2006MNRAS.367.1282K

We calculate non-local thermodynamic equilibrium (NLTE) line-driven wind models of selected O stars in the spectral range of O4 to O9 in the Small Magellanic Cloud (SMC). We compare predicted basic wind properties, i.e. the terminal velocity and the mass-loss rate with values derived from observation. We found relatively good agreement between theoretical and observed terminal velocities. On the other hand, predicted mass-loss rates and mass-loss rates derived from observation are in a good agreement only for higher mass-loss rates. Theoretical mass-loss rates lower than approximately 10^–7M_☉/yr are significantly higher than those derived from observation. These results confirm the previously reported problem of weak winds, since our calculated mass-loss rates are in fair agreement with predictions of Vink et al. We study multicomponent models for these winds. For this purpose we develop a more detailed description of wind decoupling. We show that the instability connected with the decoupling of individual wind elements may occur for low-density winds. In the case of winds with very low observed mass-loss rates the multicomponent effects are important for the wind structure, however this is not able to explain consistently the difference between the predicted mass-loss rate and the mass-loss rate derived from observation for these stars. Similar to previous studies, we found the level of dependence of the wind parameters on the metallicity. We conclude that the wind mass-loss rate significantly increases with metallicity as, whereas the terminal velocity of wind on average depends on metallicity only slightly, namely v_∞∼Z^0.06 (for studied stars).