16-20 Jupiter mass RV companion orbiting the brown dwarf candidate ChaHa8

TL;DR

This paper reports the discovery of a 16-20 Jupiter mass companion orbiting the young brown dwarf candidate ChaHa8, marking a significant step in radial velocity planet detection around brown dwarfs and very low-mass stars.

Contribution

It presents the first detection of a low-mass companion in a close orbit around a young brown dwarf using radial velocity measurements, expanding the known range of such systems.

Findings

Companion mass between 16 and 20 Jupiter masses.

Orbital period of approximately 1590 days.

Mass ratio possibly less than 0.4.

Abstract

We report the discovery of a 16-20 Jupiter mass radial velocity companion around the very young (~3 Myr) brown dwarf candidate ChaHa8 (M5.75-M6.5). Based on high-resolution echelle spectra of ChaHa8 taken between 2000 and 2007 with UVES at the VLT, a companion was detected through RV variability with a semi-amplitude 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 M2sini between 16 and 20 Jupiter masses 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. ChaHa8 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 towards RV planet detections around BDs. Further, ChaHa8 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.