The Discovery of a Companion to the Very Cool Dwarf Gliese 569B with the Keck Adaptive Optics Facility
Abstract
We report observations obtained with the Keck adaptive optics facility of the nearby (d=9.8 pc) binary Gl 569. The system was known to be composed of a cool primary (dM2) and a very cool secondary (dM8.5) with a separation of 5" (49 AU). We have found that Gl 569B is itself double with a separation of only 0.101"+/-0.002" (1 AU). This detection demonstrates the superb spatial resolution that can be achieved with adaptive optics at Keck. The difference in brightness between Gl 569B and the companion is ~0.5 mag in the J, H, and K' bands. Thus, both objects have similarly red colors and very likely constitute a very low mass binary system. For reasonable assumptions about the age (0.12-1.0 Gyr) and total mass of the system (0.09-0.15 Msolar), we estimate that the orbital period is ~3 yr. Follow-up observations will allow us to obtain an astrometric orbit solution and will yield direct dynamical masses that can constrain evolutionary models of very low mass stars and brown dwarfs.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 2000
- DOI:
- 10.1086/312450
- arXiv:
- arXiv:astro-ph/9911286
- Bibcode:
- 2000ApJ...529L..37M
- Keywords:
-
- STARS: BINARIES: GENERAL;
- STARS: EVOLUTION;
- STARS: FORMATION;
- STARS: INDIVIDUAL: ALPHANUMERIC: GL 569;
- STARS: LOW-MASS;
- BROWN DWARFS;
- SURVEYS;
- Stars: Binaries: General;
- Stars: Evolution;
- Stars: Formation;
- Stars: Individual: Alphanumeric: Gl 569;
- Stars: Low-Mass;
- Brown Dwarfs;
- Surveys;
- Astrophysics
- E-Print:
- doi:10.1086/312450