Actinide crystallization and fission reactions in cooling white dwarf stars

TL;DR

This paper proposes that actinide-rich solids forming in cooling white dwarfs could support fission reactions, potentially igniting supernova explosions and explaining certain sub-Chandrasekhar SN Ia observations.

Contribution

It introduces a novel mechanism where actinide enrichment in white dwarf solids triggers fission, leading to supernova explosions, a concept not previously explored.

Findings

Actinide enrichment in WD solids is significant due to high Z.

Fission chain reactions could ignite carbon burning in WDs.

This mechanism may explain some sub-Chandrasekhar SN Ia events.

Abstract

The first solids that form as a cooling white dwarf (WD) starts to crystallize are expected to be greatly enriched in actinides. This is because the melting points of WD matter scale as $Z^{5/3}$ and actinides have the largest charge $Z$. We estimate that the solids may be so enriched in actinides that they could support a fission chain reaction. This reaction could ignite carbon burning and lead to the explosion of an isolated WD in a thermonuclear supernova (SN Ia). Our mechanism could potentially explain SN Ia with sub-Chandrasekhar ejecta masses and short delay times.