THE PHYSICS OF MASSIVE OB STARS IN DIFFERENT PARENT GALAXIES .1. ULTRAVIOLET AND OPTICAL SPECTRAL MORPHOLOGY IN THE MAGELLANIC CLOUDS

HST/FOS and ESO 3.6-m/CASPEC observations have been made of 18 stars r anging in spectral type from O3 through B0.5 Ia, half of them in each of the Large and Small Magellanic Clouds, in order to investigate mass ive stellar winds and evolution as a function of metallicity. The spec troscopic data are initially presented and described here in an atlas format. The relative weakness of the stellar-wind features in the SMC early OV spectra, due to their metal deficiency, is remarkable. Becaus e of their unsaturated profiles, discrete absorption components can be detected in many of them, which is generally not possible in LMC and Galactic counterparts at such early types, or even in SMC giants and s upergiants. On the other hand, an O3 III spectrum in the SMC has a wea k C IV but strong N V wind profile, possibly indicating the presence o f processed material. Wind terminal velocities are also given and inte rcompared between similar spectral types in the two galaxies. In gener al, the terminal velocities of the SMC stars are smaller, in qualitati ve agreement with the predictions of radiation-driven wind theory. Fur ther analyses in progress will provide atmospheric and wind parameters for these stars, which will be relevant to evolutionary models and th e interpretation of composite starburst spectra.