close to the centromere on chromosome 3H by fine mapping. Molecular cloning and sequence analyses showed that the 'TX9425'-derived allele contained a single nucleotide substitution from A to G at position 2612 of the HvBRI1 gene. This was apparently the same mutation as that reported in six-rowed uzu barley. Markers co-segregating with the QTL were developed from the sequence of the HvBRI1 gene and were validated in the 'TX9425'/'Franklin' DH population. The other major dwarfing QTL derived from the Franklin variety was distally located on chromosome 3HL and co-segregated with the sdw1 diagnostic marker hv20ox2. A third dwarfing gene, expressed only in winter-sown trials, was identified and located on chromosome 3HS. The effects and interactions of these dwarfing genes under different growing conditions are discussed. These results improve our understanding of the genetic mechanisms controlling semi-dwarf stature in barley and provide diagnostic markers for the selection of semi-dwarfness in barley breeding programs.

  12. The Fate of Exploding White Dwarfs

    Science.gov (United States)

    Fisher, Robert

    2018-01-01

    Type Ia supernovae play an important role as standardizable candles for cosmology, providing one of the most important probes into the nature of dark energy. Yet, the nature of the stellar progenitors which give rise to Type Ia supernovae remains elusive. For decades, the leading model explaining Type Ia supernovae properties consisted of a white dwarf accreting to near the Chandrasekhar mass, in the single-degenerate channel. More recently, a variety of lines of evidence point instead towards merging binary white dwarfs, in the double-degenerate channel, as the progenitors of most Type Ia supernovae. In this talk, I will focus upon recent advances at the interface between observation and theory which will help crack the Type Ia progenitor problem. In particular, I will present new insights obtained from recent multidimensional numerical simulations of both the double-degenerate and single-degenerate channels which I have undertaken with my students and collaborators. I will discuss how new models and observations will help elucidate the long-standing mystery of Type supernovae.

  13. DWARF GALAXIES AND THE COSMIC WEB

    Energy Technology Data Exchange (ETDEWEB)

    Benitez-Llambay, Alejandro; Abadi, Mario G. [Observatorio Astronomico, Universidad Nacional de Cordoba, Cordoba X5000BGR (Argentina); Navarro, Julio F. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2 (Canada); Gottloeber, Stefan; Steinmetz, Matthias [Leibniz Institute for Astrophysics, An der Sternwarte 16, D-14482 Potsdam (Germany); Yepes, Gustavo [Departamento de Fisica Teorica, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Hoffman, Yehuda [Racah Institute of Physics, Hebrew University of Jerusalem, Jerusalem 91904 (Israel)

    2013-02-01

    We use a cosmological simulation of the formation of the Local Group of Galaxies to identify a mechanism that enables the removal of baryons from low-mass halos without appealing to feedback or reionization. As the Local Group forms, matter bound to it develops a network of filaments and pancakes. This moving web of gas and dark matter drifts and sweeps a large volume, overtaking many halos in the process. The dark matter content of these halos is unaffected but their gas can be efficiently removed by ram pressure. The loss of gas is especially pronounced in low-mass halos due to their lower binding energy and has a dramatic effect on the star formation history of affected systems. This 'cosmic web stripping' may help to explain the scarcity of dwarf galaxies compared with the numerous low-mass halos expected in {Lambda}CDM and the large diversity of star formation histories and morphologies characteristic of faint galaxies. Although our results are based on a single high-resolution simulation, it is likely that the hydrodynamical interaction of dwarf galaxies with the cosmic web is a crucial ingredient so far missing from galaxy formation models.

  14. VW Hyi - The white dwarf revealed

    Science.gov (United States)

    Mateo, M.; Szkody, P.

    1984-01-01

    Nonsimultaneous IUE, optical, and near-IR observations of VW Hyi at quiescence are presented. Using these and UV data from other investigations, a broad feature in the ultraviolet is identified with L-alpha absorption. The presence and width of the line imply that (1) the white dwarf in VW Hyi is directly visible in the UV and (2) the effective temperature of this star is approximately 18,000 + or - 2000 K for log g = 8. The continuum observations, combined with the J and K photometry of Sherrington et al., (1980), can be fit with a combination of this relatively cool white dwarf and a steady-state disk model with an accretion rate of 10 to the -11th solar masses/yr. Additional observations of the hump in the optical light curve can be reasonably fit by a 12,000-K blackbody. Such a source is consistent with the hump being a minor contribution to the system's overall continuum distribution shortward of 2000 A and longward of about 1 micron.

  15. Accretion on to Magnetic White Dwarfs

    Directory of Open Access Journals (Sweden)

    Wickramasinghe Dayal

    2014-01-01

    The polars have no counterparts in neutron star systems and their study provides unique insights into the complex nature of the magnetospheric boundary. The observed properties of accretion shocks at the white dwarf surface such as the anomalous soft-X-ray excess and its time variability provide strong support for the hypothesis that under certain circumstances the field channelled funnel flow is “blobby”. This has been attributed to interchange instabilities such as the Magnetic Rayleigh-Taylor instability in the shocked gas at the stream-magnetosphere boundary where the stream fragments into discrete clumps of gas. As the clumps penetrate into the magnetosphere, they are shredded into smaller mass blobs via the Kelvin-Helmholtz instability that then couple on to field lines over an extended inner transition region in the orbital plane. The more massive blobs penetrate deep into the photosphere of the white dwarf releasing their energy as a reprocessed soft-X-ray black body component. Although similar instabilities are expected in the inner transition region in disced accretion albeit on a different scale there has been no direct observational evidence for blobby accretion in the generally lower field and disced IPs.

  16. Star formation in blue compact dwarf Galaxies

    Science.gov (United States)

    Ramya, S.; Prabhu, T. P.; Sahu, D. K.

    Blue compact dwarf galaxies (BCDGs) are dwarfs undergoing current burst of star formation (SF). In our work, we determine the ages of the underlying old stellar population to be ˜4 Gyr that is dominating the mass of the galaxy, underlying the current burst of SF. An intermediate population of ˜500 Myr which dominates the stellar light from the galaxy is also detected. The burst of SF at the present epoch spans ˜10 Myr as estimated from various age estimators like Hα, diagnostic diagrams and colour-colour diagrams. BCDGs undergo a burst of SF for a longer duration (of about a few 100 Myr to a Gyr) followed by a short/long quiescence. The amount of column density of localized neutral hydrogen required for the current burst to occur seems to be 10^{21} cm^{-2}. This could be the threshold required for SF. Radio continuum emission reveals that the emission is coincident with the star forming regions. The star formation rates (SFR) estimated from Hα match well with the SFR estimated using non-thermal radio emission for individual star forming regions, but are ˜6-7 times less as compared to the SFR calculated from far-IR (FIR) emission.

  17. Progress report: brown bear studies - 1984

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Forty-four brown bears (22 adult female, 22 offspring) were captured in the Ayakulik River, Sturgeon River, and Frazer Lake drainages of Kodiak Island in July, 1983....

  18. Live-trapping and handling brown bear

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — In recent years bears have become increasingly important as big game animals. The brown bears (Ursus middendorfi) on the Kodiak National Wildlife Refuge, Kodiak...

  19. Brown bear telemetry and trapping: Special report

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Brown bear studies were continued during the 1967 field season with emphasis on development of techniques for instrumenting bears with radio transmitters and...

  20. The Unexpected Past of a Dwarf Galaxy

    Science.gov (United States)

    1996-08-01

    New Light on Cannibalism in the Local Group of Galaxies The Local Group of Galaxies consists of a few large spiral galaxies - for instance the Milky Way galaxy in which we live, and the Andromeda galaxy that is visible to the unaided eye in the northern constellation of the same name - as well as two dozen much smaller galaxies of mostly irregular shape. Whereas the larger galaxies have extended halos of very old stars, no such halos have ever been seen around the smaller ones. Now, however, Dante Minniti and Albert Zijlstra [1], working at the ESO 3.5-metre New Technology Telescope (NTT), have found a large halo of old and metal-poor stars around one of the dwarf galaxies in the Local Group. This finding is quite unexpected. It revises our understanding of star formation in these galaxies and provides important information about the past evolution of galaxies [2]. Galaxy halos The Milky Way galaxy is surrounded by a large, roughly spherical halo of old stars. The diameter is about 100,000 light years and the stars therein, known as Population II stars, are among the oldest known, with ages of 10 billion years or even more. They also differ from the younger stars nearer to the main plane of the Milky Way (in which our 4.7 billion year old Sun is located) by being very metal-poor. Many of the halo stars consist almost solely of hydrogen and helium, reflecting the composition of matter in the young Universe. This halo is important for our understanding of the processes that led to the formation of the Milky Way galaxy. It is believed that many of the halo stars and those of the same type found in globular clusters existed already before the Milky Way had fully formed. Galaxy cannibalism Many astronomers suspect that galaxies evolve and gradually grow larger and heavier by practising cannibalism on their own kind. In this picture, when two galaxies collide in space, the stars and nebulae in the smaller one will disperse and soon be taken over by the larger one, which

  1. Seasonality of brown recluse populations is reflected by numbers of brown recluse envenomations.

    Science.gov (United States)

    Rader, R K; Stoecker, W V; Malters, J M; Marr, M T; Dyer, J A

    2012-07-01

    A significant seasonal correlation was recently shown for brown recluse spider activity. Vetter (2011) observed brown recluse spiders were submitted by the general public predominantly during April-October. For patients with suspected brown recluse spider bites (BRSB), we have observed the same seasonality. Among 45 cases with features consistent of a BRSB, 43 (95.6%) occurred during April-October. Both the Vetter study and our study serve to demonstrate seasonal activity for brown recluse spiders. Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. Brown recluse spider bites: a case report.

    Science.gov (United States)

    Nunnelee, Janice D

    2006-02-01

    The brown recluse spider is found more commonly in the Southeast and the Central Midwest. Its bite is not common because it is a shy spider that only bites if cornered. A severe bite may necrose a large area that requires skin grafting; systemic reactions rarely occur. This article discusses the brown recluse spider and presents a case study of a patient with two spider bites that did require extensive grafting.

  3. Ecological pellets from brown coal and biomass

    OpenAIRE

    Pavel Sedláček; Nikolas Mucha; Iva Pečtová; Peter Fečko

    2007-01-01

    One way of renewable energy sources applications in the Czech republic is a cultivation of biomass plants. After the biomass reformation, it is possible to add it to palletizing mixes with coal and delulfurisative additives. Possibilities of brown coal of palletizing with biomass adds were tested recently. The product represents a new coal-biomass combustible wich can be used in some types of boilers with a low pollutant production level (specially SO2).In the past brown-coal pellets weremade...

  4. Dwarf Galaxies in the Chandra COSMOS Legacy Survey

    Science.gov (United States)

    Civano, Francesca Maria; Mezcua, Mar; Fabbiano, Giuseppina; Marchesi, Stefano; Suh, Hyewon; Volonteri, Marta; cyrille

    2018-01-01

    The existence of intermediate mass black holes (100 7. While detecting these seed black holes in the young Universe is observationally challenging, the nuclei of local dwarf galaxies are among the best places where to look for them as these galaxies resemble in mass and metallicity the first galaxies and they have not significantly grown through merger and accretion processes. We present a sample of 40 AGN in dwarf galaxies (107 Legacy survey. Once the star formation contribution to the X-ray emission is subtracted, the AGN luminosities of the 40 dwarf galaxies are in the range L(0.5-10 keV)~1039 - 1044 erg/s. With 12 sources at z > 0.5, our sample constitutes the highest-redshift discovery of AGN in dwarf galaxies. One of the dwarf galaxies is the least massive galaxy (M* = 6.6x107 Msun) found so far to host an active BH. We also present for the first time the evolution of the AGN fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies out to z = 0.7, finding that it decreases with X-ray luminosity and stellar mass. Unlike massive galaxies, the AGN fraction is found to decrease with redshift, suggesting that AGN in dwarf galaxies evolve differently than those in high-mass galaxies.

  5. SIM's Search for Planets Orbiting White Dwarfs - Final Report

    Science.gov (United States)

    Subasavage, John P., Jr.

    2010-01-01

    I propose to use Space Interferometry Mission (SIM) Lite to observe a sample ( 25-50) of nearby white dwarfs in hopes of detecting planetary companions with masses in the 1-10 Earth mass range on average. Because of the nature of white dwarfs' spectral signatures (a few broad, if any, absorption lines), current radial velocity planet hunting techniques are not viable. Astrometry is currently the only technique capable of detecting low mass planets around white dwarfs and SIM would be the best suited astrometric instrument to do so once launched. As part of a SIM Science Study, I present a detailed evaluation of the star fields in the vicinities of nearby white dwarfs within 20 pc and with V white dwarfs with accuate trigonometric parallaxes and photometry. Simulations indicate that planetary mass detections in the range of 1-10 Earth masses are possible for the majority of the 54 white dwarfs evaluated, provided the planets exist. This effort will aid in the selection of white dwarfs to be targeted for planet searches using SIM by maximizing planetary sensitivity while minimizing total mission time spent on these observations.

