Fractional excess variability (Fvar; covering frequencies 1.4 × 10−5 to 10−3 Hz, i.e., 5–70 ks timescales) above and below 10 keV observed from Holmberg IX X-1 with NuSTAR during the two epochs (see Section 4). There is tentative evidence for enhanced variability above 10 keV in the second epoch.