Abstract:
We present a UBVI 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.
