The ultraviolet spectrum of the eclipsing binary IM Aurigae.

Abstract

After recent ground-based photometry of the eclipsing Algol-type system IM Aurigae showed a rapid increase in O-C values of the primary minimum, a spectral search at ultraviolet wavelengths was conducted for evidence of a recent mass-loss "event". Low-dispersion IUE spectra were obtained at primary and secondary minima, as well as a high-dispersion spectrum near maximum. Weak, sharp absorption features are seen at two distinct velocities in the high-dispersion data. These features are attributed to circumbinary gaseous shells and/or gas streams between the stellar components. The time of primary minimum observed utilizing the Fine Error Sensor of the IUE agreed with that predicted by the original ephemeris appropriate to the time prior to the onset of the increased O-C values. The implications of the results are discussed.