Sources of sub-GZK cosmic rays

TL;DR

This paper investigates whether BL Lacertae objects are sources of ultra-high-energy cosmic rays, analyzing correlations, gamma-ray connections, and sky distributions to support the hypothesis that many 40-60 EeV cosmic rays are protons from BL Lacs.

Contribution

It provides evidence supporting BL Lacs as sources of sub-GZK cosmic rays through multiple observational signatures.

Findings

Correlations improve with Galactic magnetic field corrections.

Gamma-ray and UHECR emissions are connected.

Cosmic ray distribution over the sky is non-uniform.

Abstract

We analyze the existing evidence that BL Lacertae objects (BL Lacs) are sources of the highest-energy cosmic rays. We argue that three independent signatures observed in the real data -- (1) improvement of correlations with corrections of trajectories for the Galactic magnetic field; (2) connection between gamma-ray and UHECR emissions; (3) non-uniform distribution of correlating rays over the sky -- are consistent with the hypothesis that a substantial fraction of cosmic rays in the energy range 40-60 EeV are protons accelerated in BL Lacs.