Results for "J. Davy Kirkpatrick"

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A Candidate Wide Brown Dwarf Binary in the Argus Association: 2MASS J14504216-7841413 and 2MASS J14504113-7841383Dec 04 2017[not part of Research Note] We report the discovery of a widely-separated low-mass binary as a candidate member of the $\sim$40 Myr Argus Association. Resolved imaging and astrometry with 2MASS and LDSS-3 reveal a common proper motion pair of red sources ... More
Opportunities in Time-Domain Extragalactic Astrophysics with the NASA Near-Earth Object Camera (NEOCam)Apr 12 2019This White Pape motivates the time domain extragalactic science case for the NASA Near-Earth Object Camera (NEOCam). NEOCam is a NASA Planetary mission whose goal is to discover and characterize asteroids and comets, to assess the hazard to Earth from ... More
Effective Temperatures of late L dwarfs and the onset of Methane signaturesOct 13 2001We present a spectral analysis of a sample of late L dwarfs. We use our latest model atmospheres and synthetic spectra and optical and K band spectra to determine effective temperatures. We derive effective temperatures of 1400 K to 1700 K for L8 to L6 ... More
Physical Properties of Young Brown Dwarfs and Very Low-Mass Stars Inferred from High-Resolution Model SpectraNov 19 2009By comparing near-infrared spectra with atmosphere models, we infer the effective temperature, surface gravity, projected rotational velocity, and radial velocity for 21 very-low-mass stars and brown dwarfs. The unique sample consists of two sequences ... More
Low-Mass Tertiary Companions to Spectroscopic Binaries I: Common Proper Motion Survey for Wide Companions using 2MASSJun 19 2012We report the first results of a multi-epoch search for wide (separations greater than a few tens of AU), low-mass tertiary companions of a volume-limited sample of 118 known spectroscopic binaries within 30 pc of the Sun, using the 2MASS Point Source ... More
Brown Dwarfs and Directly Imaged Exoplanets in Young AssociationsMar 15 2019In order to understand the atmospheres as well as the formation mechanism of giant planets formed outside our solar system, the next decade will require an investment in studies of isolated young brown dwarfs. In this white paper we summarize the opportunity ... More
Discovery of Cold Brown Dwarfs or Free-Floating Giant Planets Close to the SunMar 12 2019This White Paper describes the opportunities for discovery of Jupiter-mass objects with 300K atmospheres. The discovery and characterization of such cold objects is vital for understanding the low-mass terminus of the initial mass function and for optimizing ... More
Discovery of a Possible Cool White Dwarf Companion from the AllWISE Motion SurveySep 23 2016We present optical and near-infrared spectroscopy of WISEA J061543.91$-$124726.8, which we rediscovered as a high motion object in the AllWISE survey. The spectra of this object are unusual; while the red optical ($\lambda >$ 7,000 \AA) and near-infrared ... More
2MASS Data Mining and the M, L, and T Dwarf ArchivesJul 31 2002Studies of brown dwarfs as a distinct galactic population have been largely pioneered by dedicated, vast-area surveys at deep optical and near-infrared wavebands. The Two Micron All Sky Survey has, because of its full-sky coverage and depth, been the ... More
The Next Generation Sky Survey and the Quest for Cooler Brown DwarfsJul 31 2002The 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 ... More
Outstanding Issues in Our Understanding of L, T, and Y DwarfsApr 12 2007Since the discovery of the first L dwarf 19 years ago and the discovery of the first T dwarf 7 years after that, we have amassed a large list of these objects, now numbering almost six hundred. Despite making headway in understanding the physical chemistry ... More
Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the FieldSep 23 2006We present a 20-pc, volume-limited sample of M7-L8 dwarfs created through spectroscopic follow-up of sources selected from the Two Micron All Sky Survey (2MASS) Second Incremental Release Point Source Catalog. In this paper, we present optical spectroscopy ... More
Radii of 88 M Subdwarfs and Updated Radius Relations for Low-Metallicity M Dwarf StarsOct 17 2018M subdwarfs are low-metallicity M dwarfs that typically inhabit the halo population of the Galaxy. Metallicity controls the opacity of stellar atmospheres; in metal poor stars, hydrostatic equilibrium is reached at a smaller radius, leading to smaller ... More
Unveiling the Dynamic Infrared Sky with Gattini-IRAug 16 2016While optical and radio transient surveys have enjoyed a renaissance over the past decade, the dynamic infrared sky remains virtually unexplored. The infrared is a powerful tool for probing transient events in dusty regions that have high optical extinction, ... More
Discovery of the Coolest Extreme SubdwarfMar 15 2006We report the discovery of LEHPM 2-59 as the coolest extreme M subdwarf (esdM) found to date. Optical and near infrared spectroscopy demonstrate that this source is of later spectral type than the esdM7 APMPM 0559-2903, with the presence of strong alkali ... More
Optical Spectroscopy of T DwarfsJan 15 2001Optical spectra are presented for a sample of T dwarfs, obtained using the Keck 10m Low Resolution Imaging Spectrograph. Dominant features are discussed, including possible temperature diagnostics.
