# Is there a supernova bound on axions?

## TL;DR

This paper critically reevaluates the supernova cooling bound on axions, suggesting that previous models overlooked key features like the accretion disk, which could invalidate the bound under certain supernova conditions.

## Contribution

It introduces a revised assessment of the supernova bound on axions by including the effects of accretion disks and rotation, challenging prior assumptions in the field.

## Key findings

- Accretion disks can form in certain supernova scenarios, affecting neutrino emissions.
- Axions do not influence the neutrino output from optically-thin accretion disks.
- The supernova cooling bound on axions may not be valid in cases involving accretion disks and rotation.

## Abstract

We present a critical assessment of the SN1987A supernova cooling bound on axions and other light particles. Core-collapse simulations used in the literature to substantiate the bound omitted from the calculation the envelope exterior to the proto-neutron star (PNS). As a result, the only source of neutrinos in these simulations was, by construction, a cooling PNS. We show that if the canonical delayed neutrino mechanism failed to explode SN1987A, and if the pre-collapse star was rotating, then an accretion disk would form that could explain the late-time ($t\gtrsim5$ sec) neutrino events. Such accretion disk would be a natural feature if SN1987A was a collapse-induced thermonuclear explosion. Axions do not cool the disk and do not affect its neutrino output, provided the disk is optically-thin to neutrinos, as it naturally is. These considerations cast doubt on the supernova cooling bound.