Multi-wavelength light curves during the multi-hour exposure from MAGIC and XMM-Newton on MJD 60291 (December 13, 2023). The MAGIC fluxes are calculated above 400 GeV and binned over 25-minute intervals. The XMM-Newton fluxes are computed in the same 25-minute bins as MAGIC, and in the 0.3–2 keV and 2–10 keV bands. In the third panel from the top we show the hardness ratio (F_{2 − 10 keV}/F_{0.3 − 2 keV}) from the XMM-Newton data. The bottom panels show the optical (R-band) fluxes, and the polarization in the radio and optical (R-band) with the same binning as in Fig. 1. The black markers represent the X-ray polarization from IXPE binned over 3 h intervals.