Binarity in Brown Dwarfs: T Dwarf Binaries Discovered with the Hubble Space Telescope Wide Field Planetary Camera 2

By A. Burgasser, J. D. Kirkpatrick, I. Neill Reid, Michael E. Brown, C. L. Miskey, J. Gizis. 2002

336 citations recorded by the source corpus.

We present the discovery of two T dwarf binaries, 2MASS 1225-2739AB and 2MASS 1534-2952AB, identified in a sample of 10 T dwarfs imaged with the Hubble Space Telescope (HST) Wide Field Planetary Camera 2. Companionship is established by the uniquely red F814W-F1042M colors of the binary components, caused by heavily pressure-broadened K I absorption centered at 7665 and 7699 Å. The separations of the two binary systems are 0.″282 ± 0.″005 and 0.″065 ± 0.″007, implying projected separations of 3.17 ± 0.14 and 1.0 ± 0.3 AU, respectively. These close separations are similar to those found in previous brown dwarf binary searches and permit orbital mapping over the coming decade. 2MASS 1225-2739AB has a substantially fainter secondary, with ΔMF814W = 1.59 ± 0.04 and ΔMF1042M = 1.05 ± 0.03; this system is likely composed of a T6 primary and T8 secondary with mass ratio 0.7-0.8. The observed binary fraction of our HST sample, 20%, is consistent with results obtained for late-type M and L field dwarfs and implies a bias-corrected binary fraction of 9% for a ≳ 1 AU and q ≳ 0.4, significantly lower than the binary fractions of F-G and early-type M dwarf stars. Neither of the T binaries have separations a ≳ 10 AU, consistent with results from other brown dwarf binary searches. Using the statistical models of Weinberg, Shapiro, & Wasserman, we conclude that tidal disruption by passing stars or giant molecular clouds, which limits the extent of wide stellar binaries, plays no role in eliminating wide brown dwarf binaries, implying either disruption very early in the formation process (ages ≲1-10 Myr) or a formation mechanism that precludes such systems. We find that the maximum binary separation in the brown dwarf regime appears to scale as M, a possible clue to the physical mechanism that restricts wide substellar systems.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/d1a0e577d23c34a89f0a9c5d12c7c263a61b0e77

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In Astronomy and Astrophysics

1. Michael C. Liu
2. A. Burgasser
3. J. D. Kirkpatrick
4. T. Dupuy
5. K. Luhman
6. Kelle Cruz
7. M. Marley
8. D. Schneider

Citations in the corpus

• The 2MASS Wide-Field T Dwarf Search. III. Seven New T Dwarfs and Other Cool Dwarf Discoveries (2004, methodology): “These objects exhibit a broad range of CH4 band strengths and near-infrared colors (−0.7 < J − Ks < 0.85), encompassing early, mid-, and late-type T dwarf spectral morphologies (Burgasser et al. 2002; Geballe et al. 2002).”
• ε Indi Ba,Bb: The nearest binary brown dwarf (2003, methodology): “…T dwarf systems, one (2MASS 1225−2739AB) has a possible period of∼23 years, while the period of the other (2MASS 1534−2952AB) may be only ∼8 years (Burgasser et al. 2003): however, the latter system is extremely tight with a 0.065 arcsec separation, making it very difficult to obtain separate…”
• MID-INFRARED PHOTOMETRY OF COLD BROWN DWARFS: DIVERSITY IN AGE, MASS, AND METALLICITY (2010, methodology): “We have identified known binaries in our sample by reference to the literature and known current work: Allers et al. (2010); Bouy et al. (2003); Burgasser et al. (2003a, 2005, 2006c); Freed et al. (2003); Golimowski et al. (2004b); Heintz (1972); Koerner et al. (1999); Liu & Leggett (2005); Liu et…”
• 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, background): “The transition from L to T is heralded by the appearance of CH4 absorption features centered at 1.6 and 2.2 µm (Geballe et al. 2002; Burgasser et al. 2002a) and the disappearance of silicate clouds from the photosphere.”
• Seventy-One New L and T Dwarfs from the Sloan Digital Sky Survey (2006, methodology): “…imaging searches for close-binary brown dwarfs are being conducted with the Hubble Space Telescope and ground-based adaptive optics imagers (Burgasser et al. 2003; Bouy et al. 2003; McCaughrean et al. 2004; Golimowski et al. 2004b; Liu & Leggett 2005; Liu et al. 2006; Burgasser et al.…”
• Hubble Space Telescope Observations of Binary Very Low Mass Stars and Brown Dwarfs (2003, background): “…Skrutskie et al. 1997; Cutri et al. 2000),3 and Sloan Digital Sky Survey (SDSS; York et al. 2000) have enabled the discovery of numerous cool dwarfs and led to the definition of new spectral types L (Kirkpatrick et al. 1999; Martı́n et al. 1999b) and T (Burgasser et al. 2002a; Geballe et al. 2002).”
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity (2004, methodology): “Indeed, Burgasser et al. (2002b) found that a relatively small fraction of holes would appreciably move a late L-type object toward the blue in J K.”
• Stellar Multiplicity (2013, background): “Although different functional forms and an unconfirmed discontinuity at ∼ 0.2M⊙ have been proposed (Burgasser et al. 2003, Close et al. 2003, Reid et al. 2001), this upper limit on binary separation appears to hold for both field populations and PMS systems (e.g., Faherty et al. 2011, Konopacky et…”
• THE IMPACT OF STELLAR MULTIPLICITY ON PLANETARY SYSTEMS. I. THE RUINOUS INFLUENCE OF CLOSE BINARY COMPANIONS (2016, background): “The small number of targets with M<0.5 Me might have fewer companions at 500 au (e.g., Reid et al. 2001; Burgasser et al. 2003), but the companion frequency per dex of semimajor axis is remarkably constant in the 500 au regime across the mass range our entire sample (Duchêne & Kraus 2013).”
• Infrared Parallaxes for Methane T Dwarfs (2003, methodology): “Burgasser et al. (2002c) suggested that a possible resolution for this discrepancy could be the appearance of uneven cloud cover on the surface of early T dwarfs.”