3D template-based $Fermi$-LAT constraints on the diffuse supernova axion-like particle background

TL;DR

This study uses 12 years of Fermi-LAT gamma-ray data and detailed supernova models to set new constraints on axion-like particles, considering their production in supernovae and conversion into gamma rays in the Milky Way's magnetic field.

Contribution

It introduces an improved modeling of supernova-produced ALPs, including failed supernovae, and applies a template-based analysis to gamma-ray data to constrain ALP-photon coupling.

Findings

Set an upper limit of g_{aγ} ≲ 3.76×10^{-11} GeV^{-1} for m_a ≪ 10^{-11} eV

Slightly improves the CAST bound on ALPs

Constraints are within a factor of six of the SN1987A gamma-ray burst limit

Abstract

Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe), hence the cumulative signal from all past SN events can create a diffuse flux peaked at energies of about 25~MeV. We improve upon the modeling of the ALPs flux by including a set of CC SN models with different progenitor masses, as well as the effects of failed CC SNe -- which yield the formation of black holes instead of explosions. Relying on the coupling strength of ALPs to photons and the related Primakoff process, the diffuse SN ALP flux is converted into gamma rays while traversing the magnetic field of the Milky Way. The spatial morphology of this signal is expected to follow the shape of the Galactic magnetic field lines. We make use of this via a template-based analysis that utilizes 12 years of $Fermi$-LAT data in the energy range from 50 MeV to 500 GeV. In our benchmark case of the realization of astrophysical and cosmological parameters, we find an upper limit of $g_{a\gamma} \lesssim 3.76\times10^{-11}\;\mathrm{GeV}^{-1}$ at 95$\%$ confidence level for $m_a \ll 10^{-11}$ eV, while we find that systematic deviations from this benchmark scenario induce an uncertainty as large as about a factor of two. Our result slightly improves the CAST bound, while still being a factor of six (baseline scenario) weaker than the SN1987A gamma-ray burst limit.