Two-energy plots for the three sources. Data points, obtained by a scaling at the same highest amplitude of light curves witha time resolution of 0.5 s after a smoothing over five points, are represented in red; the thick black lines correspond to equally scaled count rates, and the green solid curves are the quadratic best fits to the data. Left panel: G-2 data in the energy bands 3.22–3.94 keV on the abscissa and 10.82–11.92 keV on the ordinate with a time bin size of 1 s and 3-point running average; central panel: I-2 data in the energy bands 2–6 keV on the abscissa and 6–20 keV on the ordinate with a time bin size of 1 s and 3-point running average; right panel: M-1 and M-2 data (excluding those of the type-I event) in the ranges 2.1–3.8 keV on the abscissa and 11.4–15.2 keV on the ordinate.