Resonance Line Polarization in a Moving Medium - Solution in the Comoving Frame with Complete Frequency Redistribution

Abstract

We study the effect of differential radial velocity on the distribution of line intensities and line polarization along the line of sight of an extended stellar atmosphere stratified in parallel planes. The main purpose of this paper is to understand the behaviour of line polarization in an extended and expanding atmosphere. The atmospheric models could representt the photospheric layers of early-type stars. We consider, for simplicity, complete redistribution of frequency. The velocities of expansion of the medium are set at 5, 20 and 50 mean thermal units with two different velocity laws. The results are compared with that of the static case. It is found that large effects are generated in the polarized radiation field when differential radial expansion is taken into account