SYNTHETIC SPECTRA OF HYDRODYNAMIC MODELS OF TYPE IA SUPERNOVAE

We present detailed non-LTE synthetic spectra of hydrodynamic supernov ae (SNe) Ia models. We make no assumptions about the form of the spect rum at the inner boundary, We calculate both Chandrasekhar-mass deflag ration models and sub-Chandrasekhar ''helium detonators.'' Gamma-ray d eposition is handled in a simple, accurate manner. We have parameteriz ed the storage of energy, which arises from the time-dependent deposit ion of radioactive decay energy, in a reasonable manner that spans the expected range. We find that the Chandrasekhar-mass deflagration mode l W7 of Nomoto, Thielemann, & Yokoi shows good agreement with the obse rved spectra of SN 1992A and SN 1994D, particularly in the UV, where o ur models are expected to be most accurate. The sub-Chandrasekhar mode ls do not reproduce the UV deficit observed in normal SNe Ia They do b ear some resemblance to subluminous SNe Ia, but the shapes of the spec tra (i.e., the colors) are opposite that of the observed ones, and the intermediate-mass element lines (such as Si II and Cst II) are extrem ely weak, which seems to be a generic difficulty of the models. Althou gh the sub-Chandrasekhar models have a significant helium abundance (u nlike Chandrasekhar-mass models), helium lines are not prominent in th e spectra near maximum light and thus do not act as a spectral signatu re for the progenitor.