Keck Spectra of Pleiades Brown Dwarf Candidates and a Precise Determination of the Lithium Depletion Edge in the PleiadesApr 01 1998We have obtained intermediate resolution spectra of eleven candidate brown dwarf members of the Pleiades open cluster using the Keck II telescope and LRIS spectrograph. Our primary goal was to determine the location of the "lithium depletion edge" in ... More
Multiplicity Amongst Wide Brown Dwarf Companions to Nearby Stars: Gliese 337CDMar 17 2005We present Lick Natural Guide Star Adaptive Optics observations of the L8 brown dwarf Gliese 337C, which is resolved for the first time into two closely separated (0"53+/-0"03), nearly equal magnitude components with a K_s flux ratio of 0.93+/-0.10. Companionship ... More
Ultracool Subdwarfs: Metal-poor Stars and Brown Dwarfs Extending into the Late-type M, L and T Dwarf RegimesSep 08 2004Sep 10 2004Recent discoveries from red optical proper motion and wide-field near-infrared surveys have uncovered a new population of ultracool subdwarfs -- metal-poor stars and brown dwarfs extending into the late-type M, L and possibly T spectral classes. These ... More
The 2MASS Wide-Field T Dwarf Search. II. Discovery of Three T Dwarfs in the Southern HemisphereJul 22 2003We present the discovery of three new Southern Hemisphere T dwarfs identified in the Two Micron All Sky Survey. These objects, 2MASS 0348-6022, 2MASS 0516-0445, and 2MASS 2228-4310, have classifications T7, T5.5, and T6.5, respectively. Using linear absolute ... More
Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5Dec 01 2008We present an analysis of 23 L dwarfs whose optical spectra display unusual features. Twenty-one were uncovered during our search for nearby, late-type objects using the Two Micron All-Sky Survey while two were identified in the literature. The unusual ... More
A Method for Determining the Physical Properties of the Coldest Known Brown DwarfsOct 25 2005We present a method for measuring the physical parameters of the coldest T-type brown dwarfs using low resolution near infrared spectra. By comparing H_2O- and H_2-sensitive spectral ratios between empirical data and theoretical atmosphere models, and ... More
Optical Spectroscopy of 2MASS Color-Selected Ultracool SubdwarfsOct 03 2006We present Gemini GMOS and Magellan LDSS-3 optical spectroscopy for seven ultracool subdwarf candidates color-selected from the Two Micron All Sky Survey. Five are identified as late-type subdwarfs, including the previously reported sdM9.5 SSSPM 1013-1356 ... More
Discovery of 11 New T Dwarfs in the Two Micron All-Sky Survey, Including a Possible L/T Transition BinaryJun 12 2007Aug 04 2007We present the discovery of 11 new T dwarfs, found during the course of a photometric survey for mid-to-late T dwarfs in the 2MASS Point Source Catalog and from a proper motion selected sample of ultracool dwarfs in the 2MASS Working Database. Using the ... More
A Distant Stellar Companion in the Upsilon Andromedae SystemMay 16 2002Upsilon Andromedae is an F8V star known to have an extrasolar system of at least 3 planets in orbit around it. Here we report the discovery of a low-mass stellar companion to this system. The companion shares common proper motion, lies at a projected ... More
The Classification of T DwarfsJan 15 2001We discuss methods for classifying T dwarfs based on spectral morphological features and indices. T dwarfs are brown dwarfs which exhibit methane absorption bands at 1.6 and 2.2 ${\mu}m$. Spectra at red optical (6300--10100 {\AA}) and near-infrared (1--2.5 ... More
The Spectra of T Dwarfs. II. Red Optical DataMay 08 2003We present 6300--10100 {\AA} spectra for a sample of 13 T dwarfs observed using LRIS mounted on the Keck I 10m Telescope. A variety of features are identified and analyzed, including pressure-broadened K I and Na I doublets; narrow Cs I and Rb I lines; ... More
Infrared Parallaxes for Methane T dwarfsApr 18 2003We report final results from our 2.5 year infrared parallax program carried out with the European Southern Observatory 3.5m New Technology Telescope and the SOFI infrared camera. Our program targeted precision astrometric observations of ten T type brown ... More
