Evolution of the 3 − 25 keV count rate, of the fit photon index and disc temperature, and of the disc fraction D_F (see Eq. (1)) is shown along the four different outbursts (same colour coding and symbols as in Fig. 1). Top panels: filled coloured symbols represent the total (source plus background) 3 − 25 keV count rates, the coloured empty symbols the total count rates in the 10 − 25 keV band, and the grey symbols the background count rates in the 10 − 25 keV band. Middle-top panel: a black dashed line at Γ = 2 is shown to guide the eye, whereas the red dot-dashed line highlights the median Γ = 2.20 of the whole XRB sample used in Sect. 5.