Numerical modelling with analytical estimation of the free parameter space of GRB afterglows: The case of GRB 221009A

¹ Department of Physics, University of Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
² INFN Rome Tor Vergata, Via della Ricerca Scientifica 1, 00133 Rome, Italy
³ INFN Padova, Via Marzolo 8, 35131 Padova, Italy

^* e-mail: claudio.gasbarra@roma2.infn.it

Published online: 6 March 2025

Abstract

On date 9^th of October 2022, an exceptionally bright Gamma-Ray Burst, GRB 221009A, was detected by several observatories, both ground- and space-based. It has been the highest flux Gamma-Ray Burst ever observed, with an energy E_iso ∼ 10⁵⁵erg, and its detection was followed by many studies. In our work, we model the very high energy (E> 100 GeV) afterglow light curve published by the LHAASO Collaboration using a numerical modelling and an analytical approach to constrain the Gamma-Ray Burst free parameter space. The light curve in the (0.3 - 5) TeV range, as detected by LHAASO, shows a simple broken power law shape, with the peak around ∼11 s after the trigger. We estimated the afterglow parameters using a Maximum Likelihood Estimation followed by a Markov-Chain Monte Carlo. In this way, we obtain the fiducial confidence intervals. We found some interesting preliminary results about the parameter distributions, in reasonable agreement with other studies.