Synthetic Spectra of Hydrodynamic Models of Type Ia Supernovae

We present detailed NLTE synthetic spectra of hydrodynamic SNe Ia models. Wemake no assumptions about the form of the spectrum at the inner boundary. Wecalculate both Chandrasekhar-mass deflagration models and sub-Chandrasekhar``helium detonators.'' Gamma-ray deposition is handled in a simple, accuratemanner. We have parameterized the storage of energy that arises from the timedependent deposition of radioactive decay energy in a reasonable manner, thatspans the expected range. We find that the Chandrasekhar-mass deflagrationmodel W7 of Nomoto etal shows good agreement with the observed spectra of SN1992A and SN 1994D, particularly in the UV, where our models are expected to bemost accurate. The sub-Chandrasekhar models do not reproduce the UV deficitobserved in normal SNe Ia. They do bear some resemblance to sub-luminous SNeIa, but the shape of the spectra (i.e. the colors) are opposite to that of theobserved ones and the intermediate mass element lines such as Si II, and Ca IIare extremely weak, which seems to be a generic difficulty of the models.Although the sub-Chandrasekhar models have a significant helium abundance(unlike Chandrasekhar-mass models), helium lines are not prominent in thespectra near maximum light and thus do not act as a spectral signature for theprogenitor.