RAMAN-SCATTERING IN SYMBIOTIC STARS .2. NUMERICAL-MODELS

We present numerical models of Raman-line formation in symbiotic syste ms, based on Monte-Carlo simulations of scattering of O VI resonance-l ine photons from a hot source in the extended, expanding atmosphere of a cool companion, and we explore the sensitivity of the model results to the input parameters. The model successfully reproduces the observ ed line ratios, velocities. and polarizations, and the viewing-angle ( orbital) dependence of the line strengths and polarized intensities. I n principle, the position-angle dependence of the polarization in reso lved Raman lines provides a diagnostic of the extent of the ionized re gion in symbiotic systems; however, axisymmetric geometries with 'up-d own' symmetry, such as we use, fail to reproduce the mast commonly obs erved dependence of PA on velocity. Raman-line polarization morphology is shown to be a powerful probe of the conditions in the red-giant wi nd; this is particularly true if observations are available at differe nt orbital phases, so that geometrical and physical variables may more easily be isolated.