THE COMBINED EFFECT OF PARTIAL REDISTRIBUTION AND NONCOHERENT ELECTRON-SCATTERING ON POLARIZED RESONANCE LINE TRANSFER

The combined effect of partial frequency redistribution by atoms (PRD) and non-coherent electron scattering (NCES) on line formation is studied, taking account of the polarization state of the radiation field in resonance line scattering. For the purpose of comparison, a study is also made of redistribution by other mechanisms, namely complete redistribution (CRD) and coherent scattering (CS) combined with NCES. A static medium stratified into plane-parallel homogeneous layers is considered. A conventional two-level atom approximation is employed as the basic model. The emergent linear polarization profile exhibits interesting characteristics in its variation across the line profile. Atomic redistribution plays an important role at the line core and the near wings of the resonance line. Electron scattering, however, makes significant contributions in the far wings (x > 10). For resonance lines with high optical thickness, NCES leads to measurable changes of polarization in the far wings irrespective of the atomic scattering mechanism employed. Since electron scattering is a dominant source of the scattering of continuum and line photons in hot stars, and particularly in supernova atmospheres, it is important to include the non-coherent electron scattering mechanism correctly when computing emergent intensity and polarization profiles for these objects.