Astrometric orbits of spectral binary brown dwarfs - I. Massive T dwarf companions to 2M1059-21 and 2M0805+48
Abstract
Near-infrared spectroscopic surveys have uncovered a population of short-period, blended-light spectral binaries composed of low-mass stars and brown dwarfs. These systems are amenable to orbit determination and individual mass measurements via astrometric monitoring. Here, we present first results of a multiyear campaign to obtain high-precision absolute astrometry for spectral binaries using the Gemini-South and Gemini-North GMOS imagers. We measure the complete astrometric orbits for two systems: 2M0805+48 and 2M1059-21. Our astrometric orbit of 2M0805+48 is consistent with its 2-yr radial velocity orbit determined previously and we find a mass of 66-14+5 MJup for its T5.5 companion. For 2M1059-21, we find a 1.9-yr orbital period and a mass of 67-5+4 MJup for its T3.5 companion. We demonstrate that sub-milliarcsecond absolute astrometry can be obtained with both GMOS imagers and that this is an efficient avenue for confirming and characterizing ultracool binary systems.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- June 2020
- DOI:
- 10.1093/mnras/staa1235
- arXiv:
- arXiv:2004.14889
- Bibcode:
- 2020MNRAS.495.1136S
- Keywords:
-
- binaries: close;
- brown dwarfs;
- astrometry;
- parallaxes;
- stars: low-mass;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics
- E-Print:
- 14 pages, 13 figures, accepted for publication in MNRAS