Type la supernova diversity in three-dimensional models

Abstract

Context: The use of type la supernovae as distance indicators for cosmology has initiated a search for theoretical arguments supporting the empirical calibration methods applied. As a first step, a sound understanding of the origin of the observed diversity in type la supernova properties is needed. Aims: Here we present a systematic study of effects resulting from changing some physical parameters of three-dimensional deflagration models of thermonuclear supernovae. Methods: The high computational costs of such models restricted this survey to simple setups which are known to result in weak explosions and therefore we point out trends rather then setting the absolute scale of the variance. 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 22Ne mass fractions in the initial composition. Results: 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 56Ni and thus affects the luminosity. In contrast, the carbon-to-oxygen ratio has little effect on the 56Ni production. Conclusions. Implications of the variations of the explosion energy and the produced 56Ni mass for type la supernova diversity are discussed. © ESO 2006.