  6. Dwarf Galaxies in Voids: Dark Matter Halos and Gas Cooling

    Directory of Open Access Journals (Sweden)

    Matthias Hoeft

    2010-01-01

    Full Text Available Galaxy surveys have shown that luminous galaxies are mainly distributed in large filaments and galaxy clusters. The remaining large volumes are virtually devoid of luminous galaxies. This is in concordance with the formation of the large-scale structure in the universe as derived from cosmological simulations. However, the numerical results indicate that cosmological voids are abundantly populated with dark matter haloes which may in principle host dwarf galaxies. Observational efforts have in contrast revealed that voids are apparently devoid of dwarf galaxies. We investigate the formation of dwarf galaxies in voids by hydrodynamical cosmological simulations. Due to the cosmic ultraviolet background radiation low-mass haloes show generally a reduced baryon fraction. We determine the characteristic mass below which dwarf galaxies are baryon deficient. We show that the circular velocity below which the accretion of baryons is suppressed is approximately 40 kms−1. The suppressed baryon accretion is caused by the photo-heating due to the UV background. We set up a spherical halo model and show that the effective equation of the state of the gas in the periphery of dwarf galaxies determines the characteristic mass. This implies that any process which heats the gas around dwarf galaxies increases the characteristic mass and thus reduces the number of observable dwarf galaxies.

  7. The Local White Dwarf Population: The 25 pc Sample

    Science.gov (United States)

    Holberg, Jay B.; Sion, E. M.; Oswalt, T. D.

    2011-01-01

    Currently the most complete sample of white dwarf stars comes from the local white dwarf population within 20 pc, which is believed to be 80 percent complete. This sample contains some 132 degenerate stars. We hope to effectively double the number of known local white dwarfs by extending the sample boundary to 25 pc, while still maintaining a high level of completeness. We discuss plans for extending the local sample and some of the studies that will be possible with this enlarged population. This work was funded in part by NSF Grant AST-1008845.

  8. A heating mechanism for the chromospheres of M dwarf stars

    Science.gov (United States)

    Giampapa, M. S.; Golub, L.; Rosner, R.; Vaiana, G.; Linsky, J. L.; Worden, S. P.

    1981-01-01

    The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed.

  9. Isoleucine epimerization ages of the dwarf elephants of Sicily

    Science.gov (United States)

    Belluomini, Giorgio; Bada, Jeffrey L.

    1985-07-01

    The isoleucine epimerization reaction has been used to date tooth enamel from dwarf elephants collected from the Sicilian caves of Spinagallo and Puntali. Elephant teeth from the Isernia la Pineta deposit in central Italy, dated at ˜700 ka by potassium-argon (K-Ar) and paleomagnetics, were used for calibration of the isoleucine epimerization rate. The ages determined for the dwarf elephants found at the Spinagallo Cave are considerably older than the more robust dwarf species found at the Puntali Cave. These dates suggest that more than one invasion of continental elephants have taken place on Sicily. The subsequent isolation of the continental species has apparently produced varying stages of dwarfism.

  10. On the Stability of Strange Dwarf Hybrid Stars

    Science.gov (United States)

    Alford, Mark G.; Harris, Steven P.; Sachdeva, Pratik S.

    2017-10-01

    We investigate the stability of “strange dwarfs”: white-dwarf-sized stars with a density discontinuity between a small dense core of quark matter and a thick low-density mantle of degenerate electrons. Previous work on strange dwarfs suggested that such a discontinuity could stabilize stars that would have been classified as unstable by the conventional criteria based on extrema in the mass-radius relation. We investigate the stability of such stars by numerically solving the Sturm-Liouville equations for the lowest-energy modes of the star. We find that the conventional criteria are correct, and strange dwarfs are not stable.

  11. Star Formation History of Dwarf Galaxies in Cosmological Hydrodynamic Simulations

    Directory of Open Access Journals (Sweden)

    Kentaro Nagamine

    2010-01-01

    Full Text Available We examine the past and current work on the star formation (SF histories of dwarf galaxies in cosmological hydrodynamic simulations. The results obtained from different numerical methods are still somewhat mixed, but the differences are understandable if we consider the numerical and resolution effects. It remains a challenge to simulate the episodic nature of SF history in dwarf galaxies at late times within the cosmological context of a cold dark matter model. More work is needed to solve the mysteries of SF history of dwarf galaxies employing large-scale hydrodynamic simulations on the next generation of supercomputers.

  12. European brown hare syndrome virus in free-ranging European brown hares from Argentina

    DEFF Research Database (Denmark)

    Frolich, K.; Kujawski, G.E.J.G.; Rudolph, M.

    2003-01-01

    From 1998 to 2000, serum samples of 80 shot European brown hares (Lepus europaeus) from Argentina were examined for antibodies against European brown hare syndrome virus (EBHSV) and 80 spleen samples were tested for EBHSV-antigen by enzyme linked immunosorbent assay (ELISA). Nine hares were...

  13. GLOBAL H I KINEMATICS IN DWARF GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-03-10

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

  14. Kentsel Yeşil Alanların Düzce Akçakoca Örneğinde Ulaşabilirlik Bakımından İrdelenmesi

    Directory of Open Access Journals (Sweden)

    Zeki DEMİR

    2015-01-01

    Full Text Available Kentsel aktif yeşil alan standartları, 3194 Sayılı İmar Kanunu’nun Plan Yapımına Ait Esaslara Dair Yönetmeliği’nde minimum kişi başına 10 m2 “aktif yeşil alan” olarak tanımlanmıştır. Kentlerin düzenli ve sağlıklı bir çevreye kavuşabilmesi, Aktif yeşil alanların, kent içindeki dağılımlarının, büyüklüklerinin, işlevsel ve estetik niteliklerinin sistemli bir planlama ve kentsel tasarım anlayışı içinde gelişmesi ile mümkün olacaktır.Araştırma alanı olarak seçilen Düzce, Akçakoca ilçesi, yeşil alan açısından oldukça zengin bir potansiyele sahip olmakla beraber, aktif yeşil alanlar (kent ve mahalle parkları, çocuk bahçeleri, oyun alanları gibi nitelik ve nicelik olarak yetersiz gözükmektedir. Bu çalışmada, Akçakoca kenti yeşil alanlarının kentteki dağılım ve miktarları incelenerek, yeşil alanların mahalle ölçeğindeki dağılımları, büyüklükleri ve kişi başına düşen oranları değerlendirilmiştir. Bu çalışmada Akçakoca kentsel yeşil alanlarının ulaşabilirliği, etkili hizmet alanlarına bağlı olarak değerlendirilmiştir. Kent halkının yeşil alanlara ulaşım ve yeşil alanların kullanımı yapılan anketler ile saptanmıştır. Mevcut olan sorunların giderilmesi doğrultusunda öneriler geliştirilmiştir.Anahtar Kelimeler: Akçakoca, Yeşil alan, Ulaşabilirlik

  15. Southern rice black-streaked dwarf virus: a white-backed planthopper-transmitted fijivirus threatening rice production in Asia

    Science.gov (United States)

    Zhou, Guohui; Xu, Donglin; Xu, Dagao; Zhang, Maoxin

    2013-01-01

    Southern rice black-streaked dwarf virus (SRBSDV), a non-enveloped icosahedral virus with a genome of 10 double-stranded RNA segments, is a novel species in the genus Fijivirus (family Reoviridae) first recognized in 2008. Rice plants infected with this virus exhibit symptoms similar to those caused by Rice black-streaked dwarf virus. Since 2009, the virus has rapidly spread and caused serious rice losses in East and Southeast Asia. Significant progress has been made in recent years in understanding this disease, especially about the functions of the viral genes, rice–virus–insect interactions, and epidemiology and control measures. The virus can be efficiently transmitted by the white-backed planthopper (WBPH, Sogatella furcifera) in a persistent circulative propagative manner but cannot be transmitted by the brown planthopper (Nilaparvata lugens) and small brown planthopper (Laodelphax striatellus). Rice, maize, Chinese sorghum (Coix lacryma-jobi) and other grass weeds can be infected via WBPH. However, only rice plays a major role in the virus infection cycle because of the vector’s preference. In Southeast Asia, WBPH is a long-distance migratory rice pest. The disease cycle can be described as follows: SRBSDV and its WBPH vector overwinter in warm tropical or sub-tropical areas; viruliferous WBPH adults carry the virus from south to north via long-distance migration in early spring, transmit the virus to rice seedlings in the newly colonized areas, and lay eggs on the infected seedlings; the next generation of WBPHs propagate on infected seedlings, become viruliferous, disperse, and cause new disease outbreaks. Several molecular and serological methods have been developed to detect SRBSDV in plant tissues and individual insects. Control measures based on protection from WBPH, including seedbed coverage, chemical seed treatments, and chemical spraying of seedlings, have proven effective in China. PMID:24058362

  16. Southern rice black-streaked dwarf virus: a white-backed planthopper transmitted fijivirus threadening rice production in Asia

    Directory of Open Access Journals (Sweden)

    Guohui eZhou

    2013-09-01

    Full Text Available Southern rice black-streaked dwarf virus (SRBSDV, a nonenveloped icosahedral virus with a genome of 10 double-stranded RNA segments, is a novel species in the genus Fijivirus (family Reoviridae first recognized in 2008. Rice plants infected with this virus exhibit symptoms similar to those caused by Rice black-streaked dwarf virus. Since 2009, the virus has rapidly spread and caused serious rice losses in East and Southeast Asia. Significant progress has been made in recent years in understanding this disease, especially about the functions of the viral genes, rice–virus–insect interactions, and epidemiology and control measures. The virus can be efficiently transmitted by the white-backed planthopper (WBPH, Sogatella furcifera in a persistent circulative propagative manner but cannot be transmitted by the brown planthopper (Nilaparvata lugens and small brown planthopper (Laodelphax striatellus. Rice, maize, Chinese sorghum (Coix lacryma-jobi and other grass weeds can be infected via WBPH. However, only rice plays a major role in the virus infection cycle because of the vector's preference. In Southeast Asia, WBPH is a long-distance migratory rice pest. The disease cycle can be described as follows: SRBSDV and its WBPH vector overwinter in warm tropical or sub-tropical areas; viruliferous WBPH adults carry the virus from south to north via long-distance migration in early spring, transmit the virus to rice seedlings in the newly colonized areas, and lay eggs on the infected seedlings; the next generation of WBPHs propagate on infected seedlings, become viruliferous, disperse, and cause new disease outbreaks. Several molecular and serological methods have been developed to detect SRBSDV in plant tissues and individual insects. Control measures based on protection from WBPH, including seedbed coverage, chemical seed treatments, and chemical spraying of seedlings, have proven effective in China.

  17. Southern rice black-streaked dwarf virus: a white-backed planthopper-transmitted fijivirus threatening rice production in Asia.

    Science.gov (United States)

    Zhou, Guohui; Xu, Donglin; Xu, Dagao; Zhang, Maoxin

    2013-09-09

    Southern rice black-streaked dwarf virus (SRBSDV), a non-enveloped icosahedral virus with a genome of 10 double-stranded RNA segments, is a novel species in the genus Fijivirus (family Reoviridae) first recognized in 2008. Rice plants infected with this virus exhibit symptoms similar to those caused by Rice black-streaked dwarf virus. Since 2009, the virus has rapidly spread and caused serious rice losses in East and Southeast Asia. Significant progress has been made in recent years in understanding this disease, especially about the functions of the viral genes, rice-virus-insect interactions, and epidemiology and control measures. The virus can be efficiently transmitted by the white-backed planthopper (WBPH, Sogatella furcifera) in a persistent circulative propagative manner but cannot be transmitted by the brown planthopper (Nilaparvata lugens) and small brown planthopper (Laodelphax striatellus). Rice, maize, Chinese sorghum (Coix lacryma-jobi) and other grass weeds can be infected via WBPH. However, only rice plays a major role in the virus infection cycle because of the vector's preference. In Southeast Asia, WBPH is a long-distance migratory rice pest. The disease cycle can be described as follows: SRBSDV and its WBPH vector overwinter in warm tropical or sub-tropical areas; viruliferous WBPH adults carry the virus from south to north via long-distance migration in early spring, transmit the virus to rice seedlings in the newly colonized areas, and lay eggs on the infected seedlings; the next generation of WBPHs propagate on infected seedlings, become viruliferous, disperse, and cause new disease outbreaks. Several molecular and serological methods have been developed to detect SRBSDV in plant tissues and individual insects. Control measures based on protection from WBPH, including seedbed coverage, chemical seed treatments, and chemical spraying of seedlings, have proven effective in China.

  18. Animal vectors of eastern dwarf mistletoe of black spruce.

    Science.gov (United States)

    Michael E. Ostry; Thomas H. Nicholls; D.W. French

    1983-01-01

    Describes a study to determine the importance of animals in the spread of eastern dwarf mistletoe of black spruce. Radio telemetry, banding, and color-marking techniques were used to study vectors of this forest pathogen.

  19. General relativistic white dwarfs and their astrophysical implications

    Energy Technology Data Exchange (ETDEWEB)

    Boshkayev, Kuantay [Al-Farabi Kazakh National University, Almaty (Kazakhstan); Rueda, Jorge A.; Ruffini, Remo [Sapienza University of Rome, Rome (Italy); Siutsou, Ivan [ICRANet, Square of Republic, Pescara (Italy)

    2014-09-15

    We consider applications of general relativistic uniformly-rotating white dwarfs to several astrophysical phenomena related to the spin-up and the spin-down epochs and to delayed type Ia supernova explosions of super-Chandrasekhar white dwarfs, where we estimate the 'spinning down' lifetime due to magnetic-dipole braking. In addition, we describe the physical properties of Soft Gamma Repeaters and Anomalous X-Ray Pulsars as massive rapidly-rotating highly-magnetized white dwarfs. Particularly we consider one of the so-called low-magnetic-field magnetars SGR 0418+5729 as a massive rapidly-rotating highly- magnetized white dwarf and give bounds for the mass, radius, moment of inertia, and magnetic field by requiring the general relativistic uniformly rotating configurations to be stable.

