NLTE synthetic spectra and light curves of type Ia supernovae.

Abstract

I have modeled the spectra of Type Ia supernovae with a detailed, non-local thermodynamic equilibrium (NLTE) model atmosphere and radiative transport code, PHOENIX. I have modeled spectra of the normal, Type Ia supernova, SN 1994D in NGC 4625 for epochs from 12 days before maximum brightness to 12 days after maximum brightness using the deflagration model W7. The synthetic spectra and the derived synthetic photometry permit the analysis of the W7 model and derivation of the distance to SN 1994D. I have also modeled the spectra of SN 1984A, which is a Type Ia supernova with normal spectral features, but unusually large line-widths. The large line-widths were reproducable using delayed-detonation models which have higher densities in the fast-moving layers important to the formation of the wide spectral lines. I have also studied possible effects of progenitor evolution on the spectra of Type Ia supernovae. I have modified the heavy element content of the unburned material and studied the effects on the spectra. I found that primordial metals are important to line formation in early spectra. I have also mixed hydrogen rich material into the outer atmospheres of Type Ia supernovae and found that hydrogen must be at least one-tenth of the mass of the outer envelope to affect spectra at 10 days after explosion. I describe an extension of the energy balance methods used in these quasi-static expanding model atmospheres to include the temporal evolution of the temperature structure and luminosity of the supernova.