Exploring the brown dwarf desert: new substellar companions from the SDSS-III MARVELS survey

Abstract

Planet searches using the radial velocity technique show a paucity of\ncompanions to solar-type stars within ~5 AU in the mass range of ~10 - 80\nM$_{\\text{Jup}}$. This deficit, known as the brown dwarf desert, currently has\nno conclusive explanation. New substellar companions in this region help asses\nthe reality of the desert and provide insight to the formation and evolution of\nthese objects. Here we present 10 new brown dwarf and two low-mass stellar\ncompanion candidates around solar-type stars from the Multi-object APO\nRadial-Velocity Exoplanet Large-Area Survey (MARVELS) of the Sloan Digital Sky\nSurvey III (SDSS-III). These companions were selected from processed MARVELS\ndata using the latest University of Florida Two Dimensional (UF2D) pipeline,\nwhich shows significant improvement and reduction of systematic errors over\nprevious pipelines. The 10 brown dwarf companions range in mass from ~13 to 76\nM$_{\\text{Jup}}$ and have orbital radii of less than 1 AU. The two stellar\ncompanions have minimum masses of ~98 and 100 M$_{\\text{Jup}}$. The host stars\nof the MARVELS brown dwarf sample have a mean metallicity of [Fe/H] = 0.03\n$\\pm$ 0.08 dex. Given our stellar sample we estimate the brown dwarf occurrence\nrate around solar-type stars with periods less than ~300 days to be ~0.56%.\n