Radial X-ray surface brightness profile (red points) based on the X-ray image shown in Fig.3. The blue solid line shows a β-model with r_c = 1.3′ and β = 0.514. The best-fitting constant sky background level (shown with the dashed black line) has been subtracted from the data and the model. The error bars associated with the photon counting noise are smaller than the size of the plotted symbols. The black points with error bars show the eROSITA-only radial profile for r > 2′. The ratio of errors to the Perseus surface brightness is plotted as a green line. Near the virial radius, the statistical errors are at the ∼2% level of the observed surface brightness. At large radii (∼100′), the contribution from the telescope stray light is important (see Appendix A in Churazov et al. 2023) and makes a non-negligible contribution to the observed X-ray surface brightness.