Query : 2008A&A...490..763G

2008A&A...490..763G - Astronomy and Astrophysics, volume 490, 763-768 (2008/11-1)

Binarity at the L/T brown dwarf transition (Research Note). Adaptive optics search for companions.


Abstract (from CDS):

Current atmospheric models cannot reproduce some of the characteristics of the transition between the L dwarfs with cloudy atmospheres and the T dwarfs with dust-depleted photospheres. It has been proposed that a majority of the L/T transition brown dwarfs could actually be a combinaison of a cloudy L dwarf and a clear T dwarf. Indeed binarity seems to occur more frequently among L/T transition brown dwarfs. We aim to refine the statistical significance of the seemingly higher frequency of binaries. Co-eval binaries would also be interesting test-beds for evolutionary models. We obtained high-resolution imaging for six mid-L to late-T dwarfs, with photometric distances between 8 and 33pc, using the adaptive optics systems NACO at the VLT, and the Lick system, both with the Laser Guide Star. We resolve none of our targets. Combining our data with published results, we obtain a frequency of resolved L/T transition brown dwarfs of 31+21–15%, compared to 21+10–7% and 14+14–7% for mid-L and T dwarfs (90% of confidence level). These fractions do not significantly support, nor contradict, the hypothesis of a larger binary fraction in the L/T transition. None of our targets has companions with effective temperatures as low as 360-1000K at separations larger than 0.5".

Abstract Copyright:

Journal keyword(s): stars: low-mass, brown dwarfs - stars: atmospheres - technique: high angular resolution - stars: binaries: general - stars: binaries: visual

CDS comments: Fig.3 2MASSW J1036530-2448279 is a misprint for 2MASSW J1036530-344138.

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2023
1 SIMP J013656.5+093347.3 BD* 01 36 56.5605419830 +09 33 47.311965969           T2.0 115 0
2 2MASSI J0756252+124456 BD* 07 56 25.29120 +12 44 56.0868           L6V 12 0
3 2MASS J09393548-2448279 BD* 09 39 35.48976 -24 48 27.9432           T8 57 0
4 2MASSW J1036530-344138 BD* 10 36 53.0605368096 -34 41 38.377435973           L6 16 0
5 2MASS J14044948-3159330 BD* 14 04 49.48416 -31 59 33.0576           T1+T5 32 1
6 2MASS J16262034+3925190 BD* 16 26 20.1332795396 +39 25 19.488610341       19.67 16.68 esdL4 45 0
7 SDSS J204749.59-071818.2 BD* 20 47 49.59816 -07 18 18.2592           L9.5 15 0

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