Orateur
Description
Photon–axion-like particle (ALP) oscillations result in the survival of gamma rays from distant sources above TeV energies. Studies of events observed by CAST, Fermi-LAT, and IACT have constrained the ALP parameters. We investigate the effect of photon-ALP oscillations on the gamma-ray spectra of the first extragalactic neutrino source, TXS 0506+056, for observations by Fermi-LAT and MAGIC around the IC170922-A alert. We obtain a constraint on the ALP coupling parameter $g_{a\gamma}$ < 5 × 10$^{−11}$ GeV$^{−1}$ with 95% C.L. when focusing on the ALP mass range 0.1 neV ≤ $m_a$ ≤ 1000 neV. Importantly, we study the implications of ALP-$\gamma$ oscillations on the counterpart $\gamma$ rays of the sub-PeV neutrinos observed from TXS 0506+056. We also show the diffuse $\gamma$-ray fluxes and observabilities from FSRQs, HSP sources, and LISP sources, assuming similar gamma-ray emissions as that from TXS 0506+056.
