Adam Burgasser
University of California, San Diego, Physics, Faculty Member
Abstract We present FIRE spectroscopic observations of the ultracool (T 520 K) brown dwarf, UGPS 0722-05, obtained during instrument commissioning on the 6.5 m Baade Magellan Telescope at Las Campanas Observatory. At a distance of 4.1 pc,... more
Abstract We present FIRE spectroscopic observations of the ultracool (T 520 K) brown dwarf, UGPS 0722-05, obtained during instrument commissioning on the 6.5 m Baade Magellan Telescope at Las Campanas Observatory. At a distance of 4.1 pc, this cool brown dwarf is well-suited for detailed followup, and represents a keystone at the transition between the lowest-mass brown dwarfs and exoplanets.
Abstract The 2MASS survey allows large numbers of the new class of L dwarfs to be identified. Spectroscopic studies show that most of these objects are brown dwarfs. We propose to use K-band infrared spectroscopy to determine spectral... more
Abstract The 2MASS survey allows large numbers of the new class of L dwarfs to be identified. Spectroscopic studies show that most of these objects are brown dwarfs. We propose to use K-band infrared spectroscopy to determine spectral types for over 100 L dwarfs. This will place the field L dwarf substellar luminosity function on a firm statistical basis, and allow modelling of the substellar mass function.
Abstract 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... more
Abstract 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.
Abstract All of the young star-forming regions are distant (d> 120 pc), making it difficult to resolve structure on the scale of disks (10-100 AU) and jets (? AU). Furthermore, examining these structures around low-mass objects is... more
Abstract All of the young star-forming regions are distant (d> 120 pc), making it difficult to resolve structure on the scale of disks (10-100 AU) and jets (? AU). Furthermore, examining these structures around low-mass objects is especially prohibitive since these objects are intrinsically faint. However, recent identification of the nearby, young (10; Myr) TW Hydrae Association (TWA) has ameliorated this situation. With only 24 systems, the TWA offers unique case studies at a critical time in disk evolution and planet-building processes.
Abstract While Spitzer has already contributed significantly to the study of winds and weather on highly irradiated extrasolar planets, the atmospheres of free-floating brown dwarfs probe weather in an entirely different physical regime,... more
Abstract While Spitzer has already contributed significantly to the study of winds and weather on highly irradiated extrasolar planets, the atmospheres of free-floating brown dwarfs probe weather in an entirely different physical regime, where global atmospheric flows arise primarily from a combination of rapid rotation and internal convection, without external forcing.
Abstract: The Folded-port InfraRed Echellette (FIRE) has recently been commissioned on the Magellan 6.5 m Baade Telescope. This single object, near-infrared spectrometer simultaneously covers the 0.85-2.45 micron window in both... more
Abstract: The Folded-port InfraRed Echellette (FIRE) has recently been commissioned on the Magellan 6.5 m Baade Telescope. This single object, near-infrared spectrometer simultaneously covers the 0.85-2.45 micron window in both cross-dispersed (R~ 6000) or prism-dispersed (R~ 250-350) modes. FIRE's compact configuration, high transmission optics and high quantum efficiency detector provides considerable sensitivity in the near-infrared, making it an ideal instrument for studies of cool stars and brown dwarfs.
Abstract We have used multi-epoch Spitzer/IRAC images to search for substellar companions to several hundred nearby stars based on their common proper motions. Through this work, we have identified a very promising candidate that could be... more
Abstract We have used multi-epoch Spitzer/IRAC images to search for substellar companions to several hundred nearby stars based on their common proper motions. Through this work, we have identified a very promising candidate that could be the coldest and faintest known brown dwarf by a fairly large margin, and thus may inhabit a new spectral class (tentatively dubbed the Y class).
Abstract Over the last 3 to 4 years there has been increasing evidence, both theoretical and observational, that the fraction of wide, low-mass companions to spectroscopic binary systems is considerably higher than for single objects. Not... more
Abstract Over the last 3 to 4 years there has been increasing evidence, both theoretical and observational, that the fraction of wide, low-mass companions to spectroscopic binary systems is considerably higher than for single objects. Not only does the fraction of stellar companions increase but also that of substellar companions. We propose a survey to find benchmark brown dwarfs by taking advantage of the high fraction of wide, low-mass companions to tight spectroscopic binaries.
Abstract We propose to use HST/NICMOS to image a sample of 27 of the nearest {< 20 pc} and lowest luminosity T-type brown dwarfs in order to identify and characterize new very low mass binary systems. Only 3 late-type T dwarf binaries... more
Abstract We propose to use HST/NICMOS to image a sample of 27 of the nearest {< 20 pc} and lowest luminosity T-type brown dwarfs in order to identify and characterize new very low mass binary systems. Only 3 late-type T dwarf binaries have been found to date, despite that fact that these systems are critical benchmarks for evolutionary and atmospheric models at the lowest masses. They are also the most likely systems to harbor Y dwarf companions, an as yet unpopulated putative class of very cold {T< 600 K} brown dwarfs.