A Cross-Match of 2MASS and SDSS: Newly-Found L and T Dwarfs and an Estimate of the Space Densitfy of T DwarfsOct 22 2007We report new L and T dwarfs found in a cross-match of the SDSS Data Release 1 and 2MASS. Our simultaneous search of the two databases effectively allows us to relax the criteria for object detection in either survey and to explore the combined databases ... More
A Young Planetary-Mass Object in the rho Oph Cloud CoreDec 18 2009We report the discovery of a young planetary-mass brown dwarf in the rho Oph cloud core. The object was identified as such with the aid of a 1.5-2.4 micron low-resolution spectrum obtained using the NIRC instrument on the Keck I telescope. Based on the ... More
A 2MASS L Dwarf Companion to the Nearby K Dwarf GJ 1048Dec 20 2000We report the discovery of a probable L1 companion to the nearby K2 dwarf GJ 1048 using the Two Micron All-Sky Survey (2MASS). This source, 2MASSI J0235599-233120 or GJ 1048B, has 2MASS near-infrared colors and absolute magnitudes consistent with an early ... More
Clouds, Gravity and Metallicity in Blue L dwarfs: The Case of 2MASS J11263991-5003550Oct 05 2007Optical and near-infrared spectroscopy of the newly discovered peculiar L dwarf 2MASS J11263991-5003550 are presented. Folkes et al. identified this source as a high proper motion L9+/-1 dwarf based on its strong H2O absorption at 1.4 micron. We find ... More
Near-Infrared Spectral Classification of late-M and L DwarfsDec 12 2000We present near-infrared (1 to 2.5 micron) low-resolution spectroscopy of eleven ultracool dwarfs with spectral types ranging from M7 to L8. Combining our observations with data published previously by Leggett et al. (2001), we have measured equivalent ... More
An Improved Red Spectrum of the Methane or T-dwarf SDSS 1624+0029: Role of the Alkali MetalsMar 06 2000Apr 01 2000A Keck~II low resolution spectrum shortward of ome-micron is presented for SDSS 1624+0029, the first field methane or T dwarf discovered in the Sloan Digital Sky Survey. Significant flux is detected down to the spectrum's short wavelength limit of 6200\AA. ... More
Discovery of a High Proper Motion L Dwarf Binary: 2MASS J15200224-4422419ABNov 22 2006We report the discovery of the wide L1.5+L4.5 binary 2MASS J15200224-4422419AB, identified during spectroscopic followup of high proper motion sources selected from the Two Micron All Sky Survey. This source was independently identified by Kendall et ... More
A Keck/HST Survey for Companions to Low-Luminosity DwarfsDec 17 1999We present preliminary results of an imaging survey for companions to low-luminosity dwarfs with spectral types ranging from M7 to L9. A K-band study with the Near Infrared Camera (NIRC) at the Keck telescope discriminates against background sources by ... More
Meeting the Cool New Neighbors V: A 2MASS-Selected Sample of Ultracool DwarfsJul 24 2003We present initial results of our effort to create a statistically robust, volume-limited sample of ultracool dwarfs from the 2MASS Second Incremental Data Release. We are engaged in a multifaceted search for nearby late-type dwarfs and this is the first ... More
SDSS J042348.57-041403.5AB: A Brown Dwarf Binary Straddling the L/T TransitionOct 19 2005We present the discovery of SDSS J042348.57-041403.5 as a closely-separated (0"16) brown dwarf binary, resolved by the Hubble Space Telescope Near Infrared Camera and Multi-Object Spectrometer. Physical association is deduced from the angular proximity ... More
Searching for Binary Y dwarfs with the Gemini Multi-Conjugate Adaptive Optics System (GeMS)Jan 21 2016Jan 26 2016The 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 ... More
Discovery of an M9.5 Candidate Brown Dwarf in the TW Hydrae Association - DENIS J124514.1-442907Sep 20 2007Oct 22 2007We report the discovery of a fifth candidate substellar system in the ~5-10 Myr TW Hydrae Association - DENIS J124514.1-442907. This object has a NIR spectrum remarkably similar to that of 2MASS J1139511-315921, a known TW Hydrae brown dwarf, with low ... More
