Abstract:
Using the photometric and kinematical data from Gaia Data Release 2, three old open clusters namely Berkeley 32
(Be 32), Berkeley 98 (Be 98), and King 23 are investigated. The latter two of these clusters are poorly studied in
the literature. The numbers of the most probable cluster members are 563, 260, and 114 for Be 32, Be 98, and King
23, respectively, with membership probabilities higher than 80% and lying within the clusters’ limiting radii. Mean
proper motions (PMs; m da cos and μδ) of the clusters are determined as (−0.34 ± 0.008, −1.60 ± 0.006),
(−1.34 ± 0.007, −3.22 ± 0.008), and (−0.46 ± 0.009, −0.87 ± 0.012) mas yr−1. The errors mentioned in the PMs
are the Gaussian fitting errors. The blue straggler stars (BSS) in all three old clusters were found to exhibit
centralized radial distribution. The clusters’ radii are determined as 9 4, 12 95, and 6 6 for Be 32, Be 98, and King
23 using radial density profiles. Ages of the clusters determined by isochrone fitting are 4.90 ± 0.22, 3.23 ± 0.15,
and 1.95 ± 0.22 Gyr. The errors given in the clusters’ ages are the internal errors. The mass function slopes are
found to be flatter than Salpeter’s value for all three clusters. All three clusters are found to be dynamically relaxed.
Galactic orbits are derived for these clusters, which demonstrate that the studied clusters follow a circular path
around the Galactic center.
