Bright Cosmic-Ray Source as a Solution to Auger-TA Tensions

2025/11/12 by Alexander Korochkin, D. Semikoz, Korochkin, Alexander +3
Physics and Astronomy · #Astrophysical Phenomena and Observations #Astrophysics and Cosmic Phenomena #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #High Energy Astrophysical Phenomena (astro-ph.HE)

paper · pdf · doi:10.48550/arxiv.2511.09406

openalex publication_date 2025/11/12 · openalex created_date 2025/11/14 · openalex updated_date 2026/07/28

Abstract

The ultra-high-energy cosmic ray (UHECR) spectra measured by the Pierre Auger Observatory (Auger) and the Telescope Array (TA) agree very well below 10^19.5 eV but differ significantly at higher energies. We show that these differences can be explained by a single nearby source superimposed on a nearly isotropic background. Taking into account deflections in Galactic and extragalactic magnetic fields, such a source can account for the excess in the TA spectrum without producing excessive anisotropy. The required hard spectrum of the source and intermediate-mass composition are consistent with previous fits of the Auger-only spectrum and composition. This scenario offers several additional advantages: (i) the source produces a broad excess partially overlapping the TA hotspots, suggesting their possible explanation; (ii) without additional tuning, it reproduces the ∼90^∘ shift in dipole direction observed between the Auger-only and combined Auger-TA analyses; and (iii) the best-fit position of the source lies near M82, the brightest nearby starburst galaxy, making it a plausible source of the UHECR.

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