A Unified Near Infrared Spectral Classification Scheme for T DwarfsOct 04 2005A revised near infrared classification scheme for T dwarfs is presented, based on and superseding prior schemes developed by Burgasser et al. and Geballe et al., and defined following the precepts of the MK Process. Drawing from two large spectroscopic ... More
Deep Near-Infrared Imaging of the rho Oph Cloud Core: Clues to the Origin of the Lowest-Mass Brown DwarfsJun 13 2010A search for young substellar objects in the rho Oph cloud core region has been made using the deep-integration Combined Calibration Scan images of the 2MASS extended mission in J, H and Ks bands, and Spitzer IRAC images at 3.6, 4.5, 5.8 and 8.0 microns. ... More
The 2MASS Wide-Field T Dwarf Search. V. Discovery of a T Dwarf via Methane ImagingAug 05 2005We present the discovery of a T dwarf, 2M2151-4853, via differential imaging through methane filters. The filters are designed to highlight the strong absorption in the H band, due to methane found in the atmospheres of T dwarfs, and provide a very efficient ... More
Resolved Spectroscopy of a Brown Dwarf Binary at the T Dwarf/Y Dwarf TransitionOct 20 2011We report resolved near-infrared imaging and spectroscopic observations of the T8.5 binary WISEP J045853.90+643452.6AB obtained with Keck/NIRC2, Keck/OSIRIS and the Keck Laser Guide Star Adaptive Optics system. These data confirm common proper and radial ... More
A Survey for H-alpha Emission from Late L dwarfs and T dwarfsApr 13 2016Recently, studies of brown dwarfs have demonstrated that they possess strong magnetic fields and have the potential to produce radio and optical auroral emissions powered by magnetospheric currents. This emission provides the only window on magnetic fields ... More
A Search for Variability in the Active T dwarf 2MASS 1237+6526Jan 23 2002We present spectroscopic and imaging observations of the active T dwarf 2MASS 1237+6526, intended to investigate the emission mechanism of this cool brown dwarf. The H$\alpha$ emission line first detected in 1999 July appears to be persistent over 1.6 ... More
Three newly-discovered M-dwarf companions of Solar Neighbourhood starsApr 05 2001Apr 08 2001We present low-resolution spectroscopy of newly-discovered candidate companions to three stars in the Solar Neighbourhood. All three companions are M dwarfs, with spectral types ranging from M4 to M9.5. In two cases, G85-55`B' (M6) and G87-9`B' (M4), ... More
A search for L dwarf binary systemsOct 10 2000We present analysis of HST Planetary Camera images of twenty L dwarfs identified in the course of the Two Micron All-Sky Survey. Four of the targets have faint, red companions at separations between 0.07 and 0.29 arcseconds (1.6 to 7.6 AU). In three cases, ... More
Keck Imaging of Binary L DwarfsSep 21 1999We present Keck near-infrared imaging of three binary L dwarf systems, all of which are likely to be sub-stellar. Two are lithium dwarfs, and a third exhibits an L7 spectral type, making it the coolest binary known to date. All have component flux ratios ... More
Near-Infrared Spectroscopy of Brown Dwarfs: Methane and the Transition between the L and T Spectral TypesSep 21 2001We report the possible identification of weak methane spectral features in the near-infrared K band in two late L dwarfs, DENIS 0205-11 (L7) and 2MASS 1523+30 (L8). New, high signal-to-noise ratio flux-calibrated spectra, spanning the wavelength interval ... More
The Collapse of the Wien Tail in the Coldest Brown Dwarf? Hubble Space Telescope Near-Infrared Photometry of WISE J085510.83-071442.5May 18 2016May 19 2016We present Hubble Space Telescope (HST) near-infrared photometry of the coldest known brown dwarf, WISE J085510.83$-$071442.5 (WISE 0855$-$0714). WISE 0855$-$0714 was observed with the Wide Field Camera 3 (WFC3) aboard HST using the F105W, F125W, and ... More
The Discovery of Two Nearby Carbon DwarfsJan 17 2003The comparison of optical and 2MASS near-infrared photometry for large samples of catalogued proper motion stars has the potential to discover previously unrecognized nearby objects of rare type. In this paper we present the discovery of two new carbon ... More
