A nearby source of ultra-high energy cosmic rays

Abstract

Recently the Telescope Array collaboration reported an observation of cosmic ray event with very high energy 244 EeV ($2.44\times 10^{20}$ eV). Importantly, the event is hard to correlate with the matter distribution in the local Universe, even after taking into account deflections in magnetic fields. This implies that the event is likely a nucleus with a large charge. An attenuation length of the nucleus of such a high energy in intergalactic space is quite small, therefore its source should be relatively close to our Galaxy. Using these arguments we derive a new upper bound on a distance to the closest ultra-high energy cosmic ray (UHECR) source and a lower bound on the UHECR source number density in general. The distance to the closest source should not exceed 5 Mpc at 95% C.L. and the 95% C.L. lower-bound on the sources number density is $\rho >1.0\times 10^{-4}$ Mpc${}^{-3}$. The number density of UHECR sources emitting heavy nuclei is constrained for the first time.

Accepted for publication in JCAP

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• Cosmic Clues from Amaterasu: Blazar-Driven Ultrahigh-Energy Cosmic Rays?
• Ultraheavy Ultrahigh-Energy Cosmic Rays
• Ultra-high energy event KM3-230213A as a cosmogenic neutrino in light of minimal UHECR flux models
• An isotropic full-sky sample of optically selected blazars
• Beyond the Local Void: A data-driven search for the origins of the Amaterasu particle