Period analysis carried out on the same set of O − C data points analyzed by Maciejewski et al. (2010). Upper left panel: O−C diagram for the selected points. Upper right panel: GLS periodogram as a function of frequency ν, adopting the same plotting limits as Maciejewski et al. (2010). Bottom panel: GLS periodogram as a function of period, adopting wider limits on frequency according to the Nyquist criterion (see text for details). The red vertical line marks the peak claimed by Maciejewski et al. (2010).