The SOPHIE search for northern extrasolar planets VIII. Follow-up of ELODIE candidates: long-period brown-dwarf companions

TL;DR

This study reports the discovery of five long-period brown dwarf companions around solar-type stars, doubling the known population and highlighting their increasing occurrence with orbital separation, using 20 years of radial velocity data.

Contribution

It presents five new long-period brown dwarf detections, providing mass limits and emphasizing their suitability for direct imaging, thus advancing understanding of substellar companion demographics.

Findings

Five new brown dwarf companions with 32-83 Jupiter masses identified.

Brown dwarf occurrence increases with orbital separation.

All candidates are suitable for high-contrast imaging.

Abstract

Long-period brown dwarf companions detected in radial velocity surveys are important targets for direct imaging and astrometry to calibrate the mass-luminosity relation of substellar objects. Through a 20-year radial velocity monitoring of solar-type stars that began with ELODIE and was extended with SOPHIE spectrographs, giant exoplanets and brown dwarfs with orbital periods longer than ten years are discovered. We report the detection of five new potential brown dwarfs with minimum masses between 32 and 83 Jupiter mass orbiting solar-type stars with periods longer than ten years. An upper mass limit of these companions is provided using astrometric Hipparcos data, high-angular resolution imaging made with PUEO, and a deep analysis of the cross-correlation function of the main stellar spectra to search for blend effects or faint secondary components. These objects double the number of known brown dwarf companions with orbital periods longer than ten years and reinforce the conclusion that the occurrence of such objects increases with orbital separation. With a projected separation larger than 100 mas, all these brown dwarf candidates are appropriate targets for high-contrast and high angular resolution imaging.