# Astrophysical interpretation of Pierre Auger Observatory measurements of the UHECR energy spectrum and mass composition

## TL;DR

This paper analyzes Pierre Auger Observatory data on ultra-high-energy cosmic rays, fitting an astrophysical model to understand their sources and composition, revealing low maximum energies and hard spectra.

## Contribution

It introduces a combined fit of a simple astrophysical model to both energy spectrum and mass composition data above 5 EeV, considering systematic uncertainties.

## Key findings

- Sources have low maximum injection energies.
- Sources exhibit hard spectral indices.
- Systematic uncertainties impact the fit results.

## Abstract

We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 EeV, i.e. the region of the all-particle spectrum above the so-called "ankle" feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated with a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies and hard spectral indices. The impact of various systematic uncertainties on the above result is discussed.