X-ray spectra of the Arches cluster as measured in the MOS1 (black), MOS2 (red), and pn (green) cameras aboard XMM-Newton, compared to a) a model with only one thermal plasma component (model 1 in Table 3) and b) a model with two thermal plasma components (model 3 in Table 3). The lower panels show the associated residuals in terms of standard deviations. The second plasma of temperature kT = 0.9 keV accounts for a significant emission in the He-like Si and S Kα lines at 1.86 and 2.46 keV, respectively.