Same as Fig. 3, with data collected from 20 observations of Cal 83, divided into a total of 578 1000 s time segments. 17 of these intervals yield zero count rate and were excluded. Furthermore, all data points yielding only upper limits in amplitude were excluded, which left 202 data points, of which 34 time intervals yield a >95% detection of a periodic signal. The expected correlation between modulation amplitude and signal power (top right) is contaminated by a large number of overestimated amplitudes that are most likely caused by additional, non-periodic variability. These deviations are consistent with the large uncertainties in amplitude. The 95% threshold is corrected for oversampling, but not for multiple testing. 31 of 34 data points that are found above this threshold and yield a successful sine fit are used in the lower two rows. The variations in period of about ±3 s reported by Odendaal et al. (2014) can be recognised in the middle row and bottom right, but do not seem to correlate with count rate, amplitude, or signal power.