Evolution of the cyclotron line energy E_cyc in Her X-1. The red points until 2012 (MJD 56200) and the corresponding linear best fit (dashed line) are reproduced from Staubert et al. (2016). The black points are the new measurements by NuSTAR from 2015−2019 (see Table 1): the pulse-phase-averaged E_cyc values normalized to a reference ASM count rate of 6.8 (ASM-cts s⁻¹) using a flux dependence of 0.675 keV/(ASM-cts s⁻¹) (see Fig. 1). The solid red line represents the weighted mean of (37.44 ± 0.07) keV, demonstrating a constant value since at least 2012.