Stationary hydrodynamic models of Wolf-Rayet stars with optically thick winds

A. Heger, N. Langer

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Abstract

We investigate the influence of a grey, optically thick wind on the surface and internal structure of Wolf-Rayet (WR) stars. We calculate hydrodynamic models of chemically homogeneous helium stars with stationary outflows, solving the full set of stellar structure equations from the stellar center up to well beyond the sonic point of the wind, including the line force originating from absorption lines in a parameterized way. For specific assumptions about mass loss rate and wind opacity above our outer boundary, we find that the iron opacity peak may lead to local super-Eddington luminosities at the sonic point. By varying the stellar wind parameters over the whole physically plausible range, we show that the radius of the sonic point of the wind flow is always very close to the hydrostatic stellar radius obtained in WR star models which ignore the wind. However, our models confirm the possibility of large values for observable WR radii and correspondingly small effective temperatures found in earlier models. We show further that the energy which is contained in a typical WR wind can not be neglected. The stellar luminosity may be reduced by several 10%, which has a pronounced effect on the mass-luminosity relation. I. e., the WR masses derived for a given luminosity may be considerably larger. Thereby, also the momentum problem of WR winds is considerably reduced, as well as the scatter in the Ṁ vs. M diagram for observed hydrogen-free WN stars.

Original languageEnglish
Pages (from-to)421-431
Number of pages11
JournalAstronomy & Astrophysics
Volume315
Issue number3
Publication statusPublished - 20 Nov 1996
Externally publishedYes

Keywords

  • Mass loss
  • Massive stars
  • Wolf-Rayet stars

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