July 11-15, 2011
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Mass-loss and wind properties of six O-type stars in a low-metallicity environment

Frank Tramper (API, University of Amsterdam)

H. Sana, A. de Koter and L. Kaper, Astronomical Institute 'Anton Pannekoek', University of Amsterdam

Because the massive-star winds are mostly driven by radiation pressure on metallic ion lines, their intensity should vary with metallicity. Indeed, theory predicts the mass loss to scale as Z^0.69, and this has been verified for the most luminous massive stars in the Galaxy, LMC and SMC. To further test this prediction, we have collected X-Shooter spectra of several O-type stars in the low-metallicity galaxies IC 1613, WLM and NGC 3109 (each at Z ~ 0.14 Z_sun). This poster presents the first results of our quantitative spectroscopic analysis. Using the combination of the state-of-the-art line-blanketed NLTE atmosphere model FASTWIND with a genetic algorithm fitting approach, we have determined the stellar and wind properties of our targets. We discuss their mass-loss characteristics and their evolutionary state, as well as the implications of our findings for the stellar wind and massive star evolution theories.

Mode of presentation: poster