Balloon-borne Ultraviolet Stellar Spectrograph. II. Highlights of first observational results.

We describe a few of the most important features, visible in a first inspection of the high- resolution (0.1 A) mid-ultraviolet spectra ( A) of 33 stars obtained in two BUSS flights. The profiles of the Mg ii lines in early-type (B8-A2) supergiants show the existence of considerable mass flow, partly in irregular "puffs." The features in Mg ii in Betelgeuse are due to a cool expanding outer shell above a hotter chromospheric region. Emission features in the shell star Tau indicate infalling material, while the Be star 4) Per has a mass outflow. We have detected some 80 emission lines of Fe I, Fe ii, and Fe iii in spectra of late-type giants and supergiants. The composite spectrum of the binary a Sco (M1.5 lab + B2.5 V) is described, with particular reference to circumstellar lines. Subject headings: line identifications - stars: Be - stars: mass loss - stars: supergiants - ultraviolet: spectra