XMM pn plus MOSs cleaned image of ObsId 0112570101 (64 ks effective exposure time) for the galaxy M31. The insets show the pn power spectra (solid black lines) together with the local 3.5σ detection threshold (solid blue lines) obtained from the unbinned event lists of the three pulsating sources discovered during the EXTraS project and discussed in Sect. 4.6: J004301 (ObsId 050572030), J004222 (ObsId 0600660401, 0600660501, and 0650560601 together) and J004232 (ObsId 0764030301) from top to bottom. In the cases of J004301 and J004232, the discovered X-ray pulsars revolve around a companion star. In the corresponding insets we show the power spectra with (corrected) and without (raw) the best inferred orbital corrections (shifted by 100 in power on the y-axis for clarity).