Gamma ray signatures of ultra high energy cosmic ray accelerators: electromagnetic cascade versus synchrotron radiation of secondary electrons |
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Authors: | Stefano Gabici Felix A Aharonian |
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Institution: | (1) Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, 69117 Heidelberg, Germany |
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Abstract: | 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.
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Keywords: | Radiation mechanisms: non-thermal cosmic rays ISM: magnetic fields Gamma rays: theory |
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