Gamma-Ray Bursts:Afterglow and Prompt Emission Models

摘要

Swift observations have revealed interesting but puzzling data that demand a rethink of the origins of gamma-raybursts (GRBs) and their afterglows．The chromatic breaks in X-ray/optical afterglow lightcurves stimulated several innovativesuggestions,most invoking a non-forward-shock origin of the X-ray afterglows．The status of both the observational factsand the theoretical models iS critically reviewed Besides the late“internal”emission from a long-live central engine,mostobserved X-ray afterglows likely still include the contribution of the traditional forward shock component．The physical nature(e．g．energy dissipation mechanism,emission site,and radiation mechanism)of the GRB prompt emission is currently notidentified．The motivations and issues of three proposed prompt emission sites are reviewed．Several independent methods,invoking prompt gamma-ray,X-ray,optical and GeV emission information,respectively,have been applied to constrain theunknown emission site．Tentative evidence suggests a large prompt emission radius．Finally,the implications of the broad bandhigh quality data of the“naked eye”GRB 080319B for our understanding of the afterglow and prompt emission mechanismsare discussed．