  20. Binary helium dwarf supernovae. [numerical hydrodynamic investigation of evolution

    Science.gov (United States)

    Mazurek, T. J.

    1973-01-01

    The possibility of helium dwarf evolution to sufficiently high densities for violent helium ignition in low-massed binary systems is investigated. During accretional evolution the occurrence of thermonuclear runaway is found to be probable when the dwarf's mass approaches 1 solar mass, and steady-state discontinuous wave propagation considerations indicate that the dwarf is totally incinerated (i.e., its total mass burns to nuclear equilibrium) by a detonation wave. A numerical stellar dynamic investigation, including the full effects of nuclear statistical equilibrium and electron capture indicates total disruption for all reasonable dwarf central densities. For consistency with the cosmic element abundances, the conclusion of total disruption requires a low frequency for helium supernova events, implying that helium ignition in mass-exchanging binaries must occur at the lower densities of the relatively mild helium flash.

  1. AVOCADO: A Virtual Observatory Census to Address Dwarfs Origins

    Science.gov (United States)

    Sánchez-Janssen, Rubén; Sánchez-Janssen

    2011-12-01

    Dwarf galaxies are by far the most abundant of all galaxy types, yet their properties are still poorly understood-especially due to the observational challenge that their intrinsic faintness represents. AVOCADO aims at establishing firm conclusions on their formation and evolution by constructing a homogeneous, multiwavelength dataset for a statistically significant sample of several thousand nearby dwarfs (-18 < Mi < -14). Using public data and Virtual Observatory tools, we have built GALEX+SDSS+2MASS spectral energy distributions that are fitted by a library of single stellar population models. Star formation rates, stellar masses, ages and metallicities are further complemented with structural parameters that can be used to classify them morphologically. This unique dataset, coupled with a detailed characterization of each dwarf's environment, allows for a fully comprehensive investigation of their origins and to track the (potential) evolutionary paths between the different dwarf types.

  2. The Diversity of Rocky Bodies from White Dwarf Pollution

    Science.gov (United States)

    Feng, W.; Desch, S.

    2017-11-01

    Insight to the chemical diversity of extrasolar rocky bodies may be gained by observing heavy elements in white dwarf atmospheres. The disk accretion scenario is key to understanding the accreted rocky bodies.

  3. Circumstellar debris and pollution at white dwarf stars

    Science.gov (United States)

    Farihi, J.

    2016-04-01

    Circumstellar disks of planetary debris are now known or suspected to closely orbit hundreds of white dwarf stars. To date, both data and theory support disks that are entirely contained within the preceding giant stellar radii, and hence must have been produced during the white dwarf phase. This picture is strengthened by the signature of material falling onto the pristine stellar surfaces; disks are always detected together with atmospheric heavy elements. The physical link between this debris and the white dwarf host abundances enables unique insight into the bulk chemistry of extrasolar planetary systems via their remnants. This review summarizes the body of evidence supporting dynamically active planetary systems at a large fraction of all white dwarfs, the remnants of first generation, main-sequence planetary systems, and hence provide insight into initial conditions as well as long-term dynamics and evolution.

  4. Characterization of endangered dwarf wedgemussel (Alasmidonta heterodon) habitats in Maryland

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — The dwarf wedgemussel (Alasmidonta heterodon) has been listed by the U.S. Fish and Wildlife Service as an endangered species since 1990. This species, once found in...

  5. The small-scale clustering properties of dwarf galaxies

    Science.gov (United States)

    Vader, J. P.; Sandage, Allan

    1991-01-01

    Two results on the small-scale clustering properties of dwarf galaxies are reported, which were identified in the vicinity of early-type Shapley-Ames galaxies on high-resolution photographic plates. The first result indicates that dwarf galaxies display the same trend of stronger clustering toward earlier morphological type on small scales as their giant counterparts on larger scales. It is suggested that early-type dwarfs can be used as dynamical probes of dark halos around early-type giant galaxies and as tracers of the dynamical evolution of such halos in dense environments. The second result pertains to the trend of increasing early-type dwarf frequency per early-type giant with environment richness previously established for rich groups. It is found that a minimum value of isolated early-type galaxies is approximately 0.25, as compared to a maximum of approximately 8 in rich environments like the Virgo Cluster.

  6. Belediyelerin Raylı Ulaşım Hizmetlerinin Yaygınlaştırılması: Bursa Büyükşehir Belediyesi Örneği

    Directory of Open Access Journals (Sweden)

    Harun KILICASLAN

    2015-12-01

    Full Text Available Rail services for which substantial investment required can be provided only in cities with a certain population size. However, if a city does not have a sufficient potential for passengers to cover the operating costs, such service may not be offered. In particular, lowering the cost of rail vehicles can lead to applications in less populated cities. The purpose of this study was the investigation of encouraging domestic production, as a tool to reduce rail vehicle costs, and in the context of the relations of municipalities between central government and private sector within the framework of the public economy. For this purpose, the applications and rail transportation services of Bursa Metropolitan Municipality are discussed as examples. Büyük ölçekli yatırım gerektiren kentsel raylı ulaşım hizmetleri maliyet koşulları nedeniyle sadece belli bir nüfus büyüklüğüne sahip kentlerde sunulabilmektedir. Bununla beraber işletme giderlerini karşılamaya yetecek kadar yolcu potansiyeline sahip olmayan kentlerde söz konusu hizmet sunulamamaktadır. Özellikle araç maliyetlerinin düşürülmesi raylı sistem uygulamalarını daha az nüfuslu kentlerde de uygulanabilir duruma getirebilecektir. Araç maliyetlerinin düşürülebilmesinin bir yolu olarak yerli üretimin teşvik edilmesi ve bu bağlamda belediye ve merkezî idare ile özel kesimin rollerinin kamu ekonomisi çerçevesinde irdelenmesi bu çalışmanın amacını oluşturmuştur. Bu amaçla örnek olarak Bursa Büyükşehir Belediyesi’nin uygulamaları ve raylı ulaşım hizmetleri ele alınmıştır.

  7. 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.

  8. HIP 38939B: A NEW BENCHMARK T DWARF IN THE GALACTIC PLANE DISCOVERED WITH Pan-STARRS1

    Energy Technology Data Exchange (ETDEWEB)

    Deacon, Niall R.; Liu, Michael C.; Magnier, Eugene A.; Bowler, Brendan P.; Burgett, W. S.; Chambers, K. C.; Flewelling, H.; Kaiser, N.; Morgan, J. S.; Sweeney, W. E.; Tonry, J. L.; Wainscoat, R. J.; Waters, C. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Redstone, Joshua [Facebook, 1601 S. California Avenue, Palo Alto, CA 94304 (United States); Goldman, Bertrand [Max Planck Institute for Astronomy, Koenigstuhl 17, D-69117 Heidelberg (Germany); Price, P. A., E-mail: deacon@mpia.de [Princeton University Observatory, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544 (United States)

    2012-08-20

    We report the discovery of a wide brown dwarf companion to the mildly metal-poor ([Fe/H] = -0.24), low Galactic latitude (b = 1.{sup 0}88) K4V star HIP 38939. The companion was discovered by its common proper motion with the primary and its red optical (Pan-STARRS1) and blue infrared (Two Micron All Sky Survey) colors. It has a projected separation of 1630 AU and a near-infrared spectral type of T4.5. As such it is one of only three known companions to a main-sequence star which have early/mid T spectral types of (the others being HN Peg B and {epsilon} Indi B). Using chromospheric activity we estimate an age for the primary of 900{+-}{sup 1900}{sub 600} Myr. This value is also in agreement with the age derived from the star's weak ROSAT detection. Comparison with evolutionary models for this age range indicates that HIP 38939B falls in the mass range 38 {+-} 20 M{sub Jup} with an effective temperature range of 1090 {+-} 60 K. Fitting our spectrum with atmospheric models gives a best-fitting temperature of 1100 K. We include our object in an analysis of the population of benchmark T dwarfs and find that while older atmospheric models appeared to overpredict the temperature of the coolest objects compared to evolutionary models, more recent atmospheric models provide better agreement.

  9. Performance comparison of dwarf laying hens segregating for the naked neck gene in temperate and subtropical environments

    Directory of Open Access Journals (Sweden)

    Bordas André

    2009-01-01

    Full Text Available Abstract This study compares laying performances between two environments of dwarf laying hen lines segregating for the naked neck mutation (NA locus, a selected dwarf line of brown-egg layers and its control line. Layers with one of the three genotypes at the NA locus were produced from 11 sires from the control line and 12 sires from the selected line. Two hatches produced 216 adult hens in Taiwan and 297 hens in France. Genetic parameters for laying traits were estimated in each environment and the ranking of sire breeding values was compared between environments. Laying performance was lower, and mortality was higher in Taiwan than in France. The line by environment interaction was highly significant for body weight at 16 weeks, clutch length and egg number, with or without Box-Cox transformation. The selected line was more sensitive to environmental change but in Taiwan it could maintain a higher egg number than the control line. Estimated heritability values in the selected line were higher in France than in Taiwan, but not for all the traits in the control line. The rank correlations between sire breeding values were low within the selected line and slightly higher in the control line. A few sire families showed a good ranking in both environments, suggesting that some families may adapt better to environmental change.

  10. Temperatures rising: brown fat and bone.

    Science.gov (United States)

    Motyl, Katherine J; Rosen, Clifford J

    2011-03-01

    Caloric restriction is associated with a reduction in body weight and temperature, as well as a reduction in trabecular bone volume and paradoxically an increase in adipocytes within the bone marrow. The nature of these adipocytes is uncertain, although there is emerging evidence of a direct relationship between bone remodeling and brown adipocytes. For example, in heterotrophic ossification, brown adipocytes set up a hypoxic gradient that leads to vascular invasion, chondrocyte differentiation, and subsequent bone formation. Additionally, deletion of retinoblastoma protein in an osteosarcoma model leads to increased hibernoma (brown fat tumor). Brown adipose tissue (BAT) becomes senescent with age at a time when thermoregulation is altered, bone loss becomes apparent, and sympathetic activity increases. Interestingly, heart rate is an unexpected but good predictor of fracture risk in elderly individuals, pointing to a key role for the sympathetic nervous system in senile osteoporosis. Hence the possibility exists that BAT could play an indirect role in age-related bone loss. However, evidence of an indirect effect from thermogenic dysfunction on bone loss is currently limited. Here, we present current evidence for a relationship between brown adipose tissue and bone as well as provide novel insights into the effects of thermoregulation on bone mineral density.

  11. The colored Hanbury Brown-Twiss effect

    Science.gov (United States)

    Silva, B.; Sánchez Muñoz, C.; Ballarini, D.; González-Tudela, A.; de Giorgi, M.; Gigli, G.; West, K.; Pfeiffer, L.; Del Valle, E.; Sanvitto, D.; Laussy, F. P.

    2016-12-01

    The Hanbury Brown-Twiss effect is one of the celebrated phenomenologies of modern physics that accommodates equally well classical (interferences of waves) and quantum (correlations between indistinguishable particles) interpretations. The effect was discovered in the late thirties with a basic observation of Hanbury Brown that radio-pulses from two distinct antennas generate signals on the oscilloscope that wiggle similarly to the naked eye. When Hanbury Brown and his mathematician colleague Twiss took the obvious step to propose bringing the effect in the optical range, they met with considerable opposition as single-photon interferences were deemed impossible. The Hanbury Brown-Twiss effect is nowadays universally accepted and, being so fundamental, embodies many subtleties of our understanding of the wave/particle dual nature of light. Thanks to a novel experimental technique, we report here a generalized version of the Hanbury Brown-Twiss effect to include the frequency of the detected light, or, from the particle point of view, the energy of the detected photons. Our source of light is a polariton condensate, that allows high-resolution filtering of a spectrally broad source with a high degree of coherence. In addition to the known tendencies of indistinguishable photons to arrive together on the detector, we find that photons of different colors present the opposite characteristic of avoiding each others. We postulate that fermions can be similarly brought to exhibit positive (boson-like) correlations by frequency filtering.

  12. BVJHK observations of the dwarf Cepheid SZ Lynx

    Energy Technology Data Exchange (ETDEWEB)

    Fernley, J.A.; Jameson, R.F.; Sherrington, M.R.

    1984-06-15

    BVJHK light curves of the dwarf Cepheid SZ Lyn are presented. The findings of other observers that there are small cycle to cycle variations in the light curves are confirmed. The photometry coupled with radial velocity observations is used to determine the radius and hence the absolute magnitude and mass. The results are consistent with the post-main sequence, high mass hypothesis for the evolutionary status of dwarf Cepheids.

