The evolution of gamma-ray burst remnants

摘要

The detection of the delayed emission in X-ray, optical, and radio bands, i.e., the afterglow of γ-ray bursts (GRBs), suggests that the sources of GRBs are likely to be at cosmological distances. Here we explore the interaction of a relativistic shell with a uniform interstellar medium (ISM) and obtain the exact solution of the evolution of γ-ray burst remnants, including the radiative losses. We show that in general the evolution of the bulk Lorentz factor, γ, satisfies γ∝t~-at when γ 1; here, a_t is mainly in the range 9/22-3/8, the latter corresponding to adiabatic expansion. So it is clear that adiabatic expansion is a good approximation even when radiative loss is considered.