An alternative model for the atmospheres of Wolf-Rayet and O stars.

Abstract

The hypothesis of Beals (1929) and of Menzel (1929) that the spectrum of a Wolf-Rayet star is the result of spherically symmetric outflow of a hot, strongly ionized plasma has provided considerable insight into the physical state of the atmospheres of Wolf-Rayet stars. However, modern observations yield a number of results which are contradictory when interpreted in terms solely of spherically symmetric outflow. The present investigation is concerned with a possible approach for resolving the arising difficulties. It is found that the model of a symmetric wind which conserves mass in spherical shells and contains enough particles to account for the observed radio fluxes from Wolf-Rayet stars implies that the star imparts to the wind, in some unexplained way, 10 to 50 times the amount of momentum which is in the radiation field. It is shown that a model consisting of low-density plasma suspended in magnetically supported loops plus a low-density wind can account for the observed radio fluxes and the optical spectrum.