Author(s): Damiano F. G. Fiorillo, Ángel Gil Muyor, Georg G. Raffelt, and Edoardo Vitagliano Magnetic fields between a supernova (SN) and Earth convert axions into gamma rays. The absence of such a signal in coincidence with SN 1987A neutrinos, using the coherent Milky Way field, provides well-studied constraints on ${g}_{ap}×{g}_{aγ}$ (axion-proton times axion-photon couplings) and on ${g}… [Phys. Rev. Lett. 137, 121002] Published Tue Sep 15, 2026