Flux-normalized values of E_cut (right scale) and E_fold (left scale) as functions of time. The normalization to a reference X-ray flux of 5 (ASM-cts s⁻¹) uses the linear correlations as stated in Table 3 and shown in Figs. 7 and 8. These two continuum parameters appear to be constant (see the horizontal lines) in 2012–2019, except for February 2019, where the 35d-phase is very high (0.202).