Constant cyclotron line energy in Hercules X-1 -- Joint Insight-HXMT and NuSTAR observations

G. C. Xiao, L. Ji, R. Staubert +108

The long-term evolution of the centroid energy of the CRSF in Her X-1 is still a mystery. We report a new measurement from a campaign between {\sl Insight}-HXMT and {\sl NuSTAR} pe…