Resonance-Line Polarization in Expanding Spherical Atmospheres - Solution in the Comoving Frame

Abstract

The effect of differential radial velocity in the distribution of line intensities and line polarization along the line of sight of an extended stellar atmosphere has been studied. The medium is assumed to be inhomogeneous, isothermal and spherically symmetric. The main purpose of this paper is to understand the behaviour of line polarization in an extended and radially expanding stellar atmosphere. The atmospheric models could represent the photospheric layers of early-type stars, giant and supergiant stars as well as of luminous late-type stars. Complete redistribution of frequency has set at 0, 5, 20, and 50 mean thermal units with two different velocity laws. The results have been compared with that of the plane-parallel geometrical case. It is found that significant effects are generated in the polarized radiation field when differential radial expansion is taken into account.