2004/05/31 by Denis Gialis, Guy Pelletier, G. Pelletier · 2 citations
Physics and Astronomy · #Acceleration #Astrophysics #Astrophysics and Cosmic Phenomena #Classical mechanics #Cosmic ray #Electron #Fermi Gamma-ray Space Telescope #Fermi acceleration #Gamma-ray burst #Gamma-ray bursts and supernovae #Magnetic field #Neutrino #Nuclear physics #Particle acceleration #Photosphere #Physics #Pulsars and Gravitational Waves Research #Quantum mechanics #Radiative transfer #astro-ph
paper · pdf · doi:10.1086/430510
published as Astrophys.J. 627 (2005) 868-876 · 18 pages, 3 figures, submitted to Astrophysical Journal
arxiv created 2004/11/05 · openalex publication_date 2005/07/06 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
This paper is devoted to the analysis of particle acceleration in gamma-ray bursts (GRBs) and its radiative consequences. Therefore, we get on one hand constraints on the physics and on the other hand possible signatures of particle acceleration that could be recorded by new gamma-ray instruments. In a recent paper we have shown that UHECRs can be generated in GRBs even with conservative assumptions about the magnetic field and the scattering capability of its perturbations, provided that a suitable relativistic Fermi process is at work during the so-called internal shock phase. In this paper we extend the analysis of the consequences of these assumptions to the whole prompt emission of both electrons and protons. Indeed, assuming that the magnetic field decays as 1/ r 2 and that the scattering time of particles is longer than the Bohm assumption, in particular, with a rule derived from Kolmogorov scaling, we show that the four following events naturally happen with no other parameter adaptation than the intensity of the magnetic field, which turns out to be subequipartition: (1) UHECRs can be generated with a sufficient flux (≃1 km -2 yr -1 ) within the GZK sphere to account for the CR spectrum at the ankle. (In the previous paper, we showed that the associated p γ-neutrino emission is tiny.) (2) A thermal component below the so-called E peak is often unavoidable and even amplified when the shocks start before the photosphere. (3) The CRs could radiate gamma rays around 67 MeV (in the comoving frame, which implies ≃20 GeV for the observer) due to π 0 decay and a low-energy neutrino emission (around 0.2 GeV) associated with neutron decay and also neutrinos of energy between 5 and 150 GeV due to muon decay (as predicted in the previous paper). (4) The UHECRs radiate high-energy gamma rays between a few hundred MeV and 10 GeV (taking the pair creation process into account) due to their synchrotron emission, with a sufficient flux to be observable.