TY - JOUR
T1 - Discovery of two very low mass binaries
T2 - Final results of an adaptive optics survey of nearby M6.0-M7.5 stars
AU - Siegler, Nick
AU - Close, Laird M.
AU - Cruz, Kelle L.
AU - Martín, Eduardo L.
AU - Reid, I. Neill
N1 - Copyright:
Copyright 2015 Elsevier B.V., All rights reserved.
PY - 2005/3/10
Y1 - 2005/3/10
N2 - We present updated results of a high-resolution, magnitude-limited (K s < 12 mag) imaging survey of nearby low-mass M6.0-M7.5 field stars. The observations were carried out using adaptive optics at the Gemini North, VLT, Keck II, and Subaru telescopes. Our sample of 36 stars consists predominantly of nearby (≲30 pc) field stars, five of which we have resolved as binaries. Two of the binary systems, 2MASSI J0429184-312356 and 2MASSI J1847034+552243, are presented here for the first time. All five of the discovered binary systems have separations between 0′.08 and 0′.53 (2-9 AU) with similar mass ratios (q > 0.8, ΔKs < 1 mag). This result supports the hypothesis that wide (a > 20 AU), very low mass (VLM; Mtot < 0.19 M⊙) binary systems are rare. The projected semimajor axis distribution of these systems peak at ∼5 AU, and we report a sensitivity-corrected binary fraction of 9-3 +4 % for stars with primaries of spectral type M6.0-M7.5 with separations ≳3 AU and mass ratios q ≳ 0.6. Within these instrumental sensitivities, these results support the overall trend that both the semimajor axis distribution and binary fraction are a function of the mass of the primary star and decrease with decreasing primary mass. These observations provide important constraints for low-mass binary star formation theories.
AB - We present updated results of a high-resolution, magnitude-limited (K s < 12 mag) imaging survey of nearby low-mass M6.0-M7.5 field stars. The observations were carried out using adaptive optics at the Gemini North, VLT, Keck II, and Subaru telescopes. Our sample of 36 stars consists predominantly of nearby (≲30 pc) field stars, five of which we have resolved as binaries. Two of the binary systems, 2MASSI J0429184-312356 and 2MASSI J1847034+552243, are presented here for the first time. All five of the discovered binary systems have separations between 0′.08 and 0′.53 (2-9 AU) with similar mass ratios (q > 0.8, ΔKs < 1 mag). This result supports the hypothesis that wide (a > 20 AU), very low mass (VLM; Mtot < 0.19 M⊙) binary systems are rare. The projected semimajor axis distribution of these systems peak at ∼5 AU, and we report a sensitivity-corrected binary fraction of 9-3 +4 % for stars with primaries of spectral type M6.0-M7.5 with separations ≳3 AU and mass ratios q ≳ 0.6. Within these instrumental sensitivities, these results support the overall trend that both the semimajor axis distribution and binary fraction are a function of the mass of the primary star and decrease with decreasing primary mass. These observations provide important constraints for low-mass binary star formation theories.
KW - Binaries: general
KW - Instrumentation: adaptive optics
KW - Stars: low-mass, brown dwarfs
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U2 - 10.1086/427743
DO - 10.1086/427743
M3 - Article
AN - SCOPUS:18444375002
VL - 621
SP - 1023
EP - 1032
JO - Astrophysical Journal
JF - Astrophysical Journal
SN - 0004-637X
IS - 2 I
ER -