The Pierre Auger Observatory: Contributions to the 39th International Cosmic Ray Conference (ICRC 2025)

TL;DR

The Pierre Auger Observatory has been collecting data since 2004 to study ultra-high-energy cosmic rays, with recent upgrades enhancing detection capabilities, and recent conference contributions presenting new measurements, detector performance, and astrophysical insights.

Contribution

This compilation reports recent results from the Pierre Auger Observatory, including new measurements, detector upgrades, and investigations into cosmic ray properties and related phenomena.

Findings

Measurements of the energy spectrum and mass composition of cosmic rays.

Performance evaluation of the upgraded AugerPrime detectors.

First results on ultra-high-energy photon and neutrino searches.

Abstract

The Pierre Auger Observatory, located in La Pampa Amarilla, Argentina, has been continuously acquiring data since 2004. It comprises a surface detector array covering 3,000 km$^2$ and 27 fluorescence telescopes, designed to detect extensive air showers initiated by ultra-high-energy cosmic rays. An upgrade to the Observatory was commissioned in 2024, enhancing the existing water-Cherenkov detectors with additional radio antennas, surface scintillator detectors, and a buried scintillator array. This compilation of contributions to the 39th International Cosmic Ray Conference, held in Geneva, Switzerland (July 15-24, 2025), presents recent results from the Pierre Auger Collaboration, addressing a wide range of fundamental questions in astroparticle physics. The included papers cover measurements of the energy spectrum, mass composition, and arrival directions of ultra-high-energy cosmic rays, investigations of hadronic interactions in extensive air showers, and searches for ultra-high-energy photons and neutrinos. Additional topics include radio detection techniques, solar-related phenomena, and atmospheric events such as ELVES and TGFs. The list also contains first results and performance evaluations of the upgraded detectors, AugerPrime, along with reports on outreach and social engagement initiatives conducted by the Collaboration.