SIMBAD references

Four R CrB variable stars were monitored photometrically during 1992-1994 to detect or confirm suspected short-term variations (pulsations) of periods around 40 -80 days. The lightcurves are analysed by two independent methods. Although we find clear variations in all four objects, and determined periods are in the expected range, these variations are only weakly of periodic nature. XX Cam and UV Cas, which are R CrB variables with very rare fading events have exceptionally small amplitudes.