Multiplicity of Nearby Free-floating Ultracool Dwarfs: A Hubble Space Telescope WFPC2 Search for Companions

By H. Bouy, W. Brandner, E. Martín, X. Delfosse, F. Allard, G. Basri. 2003

258 citations recorded by the source corpus.

We present Hubble Space Telescope (HST) Wide Field Planetary Camera 2 (WFPC2) observations of a sample of 134 ultracool objects (spectral types later than M7) coming from the Deep Near Infrared Survey (DENIS), Two Micron All Sky Survey (2MASS), and Sloan Digital Sky Survey (SDSS), with distances estimated to range from 7 to 105 pc. Fifteen new ultracool binary candidates are reported here. Eleven known binaries are confirmed, and orbital motion is detected in some of them. We estimate that the closest binary systems in this sample have periods between 5 and 20 yr, and thus dynamical masses will be derived in the near future. For the calculation of binary frequency, we restrict ourselves to systems with distances less than 20 pc. After correction of the binaries bias, we find a ratio of visual binaries (at the HST limit of detection) of around 10%, and that ∼15% of the 26 objects within 20 pc are binary systems with separations between 1 and 8 AU. The observed frequency of ultracool binaries is similar to that of binaries with G-type primaries in the separation range from 2.1 to 140 AU. There is also a clear deficit of ultracool binaries with separations greater than 15 AU, and a possible tendency for the binaries to have mass ratios near unity. Most systems have indeed visual and near-infrared brightness ratios between 1 and 0.3. We discuss our results in the framework of current scenarios for the formation and evolution of free-floating brown dwarfs.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/afd3fb2583c0457d88f78c2ecff710a65e11b5ca

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In Astronomy and Astrophysics

