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

Abstract

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 ($\varepsilon/P≈ 0.021$). Fitting the $O-C$ residuals by a cubic parabola has made it possible to estimate the rate of secular decrease in the period, $dP/dt=-353.0({±}{3.6})$ s yr${}^{-1}$. The pulsation stability test proposed by Lombard and Koen in 1993 has confirmed that the decrease in the period is real.