AAS 195th Meeting, January 2000
Session 6. Early Results from the FUSE Mission
Display, Wednesday, January 12, 2000, 9:20am-6:30pm, Grand Hall

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[6.23] FUSE Observations of the Stellar Winds of Two O7 Supergiants in the Magellanic Clouds

A. W. Fullerton (UVic & JHU), J. B. Hutchings (DAO/HIA/CNRC), A. J. Willis (UCL), G. Sonneborn (NASA/GSFC), L. Bianchi (JHU), K. R. Brownsberger (CU/CASA), P. A. Crowther (UCL), D. L. Massa (Raytheon STX/GSFC), FUSE Science Team

The main goal of the FUSE hot-star program is to characterize the stellar winds of a large sample of early-type stars in the Galaxy, LMC, and SMC in order to study mass loss as a function of metallicity. As the first step in this program, we compare the stellar wind features observed in FUSE spectra of Sk~-67\circ111, an O7~Ib(f) star in the LMC, with those of Sk~80 = AV~232, an O7~Iaf+ star in the SMC. These features include the resonance doublets of S~{\sc iv} \lambda\lambda 1063, 1073, P~{\sc v} \lambda\lambda 1118, 1128 (which is blended with the excited transitions of Si~{\sc iv} \lambda\lambda 1122, 1128), and O~{\sc vi} \lambda\lambda1032, 1038. These ionic species sample a wider range of temperatures and provide a more comprehensive indication of the ionization balance at different locations in the wind than the diagnostics found in the IUE/HST wavebands. Consequently, they revive the possibility of using resonance lines to determine accurate mass-loss rates. The FUSE observations of Sk~-67\circ111 and Sk~80 reveal striking differences in the strength and morphology of the O~{\sc vi} wind profile, and confirm that stars in the SMC have smaller outflow velocities than their counterparts in the LMC.

This work is supported by NASA contract NAS5-32985.

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