Abstract We present the discovery of a candidate brown dwarf member to the TW Hydrae Association, an 8 Myr old co-moving group. This object is only the fourth candidate brown dwarf in the association, joining TWA 5B, 2MASS 1207-3932AB,... more
Abstract We present the discovery of a candidate brown dwarf member to the TW Hydrae Association, an 8 Myr old co-moving group. This object is only the fourth candidate brown dwarf in the association, joining TWA 5B, 2MASS 1207-3932AB, and 2MASS 1139-3159. Its near-infrared spectrum is remarkably similar to that of 2MASS 1139-3159, with low-gravity features showing an overall red color compared to field late-type M dwarfs, a triangular-shaped H-band, and a very weak FeH-band at 0.99 microns.
Abstract The Transiting Exoplanet Survey Satellite (TESS) is a low cost, SMEX-class planet finder. In a two year all-sky survey, TESS will observe more than two million bright, nearby stars, searching for temporary drops in brightness... more
Abstract The Transiting Exoplanet Survey Satellite (TESS) is a low cost, SMEX-class planet finder. In a two year all-sky survey, TESS will observe more than two million bright, nearby stars, searching for temporary drops in brightness that are caused by planetary transits, which occur when a planet's orbit carries it directly in front of its parent star. Such transits not only provide the means of identifying the planet, but also provide knowledge of the planet's diameter, mass density, surface gravity, temperature, and other key properties.
1. Science. 2001 Feb 23;291(5508):1487-8. What is a planet? McCaughrean M, Reid N, Tinney C, Kirkpatrick D, Hillenbrand L, Burgasser A, Gizis J, Hawley S. PMID: 11234073 [PubMed]. Publication Types: Letter.
Abstract Using multi-epoch 2MASS data, we have conducted a very large area (~ 6000 square degrees) near-infrared proper motion survey. The goal of this survey is to search for nearby, optically faint/invisible sources that would have been... more
Abstract Using multi-epoch 2MASS data, we have conducted a very large area (~ 6000 square degrees) near-infrared proper motion survey. The goal of this survey is to search for nearby, optically faint/invisible sources that would have been missed by previous optical motion surveys. Earlier near-infrared searches for nearby stars have relied solely on photometric criteria that are heavily biased toward solar-age, solar-metallicity stars and brown dwarfs.
Abstract Brown dwarf spectra are rich in diagnostics of temperature, gravity and metallicity. However, in the coldest sources, these parameters can be entangled with competing effects for a few major absorbers. We have identified three... more
Abstract Brown dwarf spectra are rich in diagnostics of temperature, gravity and metallicity. However, in the coldest sources, these parameters can be entangled with competing effects for a few major absorbers. We have identified three late-type T dwarfs that exhibit spectroscopic and kinematic indications of being either old, metal poor or both.
Abstract Recent discoveries of low-luminosity objects have now firmly established that the dwarf mass function extends below the minimum-mass hydrogen-burning limit for both field stars and binary companions. However, the exact nature of... more
Abstract Recent discoveries of low-luminosity objects have now firmly established that the dwarf mass function extends below the minimum-mass hydrogen-burning limit for both field stars and binary companions. However, the exact nature of the mass distribution is difficult to ascertain below this boundary. It is problematic to infer precise brown-dwarf masses from imaging data, since the mass-luminosity relation is heavily dependent on age.
Abstract We report the identification of the M9 dwarf SDSS J000649. 16-085246.3 as part of a tightly-separated brown dwarf binary within a low-mass triple system with the M7 star LP 704-48 as a widely-separated (600 AU) third component.... more
Abstract We report the identification of the M9 dwarf SDSS J000649. 16-085246.3 as part of a tightly-separated brown dwarf binary within a low-mass triple system with the M7 star LP 704-48 as a widely-separated (600 AU) third component. Low-resolution spectral data from IRTF/SpeX show subtle spectral features typical of a T dwarf companion, and spectral template fitting indicates component types of M8. 5 and T5±1 for the tight binary.
Abstract Ross 458C is a widely-separated (1100 AU), faint companion to the nearby M0. 5 Ve+ M7 Ross 458AB binary, identified in the UKIDSS survey by Goldman et al. and Scholz and suspected by both of being a young brown dwarf. We obtained... more
Abstract Ross 458C is a widely-separated (1100 AU), faint companion to the nearby M0. 5 Ve+ M7 Ross 458AB binary, identified in the UKIDSS survey by Goldman et al. and Scholz and suspected by both of being a young brown dwarf. We obtained near-infrared spectroscopy of this source with the newly-commissioned Folded-Port Infrared Echellette (FIRE) at the Magellan Telescopes, which revealed the presence of strong methane and water absorption consistent with a T8 dwarf.
