Evidence for accretion in a nearby, young brown dwarf

Abstract

We report on the discovery of the young, nearby, brown dwarf 2MASS J0041353-562112. The object has a spectral type of M7.5; it shows Li absorption and signatures of accretion, which implies that it still has a disk and suggests an age below 10Myr. The space motion vector and position on the sky indicate that the brown dwarf is probably a member of the ∼20Myr old Tuc-Hor association, or that it may be an ejected member of the ∼12Myr old βPic association; both would imply that 2MASS J0041353-562112 may in fact be older than 10Myr. No accreting star or brown dwarf was previously known in these associations. Assuming an age of 10Myr, the brown dwarf has a mass of about 30M Jup and is located at 35pc distance. The newly discovered object is the closest accreting brown dwarf known. Its membership to an association older than 10Myr implies that either disks in brown dwarfs can survive as long as in more massive stars, perhaps even longer, or that star formation in Tuc-Hor or β Pic occurred more recently than previously thought. The history and evolution of this object can provide new fundamental insight into the formation process of stars, brown dwarfs, and planets. © 2009. The American Astronomical Society.