The winds of hot stars in external galaxies .3. HST UV spectroscopy of O and B supergiants in M31 and M33

HST Faint Object Spectrograph (FOS) UV (1200-3300 Angstrom) spectra of nine late-O and early-B supergiants in M31, and one B1.5 supergiant in M33, are presented. The morphologies of the UV line spectra are discussed and compared with those of Galactic and Magellanic Cloud stars of similar optical spectral type. The UV spectral signatures of the M31 and M33 supergiants are similar to the comparison stars, in general, with some differences due to metallicity effects. Chemical peculiarities are seen in three M31 supergiants. The strength of the P Cygni profiles in the wind lines indicates abundances similar to the LMC in M33, and similar to our Galaxy in M31. Wind velocities in M31 supergiants are comparable to Galactic values. Narrow absorption components at high velocity are seen in the wind of the M33 supergiant, revealing clumpiness in the wind. (C) 1996 American Astronomical Society.