From top to bottom: the excess map in the time-energy plane with a resolution of 2 ks in time and 0.5 keV in energy. Light smoothing with an elliptical Gaussian kernel (2 pixel × 1 pixel in FWHM) was applied. The three light curves are derived from the excess map by projecting the multiple spectral channels, corresponding to the Fe K line core centred on the 6.5 keV (5.75–7.25 keV) and the red wing (4.25–5.75 keV), and the blueshifted absorption band (7.75–9.75 keV). The histograms were obtained from the unsmoothed map, while the grey lines stem from the smoothed map. The typical measurement error in each band is shown. In the panel of the Fe K line core variability, the 2–5 keV continuum light curve (the red solid line: adjusted to the mean and variance of the line variation) is overplotted for reference.