Leptohadronic Scenarios for TeV Extensions of Gamma-Ray Burst Afterglow Spectra

Abstract

Recent multiwavelength observations of gamma-ray burst afterglows observed in the TeV energy range challenge the simplest synchrotron self-Compton (SSC) interpretation of this emission and are consistent with a single power-law component spanning over 8 orders of magnitude in energy. To interpret this generic behavior in the single-zone approximation without adding further free parameters, we perform an exhaustive parameter space study using the public, time-dependent, multimessenger transport software AM 3 . This description accounts for the radiation from nonthermal protons and the leptohadronic cascade induced by pp and p γ interactions. We summarise the main scenarios that we have found (SSC, Extended-syn, Proton-syn, pp-cascade, and pγ-cascade) and discuss their advantages and limitations. We find that possible high-density environments, as may be typical for surrounding molecular cloud material, offer an alternative explanation for producing flat hard (source) spectra up to and beyond energies of 10 TeV.