# Multi-Messenger Physics with the Pierre Auger Observatory

## TL;DR

This paper reviews the multi-messenger capabilities of the Pierre Auger Observatory, highlighting techniques, results, and constraints in detecting ultra-high energy neutrinos, photons, and neutrons, and exploring cosmic ray sources.

## Contribution

It provides a comprehensive overview of the observatory's methods and recent results in multi-messenger astrophysics, including new bounds and source correlation analyses.

## Key findings

- Set stringent upper bounds on diffuse cosmogenic neutrinos and photons.
- Placed limits on neutrinos from binary mergers detected by LIGO/Virgo.
- Identified correlations between cosmic rays and neutrino sources.

## Abstract

An overview of the multi-messenger capabilities of the Pierre Auger Observatory is presented. The techniques and performance of searching for Ultra-High Energy neutrinos, photons and neutrons are described. Some of the most relevant results are reviewed, such as stringent upper bounds that were placed to a flux of diffuse cosmogenic neutrinos and photons, bounds placed on neutrinos emitted from compact binary mergers that were detected by LIGO and Virgo during their first and second observing runs, as well as searches for high energy photons and neutrons from the Galactic center that constrain the properties of the putative Galactic PeVatron, observed by the H.E.S.S.\ collaboration. The observation of directional correlations between ultra-high energy cosmic rays and either high energy astrophysical neutrinos or specific source populations, weighted by their electromagnetic radiation, are also discussed. They constitute additional multi-messenger approaches aimed at identifying the sources of high energy cosmic rays.