Top panel: ratio between the data points and the best-fit model. Data from EPIC-pn, MOS1, and MOS2 are shown in black, red, and blue, respectively. The model consists of a single absorbed power law describing the continuum, zoomed in on the E = 4 − 9 keV energy interval. Data are rebinned to a minimum S/N of 11σ and up to three counts only for plotting purposes. Bottom panel: contour plot describing the normalization vs. the rest-frame energy of a Gaussian line component in addition to the baseline model, consisting of a power law modified by Galactic absorption. Black, red, and green lines refer to the 68%, 90%, and 99% confidence level, respectively.