The Theory of Radiation Driven Stellar Winds and the Wolf-Rayet Phenomenon

Abstract

Peter Conti has a tradition of always talking about 0-type stars at Wolf-Rayet symposia, and Wolf-Rayet stars at 0 star symposia. Since there is no well-developed theory for the origin of the winds of WR stars, it is my pleasure to join Peter’s tradition, and to talk mainly about the theory of radiation driven winds in OB stars. The advantage of OB stars is that there exists a fairly complete wind theory, which agrees well with the available observations. The question is, can the mass loss observed from Wolf-Rayet stars be explained by a version of this wind theory which is scaled to the conditions found in the envelopes of Wolf-Rayet stars? The topics I consider are:

• The calculated radiation pressure in OB stars, and its dependence on temperature, density, and chemical composition.

• A comparison between predicted and observed mass loss rates and terminal velocities for OB stars.

• The applicability of the standard radiation driven wind models to Wolf-Rayet stars.

• Speculations on how Wolf-Rayet stars achieve their enormous mass loss rates within the context of the radiation pressure mechanism.