The 2MASS Wide-Field T Dwarf Search. IV Unting out T dwarfs with Methane ImagingAug 05 2005We present first results from a major program of methane filter photometry for low-mass stars and brown dwarfs. The definition of a new methane filter photometric system is described. A recipe is provided for the differential calibration of methane imaging ... More
Near-Infrared Variability in the 2MASS Calibration Fields: A Search for Planetary Transit CandidatesSep 08 2007The 2MASS photometric calibration observations cover ~6 square degrees on the sky in 35 "calibration fields" each sampled in nominal photometric conditions between 562 and 3692 times during the four years of the 2MASS mission. We compile a catalog of ... More
A Targeted Search for Peculiarly Red L and T Dwarfs in SDSS, 2MASS, and WISE: Discovery of a Possible L7 Member of the TW Hydrae AssociationOct 28 2015We present first results from a targeted search for brown dwarfs with unusual red colors indicative of peculiar atmospheric characteristics. These include objects with low surface gravities or with unusual dust content or cloud properties. From a positional ... More
WISEA J114724.10-204021.3: A Free-Floating Planetary Mass Member of the TW Hya AssociationMar 25 2016We present WISEA J114724.10$-$204021.3, a young, low-mass, high probability member of the TW Hya association. WISEA J114724.10$-$204021.3 was discovered based on its red AllWISE color (W1$-$W2 = 0.63 mag) and extremely red 2MASS $J-K_{\rm S}$ color ($>$ ... More
A Cross-Match of 2MASS and SDSS. II. Peculiar L Dwarfs, Unresolved Binaries, and the Space Density of T Dwarf SecondariesMar 06 2011We present the completion of a program to cross-correlate the SDSS Data Release 1 and 2MASS Point Source Catalog in search for extremely red L and T dwarfs. The program was initiated by Metchev and collaborators, who presented the findings on all newly ... More
Spitzer Light Curves of the Young, Planetary-Mass TW Hya Members 2MASS J11193254-1137466AB and WISEA J114724.10-204021.3Apr 18 2018We present Spitzer Space Telescope time-series photometry at 3.6 and 4.5 $\mu$m of 2MASS J11193254$-$1137466AB and WISEA J114724.10$-$204021.3, two planetary-mass, late-type ($\sim$L7) brown dwarf members of the $\sim$10 Myr old TW Hya Association. These ... More
Inference on the mode of weak directional signals: a Le Cam perspective on hypothesis testing near singularitiesDec 14 2015Mar 23 2016We revisit, in an original and challenging perspective, the problem of testing the null hypothesis that the mode of a directional signal is equal to a given value. Motivated by a real data example where the signal is weak, we consider this problem under ... More
Radial Velocity Variability of Field Brown DwarfsJun 09 2015Jun 11 2015We present paper six of the NIRSPEC Brown Dwarf Spectroscopic Survey, an analysis of multi-epoch, high-resolution (R~20,000) spectra of 25 field dwarf systems (3 late-type M dwarfs, 16 L dwarfs, and 6 T dwarfs) taken with the NIRSPEC infrared spectrograph ... More
Three Wide-Separation L dwarf Companions from the Two Micron All Sky Survey: Gl 337C, Gl 618.1B, and HD 89744BAug 27 2001We present two confirmed wide separation L-dwarf common proper motion companions to nearby stars and one candidate identified from the Two Micron All Sky Survey. Spectral types from optical spectroscopy are L0 V, L2.5 V, and L8 V. Near-infrared low resolution ... More
High resolution spectroscopy of ultracool M dwarfsApr 17 2002(abridged) We present high-resolution echelle spectroscopy of a photometricaly-selected sample if thirty-nine dwarfs with spectral types between M6.5 and L0.5. Two stars, 2MASSI 0253202+271333 and 2MASSW 0952219-192431, are double-lined spectroscopic ... More
The 2MASS Wide-Field T Dwarf Search. I. Discovery of a Bright T Dwarf Within 10 pc of the SunNov 06 2002We present the discovery of a bright (J = 13.94$\pm$0.03) T dwarf, 2MASS 1503+2525, identified in a new, wide-field search for T dwarfs using the recently completed Two Micron All Sky Survey (2MASS). The 1--2.5 $\micron$ spectrum of this object exhibits ... More
