Mass Reclassification of Companion Objects at the Planet–Brown Dwarf Boundary

This work focuses on the characterization of 71 stellar systems, each hosting a companion with a mass close to the planet–brown dwarf boundary (conventionally adopted as $13M_{Jup}$), orbiting around primary stars with masses below 2 solar masses. The main goal is to refine the mass classification of the companions by combining radial velocity, astrometric, and direct imaging data through the use of the \texttt{orvara} software. A final discussion on the formation mechanisms of these substellar companions is included, investigating a possible transition mass between core accretion and gravitational instability, and considering a possible dependence on the host star mass.