# Discovery of an Exceptionally Strong $\beta$-Decay Transition of $^{20}$F and Implications for the Fate of Intermediate-Mass Stars

## TL;DR

This study measures an exceptionally strong beta-decay transition in $^{20}$F, significantly impacting models of stellar evolution and supernova mechanisms in intermediate-mass stars by clarifying nuclear reaction rates.

## Contribution

It provides the first measurement of the transition strength, resolving a key nuclear physics uncertainty in stellar core evolution models.

## Key findings

- The transition strength is exceptionally large.
- Electron capture rate is increased by several orders of magnitude.
- Implications favor thermonuclear explosion over collapse in certain stars.

## Abstract

A significant fraction of stars between 7-11 solar masses are thought to become supernovae, but the explosion mechanism is unclear. The answer depends critically on the rate of electron capture on $^{20}$Ne in the degenerate oxygen-neon stellar core. However, due to the unknown strength of the transition between the ground states of $^{20}$Ne and $^{20}$F, it has not previously been possible to fully constrain the rate. By measuring the transition, we have established that its strength is exceptionally large and enhances the capture rate by several orders of magnitude. This has a decisive impact on the evolution of the core, increasing the likelihood that the star is (partially) disrupted by a thermonuclear explosion rather than collapsing to form a neutron star. Importantly, our measurement resolves the last remaining nuclear physics uncertainty in the final evolution of degenerate oxygen-neon stellar cores, allowing future studies to address the critical role of convection, which at present is poorly understood.