The Energy Spectrum of Ultra-High Energy Cosmic Rays across Declinations $-{90}^{\circ }$ to $+{44.8}^{\circ }$ as measured at the Pierre Auger Observatory

The energy spectrum of cosmic rays above 2.5 EeV has been measured across the declination range $-{90}^{\circ }\le \delta \le +{44.8}^{\circ }$ using data from $\sim \mathrm{310,000}$ events accrued at the Pierre Auger Observatory from an exposure of $(\mathrm{104,900}\pm \mathrm{3,100})$ km${}^2$sr$$yr. No significant variations of energy spectra with declination are observed, after allowing or not for non-uniformities across the sky arising from the well-established dipolar anisotropies in the arrival directions of ultra-high energy cosmic rays. Additionally, the instep feature in the spectrum at $\simeq$ 10 EeV reported previously is now established at a significance above $5\sigma$. The quasi-uniformity of the energy spectrum across declinations disfavors an origin for the instep from a few distinctive sources.