2010A&A...513L...9R

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 143mas, and the spectral types of the two components are M6.5 and M9.0. 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 ∼200Myr, and has been suspected of experiencing ongoing accretion, which implies an age as young as ∼10Myr. We estimate distance and orbital parameters of the binary as a function of age. For an age of 10Myr, the distance to the system is 50pc, the orbital period is 126yr, and the masses of the components are ∼30 and ∼15M_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.