IUE observations of mass-loss spectral features in B5-B9 supergiants.

Abstract

A survey of IUE spectra is presented for supergiants of spectral class B5-B9 illustrating the behavior of line profiles associated with mass-loss effects. The main purpose of this survey is to better identify the spectral mass-loss features which occur in such stars in order to present a clearer observational picture of the nature and the timescale of their variability. Time varying 'narrow' or 'discrete absorption components' (DAC) are detected across the full spectral class range but for the Ia supergiants only. Significant variations in the wind C IV and Si IV profiles are observed corresponding to different mass-loss episodes. The line strengths and the edge velocities of the wind profiles in the higher ionization ions and their time variability tend to decrease towards later spectral type. However, details of systematic trends with effective temperature are obscured somewhat by the scale of variability which is observed for a given star.