Time dependent numerical model for the very high energy emissions of distant gamma-ray busrt GRB 201216C

TL;DR

This paper develops a numerical model to explain the very-high-energy emission from distant gamma-ray burst GRB 201216C, accounting for EBL absorption, and compares it with other Sub-TeV GRBs to understand their common properties.

Contribution

The paper introduces a new numerical model for the afterglow emission of distant GRBs, incorporating EBL absorption effects and explaining observed VHE emissions.

Findings

Predicted 0.1 TeV flux can reach 10^{-9} - 10^{-10} erg cm^{-2} s^{-1} at 10^3-10^4 s.

Sub-TeV GRBs share similar shock parameters, such as energetic bursts and low medium density.

Maximum redshift for detection by MAGIC is estimated at z ~ 1.6.

Abstract

Recently, the MAGIC Collaboration reported a $\sim 5\sigma$ statistical significance of the very-high-energy (VHE) emission from a distant GRB, GRB 201216C. Such distant GRB may be effectively absorbed by the extragalactic background light (EBL). The origin of the VHE emission from such distant objects is still unknown. Here, we propose a numerical model for studying the afterglow emission of this distant GRB. The model solves the continuity equation governing the temporal evolution of electron distribution, and the broad-band observed data can be explained by the synchrotron plus synchrotron self-Compton (SSC) radiation of the forward shock. The predicted observed 0.1 TeV flux can reach $\sim 10^{-9} -10^{-10}\rm erg ~ cm^{-2} ~ s^{-1}$ at $t \sim 10^3 -10^4 \rm s$, even with strong EBL absorption, such strong Sub-TeV emissions still can be observed by MAGIC telescope. Using this numerical model, the shock parameters in the modeling are similar with two other Sub-TeV GRBs (i.e., GRB 190114C and GRB 180720B), implying that the Sub-TeV GRBs have some commonalities: they have energetic burst energy, low circum-burst medium density and low magnetic equipartition factor. We regard GRB 201216C as a typical GRB, and estimate the maximum redshift of GRB that can be detected by MAGIC telescope, i.e., $z \sim 1.6$. We also find that the VHE photon energy of such distant GRB can only reach $\sim 0.1 ~\rm TeV$. Improving the low energy sensitivity of the VHE telescope is very important to detect the Sub-TeV emissions of these distant GRBs.