The Evolutionary State of Zeta Aurigae

Abstract

Ultraviolet studies, originally undertaken to ascertain the state of the atmosphere of the K-supergiant component of the zeta Aurigae system, have been sidetracked by the discovery of significant accretion effects. An analysis of the phase dependence of the profiles of resonance lines in Mg II and C IV has led to a qualitative model of the wind flow from the K star. At the position of the B star, the flow velocity is about 100 km/sec and the density is 3 × 10⁻⁶ cm⁻³, leading to a mass loss rate of 2 × 10⁻⁸ solar masses per year. This wind interacts with the B star in a shock, which will be described, leading to accretion on the B star at a rate of 4 × 10⁻¹⁰ solar masses per year.