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

Abstract

On date 9th 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 Eiso ∼ 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.