We present a CCD photometric survey for the search of variable stars in four open clusters namely Berkeley 69, King 5, King 7 and Berkeley 20. The time series observations were carried out for 1 and/or 2 nights for each of the clusters in the year 1998, which have led to identify nineteen variable stars in these clusters. Out of these 19 variable stars, five stars show $$\delta $$ δ Scuti-like variability and two stars show W UMa type variability. In other stars, we could not find the periods, and hence the type of variability due to the lack of sufficient data. The periods of $$\delta $$ δ Scuti type stars are found to be in the range of 0.13–0.21 days, whereas the two stars in the cluster Berkeley 20, which showed W UMa type variability have orbital periods of 0.396 and 0.418 days, respectively. Using the Gaia data, the basic parameters of the clusters Berkeley 69, King 7 and King 5 are also revised. The age and reddening are estimated to be $$0.79\pm 0.09$$ 0.79 ± 0.09 Gyr and $$0.68\pm 0.03$$ 0.68 ± 0.03 mag for Berkeley 69, $$0.79\pm 0.09$$ 0.79 ± 0.09 Gyr and $$1.22\pm 0.03$$ 1.22 ± 0.03 mag for the cluster King 7 and $$1.59\pm 0.19$$ 1.59 ± 0.19 Gyr and $$0.63\pm 0.02$$ 0.63 ± 0.02 mag for the cluster King 5, respectively. The signature of mass segregation is found in the clusters King 7 and King 5.

中文翻译：

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在四个疏散星团中寻找变星

我们提出了一项 CCD 光度测量，用于在四个疏散星团中搜索变星，即伯克利 69、金 5、金 7 和伯克利 20。对星团中的每个星团进行了 1 和/或 2 夜的时间序列观测。 1998 年，这导致在这些星团中发现了 19 颗变星。在这 19 颗变星中，有 5 颗星表现出类似 Scuti 的变异性，两颗星表现出 W UMa 型变异性。在其他恒星中，由于缺乏足够的数据，我们无法找到周期，因此无法找到变异的类型。发现$$\delta $$ δ Scuti 型星的周期在0.13-0.21 天之间，而Berkeley 20 星团中显示W UMa 型变异的两颗恒星的轨道周期为0.396 天和0.418 天， 分别。使用盖亚数据，集群 Berkeley 69、King 7 和 King 5 的基本参数也进行了修订。年龄和变红估计为 $0.79\pm 0.09$$ 0.79 ± 0.09 Gyr 和 $0.68\pm 0.03$$ 0.68 ± 0.03 mag 伯克利 69，$0.79\pm 0.09$$ 0.09$$0.09 ± 0.09 年 ± 年pm 0.03$$ 1.22 ± 0.03 mag 集群 King 7 和 $1.59\pm 0.19$$ 1.59 ± 0.19 Gyr 和 $0.63\pm 0.02$$ 0.63 ± 0.02 mag 集群 King 5。在聚类 King 7 和 King 5 中发现了大规模隔离的特征。02 mag 分别为集群 King 5。在聚类 King 7 和 King 5 中发现了大规模隔离的特征。02 mag 分别为集群 King 5。在聚类 King 7 和 King 5 中发现了大规模隔离的特征。