Hydrodynamic model atmospheres for WR stars: Self-consistent modeling of a WC star wind
G. Gräfener and W.-R. Hamann
We present the first non-LTE atmosphere models for WR stars that incorporate
a self-consistent solution of the hydrodynamic equations. The models account
for iron-group line-blanketing and clumping, and compute the hydrodynamic
structure of a radiatively driven wind consistently with the non-LTE radiation
transport in the co-moving frame. We construct a self-consistent wind model
that reproduces all observed properties of an early-type WC star (WC5). We find
that the WR-type mass-loss is initiated at high optical depth by the so-called
`Hot Iron Bump' opacities (Fe IX-XVI). The acceleration of the outer wind
regions 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 another farther out in the wind. In addition to the radiative
acceleration, the `Iron Bump' opacities are responsible for an intense heating
of deep atmospheric layers. We find that the observed narrow OVI-emissions in
the optical spectra of WC stars originate from this region. By their dependence
on the clumping factor we gain important information about the location where
the density inhomogeneities in WR-winds start to develop.
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