On the GeV emission of the type I BdHN GRB 130427A

Abstract

It has been shown recently that the "inner engine" of a type I BdHN is composed of a uniform magnetic field of \(10^{14}\) G aligned with the rotation axis of a Kerr black hole both fulfilling the Wald solution. It is here shown using GRB 130427A as a prototype that this inner engine act in a sequence of "elementary impulses". The case of a single impulse was previously examined, showing that it can accelerate protons to \(10^{21}\) eV which, when propagating along the polar axis give origin to ultra high-energy cosmic rays (UHECRs). When propagating off the polar axis interacting with the hypernova ejecta give origin to the GeV radiation. In this letter we examine the sequence of such elementary impulses and determine their characteristic repetition time starting from \(10^{-6}\) s, slowly increasing with the time evolution. It is shown that this "inner engine" can operate in a GRB for thousand of years, and it can operate not only in GRBs but also in active galactic nuclei.