Progress in ultraviolet stellar spectrophotometry with S59

Abstract

A progress report is given of investigations related to observations of stellar spectra obtained with the ultraviolet stellar spectrophotometer S59 aboard the ESRO TD-1A satellite. We describe first the processing of the observations: intensity and wavelength calibration, identification of lines, classification of spectra. Thereafter some important groups of lines are dealt with: non-LTE computation of the Mgii lines are presented: apart from the peculiar emission line and shell stars they compare well with the observations; intensity ratios, of Feii and Feiii lines are an important temperature classification criterion. Interstellar UV lines indicate large deficiencies of some metals, as compared to solar values. A new ultraviolet continuous extinction curve is determined. We discuss the strong outstreaming motions observed in α Cygni, and the consequent mass loss of this star (< 3 × 10−10\(\mathfrak{M}_ \odot \) yr−1and finally we describe the composite spectrum of the (WC8+09I) bnary γ2 Velorum; the ultraviolet continuous spectrum of the WC star is about one magnitude brighter than any theory predicts.