Brown Dwarf Companions to G-type Stars. I: Gliese 417B and Gliese 584CMar 14 2001We present astrometric and spectroscopic observations confirming that two nearby G dwarf systems (Gliese 417 = BD+36 2162 and Gliese 584AB = eta CrB AB) have a widely separated, L dwarf, substellar companion. Using age estimates of the G dwarf primaries, ... More
A New Population of Young Brown DwarfsFeb 01 2007We report the discovery of a population of late-M and L field dwarfs with unusual optical and near-infrared spectral features that we attribute to low gravity -- likely uncommonly young, low-mass brown dwarfs. Many of these new-found young objects have ... More
Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope WPFC2Nov 21 2002(abridged) We present the discovery of two T dwarf binaries, 2MASS 1225-2739AB and 2MASS 1534-2952AB, identified in a sample of ten T dwarfs imaged with the Hubble Space Telescope Wide Field Planetary Camera 2. The separations of the two binary systems ... More
The NIRSPEC Brown Dwarf Spectroscopic Survey. I. Low-Resolution Near-Infrared SpectraSep 09 2003We present the first results of a near-infrared (0.96-2.31 micron) spectroscopic survey of M, L, and T dwarfs obtained with NIRSPEC on the Keck II telescope. Our new survey has a resolving power of R = 2000 and is comprised of two major data sets: 53 ... More
Theoretical Spectral Models of T Dwarfs at Short Wavelengths and Their Comparison with DataSep 14 2001Mar 07 2002We have generated new, self-consistent spectral and atmosphere models for the effective temperature range 600 K to 1300 K thought to encompass the known T dwarfs. For the first time, theoretical models are compared with a {\it family} of measured T dwarf ... More
Identifying Young Brown Dwarfs Using Gravity-Sensitive Spectral FeaturesSep 23 2003We report the initial results of the Brown Dwarf Spectroscopic Survey Gravity Project, to study gravity sensitive features as indicators of youth in brown dwarfs. Low-resolution (R~2000) J-band and optical (R~1000) observations using NIRSPEC and LRIS ... More
A Flaring L5 Dwarf: The Nature of HαEmission in Very Low Mass (Sub)Stellar ObjectsOct 15 2002Oct 16 2002Time series spectrophotometry of the L5 dwarf 2MASS 01443536-0716142 showed strong H\alpha emission which declined by nearly 75% in four consecutive exposures. The line was not detected in emission on a spectrum obtained eleven months later. This behavior ... More
The NIRSPEC Brown Dwarf Spectroscopic Survey II: High-Resolution J-Band Spectra of M, L and T DwarfsDec 21 2006We present a sequence of high resolution (R~20,000 or 15 km/s) infrared spectra of stars and brown dwarfs spanning spectral types M2.5 to T6. Observations of 16 objects were obtained using eight echelle orders to cover part of the J-band from 1.165-1.323 ... More
New Neighbors from 2MASS: Activity and Kinematics at the Bottom of the Main SequenceApr 26 2000We have combined 2MASS and POSS II data in a search for nearby ultracool (later than M6.5) dwarfs with K_s<12. Spectroscopic follow-up observations identify 53 M7 to M9.5 dwarfs and seven L dwarfs. The observed space density is 0.0045 +- 0.0008 M8-M9.5 ... More
The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf DiscoveriesFeb 13 2004We present the discovery of seven new T dwarfs identified in the Two Micron All Sky Survey. Low-resolution (R$\sim$150) 0.8--2.5 micron spectroscopy obtained with the IRTF SpeX instrument reveal the characteristic H$_2$O and CH$_4$ bands in the spectra ... More
S Ori 70: Just a Foreground Field Brown Dwarf?Dec 10 2003Dec 15 2003We examine recent claims that the T-type brown dwarf S Ori 053810.1-023626 (S Ori 70) is a spectroscopically verified low mass (3$^{+5}_{-1}$ M$_{Jup}$) member of the 1--8 Myr $\sigma$ Orionis cluster. Comparative arguments by Mart{\'{i}}n & Zapatero ... More
Detection of H Alpha Emission in a Methane (T-Type) Brown DwarfMar 20 2000We report the detection of H{$\alpha$} emission in the T dwarf (methane brown dwarf) 2MASSW J1237392+652615 over three days using the Keck Low Resolution Imaging Spectrograph. The measured line flux, log(L$_{H{\alpha}}$/L$_{bol}$) = $-$4.3, is roughly ... More
