Type Ia supernova diversity in three-dimensional models

The use of type Ia supernovae as distance indicators for cosmology has initiated a search for theoretical arguments supporting the empirical calibration methods applied. To this end, as a first step, a sound understanding of the origin of the observed diversity in type Ia supernova properties is needed. Here we present a first systematic study of effects resulting from changing some physical parameters of three-dimensional deflagration models of thermonuclear supernovae. In our study we vary the progenitor's carbon-to-oxygen ratio and its central density prior to ignition because both properties are not well determined by stellar evolution theory and they may change from supernova to supernova. Next we compute for these explosion models the nucleosynthesis yields in a post-processing step. This, in addition, allows us to study variations in the progenitor's metallicity by means of different $^{22}$Ne mass fractions in the initial composition. We find that the progenitor's carbon-to-oxygen ratio and its central density affect the energy release of the models and thus the expansion velocity of the supernova. Moreover, we find that changing the metallicity and the central density changes the production of radioactive $^{56}$Ni and thus affects the luminosity. In contrast, the carbon-to-oxygen ratio has little effect on the $^{56}$Ni production. Implications of the found variations of the explosion energy and the produced $^{56}$Ni mass for the type Ia supernova diversity are discussed.