Changes in the Period of SU Sct, a Population II Cepheid

The reduction of all the available photometry for the Cepheid SU Sct has allowed its $$O-C$$ diagram spanning a time interval of 60 years to be constructed. Six abrupt changes in the period have been detected. The pulsation stability test proposed by Lombard and Koen (1993) has confirmed that the changes in the period are real. The absolute magnitude of SU Sct is $$M_{V}\simeq{-}0\overset{\textrm{m}}{.}32$$ , confirming that it belongs to BL Her-type Population II Cepheids.