2012/10/29 by Patrick Crumley, Pawan Kumar
Physics and Astronomy · #Astrophysics #Astrophysics and Cosmic Phenomena #Cosmic ray #Electron #Fermi Gamma-ray Space Telescope #Gamma-ray burst #Gamma-ray bursts and supernovae #Hadron #Neutrino #Nuclear physics #Photon #Physics #Pion #Pulsars and Gravitational Waves Research #Synchrotron #Synchrotron radiation #astro-ph.HE
paper · pdf · doi:10.1093/mnras/sts581
15 pages, 3 figures; Submitted to MNRAS
arxiv created 2012/10/29 · openalex publication_date 2013/01/11 · arxiv updated 2015/06/11 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
This paper examines the possibility that hadronic processes produce the ≳ 100 MeV photons in the prompt phase of gamma-ray bursts (GRBs) observed by the Fermi-Large Area Telescope (LAT). We calculate analytically the radiation from protons and from secondary electron–positron pairs produced by high-energy protons interacting with γ-rays inside of the GRB jet. We consider both photopion and Bethe–Heitler pair production processes to create secondary electrons and positrons that then radiate via inverse Compton and synchrotron processes. We also consider synchrotron radiation from the protons themselves. We calculate the necessary energy in protons to produce typical Fermi-LAT fluxes of a few μJy at 100 MeV. For both of the photopion and Bethe–Heitler processes, we find that the required energy in protons is larger than the observed γ-ray energy by a factor of a thousand or more. For proton synchrotron, the protons have a minimum Lorentz factor ∼2 × 106. This is much larger than expected if the protons are accelerated by relativistic collisionless shocks in GRBs. We also provide estimates of neutrino fluxes expected from photohadronic processes. Although the flux from a single burst is below IceCube detection limits, it may be possible to rule out photohadronic models by adding up the contribution of several bursts. Therefore, photohadronic processes seem an unlikely candidate for producing the Fermi-LAT radiation during the prompt phase of GRBs.