Integrated fluxes at 1 AU (right-side axis) and at 0.05 AU (left-side axis, corresponding to the orbital distance of Prox Cen b). When not included in the figure, the integration range is [1, 100] Å. Star-shaped markers indicate results from this work, while round markers indicate results from other works. For the Sun (integrated over [4.1, 100] Å), the variability range over its activity cycle in quiescence and a flaring reference are taken from Peres et al. (2000). Assuming a cycle maximum-to-minimum ratio of 1.5 for Prox Cen (Wargelin et al. 2024), we show the star’s quiescent variability due to its activity cycle. To provide a reference for the amplitude of the activity cycle on the plot, we use two example spectra, the Ribas et al. (2017) spectrum (gray) and our average spectrum (azure), as mid-cycle quiescent flux references.