• R. K. S. YADAV

      Articles written in Journal of Astrophysics and Astronomy

    • Multicolour CCD Photometric Study of Galactic Star Clusters SAI 63 and SAI 75

      R. K. S. Yadav S. I. Leonova R. Sagar E. V. Glushkova

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      We present 𝑈𝐵𝑉𝐼 CCD photometric observations obtained in the field of open clusters SAI 63 and SAI 75. CCD optical data obtained for the first time for these clusters are used to derive the fundamental parameters of the clusters. Stellar surface density profile indicates that radii of SAI 63 and SAI 75 are ∼ 3'.5 and 2'.5 respectively. The reddenings 𝐸(𝐵 - 𝑉) are 0.44 ± 0.05 and 0.34 ± 0.05 mag for SAI 63 and SAI 75 respectively while the corresponding distances are 2.2 ± 0.2 and 3.5 ± 0.3 kpc. An age of 450 ± 50 Myr for SAI 63 and 90 ± 10 Myr for SAI 75 is determined using the theoretical isochrones of Z = 0.019. Our analysis shows that reddening law is normal towards SAI 75.

    • A search for variable stars in the four open star clusters

      ALOK DURGAPAL GEETA RANGWAL D. BISHT HARMEEN KAUR R. K. S. YADAV J. C. PANDEY

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      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 theseclusters. 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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