Astron. Astrophys. Suppl. Ser.
Volume 121, Number 1, January 1997
|Page(s)||15 - 44|
|Published online||15 January 1997|
Raman scattering in symbiotic stars. II. Numerical models
School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, Fife KY16 9SS, Scotland
2 Dept. of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
Corresponding author: Send offprint request to: Tim Harries, email: firstname.lastname@example.org
Accepted: 20 April 1996
We present numerical models of Raman-line formation in symbiotic systems, based on Monte-Carlo simulations of scattering of O vi resonance-line 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 observed line ratios, velocities, and polarizations, and the viewing-angle (orbital) dependence of the line strengths and polarized intensities. In principle, the position-angle dependence of the polarization in resolved Raman lines provides a diagnostic of the extent of the ionized region in symbiotic systems; however, axisymmetric geometries with `up-down' symmetry, such as we use, fail to reproduce the most commonly observed dependence of PA on velocity. Raman-line polarization morphology is shown to be a powerful probe of the conditions in the red-giant wind; this is particularly true if observations are available at different orbital phases, so that geometrical and physical variables may more easily be isolated.
Key words: stars: binaries: symbiotic / stars: mass-loss / polarization
© European Southern Observatory (ESO), 1997