The Potsdam Wolf-Rayet (PoWR) hydrodynamic model atmospheres combine fully line-blanketed NLTE models with the equations of hydrodynamics (Grafener & Hamann 2005; Hamann & Grafener 2003; Koesterke et al. 2002; Grafener et al. 2002). The wind structure (p(r) and v(r)) and the temperature structure T(r) are computed in line with the full set of NLTE populations, and the radiation field in the co-moving frame. In contrast to all previous approaches, the radiative wind acceleration arad is obtained by direct integration, instead of by making use of the Sobolev approximation. In this way, complex processes such as strong line overlap and the redistribution of radiation are automatically taken into account. Moreover, the models include small-scale wind clumping (throughout this work we assume a clumping factor of D = 10, for details see also Hamann & Koesterke (1998)). The models describe the conditions in WR
atmospheres in a realistic manner, and provide synthetic spectra, i.e. they allow direct comparison with observations.
Utilizing these models, we recently obtained the first fully self-consistent WR wind model, for the case of an early-type WC star with strong lines (Grafener & Hamann 2005). Moreover, we have examined the mass loss from late-type WN stars and its dependence on metallicity (Grafener & Hamann 2006, 2007).
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