# Synchrotron self-Compton emission from external shocks as the origin of the sub-TeV emission in GRB 180720B and GRB 190114C

## TL;DR

This paper models the sub-TeV emission in two gamma-ray bursts as synchrotron self-Compton emission from external shocks, explaining recent high-energy photon detections with standard afterglow physics.

## Contribution

It demonstrates that SSC emission from external shocks can account for the sub-TeV photons observed in GRB 180720B and GRB 190114C, providing a unified explanation.

## Key findings

- SSC emission explains sub-TeV photons in both GRBs.
- Model parameters are typical for GRB afterglows.
- Detection is linked to high burst energies and low redshifts.

## Abstract

Recently, very high-energy photons above 100 GeV were reported to be detected from GRB~190114C and GRB~180720B at, respectively, 100-1000 s and 10 hours after the burst. We model the available broad-band data of both GRBs with the synchrotron plus synchrotron self-Compton (SSC) emission of the afterglow shocks. We find that the sub-TeV emission of GRB~180720B can be interpreted as the SSC emission from afterglow shocks expanding in a constant density circum-burst medium. The SSC emission of GRB~190114C dominates over the synchrotron component from GeV energies at $\sim100$ s, which can explain the possible hard spectrum of the GeV emission at this time. The extrapolated flux of this SSC component to sub-TeV energies can explain the high-significance detection of GRB~190114C by the MAGIC telescope. The parameter values (such as the circum-burst density and shock microphysical parameters) in the modeling are not unusual for both GRBs, implying that the detection of sub-TeV photons from these two bursts should be attributed to their large burst energies and low redshifts.