Gamma ray signatures of ultra high energy cosmic ray sources

摘要

We discuss the possibility of observing distant accelerators of ultra high energy cosmic rays (UHECR) in synchrotron gamma rays. Protons propagating away from their acceleration site produce extremely energetic electrons during photopion interactions with cosmic microwave background (CMB) photons. If the magnetic field close to the accelerator is at the nG level, the synchrotron radiation from these electrons appears to a distant observer as a point-like GeV source.