Changes in the Period of V420 Cen, a W Vir-Type Cepheid

The reduction of all the available photometry for the Cepheid V420 Cen has allowed its $$O-C$$ diagram spanning a time interval of 131 years to be constructed. The data obtained provide evidence for the existence of large random fluctuations in the period ( $$\varepsilon/P\approx 0.021$$ ). Fitting the $$O-C$$ residuals by a cubic parabola has made it possible to estimate the rate of secular decrease in the period, $$dP/dt=-353.0({\pm}{3.6})$$ s yr $${}^{-1}$$ . The pulsation stability test proposed by Lombard and Koen in 1993 has confirmed that the decrease in the period is real.