A search for photons with energies above $2{\times}10^{17}$ eV using hybrid data from the low-energy extensions of the Pierre Auger Observatory

TL;DR

This paper reports a search for ultra-high-energy photons above 2×10^{17} eV using hybrid data from the Pierre Auger Observatory, setting the most stringent flux limits in this energy range to date.

Contribution

It introduces a new search for photons above 2×10^{17} eV using 5.5 years of hybrid data, providing the tightest flux upper limits in this energy region.

Findings

Most stringent upper limits on photon flux between 10^{17} and 10^{18} eV.

No detection of photons above 2×10^{17} eV.

Enhanced constraints on models of cosmic-ray and gamma-ray sources.

Abstract

Ultra-high-energy photons with energies exceeding $10^{17}$ eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent observations of photons with energies in the $10^{15}$ eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding $2{\times}10^{17}$ eV using about 5.5 years of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between $10^{17}$ and $10^{18}$ eV.