Astron. Astrophys. Suppl. Ser. 136, 363-372

The nature of the star clusters ESO 93-SC08 and ESO 452-SC11

E. Bica¹, S. Ortolani², and B. Barbuy³

1 - Universidade Federal do Rio Grande do Sul, Dept. de Astronomia, CP 15051, Porto Alegre 91500-970, Brazil
2 - Università di Padova, Dept. di Astronomia, Vicolo dell'Osservatorio 5, I-35122 Padova, Italy
3 - Universidade de São Paulo, CP 3386, São Paulo 01060-970, Brazil

Received November 13, 1998; accepted February, 1999

Abstract:

We present V and I colour-magnitude diagrams of the star clusters ESO 93-SC08 and ESO 452-SC11. Both clusters are poorly populated, and the colour-magnitude diagrams show that ESO 93-SC08 is an intermediate age open cluster, while ESO 452-SC11 is confirmed as a globular cluster. The magnitude difference between the turnoff and the clump/horizontal branch indicates an age of 4 - 5 Gyr for ESO 93-SC08, while ESO 452-SC11 has an age comparable to the average of the halo globular clusters.

ESO 93-SC08 has a reddening of E(B-V) = 0.64 and is located at $d_{\odot}\approx 13.7$ kpc from the Sun. It is a distant open cluster in the outer disk.

ESO 452-SC11 appears to be a southern counterpart of the Palomar clusters. We derive a reddening of E(B-V) = 0.58, a distance $d_{\odot}\approx 6.5$ kpc and a metallicity [Fe/H] $\approx$ -1.5 for ESO 452-SC08. The deep CMD shows evidence of depletion at the lower main sequence, similarly to other poorly populated globular clusters.

Key words: globular clusters: ESO 452-SC11, open clusters: ESO 93-SC08 -- HR diagram