Mass ratio of the 2 pc binary brown dwarf LUH 16 and limits on planetary companions from astrometry
Abstract
We analyse FORS2/VLT I-band imaging data to monitor the motions of both components in the nearest known binary brown dwarf WISE J104915.57-531906.1AB (LUH 16) over one year. The astrometry is dominated by parallax and proper motion, but with a precision of ∼0.2 mas per epoch we accurately measure the relative position change caused by the orbital motion of the pair. This allows us to directly measure a mass ratio of q = 0.78 ± 0.10 for this system. We also search for the signature of a planetary-mass companion around either of the A and B component and exclude at 3σ the presence of planets with masses larger than 2 MJ and orbital periods of 20-300 d. We update the parallax of LUH 16 to 500.51 ± 0.11 mas, i.e. just within 2 pc. This study yields the first direct constraint on the mass ratio of LUH 16 and shows that the system does not harbour any close-in giant planets.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2015
- DOI:
- 10.1093/mnrasl/slv113
- arXiv:
- arXiv:1506.07994
- Bibcode:
- 2015MNRAS.453L.103S
- Keywords:
-
- astrometry;
- parallaxes;
- binaries: visual;
- brown dwarfs;
- stars: individual: WISE J104915.57-531906.1;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 6 pages, 7 figures. Accepted for publication in MNRAS letters. Minor changes compared to previous version