Abstract We are conducting an imaging survey of the coolest known brown dwarfs using the new Keck laser guide star adaptive optics (LGS AO) system.
Abstract The Transiting Exoplanet Survey Satellite (TESS) will perform an all-sky survey in a low-inclination, low-Earth orbit. TESS's 144 GB of raw data collected each orbit will be stacked, cleaned, cut, compressed and downloaded. The... more
Abstract The Transiting Exoplanet Survey Satellite (TESS) will perform an all-sky survey in a low-inclination, low-Earth orbit. TESS's 144 GB of raw data collected each orbit will be stacked, cleaned, cut, compressed and downloaded. The Community Observer Program is a Science Enhancement Option (SEO) that takes advantage of the low-radiation environment, technology advances in flash memory, and the vast amount of astronomical data collected by TESS.
Abstract The LSST will produce a multi-color photometric catalog of half the sky to r= 27.6 (AB mag; 5-sigma). Multi-epoch observations over the survey's ten year baseline will allow variability, proper motion and parallax measurements... more
Abstract The LSST will produce a multi-color photometric catalog of half the sky to r= 27.6 (AB mag; 5-sigma). Multi-epoch observations over the survey's ten year baseline will allow variability, proper motion and parallax measurements for objects as faint as r= 24.7. These capabilities allow LSST to identify and characterize resolved stellar populations in unprecedented breadth and detail, enabling a more comprehensive and nuanced understanding of the star formation history of the Milky Way and nearby galaxies.
Abstract We report the discovery of 10 wide stellar companions to known late-type M, L, and T dwarfs deduced from common proper motion. Four of these objects have been independently reported in the literature. Applying age diagnostic... more
Abstract We report the discovery of 10 wide stellar companions to known late-type M, L, and T dwarfs deduced from common proper motion. Four of these objects have been independently reported in the literature. Applying age diagnostic tools to the primary stars, we assume co-evality and infer masses for the ultracool dwarf (UCD) secondaries. We classify four objects as stellar, two as substellar, and four could not be distinguished.
Abstract WISE is an Earth-orbiting NASA mission that surveyed the entire sky simultaneously at wavelengths of 3.4, 4.6, 12, and 22um, hereafter referred to as bands W1, W2, W3, and W4, respectively. WISE launched on 2009 December 14 and,... more
Abstract WISE is an Earth-orbiting NASA mission that surveyed the entire sky simultaneously at wavelengths of 3.4, 4.6, 12, and 22um, hereafter referred to as bands W1, W2, W3, and W4, respectively. WISE launched on 2009 December 14 and, after an in-orbit checkout, began surveying the sky on 2010 January 14.
Abstract We present a detailed examination of the components of the 2MASS J08503593+ 1057156 and 2MASS J17281150+ 3948593 multiple systems based on resolved near-infrared photometry from the Hubble Space Telescope (HST) and unresolved... more
Abstract We present a detailed examination of the components of the 2MASS J08503593+ 1057156 and 2MASS J17281150+ 3948593 multiple systems based on resolved near-infrared photometry from the Hubble Space Telescope (HST) and unresolved near-infrared spectroscopy from IRTF/SpeX. To determine component spectral types, spectra from other stellar and substellar objects of known spectral types were used as templates and combined in pairs to match the spectra of the binaries.
Abstract The Transiting Exoplanet Survey Satellite (TESS) is designed for an all-sky photometric survey of bright stars, extending over the entire celestial sphere.  TESS will catalog planetary transits of nearby stars that can be... more
Abstract The Transiting Exoplanet Survey Satellite (TESS) is designed for an all-sky photometric survey of bright stars, extending over the entire celestial sphere.  TESS will catalog planetary transits of nearby stars that can be followed-up with ground observatories.
Abstract Over the past several years, our team has spectroscopically classified hundreds of late-type dwarfs selected photometrically from 2MASS. Through this effort we have uncovered 35 low-gravity late-M and L dwarfs within the... more
Abstract Over the past several years, our team has spectroscopically classified hundreds of late-type dwarfs selected photometrically from 2MASS. Through this effort we have uncovered 35 low-gravity late-M and L dwarfs within the immediate Solar Vicinity (< 60 pc). Low gravity indicates that these objects are very young, have lower mass, and have more extended atmospheres than typical field M and L dwarfs of the same temperature.