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+150248.4Feb 06 2014As 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, ... More
Critical Sets for Sudoku and General GraphsFeb 01 2013We discuss the problem of finding critical sets in graphs, a concept which has appeared in a number of guises in the combinatorics and graph theory literature. The case of the Sudoku graph receives particular attention, because critical sets correspond ... More
Serendipitous 2MASS Discoveries Near the Galactic Plane: A Spiral Galaxy and Two Globular ClustersJun 19 2000We present the basic properties of three objects near the Galactic Plane - a large galaxy and two candidate globular clusters - discovered in the Two Micron All Sky Survey (2MASS) dataset. All were noted during spot-checks of the data during 2MASS quality ... More
The Luminosities of the Coldest Brown DwarfsOct 03 2014In recent years brown dwarfs have been extended to a new Y-dwarf class with effective temperatures colder than 500K and masses in the range 5-30 Jupiter masses. They fill a crucial gap in observable atmospheric properties between the much colder gas-giant ... More
Meeting the Cool Neighbors X: Ultracool dwarfs from the 2MASS All-Sky Data ReleaseJun 20 2008Using data from the 2MASS All-Sky Point Source Catalogue, we have extended our census of nearby ultracool dwarfs to cover the full celestial sphere above Galactic latitute 15 degrees. Starting with an initial catalogue of 2,139,484 sources, we have winnowed ... More
Substellar Companions to Main Sequence Stars: No Brown Dwarf Desert at Wide SeparationsMar 14 2001We use three field L and T dwarfs which were discovered to be wide companions to known stars by the Two Micron All-Sky Survey (2MASS) to derive a preliminary brown dwarf companion frequency. Observed L and T dwarfs indicate that brown dwarfs are not unusually ... More
Meeting the Cool Neighbors VIII: A preliminary 20-parsec census from the NLTT catalogueApr 02 2004Continuing our census of late-type dwarfs in the Solar Neighbourhood, we present BVRI photometry and optical spectroscopy of 800 mid-type M dwarfs drawn from the NLTT proper motion catalogue. The targets are taken from both our own cross-referencing of ... More
The Brown Dwarf Deficit in Taurus: Evidence for a Non-Universal IMFJul 23 2002We present the results of a deep, optical/IR wide field imaging survey of selected fields in the nearby (d ~ 140 pc) Taurus star-forming region. We report the discovery of 9 new members with spectral types M5.75-M9.5. We derive an Initial Mass Function ... More
Discovery of a Very Young Field L Dwarf, 2MASS J01415823-4633574Nov 15 2005While following up L dwarf candidates selected photometrically from the Two Micron All Sky Survey, we uncovered an unusual object designated 2MASS J01415823-4633574. Its optical spectrum exhibits very strong bands of vanadium oxide but abnormally weak ... More
Sixty-seven Additional L Dwarfs Discovered by the Two Micron All Sky Survey (2MASS)Mar 22 2000We present JHKs photometry, far red spectra, and spectral classifications for an additional 67 L dwarfs discovered by the Two Micron All Sky Survey. One of the goals of this new search was to locate more examples of the latest L dwarfs. Of the 67 new ... More
WISEP J004701.06+680352.1: An intermediate surface gravity, dusty brown dwarf in the AB Dor Moving GroupDec 04 2014We present spectroscopy, astrometry, and photometry of the brown dwarf WISEP J004701.06+680352.1 (W0047+68), an unusually red field L dwarf at a distance of $12.2 \pm 0.4$ parsecs. The three-dimensional space motion identifies it as a member of the AB ... More
SpeX Spectroscopy of Unresolved Very Low-Mass Binaries. I. Identification of Seventeen Candidate Binaries Straddling the L Dwarf/T Dwarf TransitionDec 18 2009We report the identification of 17 candidate brown dwarf binaries whose components straddle the L dwarf/T dwarf transition. These sources were culled from a large near-infrared spectral sample of L and T dwarfs observed with the Infrared Telescope Facility ... More
