Top: XMM-Newton/EPIC-PN versus Chandra/ACIS temperatures in the full energy band. The different colors correspond to the 3 different regions where the spectra could be extracted: The full 3.5′ circle (red squares), the cool core region (green circles), and the annulus between the two (black triangles). In the cool core region, the strongest influence of multitemperature plasma is expected. Bottom: degeneracy between the parameters a and b for the three cases shown above. The shaded regions correspond to 1σ, 3σ, and 5σ confidence levels.