Letter to the Editor

Discovery of a nearby young brown dwarf binary candidate

¹ Universität Göttingen, Institut für Astrophysik, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany e-mail: Ansgar.Reiners@phys.uni-goettingen.de
² Department of Physics, University of California, One Shields Avenue, Davis, CA 95616, USA

Received: 5 February 2010
Accepted: 5 March 2010

Abstract

In near-infrared NaCo observations of the young brown dwarf 2MASS J0041353-562112, we discovered a companion a little less than a magnitude fainter than the primary. The binary candidate has a separation of 143 mas, and the spectral types of the two components are M 6.5 and M 9.0. Colors and flux ratios of the components are consistent with their locations being at the same distance minimizing the probability of the secondary being a background object. The brown dwarf is known to exhibit Li absorption constraining the age to be younger than ~ 200 Myr, and has been suspected of experiencing ongoing accretion, which implies an age as young as ~ 10 Myr. We estimate distance and orbital parameters of the binary as a function of age. For an age of 10 Myr, the distance to the system is 50 pc, the orbital period is 126 yr, and the masses of the components are ~ 30 and ~ 15 M_Jup. The binary brown dwarf fills a so far unoccupied region in the parameters mass and age; it is a valuable new benchmark object for brown dwarf atmospheric and evolutionary models.