Direct-imaging discovery of a 12–14 Jupiter-mass object orbiting a young binary system of very low-mass stars^⋆

¹ UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
e-mail: Philippe.Delorme@obs.ujf-grenoble.fr
² Département de physique and Observatoire du Mont Mégantic, Université de Montréal, C.P. 6128, Succursale Centre-Ville, Montréal, QC H3C 3J7, Canada
³ European Southern Observatory, Alonso de Córdova 3107, Vitacura, Cassilla 19001, Santiago, Chile
⁴ Department of Astrophysics, American Museum of Natural History, Central Park West at 79th Street, New York, NY 10034, USA
⁵ Max Planck Institute for Astronomy, Königstuhl 17, 69117 Heidelberg, Germany

Received: 25 January 2013
Accepted: 18 March 2013

Abstract

Context. Though only a handful of extrasolar planets have been discovered via direct-imaging, each of these discoveries had a tremendous impact on our understanding of planetary formation, stellar formation, and cool atmosphere physics.

Aims. Since many of these newly imaged giant planets orbit massive A or even B stars, we investigate whether giant planets could be found orbiting low-mass stars at large separations.

Methods. We have been conducting an adaptive optic imaging survey to search for planetary-mass companions of young M dwarfs in the solar neigbourhood, in order to probe different initial conditions of planetary formation.

Results. We report here the direct-imaging discovery of 2MASS J01033563-5515561(AB)b, a 12–14 M_Jup companion at a projected separation of 84 AU from a pair of young late-M stars, with which it shares proper motion. We also detected a Keplerian-compatible orbital motion.

Conclusions. This young L-type object at the planet/brown dwarf mass boundary is the first ever imaged around a binary system at a separation compatible with formation in a disc.