2006MNRAS.367.1603K

We report the discovery of very rapid pulsations in three sdB stars from the Edinburgh-Cape blue object survey. The short periods, small amplitudes and multi-periodicity clearly establish these stars as members of the EC 14026 class. EC 11583-2708 has pulsation periods near 149, 144 and 114 s, though evidence is presented that the 149-s period is resolved into two periods at 148.87 and 148.55 s by the full photoelectric data set. The amplitudes of the detected variations are in the range 0.002-0.006 mag. The light variation of EC 20338-1925 is dominated by a period near 147 s with a very large amplitude for a variable sdB star (0.025 mag), though four other frequencies are detected with periods near 168, 151, 141 and 135 s and amplitudes in the range 0.002-0.005 mag. The third star, EC 09582-1137, displays a light curve which is virtually a textbook example of frequency beating, being produced by two pulsations of almost equal amplitude (∼0.008 mag) and periods near 136.0 and 151.2 s.