For the low-amplitude Cepheid BY Cas we have constructed an O − C diagram spanning a time interval 123 years. The O − C diagram has the shape of a parabola, which has made it possible to determine for the first time the quadratic light elements and to calculate the rate of evolutionary increase in the period, dP/dt = +0.985 (±0.091) s yr⁻¹, which points to the third crossing of the instability strip. The pulsation stability test proposed by Lombard and Koen (1993) confirms that the period increase is real.

中文翻译：

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寻找造父变星时期的进化变化：BY Cas

对于低振幅造父变星Cas，我们构建了一个跨越123年时间间隔的OC图。的-O - Ç图具有一个抛物线，这使得有可能的形状来确定用于第一次二次光元件，并计算时间段中的，进化增加的速率的dP / dt的= 0.985（±0.091）类yr ^-1，它指向不稳定带的第三个交叉点。Lombard和Koen（1993）提出的脉动稳定性测试证实了周期的增加是真实的。