Testing the blast wave model with Swift GRBs

TL;DR

This study tests the blast wave model against Swift GRB light curves, successfully interpreting most bursts and estimating key parameters, revealing diverse circumburst environments and electron energy distributions.

Contribution

It provides a comprehensive comparison of Swift GRB data with blast wave model predictions, constraining parameters and identifying jet breaks, with implications for GRB environment diversity.

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 the identification of breaks, and the interpretation of the blast wave caused by the burst, more difficult than in the pre-Swift era. We aim to identify breaks, which are possibly hidden, and 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 our 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 this framework and we can estimate, with confidence, the electron energy distribution index for 6 of the sample. Furthermore we identify jet breaks in a number 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.