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Keywords:

  • Hertzsprung–Russell and colour–magnitude diagrams;
  • Galaxy: disc;
  • open clusters and associations: general;
  • open clusters and associations: individual: Berkeley 27;
  • open clusters and associations: individual: Berkeley 34;
  • open clusters and associations: individual: Berkeley 36

ABSTRACT

In this paper, we present the investigation of the evolutionary status of three open clusters: Berkeley 27, Berkeley 34 and Berkeley 36, all located in the Galactic anticentre direction. All of them were observed with SUperb Seeing Imager 2 at the New Technology Telescope using the Bessel B, V and I filters. The cluster parameters have been obtained using the synthetic colour–magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMDs with a library of synthetic CMDs generated with different evolutionary sets (Padova, FRANEC and FST). This analysis shows that Berkeley 27 has an age between 1.5 and 1.7 Gyr, a reddening E(BV) in the range 0.40–0.50 and a distance modulus (mM)0 between 13.1 and 13.3; Berkeley 34 is older with an age in the range 2.1–2.5 Gyr, E(BV) between 0.57 and 0.64 and (mM)0 between 14.1 and 14.3; Berkeley 36, with an age between 7.0 and 7.5 Gyr, has a reddening of E(BV) ∼ 0.50 and a distance modulus (mM)0 between 13.1 and 13.2. For all the clusters, our analysis suggests a subsolar metallicity in accord with their position in the outer Galactic disc.