Multi-TeV Flaring from High-energy Blazars: An Evidence of the Photohadronic Process

Abstract

Abstract High-energy peaked blazars are known to undergo episodes of flaring in GeV–TeV gamma-rays involving different timescales. This flaring mechanism is not well understood, despite long-term simultaneous multiwavelength observations. These gamma-rays en route to Earth undergo attenuation by the extragalactic background light. Using the photohadronic model, where the seed photons follow a power-law spectrum and a template extragalactic background light model, we derive a simple relation between the observed multi-TeV gamma-ray flux and the intrinsic flux with a single parameter. We study 42 flaring epochs of 23 blazars and excellent fits to most of the observed spectra are obtained, strengthening the photohadronic origin of multi-TeV gamma-rays. We can also constrain the power spectrum of the seed photons during the flaring period. Stringent bounds on the blazars of unknown redshifts, whose multi-TeV flaring spectra are known, can be placed using the photohadronic model.