  13. Binary white dwarfs in the halo of the Milky Way

    Science.gov (United States)

    van Oirschot, Pim; Nelemans, Gijs; Toonen, Silvia; Pols, Onno; Brown, Anthony G. A.; Helmi, Amina; Portegies Zwart, Simon

    2014-09-01

    Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction. Methods: We simulate the evolution of low-metallicity halo stars at distances up to ~3 kpc using the binary population synthesis code SeBa. We use two different white dwarf cooling models to predict the present-day luminosities of halo white dwarfs. We determine the white dwarf luminosity functions (WDLFs) for eight different halo models and compare these with the observed halo WDLF of white dwarfs in the SuperCOSMOS Sky Survey. Furthermore, we predict the properties of binary white dwarfs in the halo and determine the number of halo white dwarfs that is expected to be observed with the Gaia satellite. Results: By comparing the WDLFs, we find that a standard IMF matches the observations more accurately than a top-heavy one, but the difference with a bottom-heavy IMF is small. A burst of star formation 13 Gyr ago fits slightly better than a star formation burst 10 Gyr ago and also slightly better than continuous star formation 10-13 Gyr ago. Gaia will be the first instument to constrain the bright end of the field halo WDLF, where contributions from binary WDs are considerable. Many of these will have He cores, of which a handful have atypical surface gravities (log g 0 in our standard model for WD cooling. These so called pre-WDs, if observed, can help us to constrain white dwarf cooling models and might teach us something about the fraction of halo stars that reside in binaries. Appendices are available in electronic form at http://www.aanda.org

  14. Calibrating Cosmological Chronometers: White Dwarf Masses via Astrometry

    Science.gov (United States)

    2009-01-01

    Calibrating cosmological chronometers: white dwarf masses via astrometry John P. Subasavage1, Todd J. Henry1, Wei-Chun Jao1, Edmund P. Nelan2, Hugh C...control number. 1. REPORT DATE 2009 2. REPORT TYPE 3. DATES COVERED 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE Calibrating cosmological ...Workshop on White Dwarfs Held at Kiel, Germany, 29 August - 1 September 1994. Lecture Notes in Physics vol. 443 eds D. Koester and K. Werner (Heidelberg

  15. Morphology of Dwarf Galaxies in Isolated Satellite Systems

    Science.gov (United States)

    Ann, Hong Bae

    2017-08-01

    The environmental dependence of the morphology of dwarf galaxies in isolated satellite systems is analyzed to understand the origin of the dwarf galaxy morphology using the visually classified morphological types of 5836 local galaxies with z ≲ 0.01. We consider six sub-types of dwarf galaxies, dS0, dE, dE_{bc}, dSph, dE_{blue}, and dI, of which the first four sub-types are considered as early-type and the last two as late-type. The environmental parameters we consider are the projected distance from the host galaxy (r_{p}), local and global background densities, and the host morphology. The spatial distributions of dwarf satellites of early-type galaxies are much different from those of dwarf satellites of late-type galaxies, suggesting the host morphology combined with r_{p} plays a decisive role on the morphology of the dwarf satellite galaxies. The local and global background densities play no significant role on the morphology of dwarfs in the satellite systems hosted by early-type galaxies. However, in the satellite system hosted by late-type galaxies, the global background densities of dE and dSph satellites are significantly different from those of dE_{bc}, dE_{blue}, and dI satellites. The blue-cored dwarf satellites (dE_{bc}) of early-type galaxies are likely to be located at r_{p} > 0.3 Mpc to keep their cold gas from the ram pressure stripping by the hot corona of early-type galaxies. The spatial distribution of dE_{bc} satellites of early-type galaxies and their global background densities suggest that their cold gas is intergalactic material accreted before they fall into the satellite systems.

  16. White dwarfs as physics laboratories: the case of axions

    OpenAIRE

    Isern, J.; Althaus, L.; Catalan, S.; Corsico, A.; Garcia-Berro, E.; Salaris, M.; Torres, S.

    2012-01-01

    White dwarfs are almost completely degenerate objects that cannot obtain energy from thermonuclear sources, so their evolution is just a gravothermal cooling process. Recent improvements in the accuracy and precision of the luminosity function and in pulsational data of variable white dwarfs suggest that they are cooling faster than expected from conventional theory. In this contribution we show that the inclusion of an additional cooling term due to axions able to interact with electrons wit...

  17. Agronomic characteristic of a dwarf germplasm sunflower line

    OpenAIRE

    Vassilevska-Ivanova Roumiana; Tcekova Zoja

    2005-01-01

    A new sunflower (Helianthus annuus L) dwarf line, HA-ARG-1, has been developed after interspecific hybridization between cultivated sunflower H. annuus and wild annual silver-leaf sunflower H. argophyllus. Plants were selected for reduced height and multiple branching characteristics. The agronomic, morphologic and oil content characteristics of the line were analyzed. Isolation of similar dwarfed lines illustrates the importance of using the wild sunflower germplasms in the development of sp...

  18. Dusty Dwarfs Galaxies Occulting A Bright Background Spiral

    Science.gov (United States)

    Holwerda, Benne

    2017-08-01

    The role of dust in shaping the spectral energy distributions of low mass disk galaxies remains poorly understood. Recent results from the Herschel Space Observatory imply that dwarf galaxies contain large amounts of cool (T 20K) dust, coupled with very modest optical extinctions. These seemingly contradictory conclusions may be resolved if dwarfs harbor a variety of dust geometries, e.g., dust at larger galactocentric radii or in quiescent dark clumps. We propose HST observations of six truly occulting dwarf galaxies drawn from the Galaxy Zoo catalog of silhouetted galaxy pairs. Confirmed, true occulting dwarfs are rare as most low-mass disks in overlap are either close satellites or do not have a confirmed redshift. Dwarf occulters are the key to determining the spatial extent of dust, the small scale structure introduced by turbulence, and the prevailing dust attenuation law. The recent spectroscopic confirmation of bona-fide low mass occulting dwarfs offers an opportunity to map dust in these with HST. What is the role of dust in the SED of these dwarf disk galaxies? With shorter feedback scales, how does star-formation affect their morphology and dust composition, as revealed from their attenuation curve? The resolution of HST allows us to map the dust disks down to the fine scale structure of molecular clouds and multi-wavelength imaging maps the attenuation curve and hence dust composition in these disks. We therefore ask for 2 orbits on each of 6 dwarf galaxies in F275W, F475W, F606W, F814W and F125W to map dust from UV to NIR to constrain the attenuation curve.

  19. Overexpression of rice black-streaked dwarf virus p7-1 in Arabidopsis results in male sterility due to non-dehiscent anthers.

    Directory of Open Access Journals (Sweden)

    Feng Sun

    Full Text Available Rice black-streaked dwarf virus (RBSDV, a member of the genus Fijivirus in the family Reoviridae, is propagatively transmitted by the small brown planthopper (Laodelphax striatellus Fallén. RBSDV causes rice black-streaked dwarf and maize rough dwarf diseases, which lead to severe yield losses in crops in China. Although several RBSDV proteins have been studied in detail, the functions of the nonstructural protein P7-1 are still largely unknown. To investigate the role of the P7-1 protein in virus pathogenicity, transgenic Arabidopsis thaliana plants were generated in which the P7-1 gene was expressed under the control of the 35S promoter. The RBSDV P7-1-transgenic Arabidopsis plants (named P7-1-OE were male sterility. Flowers and pollen from P7-1-transgenic plants were of normal size and shape, and anthers developed to the normal size but failed to dehisce. The non-dehiscent anthers observed in P7-1-OE were attributed to decreased lignin content in the anthers. Furthermore, the reactive oxygen species levels were quite low in the transgenic plants compared with the wild type. These results indicate that ectopic expression of the RBSDV P7-1 protein in A. thaliana causes male sterility, possibly through the disruption of the lignin biosynthesis and H2O2-dependent polymerization pathways.

  20. Gas, Stars, and Star Formation in Alfalfa Dwarf Galaxies

    Science.gov (United States)

    Huang, Shan; Haynes, Martha P.; Giovanelli, Riccardo; Brinchmann, Jarle; Stierwalt, Sabrina; Neff, Susan G.

    2012-01-01

    We examine the global properties of the stellar and Hi components of 229 low H i mass dwarf galaxies extracted from the ALFALFA survey, including a complete sample of 176 galaxies with H i masses dwarfs are faint and of low surface brightness; only 56% of those within the SDSS footprint have a counterpart in the SDSS spectroscopic survey. A large fraction of the dwarfs have high specific star formation rates (SSFRs), and estimates of their SFRs and M* obtained by SED fitting are systematically smaller than ones derived via standard formulae assuming a constant SFR. The increased dispersion of the SSFR distribution at M* approximately less than10(exp 8)M(sub 0) is driven by a set of dwarf galaxies that have low gas fractions and SSFRs; some of these are dE/dSphs in the Virgo Cluster. The imposition of an upper Hi mass limit yields the selection of a sample with lower gas fractions for their M* than found for the overall ALFALFA population. Many of the ALFALFA dwarfs, particularly the Virgo members, have H i depletion timescales shorter than a Hubble time. An examination of the dwarf galaxies within the full ALFALFA population in the context of global star formation (SF) laws is consistent with the general assumptions that gas-rich galaxies have lower SF efficiencies than do optically selected populations and that Hi disks are more extended than stellar ones.

  1. Nearby Red Dwarfs are Sexy for Planets and Life

    Science.gov (United States)

    Henry, T. J.; Jao, W.-C.; Subasavage, J. P.; RECONS Team

    2005-12-01

    The RECONS group continues to discover many nearby red dwarfs in the southern sky through a combination of proper motion surveys, literature review, and ultimately, our parallax program CTIOPI. Already, we have measured the first accurate parallaxes for 11 of the nearest 100 stellar systems, including four within 5 parsecs of the Sun. These nearby red dwarfs are prime candidates for NASA's Space Interferometry Mission (SIM) because the astrometric perturbations are largest for planets orbiting stars of low mass that are nearby. In addition, new multiple red dwarf systems can be targeted for mass determinations, thereby providing points on a comprehensive mass-luminosity relation for the most populous members of the Galaxy. Recent atmospheric modeling of planets orbiting red dwarfs indicates that even if the planets are tidally locked, heat distribution is highly effective in keeping the worlds balmy over the entire surface. Red dwarfs are therefore "back on the table" as viable hosts of life-bearing planets. Given their ubiquity, red dwarfs are being seriously considered as prime SETI targets, and will allow us to answer not only the question "Are We Alone?" but "Just How Alone Are We?" This work has been supported by the National Science Foundation, NASA's Space Interferometry Mission, and Georgia State University.

  2. Multimessenger Signatures of Massive Black Holes in Dwarf Galaxies

    Science.gov (United States)

    Bellovary, Jillian; Cleary, Colleen; Tremmel, Michael; Munshi, Ferah

    2018-01-01

    Inspired by the recent discovery of several nearby dwarf galaxies hosting active galactic nuclei, we present results from a series of cosmological hydrodynamic simulations focusing on dwarf galaxies which host supermassive black holes (SMBHs). Cosmological simulations are a vital tool for predicting SMBH populations and merger events which will eventually be observed by LISA. Dwarf galaxies are the most numerous in the universe, so even though the occupation fraction of SMBHs in dwarfs is less than unity, their contribution to the gravitational wave background could be non-negligible. We find that electromagnetic signatures from SMBH accretion are not common among most SMBH-hosting dwarfs, but the gravitational wave signatures can be substantial. The most common mass ratio for SMBH mergers in low-mass galaxy environments is ~1:20, which is an unexplored region of gravitational waveform parameter space. We discuss the occupation fraction of SMBHs in low-mass galaxies as well as differences in field and satellite populations, providing clues to search for and characterize these elusive giants lurking in the dwarfs.

  3. Epidemiology of the brown recluse spider bite.

    Science.gov (United States)

    Rhoads, Jacqueline

    2007-02-01

    The purpose of this article was to provide a comprehensive epidemiological and clinical description of the brown recluse spider bite. Review of evidenced-based scientific literature and practice guidelines. A specific descriptive case study is interwoven through the article to tie in the clinical presenting figure associated with this bite. The brown recluse lives in a circumscribed area of the United States (the south central Midwest) with a few less common recluse species living in the more sparsely populated southwest United States. In these areas, where spider populations may be dense, recluse spiders may be a cause of significant morbidity. Most spider bites are asymptomatic but what makes this bite so devastating is the toxin injected by the brown recluse spider, which can cause considerable systemic symptoms as well as necrotic skin ulcers (necrotic arachnidism). The article presents process for diagnosis and stresses the importance of identifying the spider if at all possible.

  4. Novel nuances of human brown fat

    DEFF Research Database (Denmark)

    Scheele, Camilla; Larsen, Therese Juhlin; Nielsen, Søren

    2014-01-01

    There is a current debate in the literature on whether human fat derived from the supraclavicular region should be classified as brown, or as the white fat-derived less potent, brite/beige. This commentary addresses whether the existing classification defined in mice is sufficient to describe...... the types of thermogenic adipocytes in humans. We recently published a contradictory mRNA expression signature of human supraclavicular fat defined by an upregulation of the brite marker TBX1 along with the classical brown markers ZIC1 and LHX8, as well as genes indicating brown fat activity including UCP1......, PGC-1α, and PRDM16; and, finally, a downregulation of the white/brite markers HOXC8 and HOXC9. Subcutaneous fat was used as reference material. Another recent study presents a higher expression of ZIC1 and a lower expression of TBX1 in interscapular compared with supraclavicular fat. Here, however...

