High-resolution abundance analysis of two individual stars of the bulge globular cluster NCG 6553

Abstract

A detailed abundance analysis of 2 giants of the metal-rich bulge globular cluster NGC6553 was carried out using high resolution échelle spectra obtained at the ESO 3.6m telescope. The temperature calibration of metal-rich cool giants needs high quality photometric data.We have obtained JK photometry at ESO and VI photometry with the Hubble Space Telescope for NGC6553. The main purpose of this analysis consists in the determination of elemental abundance ratios for this key bulge cluster, as a basis for the fundamental calibration of metal-rich populations. The present analysis provides a metallicity [Fe/H] = −0.55±0.2 which, combined to overabundances relative to Fe of several elements, results in an overall metallicity Z≈Zʘ.