Constraining the Origin of TeV Photons from Gamma‐Ray Bursts with Delayed MeV–GeV Emission Formed by Interaction with Cosmic Infrared/Microwave Background Photons

It has been suggested that electromagnetic cascade of very high energygamma-rays from gamma-ray bursts (GRBs) in the infrared/microwave backgroundcan produce delayed MeV-GeV photons. This delay could be caused by the angularspreading effect of the scattered microwave photons or deflection of thesecondly pairs due to intergalactic magnetic field. Very high energy TeVphotons of GRBs could be produced by a few mechanisms including theproton-synchrotron radiation and electron inverse Compton emission from GRBinternal shocks as well as external shocks. We suggest that the informationprovided by the delayed emission could give constraints on models for TeVgamma-rays. A more accurate calculation of the delayed time caused by theangular spreading effect is presented by considering recent observations of theextragalactic infrared background and the theoretic high-redshift infraredbackground. We also suggest that the dependence of the maximum time delay ofscattered photons on their energies, if determined by future GLAST detector,could differentiate the two mechanisms causing the time delay.Comment: 16 pages including 1 table, accepted for publication in Ap