Does regenerated emission change the high-energy signal from gamma-ray burst afterglows?

Shin'ichiro Ando

Published 2004-07-09Version 1

We study regenerated high-energy emission from the gamma-ray burst (GRB) afterglows, and compare its flux with the direct component from the same afterglow. When the intrinsic emission spectrum extends to 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 modeling given in literature and the reasonable choice of relevant parameters, we calculate the expected light curve due to the regeneration mechanism. As the result, 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 surrounding medium, i.e., constant or wind-like profile. This ensures us the reliable estimation of the intrinsic GRB parameters when the high-energy observation is accessible, regardless of a large amount of uncertainty concerning the CIB density as well as extragalactic magnetic field strength.