A WISE Observation of a coolest brown dwarf, CFBDSIR 1458+1013Apr 13 2011The Wide-field Infrared Survey Explorer (WISE) has detected the close binary brown dwarf system CFBDSIR 1458+1013AB as WISEP J145829.35+101341.8 with a combined magnitude at 4.6 microns of W2 = 15.488+/-0.147. This allows a comparison with another "coolest" ... More
Four nearby L dwarfsSep 20 1999We present spectroscopic, photometric and astrometric observations of four bright L dwarfs identified in the course of the 2MASS near-infrared survey. Our spectroscopic data extend to wavelengths shortward of 5000\AA in the L0 dwarf 2MASSJ0746+2000 and ... More
Discovery of the Y1 Dwarf WISE J064723.23-623235.5Aug 25 2013We 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 ... More
Discovery of Four High Proper Motion L Dwarfs, Including a 10 pc L Dwarf at the L/T TransitionAug 23 2013We discover four high proper motion L dwarfs by comparing the Wide-field Infrared Survey Explorer (WISE) to the Two Micron All Sky Survey (2MASS). WISE J140533.32+835030.5 is an L dwarf at the L/T transition with a proper motion of 0.85+/-0.02" yr^-1, ... More
Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T TransitionMay 22 2006We present the results of a Hubble Space Telescope NICMOS imaging survey of 22 T-type field brown dwarfs. Five are resolved as binary systems with angular separations of 0"05-0"35, and companionship is established on the basis of component F110W-F170M ... More
A Proper Motion Survey Using the First Sky Pass of NEOWISE-Reactivation DataDec 01 2015The Wide-field Infrared Survey Explorer (WISE) was reactivated in December of 2013 (NEOWISE) to search for potentially hazardous near-Earth objects. We have conducted a survey using the first sky pass of NEOWISE data and the AllWISE catalog to identify ... More
Discovery of the Young L Dwarf WISE J1741102.78-464225.5Nov 23 2013We report the discovery of the L dwarf WISE J174102.78$-$464225.5, that was discovered as part of a search for nearby L dwarfs using the Wide-field Infrared Survey Explorer (WISE). The distinct triangular peak of the H-band portion of its near-infrared ... More
Identifying High Metallicity M Giants at Intragroup Distances with SDSSFeb 09 2012Tidal stripping and three-body interactions with the central supermassive black hole may eject stars from the Milky Way. These stars would comprise a set of `intragroup' stars that trace the past history of interactions in our galactic neighborhood. Using ... More
WISE Brown Dwarf Binaries: The Discovery of a T5+T5 and a T8.5+T9 SystemJun 16 2011The multiplicity properties of brown dwarfs are critical empirical constraints for formation theories, while multiples themselves provide unique opportunities to test evolutionary and atmospheric models and examine empirical trends. Studies using high-resolution ... More
The First Substellar Subdwarf? Discovery of a Metal-poor L Dwarf with Halo KinematicsApr 09 2003We present the discovery of the first L-type subdwarf, 2MASS J05325346+8246465. This object exhibits enhanced collision-induced H$_2$ absorption, resulting in blue NIR colors ($J-K_s = 0.26{\pm}0.16$). In addition, strong hydride bands in the red optical ... More
Evidence for Cloud Disruption in the L/T Dwarf TransitionMay 03 2002Clouds of metal-bearing condensates play a critical role in shaping the emergent spectral energy distributions of the coolest classes of low-mass stars and brown dwarfs, L and T dwarfs. Because condensate clouds in planetary atmospheres show distinct ... More
New Y and T dwarfs from WISE identified by Methane ImagingApr 02 2018We identify new Y- and T-type brown dwarfs from the WISE All Sky data release using images obtained in filters that divide the traditional near-infrared H and J bands into two halves -- specifically CH4s & CH4l in the H and J2 & J3 in the J. This proves ... More
WISEP J061135.13-041024.0AB: A J-Band Flux Reversal Binary at the L/T TransitionMay 02 2014We present Keck II laser guide star adaptive optics observations of the brown dwarf WISEP J061135.13-041024.0 showing it is a binary with a component separation of 0.4". This system is one of the six known resolved binaries in which the magnitude differences ... More