Origin of Sub-TeV Afterglow Emission from Gamma-Ray Bursts GRB 190114C and GRB 180720B

The detection of GRB 180722B and GRB 190114C in sub-TeV gamma-rays has opened up a new window to study gamma-ray bursts in high-energy gamma-rays. Recently it has been shown that the synchrotron and inverse Compton processes are responsible for the production of these high-energy gamma-rays during the afterglow. Here, for the first time we demonstrate that the photohadronic scenario that is successful in explaining the multi-TeV flaring in high-energy blazars is also applicable for gamma-ray bursts. We show that the sub-TeV spectra of GRB 190114C and GRB 180720B are due to the interaction of high-energy protons with the background photons in the synchrotron self-Compton region and synchrotron region, respectively. The nature of the background photon distributions help us to constrain their bulk Lorentz factors.