Advisor: Dr. Antonio Mario Magalhaes
 

We have developed a Monte Carlo code in order to study the radiative transfer in stellar envelopes.  By treating all Stokes parameters of the radiation bundle, we are able to model both linear and circular polarization of the emerging light, in addition to its intensity. The scatterers may be dust grains or electrons; the applications discussed here have been restricted to electron scattering situations, however.

This work focuses on two problems. First, we have modelled the observed random variation in intensity and polarization of some isolated Wolf-Rayet (WR) stars, assuming that their winds have localized, enhanced density regions called blobs. Our study indicates that these blobs must have sizes comparable to the stellar radius and be near the base of the envelope. These sizes are in contrast to the much smaller size scales of  the instabilities expected from line driven winds, but may be identified with the so called  spectroscopic discrete absortion components.

A second problem we discuss is the intensity and polarization light curves from binary systems in which one of the components has a circumstellar envelope. Two eclipsing binaries have been studied in detail: V444 Cyg and HD 5980. We were able to fit their detailed light and polarization variabilities simultaneously and derive several parameters of interest for these systems.

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