2004MNRAS.354..414A

We study regenerated high-energy emission from the γ-ray burst (GRB) afterglows, and compare its flux with the direct component from the same afterglow. When the intrinsic emission spectrum extends to the TeV region, these very high-energy photons are significantly absorbed by the cosmic infrared background (CIB) radiation field, creating electron-positron pairs; since these pairs are highly energetic, they can scatter the cosmic microwave background radiation up to GeV energies, which may change the intrinsic afterglow light curve in the GeV region. Using the theoretical models given in the literature and a reasonable choice of the relevant parameters, we calculate the expected light curve due to the regeneration mechanism. We find that the regenerated emission could only slightly change the original light curve, even if we take a rather large value for the CIB density, independently of the density profile of the surrounding medium, i.e. constant or wind-like profile. This ensures reliable estimation of the intrinsic GRB parameters when high-energy observation is accessible, regardless of the large amount of uncertainty concerning the CIB density as well as extragalactic magnetic field strength.