On the ionization and velocity structure of expanding circumstellar envelopes.

Abstract

It is shown that the envelope line profiles formed by the scattering of stellar continuum flux in expanding atmospheres of luminous, early-type and Wolf-Rayet stars are sensitive to the variation of (1) the optical depth in the line, and (2) the velocity gradient of the stellar wind, as a function of radial distance from the star. A theoretical profile sample is presented, and UV envelope line profiles observed in the spectra of stars with rapid mass loss via stellar wind are compared with theoretically predicted profiles. A discussion is also given concerning inferences from UV spectroscopic observations of the O7f supergiant UW CMa, the interacting early-type contact binary SV Cen, and the Wolf-Rayet star HD 192163, in light of the expanding envelope models.