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Paper: Discovery of an 18-Jupiter-Mass RV Companion Orbiting the Brown Dwarf Candidate Cha Hα8
Volume: 398, Extreme Solar Systems
Page: 47
Authors: Joergens, V.; Müller, A.
Abstract: We report the discovery of a 16–20MJup radial velocity companion around the very young (∼3Myr) brown dwarf candidate ChaHα 8 (M5.75– M6.5). Based on high-resolution echelle spectra of ChaHα 8 taken between 2000 and 2007 with UVES at the VLT, a companion was detected through RV variability with a semi-amplitude of 1.6 kms−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 M2 sin i between 16 and 20MJup is derived when using model-dependent mass estimates for the primary. The mass ratio qM2/M1 might be as small as 0.2 and, with a probability of 87%, it is less than 0.4. ChaHα 8 harbors most certainly the lowest mass companion detected so far in a close (∼ 1AU) 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 towards RV planet detections around BDs. Further, ChaHα 8 is the fourth known spectroscopic brown dwarf or very low-mass binary system with an RV orbit solution and the second known very young one.
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