An Investigation of Open Clusters Berkeley 68 and Stock 20 Using CCD UBV and Gaia DR3 Data

Abstract

We performed detailed photometric and astrometric analyses of the open star clusters Berkeley 68 and Stock 20. This was based on ground-based CCD UBV photometric data complemented by space-based Gaia Data Release 3 (DR3) photometry and astrometry. A total of 198 and 51 stars were identified as likely cluster members for Berkeley 68 and Stock 20, respectively. Two-color diagrams were used to derive the reddening and photometric metallicity for each cluster. The reddening for Berkeley 68 and Stock 20 is E(B − V) = 0.520 ± 0.032 mag and 0.400 ± 0.048 mag, respectively. Photometric metallicity [Fe/H] is −0.13 ± 0.08 dex for Berkeley 68 and −0.01 ± 0.06 dex for Stock 20. Keeping as constant reddening and metallicity, we determined the distance moduli and ages of the clusters through fitting isochrones to the UBV and Gaia-based color–magnitude diagrams. Photometric distances are d = 3003 ± 165 pc for Berkeley 68 and 2911 ± 216 pc for Stock 20. The cluster ages are 2.4 ± 0.2 Gyr and 50 ± 10 Myr for Berkeley 68 and Stock 20, respectively. Present-day mass function slopes were found to be Γ = 1.38 ± 0.71 and Γ = 1.53 ± 0.39 for Berkeley 68 and Stock 20, respectively. These values are compatible with the value of Salpeter. The relaxation times were estimated as 32.55 and 23.17 Myr for Berkeley 68 and Stock 20, respectively. These times are less than the estimated cluster ages, indicating that both clusters are dynamically relaxed. Orbit integration was carried out only for Berkeley 68 since radial velocity data were not available for Stock 20. Analysis indicated that Berkeley 68 was born outside the solar circle and belongs to the thin-disk component of the Milky Way.

Astrophysical Parameters of the Open Cluster NGC 2509

“…We utilized UPMASK (Unsupervised Photometric Membership Assignment in Stellar Clusters; [29]) method by using astrometric data of Gaia DR3 for membership analyses. This methodology previously used in many studies ( [6,17,[25][26][27]). UPMASK is the method of clustering algorithm and detects spatially populated groups and identifies membership probabilities of stars.…”

Astrophysical Parameters of the Open Cluster Berkeley 6

“…Moreover, the fitting procedure gives the age and distance moduli of Be 6 to be t = 350±50 Myr and (m-MG) = 13.806±0.263 mag, respectively, which corresponds to the isochrone distance to be diso= 2625±337 pc (see Table 3). In addition to this, we calculated errors in distance moduli and distances using the relations presented in [22], [24], [25], [26]. These relations take into account the uncertainty in colour excess.…”

Exploring NGC 2345: A Comprehensive Study of a Young Open Cluster through Photometric and Kinematic Analysis

“…A star cluster comprises a collection of stars, providing a natural laboratory-like setting to develop theoretical models and apply them to gain insights into stellar evolution. Open clusters (OCs) are gatherings of stars originating from the same molecular cloud, characterized by the same age, chemical composition, and distance; however, stars' luminosity and masses are different (Yontan 2023). Typically composed of a few tens to several thousand stars, they loosely aggregate and remain gravitationally bound to each other.…”