Simplified treatment of the radiative transfer problem in expanding envelopes

Abstract

In this paper we study the application of a simplified method to solve the dynamic radiative transfer problem in expanding envelopes. The method, which requires a computational effort similar to that of the diffusion approximation, is based on the use of a generalization of the Eddington closure relationship allowing the inclusion of scattering and relativistic corrections to order (v/c). We apply this method to the calculation of light curves of type Ia supernovae, showing that it gives much more accurate results than the diffusion approximation, and that the latter is seriously in error when applied to determine emergent flux and its spectral distribution.