FAR ULTRAVIOLET SPECTROSCOPIC EXPLORER OBSERVATIONS OF THE STELLAR WINDS OF TWO O7 SUPERGIANTS IN THE MAGELLANIC CLOUDS

摘要

We compare the stellar wind features in far-UV spectra of Sk — 67°111, an O7 Ib(f) star in the LMC, with Sk 80, an O7 Iaf+ star in the SMC. The most striking differences are that Sk 80 has a substantially lower terminal velocity, much weaker O Ⅵ absorption, and stronger S Ⅳ emission. We have used line-blanketed, hydrodynamic, non-LTE atmospheric models to explore the origin of these differences. The far-UV spectra require systematically lower stellar temperatures than previous determinations for O7 supergiants derived from plane-parallel, hydrostatic models of photospheric line profiles. At these temperatures, the O Ⅵ in Sk -67°111 must be due primarily to shocks in the wind.