The SOPHIE search for northern extrasolar planets IX. Populating the brown dwarf desert

TL;DR

This study expands the sample of brown dwarf companions around solar-type stars using radial velocity and astrometric data, addressing the brown dwarf desert and informing formation theories.

Contribution

It provides new orbital and mass characterizations of 15 companions, including 9 sub-stellar objects, enhancing understanding of the brown dwarf population around solar-type stars.

Findings

Nine companions have masses between 13 and 70 M_Jup.

Six companions are stellar with masses up to 0.35 M_sun.

Improved orbital parameters for two known sub-stellar candidates.

Abstract

Radial velocity planet search surveys of nearby Solar-type stars have shown a strong deficit of brown dwarf companions within $\sim5\,\mathrm{AU}$. There is presently no comprehensive explanation of this lack of brown dwarf companions, therefore, increasing the sample of such objects is crucial to understand their formation and evolution. Based on precise radial velocities obtained using the SOPHIE spectrograph at Observatoire de Haute-Provence we characterise the orbital parameters of $15$ companions to solar-type stars and constrain their true mass using astrometric data from the Hipparcos space mission. The nine companions not shown to be stellar in nature have minimum masses ranging from ~$13$ to $70\,\mathrm{M}_{\mathrm{Jup}}$, and are well distributed across the planet/brown dwarf mass regime, making them an important contribution to the known population of massive companions around solar-type stars. We characterise six companions as stellar in nature with masses ranging from a minimum mass of $76 \pm 4\,\mathrm{M}_{\mathrm{Jup}}$ to a mass of $0.35 \pm 0.03\,\mathrm{M_\odot}$. The orbital parameters of two previously known sub-stellar candidates are improved.