SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION

By A. Burgasser, Kelle Cruz, M. Cushing, C. Gelino, D. Looper, Jacqueline K. Faherty, J. D. Kirkpatrick, I. Neill Reid. 2009

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We 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 SpeX spectrograph. Candidates were selected on the basis of spectral ratios which segregate known (resolved) L dwarf/T dwarf pairs from presumably single sources. Composite templates, constructed by combining 13,581 pairs of absolute flux-calibrated spectra, are shown to provide statistically superior fits to the spectra of our 17 candidates as compared to single templates. Ten of these candidates appear to have secondary components that are significantly brighter than their primaries over the 1.0–1.3 μm band, indicative of rapid condensate depletion at the L dwarf/T dwarf transition. Our results support prior indications of enhanced multiplicity amongst early-type T dwarfs; 53% ± 7% of the T0–T4 dwarfs in our spectral sample are found to be either resolved or unresolved (candidate) pairs, although this is consistent with an intrinsic (volume complete) brown dwarf binary fraction of only 15%. If verified, this sample of spectral binaries more than doubles the number of known L dwarf/T dwarf transition pairs, enabling a broader exploration of this poorly understood phase of brown dwarf atmospheric evolution.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/b679d8d9b06c60f4d009ac88b015ba5d0a30d3ce

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Citations in the corpus

3D-HST: A WIDE-FIELD GRISM SPECTROSCOPIC SURVEY WITH THE HUBBLE SPACE TELESCOPE (2012, methodology): “The spectral types are estimated from template fits from the SpeX spectral library (Burgasser et al. 2010), with the two best fits shown plotted along with the spectra.”
The Field Substellar Mass Function Based on the Full-sky 20 pc Census of 525 L, T, and Y Dwarfs (2020, background): “…et al. 2011, (57) Knapp et al. 2004, (58) Biller et al. 2006, (59) Burningham et al. 2009, (60) Scholz et al. 2003, (61) Burgasser et al. 2006, (62) Burgasser et al. 2010, (63) Kasper et al. 2007., (64) Pinfield et al. 2008, (65) Luhman et al. 2011, (66) Faherty et al. 2012, (67) Dupuy & Liu…”
THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, methodology): “To date, this binary is the only one with direct evidence for the brightening phenomenon extending as blue as 1 µm, though spectral decomposition suggests this occurs in other binaries (e.g., Figures 16–18, and also see Burgasser et al. 2010).”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…Golimowski et al. (2004), (46) Kirkpatrick et al. (2011), (47) Bonnefoy et al. (2014), (48) Deacon et al. (2005), (49) Looper et al. (2007), (50) Burgasser et al. (2010a), (51) Allers & Liu (2013), (52) Artigau et al. (2010), (53) Cushing et al. (2005a), (54) Wilson et al. (2001), (55) Ruiz et…”
THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, methodology): “5/L3p fld-g): Using the low resolution near-IR spectrum of (Burgasser et al. 2010), we classify 2MASS J2224−0158 as L3 fld-g.”
CLOUDS AND CHEMISTRY IN THE ATMOSPHERE OF EXTRASOLAR PLANET HR8799b (2011, background): “5 ±1 (Burgasser et al. 2010).”
HST SPECTRAL MAPPING OF L/T TRANSITION BROWN DWARFS REVEALS CLOUD THICKNESS VARIATIONS (2013, methodology): “Particularly interesting well-studied examples are see in Ross 458C (Burgasser et al. 2010; Burningham et al. 2011; Morley et al. 2012) and 2M1207b Chauvin et al. (2005); Mohanty et al. (2007); Patience et al. (2010); Barman et al. (2011b); Skemer et al. (2011).”
A STUDY OF THE DIVERSE T DWARF POPULATION REVEALED BY WISE (2013, methodology): “5 ± 2 (Burgasser et al. 2010), and is a weak binary candidate based on their analysis.”
A NEAR-INFRARED SPECTROSCOPIC STUDY OF YOUNG FIELD ULTRACOOL DWARFS (2013, methodology): “At low-spectral resolution (R ≈100), we include the spectra of field dwarf standards from Geißler et al. (2011) and Kirkpatrick et al. (2010) as well as the spectral templates from Burgasser et al. (2010).”
LARGE-AMPLITUDE VARIATIONS OF AN L/T TRANSITION BROWN DWARF: MULTI-WAVELENGTH OBSERVATIONS OF PATCHY, HIGH-CONTRAST CLOUD FEATURES (2012, background): “Burgasser et al. (2010) have suggested that 2M2139 is a binary candidate since a composite spectral template consisting of L8.”
BANYAN. VII. A NEW POPULATION OF YOUNG SUBSTELLAR CANDIDATE MEMBERS OF NEARBY MOVING GROUPS FROM THE BASS SURVEY (2015, background): “5 BD in the optical by Reid et al. (2008), and Burgasser et al. (2010) categorized it as an L4.”
THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, methodology): “Inconsistencies with both models suggests that thick condensate clouds continue to play a role in the photospheres of some cooler dwarfs (see discussion in Burgasser et al. 2010b, Marley et al. 2010).”
DISCOVERIES FROM A NEAR-INFRARED PROPER MOTION SURVEY USING MULTI-EPOCH TWO MICRON ALL-SKY SURVEY DATA (2010, methodology): “…spectra and synthetic composite spectra in Burgasser et al. (2010) and using a modified χ2 statistic (called Gk, from Cushing et al. 2008), we find that the best binary fit is a statistically significant better match than the best fit to a single source (see Equation 4 in Burgasser et al. 2010).”
WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “5 spectral binary candidate by Burgasser et al. (2010a), but identified as a J-band variable (Radigan et al. 2012) that is unresolved in HST images (Apai et al. 2013), and exhibits no radial velocity variations (Khandrika et al. 2013).”