Context. The discovery of brown dwarfs (BDs) in the solar neighborhood and
young star clusters has helped to constraint the low-mass end of the stellar
mass function and the initial mass function. We use data of the Vista Variables
in the V\'ia L\'actea (VVV), a near-infrared (NIR) multiwavelength (Z Y J H Ks)
multi-epoch (Ks) ESO Public Survey mapping the Milky Way bulge and southern
Galactic plane to search for nearby BDs.
Aims. The ultimate aim of the project is to improve the completeness of the
census of nearby stellar and substellar objects towards the Galactic bulge and
inner disk regions.
Methods. Taking advantage of the homogeneous sample of VVV multi-epoch data,
we identified stars with high proper motion (> 0.1"/yr), and then selected
low-mass objects using NIR colors. We searched for a possible parallax
signature using the all available Ks band epochs. We set some constraints on
the month-to-year scale Ks band variability of our candidates, and even
searched for possible transiting companions. We obtained NIR spectra to
properly classify spectral type and then the physical properties of the final
list of candidates.
Results. We report the discovery of VVV BD001, a new member of the local
volume-limited sample (within 20pc from the sun) with well defined proper
motion, distance, and luminosity. The spectral type of this new object is an
L5+-1, unusually blue dwarf. The proper motion for this BD is
PM(\alpha)=-0.5455+-0.004 "/yr, PM(\delta)=-0.3255+-0.004 "/yr, and it has a
parallax of 57+-4 mas which translates into a distance of 17.5 +- 1.1 pc. VVV
BD001 shows no evidence of variability (\Delta Ks <0.05mag) over two years,
especially constrained on a six month scale during the year 2012.Comment: 5 pages, 4 figures, 1 table, Accepted for publication in Astronomy
and Astrophysics Letter
