The effects of an expanding circumstellar dust shell on photospheric absorption line profiles

The Monte Carlo method is used to simulate the transfer of radiation through an expanding dust shell. The basic assumptions of the investigation include a spherically symmetric geometry, dust grains characterized by a single scattering albedo, and a scattering phase function of the Henyey-Greenstein form. The numerical results are discussed, taking into account models of constant velocity and uniform density, and models assuming a velocity law and mass continuity. Attention is given to dust scattering as origin of velocity shift, the effects of asymmetry parameter and albedo, the effects of a different velocity law, and observational implications and long-period variables.