BANYAN. VI. Discovery of a Companion at the Brown Dwarf/Planet-Mass Limit to a Tucana-Horologium M Dwarf
Abstract
We report the discovery of a substellar companion to 2MASS J02192210-3925225, a young M6 γ candidate member of the Tucana-Horologium association (30-40 Myr). This L4 γ companion has been discovered with seeing-limited direct imaging observations; at a 4″ separation (160 AU) and a modest contrast ratio, it joins the very short list of young low-mass companions amenable to study without the aid of adaptive optics, enabling its characterization with a much wider suite of instruments than is possible for companions uncovered by high-contrast imaging surveys. With a model-dependent mass of 12-15 {M}{Jup}, it straddles the boundary between the planet and brown dwarf mass regimes. We present near-infrared spectroscopy of this companion and compare it to various similar objects uncovered in the last few years. The J0219-3925 system falls in a sparsely populated part of the host mass versus mass ratio diagram for binaries; the dearth of known similar companions may be due to observational biases in previous low-mass companion searches.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2015
- DOI:
- 10.1088/0004-637X/806/2/254
- arXiv:
- arXiv:1505.01747
- Bibcode:
- 2015ApJ...806..254A
- Keywords:
-
- brown dwarfs;
- stars: late-type;
- stars: low-mass;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted for publication in ApJ