Abstract:

A sophisticated scheme to capture the effects of weak interactions and change in composition of matter burned to nuclear statistical equilibrium in hydrodynamic explosion simulations of Type Ia supernovae is developed. Coupled to a flame model, the scheme is applied to two dimensional axisymmetric simulations of Type Ia supernovae. The explosions are simulated in the gravitationally confined detonation paradigm, where a near Chandrasekhar-mass carbon-oxygen white dwarf ignites in a single "bubble" within the first ~100 km off center, and the subsequent evolution of the bubble (rise, growth, and break-out through the stellar surface) is thought to lead to the initiation of a detonation at the antipodal point of break-out. Increasingly higher-resolution simulations of the region where the detonation is purportedly initiated are presented, and detonations are indeed observed to form via the gradient mechanism in most cases. To support the validity of the initiation of a detonation in the under-resolved full star simulations, and to quantify the uncertainties and dependences of successful initiation on details of its environment (such as composition, density, peak - and background temperature, functional form of the temperature inhomogeneity), a suite of one dimensional reactive hydrodynamics calculations determining the smallest sizes of hot-spots leading to a detonation are performed for a range of conditions that might obtain in the surface layers of white dwarf stars. Finally, a novel, computationally inexpensive method to obtain full isotopic yield information of material that was burned by fusion processes to nuclear statistical equilibrium during the detonation phase of the supernova explosion is developed and applied to the aforementioned supernova simulations.