HR 2142: A Semi-Detached Interacting Binary?

Abstract

The energy distribution of HR 2142 is studied in order to test the hypothesis that this star is an interacting binary with a cool Roche–lobe filling companion. We find that, for any reasonable choice of T _eff, the companion should have been detected in the red part of the spectrum. We propose instead that the Be star is the outcome of a case B mass-transfer, which has pun it up. It is now surrounded by a mass-loss disc, rather than an accretion disc and is accompanied by either a helium star (resembling the Φ Per system) or by a white dwarf. If the binary was born spinning rapidly, alternatively the companion may be a solar-type, unevolved main sequence star. In case of a Helium star companion, there may be Helium lines visible (like in Φ Per), or the helium star may be detectable in the XUV, e.g. by the ROSAT XUV instrument. A white dwarf companion may be accreting material from the disc around the Be star and may show low luminosity X-ray emission. This emission may have been seen in the ROSAT PSPC X-Ray Survey.