Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition

By A. Burgasser, J. D. Kirkpatrick, Kelle Cruz, I. Neill Reid, S. Leggett, J. Liebert, Adam Burrows, Michael E. Brown. 2006

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We 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 colors (indicative of CH4 absorption) and low probabilities of background contamination. Prior ground-based observations show 2MASS 1553+1532AB to be a common proper-motion binary. The properties of these systems—low multiplicity fraction (12% resolved, as corrected for sample selection biases), close projected separations (ρ = 1.8-5.0 AU) and near-unity mass ratios—are consistent with previous results for field brown dwarf binaries. Three of the binaries have components that span the poorly understood transition between L dwarfs and T dwarfs. Spectral decomposition analysis of one of these, SDSS 1021-0304AB, reveals a peculiar flux reversal between its components, as its cooler T5 secondary is ~30% brighter at 1.05 and 1.27 μm than its T1 primary. This system, 2MASS 0518-2828AB, and SDSS 1534+1615AB all demonstrate that the J-band brightening observed between late-type L to mid-type T dwarfs is an intrinsic feature of this spectral transition, albeit less pronounced than previously surmised. We also find that the resolved binary fraction of L7 to T3.5 dwarfs is twice that of other L and T dwarfs, an anomaly that can be explained by a relatively rapid evolution of brown dwarfs through the L/T transition, perhaps driven by dynamic (nonequilibrium) depletion of photospheric condensates.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/beceb9e685d40a512e19b59309b3ba0f541f7e5b

