No close companions to a sample of bright sdB stars

In this article we present preliminary results on the upper limits to the mass of a companion for 8 apparently single subdwarf B stars, derived from high-precision radial velocity measurements obtained from Harps-N spectra. These limits, corresponding to a few Jupiter masses, show that these stars do not have close companions and keep open the unresolved question of the mechanism that caused the almost complete loss of the envelope for the giant precursors of these stars. For 4 stars with a larger data coverage, it was also possible to set upper limits to the mass of a more massive companion in a wider orbit.