http://arxiv.org/abs/2110.03679
Axion-like particles (ALPs) may be abundantly produced in core-collapse (CC) supernovae (SNe), hence the cumulative signal from all past SN events would contain an ALP component and create a diffuse flux peaked at energies of about 50 MeV. We update the calculation of this flux by including a set of CC SN models with different progenitor masses following the expected mass distribution. Additionally, we include 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 a diffuse gamma-ray flux 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 {\it Fermi}-LAT data in the energy range from 50 MeV to 500 GeV. This strategy yields an improvement of roughly a factor of two for the upper limit on the ALP-photon coupling constant $g_{a\gamma}$ compared to a previous analysis that accounted only for the spectral shape of the signal. While the improved SN modeling leads to a less energetic flux that is harder to detect, the combined effect is still an improvement of the limit and in particular its statistical reliability. We also show that our results are robust against variations in the modeling of high-latitude Galactic diffuse emission and systematic uncertainties of the LAT.
F. Calore, P. Carenza, C. Eckner, et. al.
Fri, 8 Oct 21
68/70
Comments: 18 pages, 10 figures