Possible Extragalactic Sources of the Highest Energy Cosmic Rays

Abstract

We give an outline of possible extragalactic explanations of the highest energy cosmic ray events. We give a classification of the possible particles which could have caused the events and try to find suitable sources for each class. In contrast to some previous investigations of other authors, we find a possible candidate of a local FR-II radio galaxy close to the Fly's Eye event, and less powerful active galaxies close to the AGASA event. We also note the interesting coincidence that we have strong, distant quasars inside the arrival direction error regimes of both the Fly's Eye and AGASA event. We briefly discuss the consequences for the cosmic ray spectrum and composition at highest energies, which could be investigated by future experiments.