  5. Brown adipogenesis of mouse embryonic stem cells in alginate microstrands

    Science.gov (United States)

    Unser, Andrea Mannarino

    The ability of brown adipocytes (fat cells) to dissipate energy as heat shows great promise for the treatment of obesity and other metabolic disorders. Employing pluripotent stem cells, with an emphasis on directed differentiation, may overcome many issues currently associated with primary fat cell cultures. However, brown adipocytes are difficult to transplant in vivo due to the instability of fat, in terms of necrosis and neovascularization, once injected. Thus, 3D cell culture systems that have the potential to mimic adipogenic microenvironments are needed, not only to advance brown fat implantation, but also to better understand the role of brown adipocytes in treating obesity. To address this need, we created 3D "Brown-Fat-in-Microstrands" by microfluidic synthesis of alginate hydrogel microstrands that encapsulated cells and directly induced cell differentiation into brown adipocytes, using mouse embryonic stem cells (ESCs) as a model of pluripotent stem cells and brown preadipocytes as a positive control. The effect of hydrogel formation parameters on brown adipogenesis was studied, leading to the establishment of "Brown-Fat-in-Microstrands". Brown adipocyte differentiation within microstrands was confirmed by lipid droplet accumulation, immunocytochemistry and qPCR analysis of gene expression of brown adipocyte marker uncoupling protein 1 (UCP1) in addition to adipocyte marker expression. Compared to a 2D approach, 3D differentiated "Brown-Fat-in-Microstrands" exhibited higher level of brown adipocyte marker expression. The functional analysis of "Brown-Fat-in-Microstrands" was attempted by measuring the mitochondrial activity of ESC-differentiated brown adipocytes in 3D using Seahorse XF24 3 Extracellular Flux Analyzer. The ability to create "Brown-Fat-in-Microstrands" from pluripotent stem cells opens up a new arena to understanding brown adipogenesis and its implications in obesity and metabolic disorders.

  6. Hanbury Brown-Twiss interference of anyons.

    Science.gov (United States)

    Campagnano, Gabriele; Zilberberg, Oded; Gornyi, Igor V; Feldman, Dmitri E; Potter, Andrew C; Gefen, Yuval

    2012-09-07

    We present a study of a Hanbury Brown-Twiss interferometer realized with anyons. Such a device can directly probe entanglement and fractional statistics of initially uncorrelated particles. We calculate Hanbury Brown-Twiss cross correlations of Abelian Laughlin anyons. The correlations we calculate exhibit partial bunching similar to bosons, indicating a substantial statistical transmutation from the underlying electronic degrees of freedom. We also find qualitative differences between the anyonic signal and the corresponding bosonic or fermionic signals, indicating that anyons cannot be simply thought of as intermediate between bosons and fermions.

  7. Briquetting of Coke-Brown Coal Mixture

    Directory of Open Access Journals (Sweden)

    Ïurove Juraj

    1998-09-01

    Full Text Available The paper presents the results of the research of briquetting a coke-brown coal composite The operation consists of the feeding crushed coal and coke to moulds and pressing into briquettes which have been made in the Laboratories at the Mining Faculty of Technical University of Košice (Slovakia. In this research, all demands will be analyzed including the different aspects of the mechanical quality of briquettes, the proportion of fine pulverulent coal and coke in bricks, the requirements for briquetting the coke-brown coal materials.

  8. Çukurova Üniversitesi Yerleşkesi Açık Alanlarının Fiziksel Engelliler Bakımından Ulaşılabilirliğinin Değerlendirilmesi

    OpenAIRE

    Sirel, Berrin; Duymuş, Halil; Boyacıgil, Onur; Konaklı, Nurgül; Altunkasa, Faruk; USLU**, Cengiz

    2012-01-01

    Çalışmada fiziksel engelli bireyler açısından Çukurova Üniversitesi yerleşkesi açık alanlarında ulaşılabilirlik kavramı konu edilmiş ve bu alanların belirlenen ölçütler üzerinden kullanılabilirliği değerlendirilmiştir. Bu kapsamda yerleşkeyi temsil ettiği düşünülen beş örnek alan belirlenmiştir. Kültür Merkezi-Güzel Sanatlar Fakültesi Aksı, Mithat Özsan Bulvarı Aksı, TARGET Kafeterya-Merkezi Kafeterya Aksı, Kütüphane ve Merkezi Derslikler Çevresi ile Tören Alanı ve Çevresi engelliler için bel...

  9. Kodiak brown bear population on Kodiak Island, Alaska

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — Methods and estimates of the Brown bear population on Kodiak Island. The total number of Kodiak Brown Bears on Kodiak Island has been estimated to be 1669. Three...

  10. Simulating Supernovae Driven Outflows in Dwarf Galaxies

    Science.gov (United States)

    Rodriguez, Jaimee-Ian

    2018-01-01

    Galactic outflows, or winds, prove to be a necessary input for galactic simulations to produce results comparable to observation, for it solves issues caused by what previous literature dubbed the “angular momentum catastrophe.” While it is known that the nature of outflows depends on the nature of the Interstellar Medium (ISM), the mechanisms behind outflows are still not completely understood. We investigate the driving force behind galactic outflows and the factors that influence their behavior, hypothesizing that supernovae within the galaxy drive these winds. We study isolated, high-resolution, smooth particle hydrodynamic simulations, focusing specifically on dwarf galaxies due to their shallow potential wells, which allow for more significant outflows. We find that outflows follow star formation (and associated supernovae) suggesting the causal relationship between the two. Furthermore, simulations with higher diffusivity differ little in star formation rate, but show significantly lower outflow rates, suggesting that environmental factors that have little effect on regulating star formation can greatly influence outflows, and so efficient outflows can be driven by a constant rate of supernovae, depending on ISM behavior. We are currently analyzing disk morphology and ambient density in order to comprehend the effect of supernovae on the immediate interstellar gas. By attaining greater understanding of the origin of galactic outflows, we will be able to not only improve the accuracy of simulations, we will also be able to gain greater insight into galactic formation and evolution, as outflows and resultant inflows may be vital to the regulation of galaxies throughout their lifetimes.

  11. Characterization of DWARF14 Genes in Populus

    Science.gov (United States)

    Zheng, Kaijie; Wang, Xiaoping; Weighill, Deborah A.; Guo, Hao-Bo; Xie, Meng; Yang, Yongil; Yang, Jun; Wang, Shucai; Jacobson, Daniel A.; Guo, Hong; Muchero, Wellington; Tuskan, Gerald A.; Chen, Jin-Gui

    2016-01-01

    Strigolactones are a new class of plant hormones regulating shoot branching and symbiotic interactions with arbuscular mycorrhizal fungi. Studies of branching mutants in herbaceous plants have identified several key genes involved in strigolactone biosynthesis or signaling. The strigolactone signal is perceived by a member of the α/β-fold hydrolase superfamily, known as DWARF14 (D14). However, little is known about D14 genes in the woody perennial plants. Here we report the identification of D14 homologs in the model woody plant Populus trichocarpa. We showed that there are two D14 homologs in P. trichocarpa, designated as PtD14a and PtD14b that are over 95% similar at the amino acid level. Expression analysis indicated that the transcript level of PtD14a is generally more abundant than that of PtD14b. However, only PtD14a was able to complement Arabidopsis d14 mutants, suggesting that PtD14a is the functional D14 ortholog. Amino acid alignment and structural modeling revealed substitutions of several highly conserved amino acids in the PtD14b protein including a phenylalanine near the catalytic triad of D14 proteins. This study lays a foundation for further characterization of strigolactone pathway and its functions in the woody perennial plants. PMID:26875827

  12. Accreting White Dwarfs as Universal Accretion Laboratories

    Science.gov (United States)

    Knigge, Christian

    Accreting white dwarfs (AWDs) are numerous, bright and nearby, making them excellent laboratories for the study of accretion physics. Since their accretion flows are unaffected by relativistic effects or ultra-strong magnetic fields, they provide a crucial "control" group for efforts to understand more complex/compact systems, such as accreting neutron stars (NSs) and black holes (BHs). Here, I will review recent work on AWDs, which has revealed that these superficially simple systems actually exhibit the full range of accretion-related phenomenology seen in accreting NSs and BHs. For example, (i) AWDs undergo mass loss in the form of both disk winds and radio jets; (ii) their disk winds are only seen in high-Mdot states, similar to what is observed in accreting BHs; (iii) they exhibit (possibly hysteretic) outbursts produced by disk instabilities, as also seen in NS and BH transients; and (iv) they produce accretion-induced stochastic variability ("flickering") that exhibits the same rms-flux relation as observed in low-mass X-ray binaries and AGN. Based on this rich and shared phenomenology, it is reasonable to hope that much of accretion physics is universal. In this context, AWDs hold great promise as observational testing grounds for attempts to model and understand these physics.

  13. Reinterpreting The Sagittarius Dwarf Tidal Debris

    Science.gov (United States)

    Newby, Matthew T.; Newberg, Heidi Jo; Thompson, Jeffery M.; Weiss, Jake

    2015-01-01

    Tidal debris from the Sagittarius dwarf galaxy (Sgr) has been used as a primary constraint in several determinations of the Milky Way Galaxy's total mass and dark matter distribution. However, the apparent "bifurcation" of both the leading and trailing tidal tails has never been satisfactorily explained. Using the powerful MilkyWay@home volunteer computing platform, we were surprised that the apparently fainter of the bifurcated tidal tails required an extremely wide stream to fit the observed stellar densities. Here, through additional analysis, we show that both the primary and secondary tidal tails of Sgr, as well as the Virgo overdensity, are all wider than previously thought, and dominate star counts in the Galactic halo. Additionally, we present evidence of a stellar "envelope" about the primary Sgr stream, which may be direct evidence for a subhalo-rich (or "lumpy") dark matter distribution. This research was supported by the NSF through grant AST 10-09670, and crowd funding from the MilkyWay@home volunteers.

  14. Tidal dwarf galaxies in cosmological simulations

    Science.gov (United States)

    Ploeckinger, Sylvia; Sharma, Kuldeep; Schaye, Joop; Crain, Robert A.; Schaller, Matthieu; Barber, Christopher

    2018-02-01

    The formation and evolution of gravitationally bound, star forming substructures in tidal tails of interacting galaxies, called tidal dwarf galaxies (TDG), has been studied, until now, only in idealized simulations of individual pairs of interacting galaxies for pre-determined orbits, mass ratios and gas fractions. Here, we present the first identification of TDG candidates in fully cosmological simulations, specifically the high-resolution simulations of the EAGLE suite. The finite resolution of the simulation limits their ability to predict the exact formation rate and survival time-scale of TDGs, but we show that gravitationally bound baryonic structures in tidal arms already form in current state-of-the-art cosmological simulations. In this case, the orbital parameter, disc orientations as well as stellar and gas masses and the specific angular momentum of the TDG forming galaxies are a direct consequence of cosmic structure formation. We identify TDG candidates in a wide range of environments, such as multiple galaxy mergers, clumpy high-redshift (up to z = 2) galaxies, high-speed encounters and tidal interactions with gas-poor galaxies. We present selection methods, the properties of the identified TDG candidates and a road map for more quantitative analyses using future high-resolution simulations.

  15. FLITECAM/SOFIA Commissioning and Early Science and A Study of Late-T Dwarf Color Outliers with NIRSPEC/Keck

    Science.gov (United States)

    Logsdon, Sarah E.

    2017-01-01

    My thesis combines the development of infrared instrumentation with the application of infrared imaging and spectroscopy to the characterization of the highest and lowest mass products of the star formation process. I supported the development and commissioning of FLITECAM, a 1-5 μm imager and spectrograph for SOFIA (Stratospheric Observatory for Infrared Astronomy), as the UCLA FLITECAM Instrument Scientist, and used FLITECAM to probe high-mass star formation. In parallel, I used the NIRSPEC spectrograph at Keck Observatory to study the lowest mass products of star formation, brown dwarfs. Here, I present an overview of FLITECAM’s in-flight performance in both imaging and spectroscopy modes. I also describe the results of an imaging survey of the NGC 2024 and W3 star-forming regions using FLITECAM’s Paschen-α (1.87 μm) and Polycyclic Aromatic Hydrocarbon (PAH; 3.3 μm) filters. These filters provide an effective way to trace the ionized gas emission and the emission from small grains. Additionally, I present the results of a NIRSPEC/Keck spectroscopic follow-up survey of 13 late-type T dwarfs (T6-T9) with unusually red or blue J-H colors. Previous work suggests that J-H color outliers may represent the high-gravity, low-metallicity (old) and low-gravity, high-metallicity (young) extremes of the late-T dwarf population. I find that the T dwarf color outliers in this sample are more homogenous than expected. Nevertheless, comparisons to spectral standards and publicly available atmospheric models do reveal subtle physical differences in their spectral morphologies.

  16. Trustworthy-looking face meets brown eyes.

    Directory of Open Access Journals (Sweden)

    Karel Kleisner

    Full Text Available We tested whether eye color influences perception of trustworthiness. Facial photographs of 40 female and 40 male students were rated for perceived trustworthiness. Eye color had a significant effect, the brown-eyed faces being perceived as more trustworthy than the blue-eyed ones. Geometric morphometrics, however, revealed significant correlations between eye color and face shape. Thus, face shape likewise had a significant effect on perceived trustworthiness but only for male faces, the effect for female faces not being significant. To determine whether perception of trustworthiness was being influenced primarily by eye color or by face shape, we recolored the eyes on the same male facial photos and repeated the test procedure. Eye color now had no effect on perceived trustworthiness. We concluded that although the brown-eyed faces were perceived as more trustworthy than the blue-eyed ones, it was not brown eye color per se that caused the stronger perception of trustworthiness but rather the facial features associated with brown eyes.

