Top: data are plotted as the ratio to a single power-law continuum model fitted to the grouped observations M4N, M8N, and M13N with XMM-Newton (black) and NuSTAR (red) simultaneous data. As indicated by the arrows, going from low to high energies, one can clearly note the presence of: a sharp low-energy cut-off, a narrow Fe K line at ~6.4 keV, some absorption feature(s) between 7−8 keV, and a high energy hump between 10−30 keV. Middle: same as top panel, but zoomed between 4 and 10 keV. Bottom: best-fit spectrum, model, and ratios plotted between 4−50 keV (see Sect. 4.1.1 for details).