Top panel: the broadband X-ray spectrum displayed by Holmberg IX X-1 during epoch 1. All the data have been unfolded through the same model, which simply consists of a count spectrum that is constant with energy. Bottom panel: data/model ratio to the power-law continuum applied to the 3–10 keV energy range, then extended out to the full broadband spectrum. Both panels clearly demonstrate that the curvature observed in the 3–10 keV bandpass is associated with a true spectral cutoff. The color scheme is the same as for Figure 3, and the data have again been rebinned for clarity.