XMM-Newton count rate light curves for EPIC pn 0.2–2.0 keV (500 s bins; blue) and for Optical Monitor UVM2 fast mode (800 s bins; orange). MET refers to Mission Elapsed Time, and the MET zeropoint used for the x-axis corresponds to 10:33:53 on 23 December 2020. Both datasets are plotted in counts per second. Whereas the X-ray emission is clearly strongly variable over the duration of the observation, the optical light curve shows no significant variability on this timescale.