Non-LTE models of WR winds

W.-R. Hamann1, L. Koesterke1, G. Gräfener2,3

1Universität Potsdam, Institut für Physik, Astrophysik
2Institut of Astronomy, ETH Zentrum, Switzerland
3PMOD/WRC, 7260 Davos Dorf, Switzerland

"Standard" Non-LTE models for WR winds treat the radiation transfer in a spherically-expanding, homogeneous and stationary atmosphere. These models have been widely applied for the spectral analysis of WR stars in the Galaxy and LMC. WN spectra can be well reproduced in general, while some work is still to be done on WC spectra.

Accounting for wind inhomogeneities (clumping) in a first-order approximation has significantly improved the agreement between synthetic and observed spectra with respect to the electron-scattering wings of strong lines. Spectral analyses with clumped models yield considerably lower mass-loss rates than obtained from homogeneous models. In typical models, the ionization stratification shows a stepwise recombination with increasing distance from the star.

The applied models account for complex model atoms of He and CNO elements. In a new version of our model code, line blanketing by iron-group elements is additionally included. The iron model atom is simplified by introducing superlevels and superlines, but otherwise the radiation transfer is fully treated. In first test models the radiation pressure is almost (i.e. within a factor of two) consistent with the observed acceleration of the stellar wind.

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