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Citations in the corpus

Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839–0446358 (2008, methodology): “…identified through high angular resolution imaging, using the Hubble Space Telescope (HST; e.g., Mart́ın, Brandner & Basri 1999; Bouy et al. 2003; Burgasser et al. 2006b; Reid et al. 2006a), ground-based adaptive optics systems (e.g., Close et al. 2003; Chauvin et al. 2004; Siegler et al.…”
THE BROWN DWARF KINEMATICS PROJECT (BDKP). III. PARALLAXES FOR 70 ULTRACOOL DWARFS (2012, methodology): “Most of the L dwarfs in our sample were classified spectrally from red optical data following the scheme of Kirkpatrick et al. (1999), while the T dwarfs were classified in the near-IR (Burgasser et al. 2006a).”
The Evolution of L and T Dwarfs in Color-Magnitude Diagrams (2008, background): “This was confirmed by the discovery of binary brown dwarfs with (coeval) components spanning the L/T transition and showing the J-band flux reversal (Burgasser et al. 2006; Liu et al. 2006).”
THE 0.8–14.5 μm SPECTRA OF MID-L TO MID-T DWARFS: DIAGNOSTICS OF EFFECTIVE TEMPERATURE, GRAIN SEDIMENTATION, GAS TRANSPORT, AND SURFACE GRAVITY (2009, methodology): “This brightening is a real effect and not due to variations in other parameters as verified by several studies of binary systems (Gizis et al. 2003, Cruz et al. 2004, Burgasser et al. 2006b, Liu et al. 2006, Looper et al. 2008).”
SpeX SPECTROSCOPY OF UNRESOLVED VERY LOW MASS BINARIES. I. IDENTIFICATION OF 17 CANDIDATE BINARIES STRADDLING THE L DWARF/T DWARF TRANSITION (2009, methodology): “While SDSS J1254-0122 also satisfied one of our binary selection criteria, it is unresolved in HST imaging observations (Burgasser et al. 2006c) so we cannot exclude the possibility that both sources are single brown dwarfs.”
Binaries and the L Dwarf/T Dwarf Transition (2006, methodology): “…from high-resolution imaging studies using the Hubble Space Telescope (HST ) and ground-based adaptive optics instrumentation (Martı́n et al. 1999a; Reid et al. 2001b, 2006a; Bouy et al. 2003; Burgasser et al. 2003c, 2006c; Close et al. 2003; Gizis et al. 2003; Liu&Leggett 2005;Gelino et al. 2006).”
WEATHER ON OTHER WORLDS. II. SURVEY RESULTS: SPOTS ARE UBIQUITOUS ON L AND T DWARFS (2014, background): “That is, it may parallel the case of the candidate spectral binary-turned-variable 2MASS J21392676+0220226.”
Stellar Multiplicity (2013, background): “8 Gaspard Duchêne & Adam Kraus tion and incompleteness effects (Allen 2007, Burgasser et al. 2006, Liu, Dupuy & Leggett 2010).”
Meeting the Cool Neighbors. IX. The Luminosity Function of M7-L8 Ultracool Dwarfs in the Field (2006, background): “…suggest that they are not as metal-poor as these L subdwarfs, and their optical spectra do not exhibit the stronger metal-hydride bands (6750 Å CaH, 8611 Å CrH, 8692 Å FeH) and weaker metal oxides bands (7053, 8432 Å TiO) expected for metal-poor ultracool dwarfs (Burgasser et al. 2006a).”
THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, methodology): “2MASS J1404−3159AB has previously been resolved by Keck LGS AO imaging (Looper et al. 2008), and 2MASS J0518−2828AB was marginally resolved in HST/NICMOS imaging (Burgasser et al. 2006c).”
MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY (2010, methodology): “The primary sample for this paper consists of T dwarfs with spectral types T7 and later, as defined by the Burgasser et al. (2006b) scheme.”
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The M-dwarfs in Multiples (MinMs) survey – I. Stellar multiplicity among low-mass stars within 15 pc (2015, methodology): “The 3 − 10, 000 au range requires samples of nearby field objects to reach the smaller projected separations, so the MINMS value is compared with field Solar-type stars (Raghavan et al. 2010) and field brown dwarfs (Burgasser et al. 2006).”
The VAST Survey - III. The multiplicity of A-type stars within 75 pc (2013, background): “The trend of a wider separation peak to the distribution as a function of increasing primary mass is consistent with previousmultiplicity surveys of brown dwarf (Burgasser et al. 2006) andMdwarf (Fischer & Marcy 1992) primaries (Figs 14 and 15).”
FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “(1) Knapp et al. (2004), (2) Burgasser et al. (2006a), (3) Kirkpatrick et al. (2010), (4) Cruz et al. (2009), (5) Goldman et al. (1999), (6) Kirkpatrick et al. (2001a), (7) Cruz & Reid (2002), (8) Kirkpatrick et al. (1995), (9) Cruz et al. (2007), (10) Faherty et al. (2009), (11) Schneider et al.…”
THE BROWN DWARF KINEMATICS PROJECT I. PROPER MOTIONS AND TANGENTIAL VELOCITIES FOR A LARGE SAMPLE OF LATE-TYPE M, L, AND T DWARFS (2008, background): “Seven percent (56) of the dwarfs analyzed in this paper are known to be close binaries and of these, most appear to be near equal-mass/equal brightness (e.g. Bouy et al. 2003; Burgasser et al. 2006b).”
Dawes Review 6: The Impact of Companions on Stellar Evolution (2016, background): “When brown dwarfs are the primaries in binaries, their companions tend to be of similar mass, suggesting a large γ (Burgasser et al., 2006).”
Individual Dynamical Masses of Ultracool Dwarfs (2017, result): “— Burg03b = Burgasser et al. (2003b); Burg06b = Burgasser et al. (2006b); Burg11 = Burgasser et al. (2011); Chiu06 = Chiu et al. (2006); Clos03 = Close et al. (2003); Cutr03 = Cutri et al. (2003); Dupu09a = Dupuy et al. (2009a); Dupu09b = Dupuy et al. (2009b); Dupu09c = Dupuy et al. (2009c); Dupu10…”
Stellar, brown dwarf and multiple star properties from a radiation hydrodynamical simulation of star cluster formation (2011, background): “VLM objects: there has been much interest in the multiplicity of VLM objects in recent years (Martı́n et al. 2000, 2003; Bouy et al. 2003, 2006; Burgasser et al. 2003, 2006; Close et al. 2003, 2007; Gizis et al. 2003; Pinfield et al. 2003; Siegler et al. 2003, 2005; Luhman 2004; Maxted & Jeffries…”