Multi-Dimensional Double Detonation of Sub-Chandrasekhar Mass White Dwarfs

TL;DR

This study uses multi-dimensional simulations to examine the conditions under which helium shell detonations in white dwarfs lead to secondary core detonations, impacting models of Type Ia supernovae.

Contribution

It demonstrates that core detonations are triggered by hot spots from compressional waves, even with complex initial ignition conditions, challenging previous assumptions about helium shell detonation requirements.

Findings

Hot spots from compressional waves can trigger core detonations.

Multiple ignition points do not prevent hot spot formation.

Low-mass helium shells can still induce core detonations.

Abstract

Using 2D and 3D simulation, we study the "robustness" of the double detonation scenario for Type Ia supernovae, in which a detonation in the helium shell of a carbon-oxygen white dwarf induces a secondary detonation in the underlying core. We find that a helium detonation cannot easily descend into the core unless it commences (artificially) well above the hottest layer calculated for the helium shell in current presupernova models. Compressional waves induced by the sliding helium detonation, however, robustly generate hot spots which trigger a detonation in the core. Our simulations show that this is true even for non-axisymmetric initial conditions. If the helium is ignited at multiple points, the internal waves can pass through one another or be reflected, but this added complexity does not defeat the generation of the hot spot. The ignition of very low-mass helium shells depends on whether a thermonuclear runaway can simultaneously commence in a sufficiently large region.