Multicolour photometry of red giants in three southern open clusters

Reddenings, distances, abundances and other physical properties are determined from new UBV, DDO and Washington photometry of stars in the southern open clusters NGC 4349 (C1221 – 578), NGC 5316 (C1350 – 616), and NGC 6494 (C1753 – 190). The application of two photometric membership criteria allowed us to discriminate between red field objects and physical members of the clusters. The derived mean colour excesses and distance moduli are in good agreement with the values previously obtained from the main-sequence stars of the three clusters by different authors. No firm evidence of CNO enhancement is found in any of the clusters. The derived mean cluster abundances are: [Fe/H] = − 0.23 ± 0.08 for NGC 4349, 0.19 ± 0.11 for NGC 5316 and − 0.14 ± 0.15 for NGC 6494. The empirical isochrone corresponding to the NGC 6475 age group of Mermilliod is now reasonably well defined. The mass results suggest that the cluster giants could have undergone mass loss during their red giant phase of evolution.