Astrometric and photometric study of NGC 6067, NGC 2506, and IC 4651 open clusters based on wide-field ground and Gaia DR2 data

Abstract

We present an analysis of three southern open star clusters NGC 6067, NGC 2506 and IC 4651 using wide-field photometric and Gaia DR2 astrometric data. They are poorly studied clusters. We took advantage of the synergy between Gaia DR2 high precision astrometric measurements and ground based wide-field photometry to isolate cluster members and further study these clusters. We identify the cluster members using proper motions, parallax and colour-magnitude diagrams. Mean proper motion of the clusters in µ α cosδ and µ δ is estimated as −1.90 ± 0.01 and −2.57 ± 0.01 mas yr −1 for NGC 6067, −2.57±0.01 and 3.92±0.01 mas yr −1 for NGC 2506 and −2.41±0.01 and −5.05 ± 0.02 mas yr −1 for IC 4651. Distances are estimated as 3.01 ± 0.87, 3.88 ± 0.42 and 1.00 ± 0.08 kpc for the clusters NGC 6067, NGC 2506 and IC 4651 respectively using parallaxes taken from Gaia DR2 catalogue. Galactic orbits are determined for these clusters using Galactic potential models. We find that these clusters have circular orbits. Cluster radii are determined as 10 for NGC 6067, 12 for NGC 2506 and 11 for IC 4651. Ages of the clusters estimated by isochrones fitting are 66 ± 8 Myr, 2.09 ± 0.14 Gyr and 1.59 ± 0.14 Gyr for NGC 6067, NGC 2506 and IC 4651 respectively. Mass function slope for the entire region of cluster NGC 2506 is found to be comparable with the Salpeter value in the mass range 0.77 -1.54 M . The mass function analysis shows that the slope becomes flat when one goes from halo to core region in all the three clusters. A comparison of dynamical age with cluster's age indicates that NGC 2506 and IC 4651 are dynamically relaxed clusters.

High Mass-ratio Binary Population in Open Clusters: Segregation of early type binaries and an increasing binary fraction with mass

“…IC 4651 is an intermediate-age OC with an age of 1.59 Gyr (Rangwal et al 2019), whereas we estimate an age of ∼ 2 Gyr. The CMD (Fig.…”

“…NGC 1039 is a young OC with an age of 250 Myr (Rangwal et al 2019). The binary sequence is sparsely populated with an increasing number of members at fainter magnitudes (Fig.…”

“…NGC 6025 is a young OC with an age of 151 Myr (Rangwal et al 2019). González & Levato (2006) calculated BF of 40-50% for spectroscopic binaries.…”

“…NGC 6281 is a young OC with an age of 302 Myr (Rangwal et al 2019). The cluster has two giant stars and a significant number of binary stars with an average f 0.6 value of 0.27 ± 0.02 (Fig.…”

Study of an Intermediate Age Open Cluster Ic 1434 Using Ground-Based Imaging and Gaia Dr2 Astrometry

“…HENDY & BISHT estimate the membership probability of stars lying towards the cluster regions (Cantat-Gaudin et al 2018;Gao 2018;Rangwal et al 2019;Bisht et al (2019Bisht et al ( , 2020aBisht et al ( , 2020b).…”