The Sobolev approximation for the line force and line source function in a spherically-symmetrical stellar wind with continuum opacity
Abstract
An expression for the force arising from diffuse line radiation is derived in the context of the Sobolev approximation for spectral line formation, as generalized by Hummer and Rybicki (1985) to include the effects of continuous opacity and emissivity in a general three-dimensional gas flow. This theory is then specialized to spherical symmetry and used to calculate the line source function and radiative pressure gradient in model stellar winds simulating essential aspects of the outflows' characteristic of O-stars and Wolf-Rayet objects. These models are compared both with models based on the Sobolev approximation without continuum opacity, and with numerically exact solutions obtained by using the co-moving frame method. The properties and methods of evaluating the special functions, Z (τ, β) and U (τ, β), arising in this work and in that of Hummer and Rybicki (1985) are discussed in the appendices.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- February 1988
- Bibcode:
- 1988A&A...191...87P
- Keywords:
-
- Early Stars;
- Radiative Transfer;
- Sobolev Space;
- Stellar Atmospheres;
- Stellar Mass Ejection;
- Stellar Winds;
- Electron Energy;
- Line Spectra;
- O Stars;
- Plancks Constant;
- Wolf-Rayet Stars;
- Astrophysics