Photometric and kinematic study of the three intermediate age open clusters NGC 381, NGC 2360, and Berkeley 68

Abstract

We present UBVR c I c photometric study of three intermediate age open star clusters NGC 381, NGC 2360, and Berkeley 68 (Be 68). We examine the cluster membership of stars using recently released Gaia DR2 proper motions and obtain a total of 116, 332, and 264 member stars in these three clusters. The mean reddening of E(B − V) = 0.36±0.04, 0.08±0.03, and 0.52±0.04 mag are found in the direction of these clusters where we observe an anomalous reddening towards NGC 381. We fitted the solar metallicity isochrones to determine age and distance of the clusters which are found to be log(Age) = 8.65±0.05, 8.95±0.05, and 9.25±0.05 yr with the respective distance of 957±152, 982±132, and 2554±387 pc for the clusters NGC 381, NGC 2360, and Be 68. A two-stage power law in the mass function (MF) slope is observed in the cluster NGC 381, however, we observe only a single MF slope in the clusters NGC 2360 and Be68. To study a possible spatial variation in the slope of MF we estimate slopes separately in the inner and the outer regions of these clusters and notice a steeper slope in outer region. The dynamic study of these clusters reveals deficiency of lowmass stars in their inner regions suggesting the mass segregation process in all these clusters. The relaxation times of 48.5, 78.9, and 87.6 Myr are obtained for the clusters NGC 381, NGC 2360, and Be 68, respectively which are well below to their respective ages. This suggests that all the clusters are dynamically relaxed.

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

“…Initially these stars are gravitationally bound into the cluster and hence share common positional and kinematic characteristics. The ages, distances, and chemical compositions of cluster member stars are similar; however, the stellar masses are different (Maurya & Joshi 2020). The study of OC stars through astrometric and photometric observations allows determination of astrometric and astrophysical parameters unavailable to the study of single stars (Dias et al 2021), partially explaining the interest in these systems.…”

“…Analyzing Two Micron All Sky Survey (2MASS) and PPMXL data, Kharchenko et al (2012) Liu & Pang (2019) employed Gaia DR2 data within an automatic isochrone fitting scheme, estimating the cluster distance, age, and proper motion as d = 3559 ± 608 pc, t = 1.45 ± 0.09 Gyr, and ( cos m d a , μ δ ) = (2.321 ± 0.227, − 1.322 ± 0.203) mas yr −1 , respectively. The first detailed CCD UBVR c I c photometric study was performed by Maurya & Joshi (2020). They combined these observations with the 2MASS JHK S near-IR data (Cutri et al 2003) and Gaia DR2 astrometry (Gaia Collaboration et al 2018).…”

“…They combined these observations with the 2MASS JHK S near-IR data (Cutri et al 2003) and Gaia DR2 astrometry (Gaia Collaboration et al 2018). Maurya & Joshi (2020) estimated the core radius of Berkeley 68 to be r c = 0 6 ± 0 3 through fitting the radial density profile (RDP) of King (1962). They also identified 264 member stars based on Gaia DR2 proper motions.…”

Open clusters with proper motions fully separatedfrom the field stars using Gaia DR2

“…In addition, OCs are significant in stellar evolution studies because member stars of a cluster are born from the same molecular cloud. Therefore they have similar ages, distances, and chemical compositions but vary in stellar mass (Maurya & Joshi 2020). Our vantage point within the Galaxy's disc helps us to see some of the finer structures in the solar neighborhood in great detail, but it limits our view of the disk's three-dimensional configuration on a broader scale, (Cantat-Gaudin et al 2018).…”

Detailed Abundances of Planet-Hosting Open Clusters. The Praesepe (Beehive) Cluster

“…This implies that the stars in a given open cluster are the same age and have the same primordial compositions. These properties allow for the systematic determination of their ages (Maurya & Joshi 2020;Sandquist et al 2016), distances (Monteiro & Dias 2019;González-Díaz et al 2019), kinematic properties (Maurya & Joshi 2020;Geller et al 2015), and detailed compositions (Lum & Boesgaard 2019;Liu et al 2016). There may be more useful information available about the cluster environment than there would be about a wide binary system, such as more accurate age determinations.…”