Tree-structured grid model of line and polarization variability from massive binaries

We have developed a 3-D Monte Carlo radiative transfer model which computes line and continuum polarization variability for a binary system with an optically thick non-axisymmetric envelope. This allows us to investigate the complex (phase-locked) line and continuum polarization variability features displayed by many massive binaries: W-R+O, O+O, etc. An 8-way tree data structure constructed via a cell-splitting method allows for high precision with efficient use of computer resources. The model is not restricted to binary systems; it can easily be adapted to a system with an arbitrary density distribution and large density gradients. As an application to a real system, the phase dependent Stokes parameters (I, Q, U) and the phase dependent He I (lambda 5876) profiles of the massive binary system V444 Cyg (WN5+O6 III-V) are computed.