Evolution of the pulse profiles during the outburst. Top: color-coded pulse profiles as observed by Fermi/GBM in units of relative intensities (see Appendix A.2 in Wilson-Hodge et al. 2018); yellow corresponds to the maxima of the pulse and dark blue to the minima. The black dashed line shows the evolution of the pulsed flux in the 12–50 keV range during the outburst as seen by Fermi/GBM (https://gammaray.nsstc.nasa.gov/gbm/science/pulsars/lightcurves/swiftj0243.html) with the peak flux being 4.8 × 10⁻⁹ erg cm⁻² s⁻¹. The shaded vertical stripes mark the times of IXPE observations. Bottom: normalized pulse profiles in the 2–8 keV band as observed by IXPE in three observations and shown with the solid orange, dotted green, and dashed blue lines for Obs. 1, 2, and 3, respectively.