Search for Evolutionary Changes in the Period of the Classical Cepheid EV Aql

Abstract

The reduction of all the available photometry for the Cepheid EV Aql has allowed its $O-C$ diagram spanning a time interval of 130 years to be constructed. This has made it possible to calculate the rate of evolutionary decrease in the period, $dP/dt=-33.2({±}{6.9})$ s yr${}^{-1}$, in agreement with the results of model calculations for the second crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen has confirmed that the decrease in the period is real.