At that distance, the visual magnitude of the star is diminished by an estimated extinction factor of 0m.02 because of interstellar dust.
[4] The chemical abundance of elements other than hydrogen and helium, what astronomers term the star's metallicity, is less than half that in the Sun.
The method consists of taking the host star's RUWE level—an astrometirc indicator— from the astrometric solution.
A large RUWE could imply that there is an unseen companion around the star, or that there are systematic calibration errors in the astrometric solution.
Assuming the former scenario, the mass of Upsilon Leonis b is measured at 29.2 MJ, indicating that it is a brown dwarf, but the latter scenario is still a possibility, which means that this measured mass is likely an upper limit.