Properties of Convective Oxygen and Silicon Burning Shells in Supernova Progenitors

TL;DR

This study investigates the properties of convective shells in supernova progenitors, highlighting the conditions under which perturbation-aided explosions are most likely, especially in certain mass ranges with large-scale convective overturn.

Contribution

It provides a comprehensive analysis of convective properties in presupernova models across a broad mass range, identifying conditions favorable for perturbation-aided supernova explosions.

Findings

Optimal conditions for perturbation-aided explosions are in 16-26 solar mass progenitors.

High convective Mach numbers up to 0.3 are found mainly in low-mass progenitors' oxygen shells.

About 40% of progenitors in the key mass range have shell mergers involving oxygen and neon.

Abstract

Recent three-dimensional simulations have suggested that convective seed perturbations from shell burning can play an important role in triggering neutrino-driven supernova explosions. Since isolated simulations cannot determine whether this perturbation-aided mechanism is of general relevance across the progenitor mass range, we here investigate the pertinent properties of convective oxygen and silicon burning shells in a broad range of presupernova stellar evolution models. We find that conditions for perturbation-aided explosions are most favourable in the extended oxygen shells of progenitors between about 16 and 26 solar masses, which exhibit large-scale convective overturn with high convective Mach numbers. Although the highest convective Mach numbers of up to 0.3 are reached in the oxygen shells of low-mass progenitors, convection is typically dominated by small-scale modes in these shells, which implies a more modest role of initial perturbations in the explosion mechanism. Convective silicon burning rarely provides the high Mach numbers and large-scale perturbations required for perturbation-aided explosions. We also find that about $40\%$ of progenitors between 16 and 26 solar masses exhibit simultaneous oxygen and neon burning in the same convection zone as a result of a shell merger shortly before collapse.