Mass function and dynamical study of the open clusters Berkeley 24 and Czernik 27 using ground based imaging and Gaia astrometry

Abstract

We present a U BV I photometric study of the open clusters Berkeley 24 (Be 24) and Czernik 27 (Cz 27). The radii of the clusters are determined as 2. ′ 7 and 2. ′ 3 for Be 24 and Cz 27, respectively. We use the Gaia Data Release 2 (GDR2) catalogue to estimate the mean proper motions for the clusters. We found the mean proper motion of Be 24 as 0.35 ± 0.06 mas yr −1 and 1.20 ± 0.08 mas yr −1 in right ascension and declination for Be 24 and −0.52 ± 0.05 mas yr −1 and −1.30 ± 0.05 mas yr −1 for Cz 27. We used probable cluster members selected from proper motion data for the estimation of fundamental parameters. We infer reddenings E(B − V ) = 0.45 ± 0.05 mag and 0.15 ± 0.05 mag for the two clusters. Analysis of extinction curves towards the two clusters show that both have normal interstellar extinction laws in the optical as well as in the near-IR band. From the ultraviolet excess measurement, we derive metallicities of [Fe/H]= −0.025 ± 0.01 dex and −0.042 ± 0.01 dex for the clusters Be 24 and Cz 27, respectively. The distances, as determined from main sequence fitting, are 4.4 ± 0.5 kpc and 5.6 ± 0.2 kpc. The comparison of observed CMDs with Z = 0.01 isochrones, leads to an age of 2.0 ± 0.2 Gyr and 0.6 ± 0.1 Gyr for Be 24 and Cz 27, respectively.In addition to this, we have also studied the mass function and dynamical state of these two clusters for the first time using probable cluster members. The mass function is derived after including the corrections for data incompleteness and field star contamination. Our analysis shows that both clusters are now dynamically relaxed.

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

“…There are many methods to determine the membership of cluster stars using photometric, proper motions, radial velocities, polarimetric data and their combinations (Joshi et al 2012;Medhi & Tamura 2013;Gao 2014). Recently, with the availability of the Gaia DR2 catalog (Gaia Collaboration et al 2018) having unprecedented astrometric precision, the membership determination based on kinematic method (proper motions or radial velocities) becomes a reliable tool to identify the cluster members (e.g., Cantat-Gaudin et al 2018Castro-Ginard et al 2018Bisht et al 2019;Joshi et al 2020). The precise knowledge of cluster membership helps us to study the distribution of stellar mass, also known as MF, which has a fundamental importance in the study of dynamic evolution of star clusters.…”

An Astrometric and Photometric Study of the Intermediate-Age Open Cluster NGC 2158 and Its Eclipsing Binary [Nbn2015]78

“…Our membership criterion depends on the chosen overdensity region to define the members of the cluster from the VPD, which obviously is a compromise between losing cluster members and including field stars (see Bisht et al 2019). To minimize the field contamination, we used the Blob subset from TOPCAT for selecting the cluster region in the VPD.…”

An investigation of poorly studied open cluster NGC 4337 using multi-color photometric and Gaia DR2 astrometric data

“…Proper motions (PMs) play a vital role in order to separate field stars from the main sequence and to derive authentic fundamental parameters as well (Yadav et al 2013;Sariya et al 2018a;Bisht et al 2019). Proper motion and parallax are very reliable parameters to extract field stars from the cluster zone, because cluster stars share the same kinematical properties and distances (Rangwal et al 2019).…”