CAPTURE OF FIELD STARS BY GLOBULAR-CLUSTERS IN DENSE BULGE REGIONS

The recent detection of a double red giant branch (RGB) in the optical color-magnitude diagram of the bulge globular cluster HP 1-a more pop ulated, metal-poor, steep giant branch corresponding to the cluster it self and another that is metal rich and curved-led us to explore in th e present Letter the possibility that field stars are captured by a gl obular cluster orbiting in dense bulge regions over several gigayears. Analytical arguments, as well as N-body calculations for a cluster mo del of 10(5) M. in a bulgelike environment, suggest that a significant fraction of cluster stars may consist of captures. Metal-poor globula r clusters in the inner bulge, like HP 1, contrasting in Delta[Fe/H] b y at least 1.0 dex with respect to the surrounding metal-rich stars, a re ideal probes to further test the capture scenario. In turn, if this scenario is confirmed, the double RGB of HP 1 could provide direct es timates of blanketing amounts, which is fundamental for the photometri c calibration of metal-rich stellar populations.