Calorimetry of GRB 030329: Simultaneous Fitting to the Broadband Radio Afterglow and the Observed Image Expansion Rate

TL;DR

This paper performs detailed calorimetry on GRB 030329 by fitting broadband radio afterglow data and image expansion rates using a semi-analytic MHD model that accounts for relativistic and non-relativistic regimes and interstellar scintillation effects.

Contribution

It introduces a semi-analytic method for fitting GRB afterglow data that is valid across different regimes and includes scintillation modeling, providing new insights into the burst parameters and jet dynamics.

Findings

Initial burst parameters determined

Circumburst medium properties explored

Initial Lorentz factor estimated

Abstract

We perform calorimetry on the bright gamma ray burst (GRB) 030329 by fitting simultaneously the broadband radio afterglow and the observed afterglow image size to a semi-analytic magnetohydrodynamical (MHD) and afterglow emission model. Our semi-analytic method is valid in both the relativistic and non-relativistic regimes, and incorporates a model of the interstellar scintillation that substantially effects the broadband afterglow below 10 GHz. The model is fitted to archival measurements of the afterglow flux from 1 day to 8.3 years after the burst. Values for the initial burst parameters are determined and the nature of the circumburst medium is explored. Additionally, direct measurements of the lateral expansion rate of the radio afterglow image size allow us to estimate the initial Lorentz factor of the jet.