Planets Around Low-Mass Stars (PALMS). II. A Low-Mass Companion to the Young M Dwarf GJ 3629 Separated By 0.2"

TL;DR

This paper reports the discovery of a low-mass brown dwarf companion to the young M dwarf GJ 3629, confirmed through high-contrast imaging, with potential for dynamical mass measurement in the near future.

Contribution

First direct imaging detection of a low-mass companion to GJ 3629 with orbital and age constraints, enabling future dynamical mass determination.

Findings

Companion is below hydrogen burning limit with ~46 Mjup.

System is younger than ~300 Myr based on activity indicators.

Projected orbital period is approximately 21 years.

Abstract

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 Mjup 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.