16-20 MJup radial velocity companion orbiting the brown dwarf candidate Cha Hα 8.
JOERGENS V. and MULLER A.
Abstract (from CDS):
We report the discovery of a 16-20 MJup radial velocity companion around the very young (∼3 Myr) brown dwarf candidate Cha Hα 8 (M5.75-M6.5). Based on high-resolution echelle spectra of Cha Hα 8 taken between 2000 and 2007 with UVES at the VLT, a companion was detected through RV variability with a semiamplitude of 1.6 km/s. A Kepler fit to the data yields an orbital period of the companion of 1590 days and an eccentricity of e=0.49. A companion minimum mass M2 sini between 16 and 20 MJupis derived when using model-dependent mass estimates for the primary. The mass ratio q≡M2/M1 might be as small as 0.2 and, with a probability of 87%, it is less than 0.4. Cha Hα 8 harbors most certainly the lowest mass companion detected so far in a close (∼1 AU) orbit around a brown dwarf or very low mass star. From the uncertainty in the orbit solution, it cannot completely be ruled out that the companion has a mass in the planetary regime. Its discovery is in any case an important step toward RV planet detections around brown dwarfs. Further, Cha Hα 8 is the fourth known spectroscopic brown dwarf or very low mass binary system with an RV orbital solution and the second known very young one.
Stars: Binaries: Spectroscopic - Stars: Planetary Systems - stars: individual ([NC98] Cha HA 8) - Stars: Low-Mass, Brown Dwarfs - Stars: Pre-Main-Sequence - Techniques: Radial Velocities