eROSITA spectrum of the 60–80 arcmin ring around the Coma cluster. The spectra are presented as count rate per square arcminute and per one (out of seven) eROSITA telescope module, hence the units are cnt/s/keV/arcmin²/tel. Different spectra show the total measured spectrum (T, black), detector internal background spectrum (B, red), sky spectrum without detector background, extracted from the circular ‘background’ region (S, green), net spectrum in the direction of the Coma cluster (N = T-B-S, blue). For comparison, the orange points show the background-subtracted spectrum extracted from the innermost ring 0–20 arcmin. The blue histogram shows the best fitting single temperature APEC model with fixed absorption |${\rm NH}=1.03\times 10^{20}\, {\rm cm^{-2}}$| and |$kT=3.3\pm 0.2\, {\rm keV}$|⁠. In terms of projected emission measure, the normalization of the observed Coma spectrum in the 60–80 arcmin ring corresponds to |${\rm EM_{\it l}}=2.1\times 10^5\, {\rm Mpc}$|⁠. For comparison, the black dashed line shows the APEC spectrum with |$T=10^6\, {\rm K}$|⁠, abundance Z/Z_⊙ = 0.2 and EM_l = 9 × 10⁵ Mpc. This would correspond to the normalization suggested in (Bonamente et al. 2022). The magenta dashed line shows the same spectrum with EM_l = 10³ Mpc motivated by the Magneticum simulations. We note here that WHIM signatures, especially for low overdensities and temperatures can be substantially different from the APEC model. Also, the true WHIM metallicity can be much lower than Z = 0.2 adopted for this plot.