The ultra-violet spectrum of the peculiar early-type supergiant, HD 157038.

Abstract

Ultra-violet spectra of the nitrogen rich supergiant, HD 157038, are presented and compared with those of the normal supergiant, HD 148379. The P-Cygni profiles of the Si IV and C IV resonance lines are very similar, implying that the stars have similar masses; this is evidence against HD 157038 being in a post red supergiant evolutionary stage and evolving toward higher effective temperatures. Comparison of observed fluxes with those deduced from LTE model atmosphere calculations, confirms the peculiar far ultra-violet extinction in the spectra of HD 157038. The possibility that this is due to circumstellar material is briefly discussed.