Abstract:
The Telescope Array Collaboration has observed a cosmic-ray event with
estimated primary energy of $1.38 \cdot 10^{20}$ eV whose arrival
direction coincides
[T. Abu-Zayyad et al. (Telescope Array Collaboration), arXiv:1205.5984],
given the angular resolution of
$1.5^{\circ}$, with that of an event with estimated primary energy of
$1.23 \cdot 10^{20}$ 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.
Fulltext:
PDF file (274 kB)