The flux of ultra-high energy cosmic rays after ten years of operation of the Pierre Auger Observatory

Abstract

The flux of ultra-high energy cosmic rays has been measured with unprecedented precision at the Pierre Auger Observatory. We report an update of the all-sky flux of cosmic rays above 3-1017 eV obtained by combining four independent data sets. These measurements are based on data from the surface detector arrays (divided into two sets according to the shower zenith angle), from a nested, denser, detector array, and hybrid events measured simultaneously with both the fluorescence detector and the surface detector array. The spectral features are presented in detail and the systematic uncertainties are addressed. The huge amount of data collected to date, with a total exposure exceeding 50,000 km2 sr yr, together with the wide range of sky observed (in declination from 90 to 45) also allow us to measure the energy spectrum from different regions of the sky. We present the results of the search for a dependence of the measured flux on the declination of the incoming directions.