Axion-sourced fireballs from supernovae

New feebly interacting particles would emerge from a supernova core with 100-MeV-range energies and produce $\gamma$-rays by subsequent decays. These contribute to the diffuse cosmic $\gamma$-ray background or have shown up in Solar Maximum Mission (SMM) satellite SN~1987A. However, we show for example of axion-like (ALPs) that, even at distances beyond progenitor star, decay photons may not escape, can instead form fireball, plasma shell $T\lesssim 1$ MeV. Thus, existing arguments do exclude ALPs few 10 MeV masses two-photon coupling $10^{-10}~{\rm GeV}^{-1}$. energy showed sub-MeV photons, which were seen SN 1987A Pioneer Venus Orbiter (PVO), closing again this new window. A careful re-assessment is required other that constrained similar ways.