IUE and ground based observations of the LMC star S Dor.

Abstract

IUE and ground-based spectrograms of the luminous Hubble-Sandage variable S Doradus of the Large Magellanic Cloud are presented. The two low-resolution IUE spectrographs covering the range 1150-3100 A are found to be dominated by strong absorption features of singly ionized metallic lines, with the resonance lines of C IV at 1548 and 1551 A and of Si IV at 1394 and 1402 A also apparent. High-resolution ground based coude spectrograms otained at stellar maximum reveal V magnitudes in agreement with IUE values and are dominated by strong Balmer lines and metallic lines characteristic of spectral type A2-A5. The observed continuum energy distribution is explained by the superposition of the radiation of an early A type supergiant photosphere and a surrounding envelope which produces Balmer continuum radiation. The visual line profiles indicate a time-dependent mass loss rate of approximately 0.0007 solar masses/year, and implications of this very strong mass loss on the evolution of S Dor are discussed.