No close companions to a sample of bright sdB stars

TL;DR

This study uses high-precision radial velocity data to set upper limits on the presence of close companions around bright sdB stars, finding no evidence of such companions and highlighting unresolved questions about their formation.

Contribution

It provides the first high-precision radial velocity constraints on the masses of potential close and wider companions to bright sdB stars.

Findings

No close companions detected above a few Jupiter masses.

Upper limits established for wider orbit companions for some stars.

Results suggest these sdB stars are likely single or have very low-mass companions.

Abstract

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.