The Lowest Mass Member of the beta Pictoris Moving Group

We present spectral and kinematic evidence that 2MASS J06085283-2753583 (M8.5gamma) is a member of the beta Pictoris Moving Group (BPMG, age ~12 Myr), making it the latest-type known member of this young, nearby association. We confirm low-gravity spectral morphology at both medium and high resolutions in the near-infrared. We present new radial velocity and proper motion measurements and use these to calculate galactic location and space motion consistent with other high-probability members of the BPMG. The predicted mass range consistent with the object's effective temperature, surface gravity, spectral type, and age is 15-35 M_Jup, placing 2MASS 0608-27 well within the brown dwarf mass regime. 2MASS J06085283-2753583 is thus confidently added to the short list of very low mass, intermediate age benchmark objects that inform ongoing searches for the lowest-mass members of nearby young associations.