A search for variable stars in the four open star clusters

Abstract

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 \(\delta \) 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 \(\delta \) 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 \(0.79\pm 0.09\) Gyr and \(0.68\pm 0.03\) mag for Berkeley 69, \(0.79\pm 0.09\) Gyr and \(1.22\pm 0.03\) mag for the cluster King 7 and \(1.59\pm 0.19\) Gyr and \(0.63\pm 0.02\) mag for the cluster King 5, respectively. The signature of mass segregation is found in the clusters King 7 and King 5.

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Acknowledgements

This work has been partially supported by the Natural Science Foundation of China (NSFC-11590782, NSFC-11421303). This work has made use of data from the European Space Agency (ESA) mission GAIA processed by Gaia Data processing and Analysis Consortium (DPAC), (https://www.cosmos.esa.int/web/gaia/dpac/consortium).

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Correspondence to Geeta Rangwal.

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Durgapal, A., Rangwal, G., Bisht, D. et al. A search for variable stars in the four open star clusters. J Astrophys Astron 41, 13 (2020). https://doi.org/10.1007/s12036-020-09628-9

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Keywords

  • Star cluster: individual (King 5, King 7, Berkeley 69 and Berkeley 20)
  • star: astrometry
  • stars: variable