A doublet of cosmic-ray events with primary energies >1020 eV
S. V. Troitsky
Institute for Nuclear Research of the RAS, 117312 Moscow, Russia
Abstract
The Telescope Array Collaboration has observed a cosmic-ray event with
estimated primary energy of 1.38 • 1020 eV whose arrival
direction coincides
[T. Abu-Zayyad et al. (Telescope Array Collaboration), arXiv:1205.5984],
given the angular resolution of
1.5°, with that of an event with estimated primary energy of
1.23 • 1020 eV observed by the Pierre Auger Observatory. The
total number of events with energies >1020 eV published by both
experiments is six. I estimate the statistical significance of the
doublet, which is rather weak, and point out that the arrival directions
of events in the doublet coincide with the Galactic X-ray source Aql X-1.