Far Ultraviolet Spectroscopic Explorer observations of the stellar winds of two O7 supergiants in the magellanic clouds

We compare the stellar wind features in far-UV spectra of Sk -67 degrees 11 1, 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 termina l velocity, much weaker O VI absorption, and stronger S IV emission. We hav e used line-blanketed, hydrodynamic, non-LTE atmospheric models to explore the origin of these differences. The Tar-UV spectra require systematically lower stellar temperatures than previous determinations for O7 supergiants derived from plane-parallel, hydrostatic models of photospheric line profil es. At these temperatures, the O VI in Sk -67 degrees 111 must be due prima rily to shocks in the wind.