Probing Spectral Formation of Type Ia Supernovae using PHOENIX

Radiative transfer simulations of Type Ia supernova spectra provide the opportunity to compare theoretical models to observations, and to probe the impact of individual physical variations on spectral formation. I will discuss recent work using the generalized stellar atmospheres code PHOENIX probing the UV spectra of SN 2011fe, including the first known detections of C IV and Si IV in a UV supernova spectrum. The impact of other spectral formation mechanisms on the UV are also addressed, including photoionization edges, line blanketing by iron group elements, and spectral temperature dependencies. Additionally I will discuss work in progress focusing on understanding the origins of why a subset of broad-lined Ia spectra appear to be Doppler-shifted versions of core-normal spectra.