BS 196 : an old star cluster far from the Small Magellanic Cloud main body

Abstract

We present B and V photometry of the outlying Small Magellanic Cloud (SMC) star cluster BS 196 with the 4.1-m SOAR telescope. The photometry is deep (to V≈25), showing ≈ 3 mag below the cluster turnoff point at MV = 2.5 (1.03Mʘ). The cluster is located at the SMC distance. The colour–magnitude diagram and isochrone fittings provide a cluster age of 5.0 ± 0.5Gyr, indicating that this is one of the 12 oldest clusters so far detected in the SMC. The estimated metallicity is [Fe/H]=−1.68 ±0.10. The structural analysis gives by means of the King profile fittings a core radius Rc = 8.7 ± 1.1 arcsec (2.66 ± 0.14 pc) and a tidal radius Rt = 69.4 ± 1.7 arcsec (21.2 ± 1.2 pc). BS 196 is rather loose with a concentration parameter c = 0.90. With MV =−1.89 ± 0.39, BS 196 belongs to the class of intrinsically fainter SMC clusters, which have started to be explored as compared to the well-known populous ones.