* Astronomy

Title: Planets Around Low-Mass Stars (PALMS). II. A Low-Mass Companion to the Young M Dwarf GJ 3629 Separated By 0.2"
Authors: Brendan P. Bowler, Michael C. Liu, Evgenya L. Shkolnik, Motohide Tamura

We present the discovery of a 0.2" companion to the young M dwarf GJ 3629 as part of our high contrast adaptive optics imaging search for giant planets around low-mass stars with the Keck-II and Subaru telescopes. Two epochs of imaging confirm the pair is co-moving and reveal signs of orbital motion. The primary exhibits saturated X-ray emission, which together with its UV photometry from GALEX point to an age younger than ~300 Myr. At these ages the companion lies below the hydrogen burning limit with a model-dependent mass of 46 ±16 Jupiter masses based on the system's photometric distance of 22 ±3 pc. Resolved YJHK photometry of the pair indicates a spectral type of M7 ±2 for GJ 3629 B. With a projected separation of 4.4 ±0.6 AU and an estimated orbital period of 21 ±5 yr, GJ 3629 AB is likely to yield a dynamical mass in the next several years, making it one of only a handful of brown dwarfs to have a measured mass and an age constrained from the stellar primary.

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