Type Ia supernovae: An explosion in the regime of a convergent delayed detonation wave

Abstract

The model of a presupernova’s carbon-oxygen (C-O) core with an initial mass of 1.33 M ⊙, an initial carbon abundance X C (0) =0.27, and a mean rate of increase in mass of 5 × 10−7 M ⊙ yr−1 through accretion in a binary system evolved from the central density and temperature ρc=109 g cm−3 and T c=2.05 × 108K, respectively, by forming a convective core and its subsequent expansion to an explosive fuel ignition at the center. The evolution and explosion equations included only the carbon burning reaction 12C+12C with energy release corresponding to the complete conversion of carbon and oxygen (at the same rate as that of carbon) into 56Ni. The ratio of mixing length to convection-zone size αc was chosen as the parameter. Although the model assumptions were crude, we obtained an acceptable (for the theory of supernovae) pattern of explosion with a strong dependence of its duration on αc. In our calculations with sufficiently large values of this parameter, αc=4.0 × 10−3 and 3.0×10−3, fuel burned in the regime of prompt detonation. In the range 2.0×10−3≥αc≥3.0×10−4, there was initially a deflagration with the generation of model pulsations whose amplitude gradually increased. Eventually, the detonation regime of burning arose, which was triggered from the model surface layers (with m ≃ 1.33 M ⊙) and propagated deep into the model up to the deflagration front. The generation of model pulsations and the formation of a detonation front are described in detail for αc=1.0 × 10−3.