Observable signatures of enhanced axion emission from protoneutron stars

TL;DR

This study uses relativistic supernova simulations to identify observable signatures of axion emission from pion interactions in protoneutron stars, predicting detectable effects on neutrino signals that could improve axion constraints.

Contribution

It introduces a detailed model including pions in supernova simulations, highlighting pion-induced axion production as dominant and predicting observable neutrino and axion signatures.

Findings

Pion-induced axion emission dominates over nucleon-nucleon bremsstrahlung.

Neutrino luminosity is significantly suppressed during the first 10 seconds.

Predicted signatures can improve constraints on axion properties from future supernova observations.

Abstract

We perform general relativistic one-dimensional supernova (SN) simulations to identify observable signatures of enhanced axion emission from the pion-induced reaction $\pi^- + p \rightarrow n + a$ inside a newly born protoneutron star (PNS).We focus on the early evolution after the onset of the supernova explosion to predict the temporal and spectral features of the neutrino and axion emission during the first 10 s. Pions are included as explicit new degrees of freedom in hot and dense matter. Their thermal population and their role in axion production are both determined consistently to include effects due to their interactions with nucleons. For a wide range of ambient conditions encountered inside a PNS, we find that the pion-induced axion production dominates over nucleon-nucleon bremsstrahlung processes. By consistently including the role of pions on the dense matter equation of state and on the energy loss, our simulations predict robust discernible features of neutrino and axion emission from a galactic supernova that can be observed in terrestrial detectors. For axion couplings that are compatible with current bounds, we find a significant suppression with time of the neutrino luminosity during the first 10 s. This suggests that current bounds derived from the neutrino signal from SN 1987A can be improved and that future galactic supernovae may provide significantly more stringent constraints.