  17. Natural history of presumed congenital Brown syndrome.

    Science.gov (United States)

    Kaban, T J; Smith, K; Orton, R B; Noel, L P; Clarke, W; Cadera, W

    1993-07-01

    To evaluate the stability of the ocular alignment in patients with presumed congenital Brown syndrome. A retrospective review of patients with Brown syndrome with an emphasis on nonsurgical cases. Follow-up of at least 1 year was required for inclusion in the study. Patients were selected for this study from the pediatric ophthalmology services at the Ivey Institute of Ophthalmology, London, Ontario, and the Children's Hospital of Eastern Ontario, Ottawa. A cohort of 71 patients with presumed congenital Brown syndrome. Two cases were bilateral. Eleven cases were excluded because of insufficient length of follow-up, leaving 60 patients with an average follow-up of 46 months. All patients were assessed and followed up by a pediatric ophthalmologist. Of 38 patients who had no hypotropia in primary position at presentation, only two (5%) patients experienced a worsening with the development of a small vertical strabismus during the follow-up period. Six (10%) of the entire group of 60 patients experienced a complete spontaneous resolution of the deficiency in elevation at 4, 6, 8, 10, 12, and 15 years of age. Among patients with congenital Brown syndrome, those who are orthotropic in the primary position tend to remain stable or improve over time without surgical intervention.

  18. Brown Bodies, Racialisation and physical education

    Science.gov (United States)

    Fitzpatrick, Katie

    2013-01-01

    This article explores how school physical education (PE) can both reinforce stereotyped notions of the brown body as inherently physical while also allowing young people to gain educational success. Drawing on a critical ethnographic study of Maori and Pasifika (Pacific Island) youth in PE in New Zealand, the article explores how the academic…

  19. Maxillary brown tumour: unusual presentation of parathyroid ...

    African Journals Online (AJOL)

    This is a report of a maxillary brown tumour caused by primary hyperparathyroidism (HPT) secondary to parathyroid carcinoma. A 62-year-old man presented with a large swelling in the right maxilla, which caused right-sided nasal obstruction, intermittent bleeding and diplopia. A computed tomography scan demonstrated ...

  20. Molecular Selectivity of Brown Carbon Chromophores

    Energy Technology Data Exchange (ETDEWEB)

    Laskin, Julia; Laskin, Alexander; Nizkorodov, Sergey; Roach, Patrick J.; Eckert, Peter A.; Gilles, Mary K.; Wang, Bingbing; Lee, Hyun Ji; Hu, Qichi

    2014-10-21

    Complementary methods of high-resolution mass spectrometry and micro-spectroscopy were utilized for molecular analysis of secondary organic aerosol (SOA) generated from ozonolysis of two structural monoterpene isomers: D-limonene (LSOA) and a-pinene (PSOA). Laboratory simulated aging of LSOA and PSOA, through conversion of carbonyls into imines mediated by NH3 vapors in humid air, resulted in selective browning of the LSOA sample, while the PSOA sample remained white. Comparative analysis of the reaction products in the aged LSOA and PSOA samples provided insights into chemistry relevant to formation of brown carbon chromophores. A significant fraction of carbonyl-imine conversion products with identical molecular formulas were detected in both samples. This reflects the high level of similarity in the molecular composition of these two closely related SOA materials. Several highly conjugated products were detected exclusively in the brown LSOA sample and were identified as potential chromophores responsible for the observed color change. The majority of the unique products in the aged LSOA sample with the highest number of double bonds contain two nitrogen atoms. We conclude that chromophores characteristic of the carbonyl- imine chemistry in LSOA are highly conjugated oligomers of secondary imines (Schiff bases) present at relatively low concentrations. Formation of this type of conjugated compounds in PSOA is hindered by the structural rigidity of the a-pinene oxidation products. Our results suggest that the overall light-absorbing properties of SOA may be determined by trace amounts of strong brown carbon chromophores.

  1. The browning of Alaska's boreal forest

    Science.gov (United States)

    Mary Beth Parent; David. Verbyla

    2010-01-01

    We used twelve Landsat scenes from the 1980s-2009 and regional 2000-2009 MODIS data to examine the long-term trend in the normalized difference vegetation index (NDVI) within unburned areas of the Alaskan boreal forest. Our analysis shows that there has been a declining trend in NDVI in this region, with the strongest "browning trend" occurring in eastern...

  2. Phospholipids of New Zealand Edible Brown Algae.

    Science.gov (United States)

    Vyssotski, Mikhail; Lagutin, Kirill; MacKenzie, Andrew; Mitchell, Kevin; Scott, Dawn

    2017-07-01

    Edible brown algae have attracted interest as a source of beneficial allenic carotenoid fucoxanthin, and glyco- and phospholipids enriched in polyunsaturated fatty acids. Unlike green algae, brown algae contain no or little phosphatidylserine, possessing an unusual aminophospholipid, phosphatidyl-O-[N-(2-hydroxyethyl) glycine], PHEG, instead. When our routinely used technique of 31P-NMR analysis of phospholipids was applied to the samples of edible New Zealand brown algae, a number of signals corresponding to unidentified phosphorus-containing compounds were observed in total lipids. NI (negative ion) ESI QToF MS spectra confirmed the presence of more familiar phospholipids, and also suggested the presence of PHEG or its isomers. The structure of PHEG was confirmed by comparison with a synthetic standard. An unusual MS fragmentation pattern that was also observed prompted us to synthesise a number of possible candidates, and was found to follow that of phosphatidylhydroxyethyl methylcarbamate, likely an extraction artefact. An unexpected outcome was the finding of ceramidephosphoinositol that has not been reported previously as occurring in brown algae. An uncommon arsenic-containing phospholipid has also been observed and quantified, and its TLC behaviour studied, along with that of the newly synthesised lipids.

  3. Brown hares on the edge: Genetic population structure of the Danish brown hare

    DEFF Research Database (Denmark)

    Andersen, Liselotte W.; Fredsted, Tina; Wincentz, Trine

    2009-01-01

    Andersen L. W., Fredsted T., Wincentz T. and Pertoldi C. 2009. Brown hares on the edge: Genetic population structure of the Danish brown hare. Acta Theriologica 54: 97-110. Denmark lies on the edge of the distributional range of the brown hare Lepus europaeus Pallas, 1778, where population......-69.8 respectively). There was no correlation between the geographic and the genetic distance. Population structure was influenced by genetic drift, anthropogenic effects (eg translocation and escapes from hare-farms) and by post-glacial recolonization from southern refuges or refuges north east of the Black Sea...... glaciations or by stocking effects. Colonization from southern refuges was supported by the observation that haplotype 2 in the Danish brown hare was identical to the central European ancestral haplotype c07....

  4. Kenai Peninsula Brown Bear Studies : Report of the Interagency Brown Bear Study Team, 1986

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This report summarizes work conducted during the 1986 field season on brown bear (Ursus arctos) from the Kenai Peninsula, Alaska. Ground surveys were conducted to...

  5. Sweating the small stuff: simulating dwarf galaxies, ultra-faint dwarf galaxies, and their own tiny satellites

    Science.gov (United States)

    Wheeler, Coral Rose

    We study dwarf satellite galaxy quenching using observations from the Geha et al. (2012) NSA/SDSS catalog together with CDM cosmological simulations to facilitate selection and interpretation. We show that fewer than 30% of dwarfs (M* ˜ 108.5-9.5 Msun ) identified as satellites within massive host halos (M host ˜ 1012.5-14 Msun) are quenched. We conclude that whatever the action triggering environmental quenching of dwarf satellites, the process must be highly inefficient. We investigate a series of simple, one-parameter quenching models in order to understand what is required to explain the low quenched fraction and conclude that either the quenching timescale is very long (> 9.5 Gyr, a "slow starvation" scenario) or that the environmental trigger is not well matched to accretion within the virial volume. We further present FIRE/Gizmo hydrodynamic zoom-in simulations of isolated dark matter halos, two each at the mass of classical dwarf galaxies (Mvir ˜ 1010 Msun) and ultra-faint galaxies (Mvir ˜ 10 9 Msun). The resulting central galaxies lie on an extrapolated abundance matching relation from M* ˜ 106 to 104 Msun without a break. Our dwarfs with M* ˜ 106 Msun each have 1-2 well-resolved satellites with M* = 3 - 200 x 103 Msun. Even our isolated ultra-faint galaxies have star-forming subhalos. We combine our results with the ELVIS simulations to show that targeting the ˜ 50 kpc regions around nearby isolated dwarfs could increase the chances of discovering ultra-faint galaxies by ˜35% compared to random pointings. The well-resolved ultra-faint galaxies in our simulations (M * ˜ 3 - 30 x 103 Msun) form within Mpeak ˜ 0.5 - 3 x 109 Msun halos. Each has a uniformly ancient stellar population (> 10 Gyr) owing to reionization-related quenching. More massive systems, in contrast, all have late-time star formation. Our results suggest that Mhalo ˜ 5 x 109 Msun is a probable dividing line between halos hosting reionization "fossils" and those hosting dwarfs

  6. Gas exchange and brown heart in conference pears

    NARCIS (Netherlands)

    Otma, E.C.; Peppelenbos, H.W.

    2003-01-01

    Brown heart is a tissue disorder found in Conference pears during CA storage. Differences in susceptibility for brown heart have been found between countries, orchards, harvest dates and storage conditions. One hypothesis is that brown heart is caused by increased internal CO2. This research

  7. 49 CFR 173.216 - Asbestos, blue, brown or white.

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Asbestos, blue, brown or white. 173.216 Section... Class 7 § 173.216 Asbestos, blue, brown or white. (a) Asbestos, blue, brown or white, includes each of the following hydrated mineral silicates: chrysolite, crocidolite, amosite, anthophyllite asbestos...

  8. Simulationsverfahren fuer Brown-Resnick-Prozesse (Simulation Techniques for Brown-Resnick Processes)

    OpenAIRE

    Oesting, Marco

    2009-01-01

    Generalized Brown-Resnick processes form a flexible class of stationary max-stable processes based on Gaussian random fields. With regard to applications fast and accurate simulation of these processes is an important issue. In fact, Brown-Resnick processes that are generated by a dissipative flow do not allow for good finite approximations using the definition of the processes. On large intervals we get either huge approximation errors or very long operating times. Looking for solutions of t...

  9. 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

    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

  10. Results of the NaCo Large Program: probing the occurrence of exoplanets and brown dwarfs at wide orbit

    OpenAIRE

    2014-01-01

    Over the past decade, a growing number of deep imaging surveys have started to provide meaningful constraints on the population of extrasolar giant planets at large orbital separation. Primary targets for these surveys have been carefully selected based on their age, distance and spectral type, and often on their membership to young nearby associations where all stars share common kinematics, photometric and spectroscopic properties. The next step is a wider statistical analysis of the freque...

  11. WISEP J004701.06+680352.1: An Intermediate Surface Gravity, Dusty Brown Dwarf in the AB Dor Moving Group

    Science.gov (United States)

    2015-02-01

    continuum lying too low, but the Teff = 1300 K, log g = 4.0 model is reasonably similar in overall morphology and slope, though it lacks the hydrides; CrH...Kingdom), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), CNPq (Brazil), and CONICET (Argentina

  12. Rotation periods and photometric variability of rapidly rotating ultracool dwarfs

    Science.gov (United States)

    Miles-Páez, P. A.; Pallé, E.; Zapatero Osorio, M. R.

    2017-12-01

    We used the optical and near-infrared imagers located on the Liverpool, the IAC80, and the William Herschel telescopes to monitor 18 M7-L9.5 dwarfs with the objective of measuring their rotation periods. We achieved accuracies typically in the range ±1.5-28 mmag by means of differential photometry, which allowed us to detect photometric variability at the 2σ level in the 50 per cent of the sample. We also detected periodic modulation with periods in the interval 1.5-4.4 h in 9 out of 18 dwarfs that we attribute to rotation. Our variability detections were combined with data from the literature; we found that 65 ± 18 per cent of M7-L3.5 dwarfs with v sin I ≥ 30 km s-1 exhibit photometric variability with typical amplitudes ≤20 mmag in the I band. For those targets and field ultracool dwarfs with measurements of v sin I and rotation period we derived the expected inclination angle of their rotation axis, and found that those with v sin I ≥ 30 km s-1 are more likely to have inclinations ≳40 deg. In addition, we used these rotation periods and others from the literature to study the likely relationship between rotation and linear polarization in dusty ultracool dwarfs. We found a correlation between short rotation periods and large values of linear polarization at optical and near-infrared wavelengths.

  13. White dwarf stars exceeding the Chandrasekhar mass limit

    Science.gov (United States)

    Tomaschitz, Roman

    2018-01-01

    The effect of nonlinear ultra-relativistic electron dispersion on the mass-radius relation of high-mass white dwarfs is studied. The dispersion is described by a permeability tensor in the Dirac equation, generated by the ionized high-density stellar matter, which constitutes the neutralizing background of the nearly degenerate electron plasma. The electron dispersion results in a stable mass-radius relation for high-mass white dwarfs, in contrast to a mass limit in the case of vacuum permeabilities. In the ultra-relativistic regime, the dispersion relation is a power law whose amplitude and scaling exponent is inferred from mass and radius estimates of two high-mass white dwarfs, Sirius B and LHS 4033. Evidence for the existence of super-Chandrasekhar mass white dwarfs is provided by several Type Ia supernovae (e.g., SN 2013cv, SN 2003fg, SN 2007if and SN 2009dc), whose mass ejecta exceed the Chandrasekhar limit by up to a factor of two. The dispersive mass-radius relation is used to estimate the radii, central densities, Fermi temperatures, bulk and compression moduli and sound velocities of their white dwarf progenitors.

