Top: light curves of source 141 (upper panels) and source 153 (lower panels). Left panels: entire pn light curve (black, 0.2–5.0 keV) with a smoothing fit overlaid in red. The background light curve is shown in grey. MOS light curves are not shown since the photon statistics are too low. Right panels: analysis of the individual stages of the flare in a time window around it. Blue data points show the rise to maximum. The early decline (orange) in both sources can be reasonably well modelled with an exponential decline (blue fit curve; compare the red smoothing fit). The decline rates are given in units of cts s⁻¹. Before the flare there are no indications for variability in either source. The binned count rates are entirely consistent with a Poisson process.