Diverse Temporal Properties of Gamma‐Ray Burst Afterglows

Abstract

The detection of delayed X-ray, optical, and radio emission, the ``afterglow'' associated with gamma-ray bursts (GRBs), is consistent with fireball models, in which the emission is produced by a relativistic expanding blast wave, driven by an expanding fireball at cosmological distances. The emission mechanisms of GRB afterglows have been discussed by many authors, and synchrotron radiation is believed to be the main mechanism. The observations show that the optical light curves of two observed gamma-ray bursts, GRB 970228 and GRB 970508, can be described by a simple power law, which seems to support the synchrotron radiation explanation. However, here we show that under some circumstances, inverse Compton scattering (ICS) may play an important role in the emission spectrum, and this may influence the temporal properties of GRB afterglows. We expect that the light curves of GRB afterglows may consist of multiple components, depending on the fireball parameters.