Mrk 421 multiwavelength light curves

The data were collected as part of an extensive multiwavelength campaign carried out between May and June 2022 using MAGIC, Fermi-LAT, NuSTAR, XMM-Newton, Swift, and several optical and radio telescopes to complement IXPE data. During the IXPE exposures, the measured 0.2-1TeV flux was close to the quiescent state and ranged from 25% to 50% of the Crab Nebula without intra-night variability.

Throughout the campaign, the very high-energy (VHE) and X-ray emission are positively correlated at a 4{sigma} significance level. The IXPE measurements reveal an X-ray polarization degree that is a factor of 2-5 higher than in the optical/radio bands; that implies an energy-stratified jet in which the VHE photons are emitted co-spatially with the X-rays, in the vicinity of a shock front. The June 2022 observations exhibit a rotation of the X-ray polarization angle.