The Association Analysis Of Gamma-Ray Burst Optical And X-Ray Afterglows

Both observatiuonal and theoretical progress on gamma-ray bursts (GRBs) in recent years is briefly summarized, and our associatation analyses on the afterglow components decomposed from the optical and x-ray aftglow lightcurves are present in order to diagnose their possible origins.We collect a sample of104GRBs with well-sampled optical and X-ray afterglow lightcurves and decompose various emission components based on our empirical fits. We focus on the afterglow component that are power-law decayed and may be produced by forward shocks of the GRB fireball. Our analysis shows that the association of the afterglows in the X-ray and optical bands are classified into three groups. First, at least one break is detected in both the two energy bands (18GRBs out of the104GRBs, Group I). Second, there is a break in either optical or X-ray band (18GRBs out of the104GRBs, among them15GRBs in the X-ray band and3in the optical band; Group II). Third, the other68GRBs (Group III) whose lightcurves in the two energy bands are unassociated at all or lack of the same temporal coverage to verify the temporal features of the lightcurves in the two energy bands. We test the physical origin of both the X-ray and optical afterglows of the GRBs in Group I based on the standard GRB models. Poosible energy injection is observed for some GRBs in this group. The X-ray and optical breaks are usually chromatic, but a tentative correlation is found. A large fraction of the decay slopes post the break times of optical lightcurves are consistent with the jet model while X-ray data are not. Our analysis on the Group II and III shows that the afterglow emission in the X-ray and optical bands could be dominated by components from different physical origins.