Fractional variability (F_var) as a function of the frequency during the IXPE epochs. F_var is computed using all data from Fig. 1 that are within the IXPE time windows. In the radio, we consider slightly relaxed simultaneity criteria and also include measurements that took place less than half a day before the start or after the end of the IXPE observing times (see the main text for more details). Radio, optical, IR, and Swift data are daily binned. We include the F_var from the NuSTAR and XMM-Newton multi-hour exposures using ≈30 min binning. These measurements are plotted in the gray since the two instruments did not gather data for all IXPE epochs, which biases the comparison with other wavebands.