Substellar Companions to Main-sequence Stars: No Brown Dwarf Desert at Wide Separations

We use three field L and T dwarfs that were discovered to be wide companions to known stars by the Two Micron All-Sky Survey to derive a preliminary brown dwarf companion frequency. Observed L and T dwarfs indicate that brown dwarfs are not unusually rare as wide ( AU) systems to F–M0 main-sequence stars D 1 1000 ( , ), even though they are rare at close separation ( AU; the “brown dwarf desert”). M 1 0.5 M M ! 9.5 D ! 3 , V Stellar companions in these separation ranges are equally frequent, but brown dwarfs are 10 times as frequent for wide than close separations. A brown dwarf wide-companion frequency as low as the 0.5% seen in the brown dwarf desert is ruled out by currently available observations. Subject headings: binaries: general — stars: low-mass, brown dwarfs