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Title:
16-20 MJup Radial Velocity Companion Orbiting the Brown Dwarf Candidate Cha Halpha 8
Authors:
Joergens, V.; Müller, A.
Affiliation:
AA(Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany ), AB(Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg, Germany )
Publication:
The Astrophysical Journal, Volume 666, Issue 2, pp. L113-L116. (ApJL Homepage)
Publication Date:
09/2007
Origin:
UCP
Astronomy Keywords:
Stars: Binaries: Spectroscopic, Stars: Planetary Systems, stars: individual ([NC98] Cha HA 8), Stars: Low-Mass, Brown Dwarfs, Stars: Pre-Main-Sequence, Techniques: Radial Velocities
DOI:
10.1086/521825
Bibliographic Code:
2007ApJ...666L.113J

Abstract

We report the discovery of a 16-20 MJup radial velocity companion around the very young (~3 Myr) brown dwarf candidate Cha Halpha 8 (M5.75-M6.5). Based on high-resolution echelle spectra of Cha Halpha 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-1. 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 M2sini between 16 and 20 MJup is 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 Halpha 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 Halpha 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.

Based on observations obtained at the Very Large Telescope of the European Southern Observatory at Paranal, Chile, in programs 75.C-0851(C), 77.C-0831(A+D), and 278.C-5061(A).

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