Temporal evolution of the likely Si fluorescence line at ∼1.7 keV. The top panel shows the 0.5–10 keV light curve. The associated uncertainties are reported at a level of statistical confidence of 90 percent. Star-shaped points represent fixed values for the parameters. The spectral parameters are reported in Table B.3. The yellow-shaded region indicates the time interval in which the phase jump occurs (see Sect. 3.3).