We have used the 2MASS all-sky survey and the WISE to look for ultracool dwarfs that are part of multiple systems containing main sequence stars. We cross-matched L dwarf candidates from the surveys with Hipparcos and Gliese stars, finding two new systems. The first system, G255-34AB is an L2 dwarf companion to a K8 star, at a distance of 36 pc. We estimate its bolometric luminosity as log (L/Lsolar) = -3.78 +/- 0.045 and Teff = 2080 +/- 260 K. The second system, GJ499ABC, is a triple, with an L5 dwarf as a companion to a binary with an M4 and K5 star. These two new systems bring the number of L dwarf plus main sequence star multiple systems to twenty four, which we discuss. We consider the binary fraction for L dwarfs and main sequence stars, and further assess possible unresolved multiplicity within the full companion sample. This analysis shows that some of the L dwarfs in this sample might actually be unresolved binaries themselves, since their MJ appears to be brighter than the expected for their spectral types.
@article{arxiv.1303.2268,
title = {Two new ultra-cool benchmark systems from WISE+2MASS},
author = {J. I. Gomes and D. J. Pinfield and F. Marocco and A. C. Day-Jones and B. Burningham and Z. H. Zhang and H. R. A. Jones and L. van Spaandonk and D. Weights},
journal= {arXiv preprint arXiv:1303.2268},
year = {2015}
}