Non-LTE models of WR winds
W.-R. Hamann1, L. Koesterke1, G. Gräfener2,3
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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