5 Conclusions

Using the concept of super-levels, the line-blanketing by $\approx$10⁷ spectral lines of iron group elements is successfully implemented into our non-LTE model atmospheres for WR stars. Due to the more realistic model physics, the spectral fit quality is improved with respect to former un-blanketed model calculations.

The iron group opacities significantly affect the emergent flux distribution and the ionization structure of the model atmosphere. The blanketing effects on the emergent flux distribution lead to an increase of the derived stellar luminosity. Due to changes in the ionization structure a lower mass loss rate is obtained from the spectral analysis with blanketed models. Furthermore, the derived mass loss rate becomes even lower when accounting for clumping.

With the lower mass loss rate and the higher luminosity we get a low value for the "observed'' wind efficiency ($\eta = 4.8$). Thanks to the exact treatment of a very large number of spectral lines (i.e. fully accounting for multiple scattering effects), we obtain a radiative acceleration for the WR 111 model which supplies about 40% of the "observed'' mechanical wind luminosity. Attributing the remaining discrepancy to the incompleteness of the opacities accounted for, we conclude that radiation pressure may be the main driving mechanism for WR winds.

Acknowledgements

This work was supported by the Deutsche Agentur für Raumfahrtangelegenheiten under grants DARA 50 OR 9605 7 and DARA OR 0008, and by the Swiss National Science Foundation.