Eclipsing binary V658 Carinae (HD 92406) containing a shell star and a hot low-mass star in the post-Algol stage

Abstract

Further studies of the binary V658 Car (HD 92406) have now confirmed its unique main features, i.e. a shell star primary component being eclipsed by a hot low-mass star. Obviously, this binary is in its post-Algol evolutionary stage, and containing a rapidly rotating primary star and a contracting hot companion star. The analysis of old radial-velocity data indicating a primary star of lower mass has now resulted in amended parameters for the binary. According to stellar models the primary star should have a mass of 2.16 +/- 0.14 Msun and a radius of 1.64 +/- 0.04 Rsun for a Teff of 9700 +/- 500 K based on known spectral type A0p. For the secondary star 1.46 +/- 0.04 Rsun and 12750 +/- 700 K Teff have been derived and are fitting well to an existing evolutionary track for a contracting white dwarf precursor of 0.28 Msun. Our photometric results have confirmed the concave shape of the large decretion disk surrounding the primary star, as predicted by existing models.