  14. Left Behind: A Bound Remnant from a White Dwarf Supernova?

    Science.gov (United States)

    Jha, Saurabh

    2017-08-01

    Type Ia supernovae (SN Ia) have enormous importance to cosmology and astrophysics, but their progenitors and explosion mechanisms are not understood in detail. Recently, observations and theoretical models have suggested that not all thermonuclear white-dwarf supernova explosions are normal SN Ia. In particular, type Iax supernovae (peculiar cousins to SN Ia), are thought to be exploding white dwarfs that are not completely disrupted, leaving behind a bound remnant. In deep and serendipitous HST pre-explosion data, we have discovered a luminous, blue progenitor system for the type Iax SN 2012Z in NGC 1309, which we interpret as a helium-star donor to the exploding white dwarf. HST observations of SN 2012Z in 2016, when the supernova light was expected to have faded away, still show a source at the location, as expected in our model where the pre-explosion flux was coming from the companion. However, the 2016 data also show a surprise: an excess flux compared to the progenitor system. Our proposed observations here will help unravel the mystery of that excess flux: is it from the bound ex-white dwarf remnant? Or is it from the shocked companion star that has been bombarded by supernova ejecta? Either of these possibilities would provide key new evidence as to the nature of these white dwarf supernovae.

  15. 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.

  16. Interacting galaxy NGC4656 and its unusual dwarf companion

    Science.gov (United States)

    Zasov, Anatoly V.; Saburova, Anna S.; Egorov, Oleg V.; Uklein, Roman I.

    2017-08-01

    We studied the nearby edge-on galaxy NGC4656 and its dwarf low surface brightness companion with the enhanced UV brightness, NGC4656UV, belonging to the interacting system NGC4631/56. Regular photometric structure and relatively big size of NGC4656UV allows us to consider this dwarf galaxy as a separate group member rather than a tidal dwarf. Spectral long-slit observations were used to obtain the kinematical parameters and gas-phase metallicity of NGC4656UV and NGC4656. Our rough estimate of the total dynamical mass of NGC4656UV allowed us to conclude that this galaxy is the dark-matter dominated LSB dwarf or ultradiffuse galaxy. Young stellar population of NGC4656UV, as well as strong local non-circular gas motions in NGC4656 and the low oxygen gas abundance in the region of this galaxy adjacent to its dwarf companion, give evidence in favour of the accretion of metal-poor gas on to the discs of both galaxies.

  17. Stellar explosions from accreting white dwarfs

    Science.gov (United States)

    Moore, Kevin L.

    Unstable thermonuclear burning on accreting white dwarfs (WDs) can lead to a wide variety of outcomes, and induce shock waves in several contexts. In classical and recurrent novae, a WD accreting hydrogen-rich material from a binary companion can experience thermonuclear runaways, ejecting mass into the interstellar/circumbinary environment at ~1000 km/s. This highly supersonic ejecta drives shock waves into the interstellar gas which may be relevant for sweeping out gas from globular clusters or forming circumstellar absorption regions in interacting supernovae. While runaway nuclear burning in novae releases enough energy for these objects to brighten by a factor of ~10 4 over roughly a weeklong outburst, it does not become dynamically unstable. In contrast, certain helium accretion scenarios may allow for dynamical burning modes, in part due to the higher temperature sensitivity of helium burning reactions and larger accreted envelopes. The majority of this thesis involves such dynamical burning modes, specifically detonations - shock waves sustained by nuclear energy release behind the shock front. We investigate when steady-state detonations are realizable in accreted helium layers on WDs, and model their strength and burning products using both semi-analytic and numerical models. We find the minimum helium layer thickness that will sustain a steady laterally propagating detonation and show that it depends on the density and composition of the helium layer, specifically 12 C and 16O. Though gravitationally unbound, the ashes still have unburned helium (~80% in the thinnest cases) and only reach up to heavy elements such as 40Ca, 44Ti, 48Cr, and 52Fe. It is rare for these thin shells to generate large amounts of radioactive isotopes necessary to power light curves, such as 56Ni. This has important implications on whether the unbound helium burning ashes may create faint and fast peculiar supernovae or events with virtually no radioactivity, as well as on off

  18. Dwarf cashew growth irrigated with saline waters

    Directory of Open Access Journals (Sweden)

    Hugo Orlando Carvallo Guerra

    2009-12-01

    Full Text Available The cashew production is one of the most important agricultural activities from the social-economical viewpoint for the North East of Brazil; besides to produce a great deal of hand labor, it is very important as an exporting commodity. The inadequate use of irrigation in the semi arid regions of the North East of Brazil has induced soil salinization and consequently problems for the irrigated agriculture. In spite of this, few works have been conducted to study the effect of saline stress on the growth and development of the cashew. Because of the lack of information for this crop, an experiment was conducted to study the effect of salinity stress on the phytomass production and nutrient accumulation on the different organs of the precocious dwarf cashew (Anacardium occidentale L. clone CCP76. The study was conducted under controlled conditions using as statistical scheme a randomized block design factorial with six replicates. Five salinity treatments were considered for the irrigation water (electrical conductivities of 0.8, 1.6, 2.4, 3.2 and 4.0 dS m-1 at 25oC. The increasing in salinity of the irrigation water reduced the phytomass at different organs of the studied plant. The nitrogen, phosphorus, potassium, chloride and sodium in the plant varied with the salinity of the irrigation water according with the part of the plant analyzed; in some parts increased, in others decreased, in others increased initially and decreased afterwards, and finally, in other part of the plant the salinity of the irrigation water did not affect the nutrient concentration.

  19. Two new color-selected magnetic DA white dwarfs

    Science.gov (United States)

    Liebert, J.; Schmidt, G. D.; Sion, E. M.; Starrfield, S. G.; Green, R. F.; Boroson, T. A.

    1985-01-01

    The discovery of two magnetic white dwarfs culled from blue star surveys is reported. The surveys were carried out with the Mount Lemnon 1.5-meter reflecting telescope attached to a two-holer polarimeter/photometer. Spectral observations of the objects, (PG 1533 - 057, and K813 - 14), indicate the presence of hydrogen and Zeeman components. On the basis of dipolar field simulations, it is shown that PG 1533 - 057 has a polar field strength of 31 megagauss (MG) while K813 - 14 has a polar field strength of 29 MG. A third known white dwarf has a polar field strength of 18 MG. All the dwarfs had temperatures in the 11,000-20,000 K range. The possibility that a significant fraction of isolated magnetic degenerate stars could be the progeny of magnetic accreting binary systems is considered.

  20. A catalogue of white dwarf candidates in VST ATLAS

    Science.gov (United States)

    Gentile Fusillo, Nicola Pietro; Raddi, Roberto; Gänsicke, Boris T.; Hermes, J. J.; Pala, Anna F.; Fuchs, Joshua T.; Chehade, Ben; Metcalfe, Nigel; Shanks, Tom

    2017-07-01

    The Sloan Digital Sky Survey (SDSS) has created a knowledge gap between the Northern and the Southern hemispheres, which is very marked for white dwarfs: Only ≃15 per cent of the known white dwarfs are south of the equator. Here, we make use of the VLT Survey Telescope (VST) ATLAS survey, one of the first surveys obtaining deep, optical, multiband photometry over a large area of the southern skies, to remedy this situation. Applying the colour and proper-motion selection developed in our previous work on SDSS to the most recent internal data release (2016 April 25) of VST ATLAS, we created a catalogue of ≃4200 moderately bright (g ≤ 19), high-confidence southern white dwarf candidates, which can be followed up individually with both the large array of southern telescopes or in bulk with ESO's forthcoming multi-object spectrograph 4MOST.

  1. Disk Accretion of Tidally Disrupted Rocky Bodies onto White Dwarfs

    Science.gov (United States)

    Feng, W.; Desch, S.

    2017-03-01

    The prevailing model for the pollution of white dwarf photospheres invokes accretion from a disk of gas and solid particles, fed by tidal disruption of rocky bodies inside the Roche radius. Current models can successfully explain the accretion rates of metals onto white dwarfs, provided the gaseous disks viscously spread at rates consistent with a partially suppressed magnetorotational instability (Metzger et al. 2012); however, these models do not explore the extent of the magnetorotational instability in disks by calculating the degree of ionization. We present ionization fractions for thermal and non-thermal processes to assess the extent of the magnetorotational instability in white dwarf disks. We determine that the disk viscosity parameter α can be as high as 0.1 in white disks, implying that the magnetorotational instability must be carefully modeled.

  2. Far-infrared line images of dwarf galaxies

    Science.gov (United States)

    Poglitsch, A.; Geis, N.; Herrmann, F.; Madden, S. C.; Stacey, G. J.; Townes, C. H.; Genzel, R.

    1993-01-01

    Irregular dwarf galaxies are about ten times more widespread in the universe than regular spiral galaxies. They are characterized by a relatively low metallicity, i.e., lower abundance of the heavier elements (metals) with respect to hydrogen than in the solar neighborhood. These heavier elements in the form of molecules, atoms, or ions, which have radiative transitions in the infrared play a decisive role in the energy balance of the ISM and thereby for the formation of stars. Dwarf galaxies are thus model cases for the physical conditions in the early phase of the universe. Large Magellanic Cloud: 30 Doradus. The two nearest dwarf galaxies are the Magellanic clouds at a distance approximately 50 kpc. The LMC contains 30 Dor, a region with young, extremely massive stars which strongly interact with the surrounding ISM on account of their stellar winds and intense UV radiation. 30 Dor is the brightest object in the LMC at almost all wavelengths.

  3. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Energy Technology Data Exchange (ETDEWEB)

    Córsico, A.H.; Althaus, L.G. [Grupo de Evolución Estelar y Pulsaciones, Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata, Paseo del Bosque s/n, (1900) La Plata (Argentina); Bertolami, M.M. Miller [Instituto de Astrofísica La Plata, CONICET-UNLP, Paseo del Bosque s/n, (1900) La Plata (Argentina); Kepler, S.O. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul, Av. Bento Goncalves 9500, Porto Alegre 91501-970, RS (Brazil); García-Berro, E., E-mail: acorsico@fcaglp.unlp.edu.ar, E-mail: althaus@fcaglp.unlp.edu.ar, E-mail: marcelo@MPA-Garching.MPG.DE, E-mail: kepler@if.ufrgs.br, E-mail: enrique.garcia-berro@upc.edu [Departament de Física Aplicada, Universitat Politècnica de Catalunya, c/Esteve Terrades 5, 08860, Castelldefels (Spain)

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μ{sub ν}) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pidot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pidot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μ{sub ν} ∼< 10{sup -11} μ{sub B}. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  4. Constraining the neutrino magnetic dipole moment from white dwarf pulsations

    Science.gov (United States)

    Córsico, A. H.; Althaus, L. G.; Miller Bertolami, M. M.; Kepler, S. O.; García-Berro, E.

    2014-08-01

    Pulsating white dwarf stars can be used as astrophysical laboratories to constrain the properties of weakly interacting particles. Comparing the cooling rates of these stars with the expected values from theoretical models allows us to search for additional sources of cooling due to the emission of axions, neutralinos, or neutrinos with magnetic dipole moment. In this work, we derive an upper bound to the neutrino magnetic dipole moment (μν) using an estimate of the rate of period change of the pulsating DB white dwarf star PG 1351+489. We employ state-of-the-art evolutionary and pulsational codes which allow us to perform a detailed asteroseismological period fit based on fully DB white dwarf evolutionary sequences. Plasmon neutrino emission is the dominant cooling mechanism for this class of hot pulsating white dwarfs, and so it is the main contributor to the rate of change of period with time (Pi dot) for the DBV class. Thus, the inclusion of an anomalous neutrino emission through a non-vanishing magnetic dipole moment in these sequences notably influences the evolutionary timescales, and also the expected pulsational properties of the DBV stars. By comparing the theoretical Pi dot value with the rate of change of period with time of PG 1351+489, we assess the possible existence of additional cooling by neutrinos with magnetic dipole moment. Our models suggest the existence of some additional cooling in this pulsating DB white dwarf, consistent with a non-zero magnetic dipole moment with an upper limit of μν lesssim 10-11 μB. This bound is somewhat less restrictive than, but still compatible with, other limits inferred from the white dwarf luminosity function or from the color-magnitude diagram of the Globular cluster M5. Further improvements of the measurement of the rate of period change of the dominant pulsation mode of PG 1351+489 will be necessary to confirm our bound.

  5. Guide to the universe asteroids, comets, and dwarf planets

    CERN Document Server

    Rivkin, Andrew

    2009-01-01

    This volume in the Greenwood Guides to the Universe series covers asteroids, comets, and dwarf planets-those small bodies that revolve the Sun-and provides readers with the most up-to-date understanding of the current state of scientific knowledge about them. Scientifically sound, but written with the student in mind, Asteroids, Comets, and Dwarf Planets is an excellent first step for researching the exciting scientific discoveries of the smallest celestial bodies in the solar system.||The book will introduce students to all of the areas of research surrounding the subject, answering many intr

  6. Properties of O dwarf stars in 30 Doradus

    Science.gov (United States)

    Sabín-Sanjulián, Carolina; VFTS Collaboration

    2017-11-01

    We perform a quantitative spectroscopic analysis of 105 presumably single O dwarf stars in 30 Doradus, located within the Large Magellanic Cloud. We use mid-to-high resolution multi-epoch optical spectroscopic data obtained within the VLT-FLAMES Tarantula Survey. Stellar and wind parameters are derived by means of the automatic tool iacob-gbat, which is based on a large grid of fastwind models. We also benefit from the Bayesian tool bonnsai to estimate evolutionary masses. We provide a spectral calibration for the effective temperature of O dwarf stars in the LMC, deal with the mass discrepancy problem and investigate the wind properties of the sample.

