Temporal and spectral characteristics of GRBs deduced from the curvature effect.

Emission from an expanding fireball surface must be influenced by the delay of time of different areas of the fireball surface, the variation of the intensity due to the growing of the fireball radius, the variation of the time contracted factor and the shifting of the intrinsic spectrum associated with the angle relative to the line of sight. Besides these, the emission is confined by the fireball surface itself, which together with the intrinsic emission limits will play a role in constraining photons that will reach the observer expected at any particular observation time. Taking all these factors into account comes to a full knowledge of the so-called curvature effect. I present a summary of our group’s work carried on in the past few years. Our work covers the derivation of basic formulas of the curvature effect, its application to the prompt emission of GRBs, and the application to the early X-ray afterglow emission of the events. In particular, an interpretation based on the curvature effect, for the new puzzling finding of the softening process detected in the early X-ray emission of Swift bursts is presented. [ABSTRACT FROM AUTHOR]