Measured amplitudes of the 4 periodicities listed in Table 2 over the last 12 years. Apart from the most recent data points, which were taken from the observations presented here, the measurements were kindly made available to us by Kilkenny. The errors were not provided, but should be similar to or smaller than those shown for our data. Zero amplitudes imply that the pulsation was not detected in a particular data set down to a threshold of  ~0.1%.