Light curves and hardness ratio. Upper panel: pn light curve binned into 100 s bins (black solid line) with the long-term flux evolution shown as a low-resolution version of the light curve binned into 10 ks bins (red line). Arrows with labels show the corresponding count rate (in the red line) at selected points where the trend of the low resolution light curve changes. Lower panel: Hardness ratio (1.0–10.0 keV band divided by 0.2–1.0 keV band) calculated from low-resolution light curves binned into 10-ks bins.