Lomb-Scargle periodogram of the sources listed in Table A.1. The periodograms are constructed using 2–10 keV EPIC-pn light curves. The horizontal green and red lines indicate the 2σ and 3σ confidence levels, respectively, computed from simulations, and the blue line indicates the false alarm probability (3σ confidence level) estimated from the analytical approximation from Baluev (2008). The small inset shows the folded light curve.