Top panel. First row: periodogram of the subtraction residuals of two Keplerians with periods of 30.6 and 123.6 d, dominated by a 48 d peak. The horizontal lines represent FAP levels, as described in the captions of Fig. 2. Second row: periodogram of the residuals after subtracting three Keplerians with periods of 30.6, 123.6, and 439 d. The vertical dash-dotted line marks a P = 48 d period. Third row: periodogram of the residuals after subtracting Keplerians with periods of 30.6, 123.6, and 48 d. Bottom panel: periodogram of the residuals after subtracting the 30.6 and 123.6 d signals for each subset of epochs described in the captions of Fig. 2. The 48 d signal is not seen for the 2010−2011 observational epochs, which have a poor sensitivity to that period range because their sampling incidentally concentrates around just two phases.