On 9 October, 2022, an extremely powerful gamma-ray burst, GRB 221009A, was
detected by several instruments. Despite being obstructed by the Milky Way
galaxy, its afterglow outburst outshone all other GRBs seen before. LHAASO
detected several thousands very-high energy photons extending up to 18 TeV.
Detection of such energetic photons are unexpected due to the large opacity of
the Universe. It is possible that in the afterglow epoch the intrinsic very
high-energy photon flux from the source might have increased manifolds, which
could compensate the attenuation by pair-production with the extragalactic
background light. We propose such a scenario and show that very high-energy
photons can be observed on the Earth from the interaction of very-high energy
protons with the seed synchrotron photons in the external forward shock region
of the GRB jet.
Comment: 7 pages, 2 figures
Subjects: Astrophysics - High Energy Astrophysical Phenomena; High Energy Physics - Phenomenology