Swift GRBs and the blast wave model

TL;DR

This study analyzes Swift GRB light curves to constrain blast wave parameters, revealing diverse electron distributions and circumburst media, and successfully interprets most bursts within the blast wave model framework.

Contribution

It provides the first comprehensive constraints on blast wave parameters for a sample of Swift GRBs, highlighting variability in electron distributions and circumburst environments.

Findings

Most bursts fit the blast wave model

Electron energy index p varies across the sample

Circumburst density profiles are diverse

Abstract

The complex structure of the light curves of Swift GRBs has made their interpretation and that of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to constrain the blast wave parameters: electron energy distribution, p, density profile of the circumburst medium, k, and the continued energy injection index, q. We do so by comparing the observed multi-wavelength light curves and X-ray spectra of a Swift sample to the predictions of the blast wave model. We can successfully interpret all of the bursts in our sample of 10, except two, within the framework of the blast wave model, and we can estimate with confidence the electron energy distribution index for 6 of the sample. Furthermore we identify jet breaks in half of the bursts. A statistical analysis of the distribution of p reveals that, even in the most conservative case of least scatter, the values are not consistent with a single, universal value. The values of k suggest that the circumburst density profiles are not drawn from only one of the constant density or wind-like media populations.