We derive new constraints on the coupling of heavy pseudoscalar (axion-like) particles to photons, based on the gamma ray flux expected from the decay of these particles into photons. After being produced in the supernova core, these heavy axion-like particles would escape and a fraction of them would decay into photons before reaching the Earth. We have calculated the expected flux on Earth of these photons from the supernovae SN 1987A and Cassiopeia A and compared our results to data from the Fermi Large Area Telescope. This analysis provides strong constraints on the parameter space for axion-like particles. For a particle mass of 100 MeV, we find that the Peccei-Quinn constant, f a , must be greater than about 10 15 GeV. Alternatively, for f a = 10 12 GeV, we exclude the mass region between approximately 100 eV and 1 GeV.

Several models predict the existence of heavy (mass ∼ MeV or so) pseudoscalar (axion-like) particles. This possibility is permitted only if the relation between the axion mass and the PecceiQuinn constant is relaxed.Here we consider a possible phenomenological consequence of these models. After being produced in the supernova core, these heavy axions would escape and a fraction of them would decay into photons before reaching the earth. We calculated the expected spectrum of these photons from the supernovae SN1987A and CAS A, in terms of the axion mass and the Peccei-Quinn constant f a , and compared our results to the data from the FERMI Large Area Telescope. The analysis provides strong constraints on the allowed region in the axion parameter space for 100keV m a 1 GeV. This mass region is completely excluded unless f a > 10 12 GeV. For axion masses ∼ 100MeV, the constraint is stronger f a > a few 10 14 GeV.