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Keywords:

  • methods: observational;
  • techniques: photometric;
  • open clusters and associations: individual: NGC 1245;
  • open clusters and associations: individual: NGC 2506

ABSTRACT

We have conducted VI CCD photometry of the two open clusters NGC 1245 and NGC 2506 using the CFH12K CCD camera. Our photometry covers a sky area of 84 × 82 and 42 × 81 arcmin2 for the two clusters, respectively, and reaches down to V ≈ 23. We derived the physical parameters using detailed theoretical isochrone fittings using χ2 minimization. The derived cluster parameters are E(BV) = 0.24 ± 0.05 and 0.03 ± 0.04, (VMV)0 = 12.25 ± 0.12 and 12.47 ± 0.08, age (Gyr) = 1.08 ± 0.09 and 2.31 ± 0.16, and [Fe/H] = −0.08 ± 0.06 and −0.24 ± 0.06, respectively, for NGC 1245 and NGC 2506. We present the luminosity functions of the two clusters, which reach down to MV ≈ 10, and derive mass functions with slopes of Γ = −1.29 for NGC 1245 and Γ = −1.26 for NGC 2506. The slopes are slightly shallower than that of the solar neighbourhood, implying the existence of dynamical evolution that drives the evaporation of the low-mass stars in the clusters.