Three new bricks in the wall: Berkeley 23, Berkeley 31, and King 8
  A comprehensive census of Galactic open cluster properties places unique
constraints on the Galactic disc structure and evolution. In this framework we
investigate the evolutionary status of three poorly-studied open clusters,
Berkeley 31, Berkeley 23 and King 8, all located in the Galactic anti-centre
direction. To this aim, we make use of deep LBT observations, reaching more
than 6 mag below the main sequence Turn- Off. To determine the cluster
parameters, namely age, metallicity, distance, reddening and binary fraction,
we compare the observational colour-magnitude diagrams (CMDs) with a library of
synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and
FST) and metallicities. We find that Berkeley 31 is relatively old, with an age
between 2.3 and 2.9 Gyr, and rather high above the Galactic plane, at about 700
pc. Berkeley 23 and King 8 are younger, with best fitting ages in the range
1.1-1.3 Gyr and 0.8-1.3 Gyr, respectively. The position above the Galactic
plane is about 500- 600 pc for the former, and 200 pc for the latter. Although
a spectroscopic confirmation is needed, our analysis suggests a sub-solar
metallicity for all three clusters.