  7. Astro-archaeology - The white dwarfs and hot subwarfs

    Science.gov (United States)

    Van Horn, Hugh M.

    1991-01-01

    By 'astroarcheology' is presently meant the effort to ascertain the Galaxy's past in light of what is found in its most ancient, white dwarf constituents. Attention is given to the controversial role of the hot subdwarfs and the theory of white dwarf spectral evolution, as well as to the concept of the 'Whole Earth Telescope', involving continuous photometric coverage of rapidly varying astronomical sources and thereby eliminating the otherwise troublesome diurnal gaps in data. Much higher resolution of the power spectra of these objects is attainable by these means than any current alternative.

  8. Pulsations powered by hydrogen shell burning in white dwarfs

    Science.gov (United States)

    Camisassa, M. E.; Córsico, A. H.; Althaus, L. G.; Shibahashi, H.

    2016-10-01

    Context. In the absence of a third dredge-up episode during the asymptotic giant-branch phase, white dwarf models evolved from low-metallicity progenitors have a thick hydrogen envelope, which makes hydrogen shell burning be the most important energy source. Aims: We investigate the pulsational stability of white dwarf models with thick envelopes to see whether nonradial g-mode pulsations are triggered by hydrogen burning, with the aim of placing constraints on hydrogen shell burning in cool white dwarfs and on a third dredge-up during the asymptotic giant-branch evolution of their progenitor stars. Methods: We construct white-dwarf sequences from low-metallicity progenitors by means of full evolutionary calculations that take into account the entire history of progenitor stars, including the thermally pulsing and the post-asymptotic giant-branch phases, and analyze their pulsation stability by solving the linear, nonadiabatic, nonradial pulsation equations for the models in the range of effective temperatures Teff 15 000-8000 K. Results: We demonstrate that, for white dwarf models with masses M⋆ ≲ 0.71 M⊙ and effective temperatures 8500 ≲ Teff ≲ 11 600 K that evolved from low-metallicity progenitors (Z = 0.0001, 0.0005, and 0.001), the dipole (ℓ = 1) and quadrupole (ℓ = 2) g1-modes are excited mostly as a result of the hydrogen-burning shell through the ɛ-mechanism, in addition to other g-modes driven by either the κ - γ or the convective driving mechanism. However, the ɛ mechanism is insufficient to drive these modes in white dwarfs evolved from solar-metallicity progenitors. Conclusions: We suggest that efforts should be made to observe the dipole g1-mode in white dwarfs associated with low-metallicity environments, such as globular clusters and/or the galactic halo, to place constraints on hydrogen shell burning in cool white dwarfs and the third dredge-up episode during the preceding asymptotic giant-branch phase.

  9. Bifurcation in tidal streams of Sagittarius Dwarf Galaxy: Numerical Simulations

    Science.gov (United States)

    Camargo Camargo, Y.; Casas-Miranda, R.

    2018-01-01

    We performed N-body simulations between Sagittarius dwarf galaxy and the Milky Way. The Sagittarius galaxy is modeled with two components: dark matter halo and stellar disc. The Milky Way is modeled with three components: dark matter halo, stellar disc and bulge. The goal of this work is to reproduce the bifurcations in the tidal tails and the physical properties of the Sagittarius dwarf galaxy. For it, we simulated the interaction of the progenitor of this galaxy with the Milky Way. Although bifurcations could be reproduced, the position and physical properties of Sagittarius remnant could not be obtained simultaneously.

  10. Mandibular brown tumor in renal osteodystrophy

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jin Woo; Choi, Bo Ram; Huh, Kyung Hoe; Yi, Won Jin; Choi, Soon Chul [Department of Oral and Maxillofacial Radiology, School of Dentistry, Seoul National University, Seoul (Korea, Republic of); Gang, In Tae [Department of Oral and Maxillofacial Surgery, Kangnam Sacred Heart Hospital, Hallym Medical Center, Seoul (Korea, Republic of)

    2008-12-15

    Brown tumor is a histologically benign lesion that is a serious complication of renal osteodystrophy because it may result in severe deformity and discomfort. We report a case of brown tumor, which occurred in a 35-year-old woman with chronic renal failure, who had been treated with hemodialysis for 14 years. The lesion was found on the lingual side of the mandible. Standard panoramic radiograph showed generally decreased bone mineral density, loss of lamina dura, and thin cortical plates. Computed tomography (CT) revealed multilocular expansible lesions with heterogeneous attenuation in the anterior mandible, as well as generalized trabecular alteration with homogeneous sclerosis, and thinning or obliteration of cortical plates. Excision of the mandibular lesion and curettage of the affected bone were performed.

  11. Identifying and misidentifying the brown recluse spider.

    Science.gov (United States)

    Vetter, R

    1999-11-01

    The brown recluse spider, Loxosceles reclusa, is often implicated as a cause of necrotic skin lesions.[1-3] Diagnoses are most commonly made by clinical appearance and infrequently is a spider seen, captured or identified at the time of the bite.[1, 2, 4-6] The brown recluse lives in a circumscribed area of the U.S. (the south central Midwest) with a few less common recluse species living in the more sparsely-populated southwest U.S.[7] In these areas, where spider populations may be dense, recluse spiders may be a cause of significant morbidity. However, outside the natural range of these recluse species, the conviction that they are the etiological agents behind necrotic lesions of unknown origin is widespread, and most often erroneous. In some states such as California, unsubstantiated reports concerning recluse spider bites have taken on the status of "urban legend" leading to overdiagnosis and, therefore, inappropriate treatment.

  12. Histological findings after brown recluse spider envenomation.

    Science.gov (United States)

    Elston, D M; Eggers, J S; Schmidt, W E; Storrow, A B; Doe, R H; McGlasson, D; Fischer, J R

    2000-06-01

    Histologic specimens from 41 rabbits were studied for changes resulting from the manual injection of brown recluse spider venom. Major findings included a mixed inflammatory cell infiltrate, coagulative tissue necrosis, and vasculitis. All specimens demonstrated a well-delineated zone of eosinophilic staining recognizable as "mummified" coagulative necrosis of the epidermis and dermis. A dense band of neutrophils bordered the zone of necrosis. Immediately adjacent to the neutrophilic band, small vessel vasculitis was a universal finding. Degranulated eosinophils and neutrophils and macrophages filled with eosinophilic granules were common. Inflammatory foci were often centered on groups of lipocytes within the dermis. Large vessel vasculitis resembling that seen in polyarteritis nodosa was present deep to 7 of the 40 eschars. Large vessel vasculitis may contribute to the large zones of necrosis seen after some brown recluse spider bites. Eosinophils may play a role in tissue damage after envenomation.

  13. Thermodynamic study of brown-coal gasification

    Energy Technology Data Exchange (ETDEWEB)

    Vonka, P.; Holub, R.; Schoengut, S.; Schoengut, J.

    1988-04-01

    Describes a method for calculating and assessing results of partial adiabatic oxidation of brown coal from the North Bohemian brown-coal field, which may in future act as a source of raw material for production of energy and synthesis gas. Calculations assume idealized fluid and burner generators and reaction parameters were selected to cover a range of operational values (these parameters include pressure, temperature, gasification ratio, water content, ash content and degree of coal conversion). After describing mathematics involved, concludes that thermodynamic analysis shows burner generator to have some advantages over fluid generator for production of synthesis gas, and vice versa for production of energy gas. However, final conclusions must await experimental evidence with regard to degree of conversion and composition of gas mixture; also, validity of this assessment is limited by the fact that no account was taken of the possibility of using reaction heat for production of steam or of any energy consumption involved. 10 refs.

  14. Ecological pellets from brown coal and biomass

    Directory of Open Access Journals (Sweden)

    Pavel Sedláček

    2007-04-01

    Full Text Available One way of renewable energy sources applications in the Czech republic is a cultivation of biomass plants. After the biomass reformation, it is possible to add it to palletizing mixes with coal and delulfurisative additives. Possibilities of brown coal of palletizing with biomass adds were tested recently. The product represents a new coal-biomass combustible wich can be used in some types of boilers with a low pollutant production level (specially SO2.In the past brown-coal pellets weremade with an addition of melted wood mass (wood fibres, wood wastes and mustard straw. Practical tests have shown of an extension the waste field of coal-pellets utilization.

  15. Deterministic remote preparation via the Brown state

    Science.gov (United States)

    Ma, Song-Ya; Gao, Cong; Zhang, Pei; Qu, Zhi-Guo

    2017-04-01

    We propose two deterministic remote state preparation (DRSP) schemes by using the Brown state as the entangled channel. Firstly, the remote preparation of an arbitrary two-qubit state is considered. It is worth mentioning that the construction of measurement bases plays a key role in our scheme. Then, the remote preparation of an arbitrary three-qubit state is investigated. The proposed schemes can be extended to controlled remote state preparation (CRSP) with unit success probabilities. At variance with the existing CRSP schemes via the Brown state, the derived schemes have no restriction on the coefficients, while the success probabilities can reach 100%. It means the success probabilities are greatly improved. Moreover, we pay attention to the DRSP in noisy environments under two important decoherence models, the amplitude-damping noise and phase-damping noise.

  16. [Cancer cachexia and white adipose tissue browning].

    Science.gov (United States)

    Zhang, S T; Yang, H M

    2016-08-01

    Cancer cachexia occurs in a majority of advanced cancer patients. These patients with impaired physical function are unable to tolerance cancer treatment well and have a significantly reduced survival rate. Currently, there is no effective clinical treatment available for cancer cachexia, therefore, it is necessary to clarify the molecular mechanisms of cancer cachexia, moreover, new therapeutic targets for cancer cachexia treatment are urgently needed. Very recent studies suggest that, during cancer cachexia, white adipose tissue undergo a 'browning' process, resulting in increased lipid mobilization and energy expenditure, which may be necessary for the occurrence of cancer cachexia. In this article, we summarize the definition and characteristics of cancer cachexia and adipose tissue 'browning', then, we discuss the new study directions presented in latest research.

  17. Browning boreal forests of western North America

    Science.gov (United States)

    David. Verbyla

    2011-01-01

    The GIMMS NDVI dataset has been widely used to document a “browning trend” in North American boreal forests (Goetz et al. 2005, Bunn et al. 2007, Beck and Goetz 2011). However, there has been speculation (Alcaraz-Segura et al. 2010) that this trend may be an artifact due to processing algorithms rather than an actual decline in vegetation activity. This conclusion was...

  18. Finding Brown's peony a sweet attraction

    Science.gov (United States)

    Nan. Vance

    2012-01-01

    I first encountered Brown’s peony (Paeonia brownie) with its verdant, lavender-tinged leaves and elegantly nodding maroon flowers growing among bitterbrush and bunchgrass on the eastern flank of the Oregon Cascades. My first thought was “What is a plant like you doing in a place like this?” It would be natural to visualize this native wild peony as...

  19. Drivers of hibernation in the brown bear

    OpenAIRE

    Evans, Alina; Singh, N.J.; Friebe, A.; Arnemo, Jon M.; Laske, T.G.; Fröbert, O.; Swenson, Jon E.; Blanc, S.

    2016-01-01

    Background Hibernation has been a key area of research for several decades, essentially in small mammals in the laboratory, yet we know very little about what triggers or ends it in the wild. Do climatic factors, an internal biological clock, or physiological processes dominate? Using state-of-the-art tracking and monitoring technology on fourteen free-ranging brown bears over three winters, we recorded movement, heart rate (HR), heart rate variability (HRV), body temperature (Tb), physical a...

  20. A Pulsar and White Dwarf in an Unexpected Orbit

    Science.gov (United States)

    Kohler, Susanna

    2016-11-01

    Astronomers have discovered a binary system consisting of a low-mass white dwarf and a millisecond pulsar but its eccentric orbit defies all expectations of how such binaries form.Observed orbital periods and binary eccentricities for binary millisecond pulsars. PSR J2234+0511 is the furthest right of the green stars that mark the five known eccentric systems. [Antoniadis et al. 2016]Unusual EccentricityIt would take a low-mass (0.4 solar masses) white dwarf over 100 billion years to form from the evolution of a single star. Since this is longer than the age of the universe, we believe that these lightweights are instead products of binary-star evolution and indeed, we observe many of these stars to still be in binary systems.But the binary evolution that can create a low-mass white dwarf includes a period of mass transfer, in which efficient tidal dissipation damps the systems orbital eccentricity. Because of this, we would expect all systems containing low-mass white dwarfs to have circular orbits.In the past, our observations of low-mass white dwarfmillisecond pulsar binaries have all been consistent with this expectation. But a new detection has thrown a wrench in the works: the unambiguous identification of a low-mass white dwarf thats in an eccentric (e=0.13) orbit with the millisecond pulsar PSR J2234+0511. How could this system have formed?Eliminating Formation ModelsLed by John Antoniadis (Dunlap Institute at University of Toronto), a team of scientists has used newly obtained optical photometry (from the Sloan Digital Sky Survey) and spectroscopy (from the Very Large Telescope in Chile) of the white dwarf to confirm the identification of this system.Antoniadis and collaborators then use measurements of the bodies masses (0.28 and 1.4 solar masses for the white dwarf and pulsar, respectively) and velocities, and constraints on the white dwarfs temperature, radius and surface gravity, to address three proposed models for the formation of this system.The 3D