From blast wave to observation

TL;DR

This paper introduces a versatile code for modeling GRB afterglows, enabling detailed analysis of fluid dynamics and spectral evolution beyond analytical methods, and applies it to real GRB data and complex environmental interactions.

Contribution

The authors present a new computational tool that reconstructs spectra and light curves from arbitrary fluid configurations, extending modeling capabilities for GRB afterglows.

Findings

The code successfully fits theoretical afterglow models to observational data.

It extends previous models to include diverse circumburst density profiles.

The transition from wind to interstellar medium environments appears smooth in simulations.

Abstract

Gamma-ray burst (GRB) afterglows are well described by synchrotron emission originating from the interaction between a relativistic blast wave and the external medium surrounding the GRB progenitor. We introduce a code to reconstruct spectra and light curves from arbitrary fluid configurations, making it especially suited to study the effects of fluid flows beyond those that can be described using analytical approximations. As a check and first application of our code we use it to fit the scaling coefficients of theoretical models of afterglow spectra. We extend earlier results of other authors to general circumburst density profiles. We rederive the physical parameters of GRB 970508 and compare with other authors. We also show the light curves resulting from a relativistic blast wave encountering a wind termination shock. From high resolution calculations we find that the observed transition from a stellar wind type light curve to an interstellar medium type light curve is smooth and without short-time transitory features.