HD 160538 and HD 185510 : two active-chromosphere stars with hot companions.

Abstract

Short-wavelength ultraviolet spectra of two active-chromosphere giants, HD 160538 and HD 185510, show hot stellar continua and Lα absorption features. The hot companion of HD 160538 is a white dwarf whose ultraviolet spectrum is matched best to the energy distribution of a T_eff = 30000K and log g = 8 model atmosphere. The ultraviolet spectrum of HD 185510 shows numerous absorption features and is identified as a B subdwarf. Since the giant star of each of these binary systems has no known abundance anomalies, these systems appear to be consistent with the mass-transfer scenario of barium-star formation.