Evidence for a high-temperature accretion region in Algol-type binarysystems.

Abstract

The recent discovery of strong absorption lines of N V, C IV, and Si IV in the UV spectra of Algol primaries, whose photospheric temperatures are much too cool to form such ions, has suggested the presence of a high-temperature component in the circumstellar matter in these systems. The authors have employed timed, high-resolution IUE observations to determine the location and distribution of this gas and the type of system in which it is found. The observed radial velocity behavior and phase dependence in the strengths of the lines provide compelling evidence that the high-temperature matter is associated with the primary, and the source of the heating is the shock from the impact of the gas stream onto the stellar surface. It is postulated that the accretion region is formed from recently transferred matter from the original core of the mass-losing secondary.