The theory of radiatively driven stellar winds. I. A physical interpretation.
Abstract
From the characteristics of the equations of motion, it is demonstrated that 'radiative-acoustic' waves propagate in a slow mode in the forward direction and a fast mode in the backward direction. The critical point defined by the Castor, Abbott, Klein (CAK) theory under consideration marks where the radiative-acoustic wave speed equals the flow velocity. This critical speed is supersonic for winds and subsonic for accretion. The physical interpretation of the critical point in a line-driven wind becomes completely analogous to that of the sonic point in thermally driven winds or in supersonic nozzle flow, in that beyond the critical point information no longer propagates upstream. Unlike supersonic nozzle flow, in a line-driven wind the throat geometry and flow solutions are interdependent. In the CAK model this feedback amplifies small modifications to the force terms into large changes in the final velocity law. It is therefore determined that the presence in early-type stars of rotation, coronal gas, and gradients in the line force are sufficient to ensure that the velocity law of these stars must deviate from the CAK result.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 1980
- DOI:
- 10.1086/158550
- Bibcode:
- 1980ApJ...242.1183A
- Keywords:
-
- Early Stars;
- Radiative Transfer;
- Stellar Mass Ejection;
- Stellar Winds;
- Gas Pressure;
- Interstellar Matter;
- Mathematical Models;
- Sound Waves;
- Stellar Magnetic Fields;
- Stellar Rotation;
- Wave Propagation;
- Astrophysics