Testing the blast wave model with Swift GRBs

Abstract

The complex structure of the light curves of Swift Gamma-Ray Bursts (GRBs) has made theidentification of breaks, and the interpretation of the blast wave caused by the burst, moredifficult than in the pre-Swift era. We aim to identify breaks, which are possibly hidden, andto constrain the blast wave parameters; electron energy distribution, p, density profile of thecircumburst medium, k, and the continued energy injection index, q. We do so by comparingthe observed multiwavelength light curves and X-ray spectra of our sample to the predictionsof the blast wave model. We can successfully interpret all of the bursts in our sample of 10,except two, within this framework and we can estimate, with confidence, the electron energydistribution index for 6 of the sample. Furthermore, we identify jet breaks in a number of thebursts. A statistical analysis of the distribution of p reveals that, even in the most conservativecase of least scatter, the values are not consistent with a single, universal value. The valuesof k suggest that the circumburst density profiles are not drawn from only one of the constantdensity or wind-like media populations.