Hydrodynamic model atmospheres for WR stars: first results and their consequences for interacting winds in massive binary systems

G. Gräfener and W.-R. Hamann

Universität Potsdam, Institut für Physik, Astrophysik

We present the first models for the expanding atmospheres of WR stars that combine a full non-LTE radiative transfer with a self-consistent hydrodynamic solution for the wind structure. By the inclusion of the Fe M-shell ions (the so-called "Hot Iron Bump" opacities) in our models, the radiative driving in deep atmospheric layers is considerably increased. For the case of an early-type WC star we find that the WR wind is initiated by the radiative driving on these opacities, at large optical depth. The acceleration of the outer part of the wind is performed by iron-group ions of lower excitation in combination with C and O. Consequently, the wind structure shows two acceleration regions. One close to the hydrostatic wind base in the optically thick part of the atmosphere, and one farther out in the wind. In addition, our calculations provide important parameters for the modeling of interacting winds in massive binary systems. In particular, the force multiplier parameters as determined within our models, are qualitatively different from the values derived for O-star winds.

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