Gamma ray signatures of ultra high energy cosmic ray accelerators: electromagnetic cascade versus synchrotron radiation of secondary electrons

Conference paper


We discuss the possibility of observing ultra high energy cosmic ray sources in high energy gamma rays. Protons propagating away from their accelerators produce secondary electrons during interactions with cosmic microwave background photons. These electrons start an electromagnetic cascade that results in a broad band gamma ray emission. We show that in a magnetized Universe (B≳10−12 G) such emission is likely to be too extended to be detected above the diffuse background. A more promising possibility comes from the detection of synchrotron photons from the extremely energetic secondary electrons. Although this emission is produced in a rather extended region of size ∼10 Mpc, it is expected to be point-like and detectable at GeV energies if the intergalactic magnetic field is at the nanogauss level.


Radiation mechanisms: non-thermal cosmic rays ISM: magnetic fields Gamma rays: theory 


98.70.Sa 98.70.Rz 


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Copyright information

© Springer 2007

Authors and Affiliations

  1. 1.Max-Planck-Institut für KernphysikHeidelbergGermany

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