A new interpretation of the gamma-ray observations of active galactic nuclei

TL;DR

This paper proposes that secondary photons produced by cosmic rays from active galactic nuclei can explain unexpected gamma-ray observations, impacting our understanding of gamma-ray astronomy and cosmic ray physics.

Contribution

It introduces a new interpretation where secondary photons from cosmic ray interactions account for gamma-ray observations without requiring attenuation.

Findings

Secondary photons match observed gamma-ray spectra.

Cosmic ray interactions explain orphan flares and variability.

Implications for EBL and intergalactic magnetic fields.

Abstract

Gamma-ray telescopes have reported some surprising observations of multi-TeV photons from distant active galactic nuclei (AGN), which show no significant attenuation due to pair production on either the extragalactic background light (EBL), or the photons near the source. We suggest a new interpretation of these observations, which is consistent with both the EBL calculations and the AGN models. Cosmic rays with energies below 50 EeV, produced by AGN, can cross cosmological distances, interact with EBL relatively close to Earth, and generate the secondary photons observed by gamma-ray telescopes. We calculate the spectrum of the secondary photons and find that it agrees with the gamma-ray data. The delays in the proton arrival times can explain the orphan flares, the lack of time correlations, and the mismatch of the variability time scales inferred from the multiwavelength observations. The gamma-ray data are consistent with the detection of the secondary photons, which has important ramifications for gamma-ray astronomy, cosmic ray physics, EBL, and the intergalactic magnetic fields (IGMF).