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

In Instrumentation

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

Citations in the corpus

• Binaries and the L Dwarf/T Dwarf Transition (2006, methodology): “These values are fully consistent with earlier estimates of the volume-limited, resolved binary fraction of L and T dwarfs, also ranging over 0.09–0.15 (Bouy et al. 2003; Burgasser et al. 2003c, 2006c; Reid et al. 2006a).”
• THE ASTRALUX LARGE M-DWARF MULTIPLICITY SURVEY (2012, background): “There is some ambiguity to this classification in that Bouy et al. (2003) find it to be a brown dwarf of type L4.”
• THE NIRSPEC ULTRACOOL DWARF RADIAL VELOCITY SURVEY (2010, background): “…close to edge-on and observed at a very unfavorable phase, then such a binary would have been readily resolved in the high-resolution imaging observations presented by Bouy et al. (2003) and Reid et al. (2006) who found no luminous (Δm < 5 mag) companions to 2M1507−16 over a range of separations 0.”
• THE HAWAII INFRARED PARALLAX PROGRAM. I. ULTRACOOL BINARIES AND THE L/T TRANSITION, (2012, unknown): “— (1) This work; (2) Liu et al. (in preparation); (3) Allers et al. (2009); (4) Biller et al. (2006); (5) Biller et al. (2010); (6) Bouy et al. (2003); (7) Bouy et al. (2004); (8) Bouy et al. (2005); (9) Bouy et al. (2008); (10) Bouy et al. (2011); (11) Brandner et al. (2004); (12) Burgasser et al.…”
• Stellar Multiplicity (2013, background): “At larger separations (a & 2AU), high-resolution imaging surveys indicate an observed binary frequency of about 15±3% after correction for their inherent Malmquist bias (Bouy et al. 2003, Burgasser et al. 2007).”
• Stellar, brown dwarf and multiple star properties from hydrodynamical simulations of star cluster formation (2008, background): “…in the multiplicity of VLM objects in recent years (Martı́n et al. 2000, 2003; Close et al. 2003, 2007; Gizis et al. 2003; Pinfield et al. 2003; Bouy et al. 2003, 2006; Siegler et al. 2003, 2005; Luhman 2004; Maxted & Jeffries 2005; Kraus, White & Hillenbrand 2005, 2006; Basri & Reiners…”
• Subtle Signatures of Multiplicity in Late-type Dwarf Spectra: The Unresolved M8.5 + T5 Binary 2MASS J03202839–0446358 (2008, methodology): “…majority have been 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;…”
• YOUNG L DWARFS IDENTIFIED IN THE FIELD: A PRELIMINARY LOW-GRAVITY, OPTICAL SPECTRAL SEQUENCE FROM L0 TO L5 (2008, background): “Three low-gravity L dwarfs found during the 20-pc census were also independently identified in the Southern Sample of Kirkpatrick et al. (2008): 2M 0033−15, 2M 0141−46, and 2M 0357−44 (aka DENIS 0357−44, Bouy et al. 2003).”
• Hubble Space Telescope NICMOS Observations of T Dwarfs: Brown Dwarf Multiplicity and New Probes of the L/T Transition (2006, methodology): “This is similar to resolved binary fractions measured for other large high resolution imaging samples of VLM field dwarfs (Reid et al. 2001, 2006a; Bouy et al. 2003; Close et al. 2003; Gizis et al. 2003; Siegler et al. 2005).”
• The stellar and sub-stellar IMF of simple and composite populations (2011, background): “BD–BD binary systems are known to exist (Basri 2000), in the field (Bouy et al. 2003; Close et al. 2003) and in clusters (Mart́ın et al. 2003).”
• MAPPING THE SHORES OF THE BROWN DWARF DESERT. II. MULTIPLE STAR FORMATION IN TAURUS–AURIGA (2011, background): “These surveys (e.g. Duquennoy & Mayor 1991, hereafter DM91; Fischer & Marcy 1992, hereafter FM92; Close et al. 2003; Bouy et al. 2003; Burgasser et al. 2003; Raghavan et al. 2010) have found that binary frequencies and properties are very strongly dependent on mass. Solar-mass stars have high…”
• Giant Planet Companion to 2MASSW J1207334-393254 (2005, background): “2M1207A and b is very different from known brown dwarf binaries discovered in the field (Close et al. 2003, Gizis et al. 2003, Burgasser et al. 2003, Bouy et al. 2003) and within star forming regions (Neuhäuser et al. 2002), which are characte - ized by semi-major axes< 15 AU and a trend toward…”
• Stellar Multiplicity and the Initial Mass Function: Most Stars Are Single (2006, background): “Bouy et al. (2003) examined the binary statistics for a sample of 134 late M and L field dwarfs and estimated a binary fraction for a separation range of about 2 - 140 AU of only 10% corresponding to a SSF of 90% for these objects.”
• ε Indi Ba,Bb: The nearest binary brown dwarf (2003, methodology): “Based on observations collected with the ESO VLT, Paranal, Chile. dwarfs imaged with the HST have been shown to have candidate companions at projected separations of 1–10AU (Reid et al. 2001; Bouy et al. 2003; Burgasser et al. 2003).”
• Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity (2004, unknown): “…DENIS-P J0205 1159AB (Koerner et al. 1999; Leggett et al. 2001; Bouy et al. 2003); DENIS-P J1228 1547AB (Koerner et al. 1999; Martı́n et al. 1999a; Bouy et al. 2003); 2MASS J0746+2000AB and 2MASS J0850+1057AB (Reid et al. 2001; Bouy et al. 2003); 2MASS J1225 2739AB and 2MASS J1534 2952AB…”
• New spectral types L and T (2005, methodology): “Note: Bouy et al. (2003) estimate L spectral types for 31 objects using I − J colors.”
• 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. 2006b).”
• THE HAWAII INFRARED PARALLAX PROGRAM. II. YOUNG ULTRACOOL FIELD DWARFS (2016, background): “The vast majority of our field ultracool sample (both our CFHT targets and the literature objects described in Section 2.5.2) have been imaged at high angular resolution, either with HST (e.g. Bouy et al. 2003; Gizis et al. 2003) or with Keck LGS AO by us.”
• FUNDAMENTAL PARAMETERS AND SPECTRAL ENERGY DISTRIBUTIONS OF YOUNG AND FIELD AGE OBJECTS WITH MASSES SPANNING THE STELLAR TO PLANETARY REGIME (2015, unknown): “…(48) Reid et al. (2008), (49) Chiu et al. (2006), (50) Pokorny et al. (2004), (51) Phan-Bao et al. (2006), (52) Kirkpatrick et al. (1999), (53) Bouy et al. (2003), (54) Kendall et al. (2003), (55) Phan-Bao et al. (2003), (56) Burgasser et al. (2003b), (57) Fan et al. (2000), (58) Burgasser et…”