Effects of dust on equivalent widths of spectral lines formed in expanding spherically symmetric shells

Abstract

A study is made of the effects of the presence of dust and radial expansion of the spherical shells around stars on the equivalent widths of the lines formed in such shells. A non-LTE, two-level atom approximation is considered, and it is assumed that the dust scatters isotropically; 30 shells and an optical depth of 300 are considered. Two types of expanding shells are treated: with velocity gradients and without velocity gradients. Depending upon the parameters used, the equivalent widths change considerably