VLT-UVES abundance analysis of four giants in NGC 6553

Abstract

Context. Metal-rich globular clusters trace the formation of bulges. Abundance ratios in the metal-rich globular clusters such as NGC 6553 can constrain the formation timescale of the Galactic bulge. Aims. The purpose of this study is to determine the metallicity and elemental ratios in individual stars of the metal-rich bulge globular cluster NGC 6553.

Methods. A detailed abundance analysis of four giants in NGC 6553 is carried out, based on optical high-resolution echelle spectra obtained with UVES at the ESO VLT-UT2 Kueyen telescope.

Results. A metallicity [Fe/H] = -0.20 dex is derived, together with alpha-element enhancement of Mg and Si ([Mg/Fe] = +0.28, [Si/Fe] = +0.21), solar Ca and Ti ([Ca/Fe]=+0.05, [Ti/Fe] = -0.01), and a mild enhancement of the r-process element Eu with [Eu/Fe]=+0.10. A mean heliocentric radial velocity of -1.86 km s(-1) is measured. We compare our results with previous investigations of the cluster.