http://arxiv.org/abs/1809.08244
Context. The second Gaia data release (Gaia DR2) contains high precision positions, parallaxes and proper motions for 1.3 billion sources. The resulting Hertzsprung-Russel diagram reveals fine structures all over the mass range.
Aims. This paper aims to investigate the content of Gaia DR2 at the low-mass end and to characterize ultra-cool and brown dwarfs.
Methods. We first retrieve the sample of spectroscopically confirmed ultra-cool and brown dwarfs in Gaia DR2. We use their locus in the precise Hertzsprung-Russel diagram to select new candidates, and to investigate their properties.
Results. The number of spectroscopically confirmed objects recovered in Gaia DR2 corresponds to 62 %, and 71 %, of the expected number of objects with and estimated Gaia magnitude Gest $\leq$ 21.5, and 20.3, respectively, significantly filling the gap with Gaia DR1. Furthermore Gaia DR2 contains ~13 000 $\geq$M7 and 679 new L candidates. A tentative classification suggests that a few hundreds are young or subdwarf candidates. Their distance distribution shows that the solar neighborhood census is still incomplete.
Conclusions. Gaia DR2 offers a great wealth of information on the low-mass objects. It provide a homogeneous and precise catalog of candidates worthwhile to be further characterized with spectroscopic observations.
C. Reylé
Tue, 25 Sep 18
53/88
Comments: accepted for publication in A&A, 9 pages
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