2007ApJ...666L.113J

We report the discovery of a 16-20 M_Jup 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 M_Jupis 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.