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The sources of ultra-high energy cosmic rays are not yet known. However, the discovery of anisotropic cosmic rays above 57x10^18 eV by the Pierre Auger Observatory suggests that a direct source detection may soon be possible. The near-future prospects for such a measurement are heavily dependent on the flux of the brightest source. In this work, we show that the flux of the brightest source above 57x10^18 eV is expected to comprise 10% or more of the total flux if two general conditions are true. The conditions are: 1.) the source objects are associated with galaxies other than the Milky Way and its closest neighbors, and 2.) the cosmic ray particles are protons or heavy nuclei such as iron and the Greisen-Zatsepin-Kuzmin effect is occurring. The Pierre Auger Observatory collects approximately 23 events above 57x10^18 eV per year. Therefore, it is plausible that, over the course of several years, tens of cosmic rays from a single source will be detected.
We introduce a method to constrain the characteristic angular size of the brightest cosmic-ray sources observed above 57 times 1018 eV. By angular size of a source, we mean the effective angular extent over which cosmic-rays from that source arrive a
We report a measurement of the energy spectrum of cosmic rays for energies above $2.5 {times} 10^{18}~$eV based on 215,030 events recorded with zenith angles below $60^circ$. A key feature of the work is that the estimates of the energies are indepen
The amplitude and phase of the cosmic ray anisotropy are well established experimentally between 10^{11} eV and 10^{14} eV. The study of their evolution into the energy region 10^{14}-10^{16} eV can provide a significant tool for the understanding of
Comparing the signals measured by the surface and underground scintillator detectors of the Yakutsk Extensive Air Shower Array, we place upper limits on the integral flux and the fraction of primary cosmic-ray photons with energies E > 10^18 eV, E >
We present the results of the search for ultra-high-energy photons with nine years of data from the Telescope Array surface detector. A multivariate classifier is built upon 16 reconstructed parameters of the extensive air shower. These parameters ar