Late-phase radiative transfer of Type Ia supernovae

Type Ia supernovae almost certainly involve the thermonuclear explosion and unbinding of a carbon-oxygen white dwarf, but understanding both the possible role of a binary companion and the mechanism of explosion remain open problems in supernova research. Thanks to theoretical developments in the last decade, we now have a variety of 3D hydrodynamic explosion models for several candidate scenarios. These can can be tested with nucleosynthesis and radiative transfer simulations to compare to observational light curves and spectra. We present recent work to improve the physics of the ARTIS radiation transport code to extend its validity to late times (>100 days in the nebular phase) for application to existing 3D explosion models. The code developments are initially tested with 1D models, including the well-known W7 fast-deflagration model, and then applied to sub-Chandrasekhar mass detonation models that account for the effect of gravitational settling in the progenitor white dwarf. We also outline the next step to three-dimensional radiative transfer simulations of 3D hydrodynamic explosion models