Stellar Winds in the Small Magellanic Cloud

Abstract

According to the predictions of line-driven stellar wind theory, the mass loss from luminous stars should be proportional to some power of the metallicity, yet previous studies have not shown this effect clearly. We have observed 22 main-sequence and giant O-type stars in the SMC with the low-resolution mode of the IUE in order to study the stellar winds in a particularly metal-poor galaxy. These stars are compared with carefully selected Galactic counterparts for wind terminal velocities and line strengths of C IV and N V. While the wind velocities in the SMC stars are confirmed to be systematically lower than in Galactic stars, as theory predicts, the mass-loss rates which are inferred from these data are comparable to those in the Galactic stars. We discuss the possible reasons for this result, including systematic effects in the data, assumed metal abundance, different ionization structure, and different physical parameters for the SMC stars.