Energy Spectrum of Ultrahigh-Energy Cosmic Rays across Declinations -90° to +44.8° as Measured at the Pierre Auger...

The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range -90°≤δ≤+44.8° using ∼310 000 events accrued at the Pierre Auger Observatory from an exposure of (104 900±3 100)  km^{2} sr yr. No significant variations of energy spectra with declination are observed, after allowing or not for nonuniformities across the sky arising from the well-established dipolar anisotropies in the arrival directions of ultrahigh-energy cosmic rays. The instep feature in the spectrum at ≃10  EeV reported previously is now established at a significance above 5σ. Within the statistics, the energy spectra are indistinguishable across declinations so disfavoring an origin for the instep from a few distinctive sources.