Changes in the Period of the Population II Cepheid CC Lyr

Abstract

The reduction of all the available photometry for the Cepheid CC Lyr has allowed its $O-C$ diagram spanning a time interval of 124 years to be constructed. The data obtained provide evidence for the existence of large random fluctuations in the period ($\varepsilon/P≈ 0.046$). A formal fitting of the $O-C$ residuals has made it possible to estimate the rate of secular increase in the period, $dP/dt=229.3({±}{14.8})$ s yr${}^{-1}$. The pulsation stability test proposed by Lombard and Koen (1993) has confirmed that the increase in the period is real.