Synchrotron Self-Compton Afterglow Closure Relations and Fermi-LAT-detected Gamma-Ray Bursts

Abstract The Fermi Large Area Telescope (Fermi-LAT) Collaboration reported the Second Gamma-ray Burst Catalog (2FLGC), which comprises a subset of 29 bursts with photon energies above 10 GeV. Although standard synchrotron forward-shock model has successfully explained gamma-ray burst (GRB) afterglow observations, energetic photons higher than GeV from these transient events can hardly be described in this scenario. We present closure relations (CRs) self-Compton (SSC) adiabatic and radiative scenario, when central engine injects continuous energy into blast wave to study evolution spectral temporal indexes those 2FLGC. consider SSC evolving stellar-wind interstellar medium (ISM), CRs as function parameter, injection index, electron index for 1 < p 2 ? . select all GRBs that have been modeled both simple or broken power law found satisfy significant fraction cannot interpreted even though require an intermediate density profile (e.g., GRB 130427A) atypical total given amplify magnetic field ( ? B ). value parameter ranges ? ?5 ? ?4 ) cooling break corresponds Fermi-LAT band typical values afterglow. analysis shows ISM is preferred scenario without