BS 196 : an old star cluster far from the SMC main body ⋆

We present B and V photometry of the outlying 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 (TO) at MV=2.5 (1.03M⊙). The cluster is located at the SMC distance. The colour-magnitude diagram (CMD) 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 King profile fittings a core radius Rc=8.7±1.1arcsec (2.66±0.14pc) and a tidal radius Rt=69.4±1.7arcsec (21.2±1.2pc). 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, as compared to the well-known populous ones, which starts to be explored.