Abstract The distances and kinematics of brown dwarfs provide key statistical constraints on their ages, moving group membership, absolute brightnesses, evolutionary trends, and multiplicity. Yet fundamental measurements of parallax,... more
Abstract The distances and kinematics of brown dwarfs provide key statistical constraints on their ages, moving group membership, absolute brightnesses, evolutionary trends, and multiplicity. Yet fundamental measurements of parallax, proper motion and radial velocity have been made for only a relatively small fraction of the known brown dwarf population.
Abstract Clouds play a fundamental role in the emergent spectral energy distributions and observed variability of very low mass stars and brown dwarfs, yet hey have only been studied indirectly thus far. Recent indications of a broad... more
Abstract Clouds play a fundamental role in the emergent spectral energy distributions and observed variability of very low mass stars and brown dwarfs, yet hey have only been studied indirectly thus far. Recent indications of a broad silicate grain absorption feature in the 8-11 micron spectra of mid-type L dwarfs, and evidence that the strength of this absorption varies according to broad-band near-infrared color, may finally allow the first direct studies of clouds and condensate grain properties in brown dwarf atmospheres.
Abstract During the Phase A for TESS, simulations of planetary transits were performed to confirm the instrument's ability to detect transits. The simulations cover the full TESS discovery space in the planet period-transit duration... more
Abstract During the Phase A for TESS, simulations of planetary transits were performed to confirm the instrument's ability to detect transits. The simulations cover the full TESS discovery space in the planet period-transit duration plane. Examples included a 36-day period planet, two previously known systems (HAT-P-11 and CoRoT 7B), and one Earth and one SuperEarth. In addition, a broad matrix of planetary periods and transit depths were also simulated.
Abstract The distances and kinematics of brown dwarfs provide key statistical constraints on their ages, moving group membership, absolute brightnesses, evolutionary trends, and multiplicity. Yet fundamental measurements of parallax,... more
Abstract The distances and kinematics of brown dwarfs provide key statistical constraints on their ages, moving group membership, absolute brightnesses, evolutionary trends, and multiplicity. Yet fundamental measurements of parallax, proper motion and radial velocity have been made for only a relatively small fraction of the known brown dwarf population.
Abstract Theoretical models predict that sub-stellar objects are much more luminous and hotter when very young. Consequently, deep imaging surveys of young clusters can yield very low mass sub-stellar objects that will be too faint to... more
Abstract Theoretical models predict that sub-stellar objects are much more luminous and hotter when very young. Consequently, deep imaging surveys of young clusters can yield very low mass sub-stellar objects that will be too faint to study once they have aged, unless they are located extremely close to the Sun. Candidate member samples of these clusters can suffer contamination from foreground and background much older field brown dwarfs.
Action-angle variables provide an instructive alternative viewpoint for studying the dynamical properties of objects in our Galaxy.
Abstract Wide-field near-infrared surveys such as 2MASS, DENIS, and SDSS have uncovered a vast population of ultracool stars and brown dwarfs in the Solar Neighborhood, the majority of which are Solar metallicity members of the disk... more
Abstract Wide-field near-infrared surveys such as 2MASS, DENIS, and SDSS have uncovered a vast population of ultracool stars and brown dwarfs in the Solar Neighborhood, the majority of which are Solar metallicity members of the disk population. In the past year, a number of ultracool dwarfs with spectral features indicating subsolar metallicity, as well as halo kinematics, have been identified.
Abstract Indirect and direct spectroscopic studies of exoplanets are beginning to probe the most prominent chemical constituents and processes in their atmospheres. However, studies of equivalently low-temperature brown dwarfs have been... more
Abstract Indirect and direct spectroscopic studies of exoplanets are beginning to probe the most prominent chemical constituents and processes in their atmospheres. However, studies of equivalently low-temperature brown dwarfs have been taking place for over a decade.
Abstract We present preliminary results from ACCOLADES, a study of high proper motion, low-mass dwarfs, identified from two-epoch photometric observations in SDSS. The chip gap geometry in the SDSS photometric camera required that a small... more
Abstract We present preliminary results from ACCOLADES, a study of high proper motion, low-mass dwarfs, identified from two-epoch photometric observations in SDSS. The chip gap geometry in the SDSS photometric camera required that a small amount of each CCD column be imaged twice to ensure full spatial coverage in a given SDSS stripe. Occasionally, these overlapping regions were imaged months or years apart.
Abstract The lowest mass objects directly observable outside of the Solar system are T dwarfs-with atmospheres so cool that methane and water vapor are their major constituents. Since they have no internal energy source, they are, by far,... more
Abstract The lowest mass objects directly observable outside of the Solar system are T dwarfs-with atmospheres so cool that methane and water vapor are their major constituents. Since they have no internal energy source, they are, by far, at their brightest upon formation, when they are young, and subsequently cool over their long lifetimes. T dwarfs in the Solar neighborhood are rather old, and have cooled considerably, such that their typical masses are in the range 10-60 Jupiter masses (M_Jup).