Long-term view of the variations in γ Cas. Top panel: longterm behaviour of EW(Hα) with data from Pollmann et al. (2014) in black and data from the present study in orange. Second panel: APT V-band photometry (blue open circles) and the V-band photometry by AAVSO observer Wolfgang Vollmann (black crosses). Third and fourth panels: observed soft and hard X-ray fluxes inferred from Chandra and XMM-Newton spectra (see Table 4). Finally, the bottom panel yields the evolution of the 1.5–12 keV X-ray flux of γ Cas, averaged over the yearly observing seasons as in Fig. 15. The fluxes in the same band derived from the Chandra and XMM-Newton observations (Table 4) are illustrated by the magenta triangles.