Autocorrelation function (in period space) of the original Scargle periodogram (black solid line) and of a modified periodogram where the 346 significant frequencies were given an artificial power, while all others were given zero power (red solid line), both calculated from the frequency range of 0.15 d^-1 to 1.1 d^-1. Candidate spacings are marked with triangles using a colour according to the corresponding function. See text for further explanation.