The white dwarf's carbon fraction as a secondary parameter of Type Ia supernovae
Context. Binary stellar evolution calculations predict that Chandrasekhar-mass carbon/oxygen white dwarfs (WDs) show a radially varying profile for the composition with a carbon depleted core. Many recent multi-dimensional simulations of Type Ia supernovae (SNe Ia), however, assume the progenitor WD has a homogeneous chemical composition. Aims. In this work, we explore the impact of di erent initial carbon profiles of the progenitor WD on the explosion phase and on synthetic observables in the Chandrasekhar-mass delayed detonation model. Spectra and light curves are compared to observations to judge the validity of the model. Methods. The explosion phase is simulated using the finite volume supernova code Leafs, which is extended to treat di erent compositions of the progenitor WD. The synthetic observables are computed with the Monte Carlo radiative transfer code Artis. Results. Di erences in binding energies of carbon and oxygen lead to a lower nuclear energy release for carbon depleted material; thus, the burning fronts that develop are weaker and the total nuclear energy release is smaller. For otherwise identical conditions, carbon depleted models produce less 56 Ni. Comparing di erent models with similar 56 Ni yields shows lower kinetic energies in the ejecta for carbon depleted models, but only small di erences in velocity distributions and line velocities in spectra. The light curve width‐luminosity relation (WLR) obtained for models with di ering carbon depletion is roughly perpendicular to the observed WLR, hence the carbon mass fraction is probably only a secondary parameter in the family of SNe Ia.