Transfer of line radiation in differentially expanding atmospheres, IV: The two-level atom in plane parallel geometry solved by the Feautrier method.
Abstract
We have solved the radiative transfer problem for a two-level atom in plane-parallel geometry in an expanding atmosphere with Schuster-type boundary conditions, by applying the Feautrier method in the fluid rest frame. The line profiles are relatively smooth and very approximately symmetric about their minima, except when the temperature in the atmosphere exceeds that of the photosphere, in which case a redward emission wing appears. Radiation pressure is evaluated and is found to compress the inner part of the atmosphere and to expand the outer part. This suggests that radiation pressure will disrupt QSO absorption clouds, as found by Williams for nonexpanding clouds. The method is stable, accurate, and fast for all optical depths and expansion rates tested, which comprise a vast range.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- November 1974
- DOI:
- 10.1086/153203
- Bibcode:
- 1974ApJ...193..651N
- Keywords:
-
- Atomic Energy Levels;
- Line Spectra;
- Numerical Integration;
- Radiative Transfer;
- Stellar Atmospheres;
- Stellar Spectra;
- Atmospheric Temperature;
- Boundary Conditions;
- Boundary Value Problems;
- Doppler Effect;
- Light Scattering;
- Matrix Theory;
- Optical Thickness;
- Astrophysics