Very-High-Energy Gamma-Ray Signal from Nuclear Photodisintegration as a Probe of Extragalactic Sources of Ultrahigh-Energy Nuclei

TL;DR

This paper proposes that gamma-ray signals resulting from nuclear photodisintegration in ultrahigh-energy cosmic-ray sources can serve as unique indicators for identifying and studying these astrophysical accelerators.

Contribution

It introduces a novel diagnostic gamma-ray signal from de-excitation following photodisintegration, providing a new method to probe the composition and properties of UHECR sources.

Findings

Predicted gamma-ray signals are detectable by current and next-generation telescopes.

Heavy nuclei can survive in sources and produce distinctive gamma-ray signatures.

The method offers a new way to identify and analyze UHECR accelerators.

Abstract

It is crucial to identify the ultrahigh-energy cosmic-ray (UHECR) sources and probe their unknown properties. Recent results from the Pierre Auger Observatory favor a heavy nuclear composition for the UHECRs. Under the requirement that heavy nuclei survive in these sources, using gamma-ray bursts as an example, we predict a diagnostic gamma-ray signal, unique to nuclei - the emission of de-excitation gamma rays following photodisintegration. These gamma rays, boosted from MeV to TeV-PeV energies, may be detectable by gamma-ray telescopes such as VERITAS, HESS, and MAGIC, and especially the next-generation CTA and AGIS. They are a promising messenger to identify and study individual UHE nuclei accelerators.