Abstract

For two classical Cepheids, CEa Cas and CEb Cas, members of the open cluster NGC 7790, we have constructed \(O-C\) diagrams spanning a time interval of 125 years. The \(O-C\) diagrams have the shape of parabolas, which has allowed us for the first time to determine the quadratic light elements and to calculate the rates of evolutionary changes in their periods: \(dP/dt={-}0.038({\pm}{0.017})\) s yr\({}^{-1}\) for CEa Cas and \(dP/dt={+}0.099({\pm}{0.010})\) s yr\({}^{-1}\) for CEb Cas, in agreement with the theoretical calculations for the second and third crossings of the instability strip, respectively. The pulsation stability test proposed by Lombard and Koen has confirmed that the changes in the periods are real.

中文翻译：

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寻找造父变星CEa Cas和CEb Cas时期的进化变化

摘要

对于两个经典造父变星CEa Cas和CEb Cas，它们是开放星团NGC 7790的成员，我们构造了\（OC \）图，跨越了125年的时间间隔。的\（OC \）的图表具有抛物线的形状，这也使我们首次确定二次光元件，并计算在它们的周期的进化变化率：\（DP / DT = { - } 0.038（ {\ pm} {0.017}）\）年\（{} ^ {-1} \）对于CEa Cas和\（dP / dt = {+} 0.099（{\ pm} {0.010}）\）年\（{} ^ {-1} \）对于CEb Cas，分别与不稳定性带第二个和第三个交叉点的理论计算相一致。Lombard和Koen提出的脉动稳定性测试已经证实，周期的变化是真实的。