Correlation between the measured values of the pulse-phase-averaged cyclotron line energy and the X-ray flux (at the maximum of the respective 35d main-on), as measured by Swift/BAT (in units of (ASM-cts s⁻¹)) for all NuSTAR observations between 2012 and March 2019 (see Table 1). We note that 1 (ASM-cts s⁻¹) equals 93.0 (Swift/BAT-cts)/(cm² s) (Staubert et al. 2016) and 0.224 (keV cm⁻² s) in (2−10 keV). The best-fit line defines a slope of (0.675 ± 0.075) keV/(ASM-cts s⁻¹). The Pearson linear correlation coefficient is 0.98. For the mean power-law index of −0.953 and an adopted distance of 6.6 kpc (Reynolds et al. 1997), the Her X-1 luminosity is L_X(2−10 keV) [10³⁷ erg s⁻¹] = 0.187(1) × (ASM-cts s⁻¹).