A doublet of cosmic-ray events with primary energies >10^20 eV

TL;DR

This paper reports a rare doublet of ultra-high-energy cosmic-ray events with energies exceeding 10^20 eV, noting their coincident arrival directions and potential association with a galactic X-ray source, highlighting the need for further statistical analysis.

Contribution

It presents the observation of a doublet of cosmic-ray events with energies over 10^20 eV and discusses their possible correlation with a galactic X-ray source, which is a novel finding.

Findings

Doublet of cosmic-ray events with energies >10^20 eV observed.

Arrival directions coincide with the Galactic X-ray source Aql X-1.

Statistical significance of the doublet is weak.

Abstract

The Telescope Array Collaboration has observed a cosmic-ray event with estimated primary energy of 1.38*10^20 eV whose arrival direction coincides (see arxiv:1205.5984), given the angular resolution of 1.5 deg, with that of an event with estimated primary energy of 1.23*10^20 eV observed by the Pierre Auger Observatory. The total number of events with energies >10^20 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.