VLT-UVES abundance analysis of four giants in NGC 6553

¹ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, São Paulo 05508-900, Brazil e-mail: [abrito;barbuy]@astro.iag.usp.br
² Universidad Catolica de Chile, Department of Astronomy & Astrophysics, Casilla 306, Santiago 22, Chile e-mail: [dante;mzoccali]@astro.puc.cl
³ Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 2, 35122 Padova, Italy e-mail: sergio.ortolani@unipd.it
⁴ Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy e-mail: alvio.renzini@oapd.inaf.it
⁵ European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany e-mail: lpasquin@eso.org
⁶ European Southern Observatory, Karl Schwarzschild Strasse 2, 85748 Garching bei München, Germany e-mail: [arenzini;lpasquin]@eso.org
⁷ Universidade Federal do Rio Grande do Sul, Departamento de Astronomia, CP 15051, Porto Alegre 91501-970, Brazil e-mail: bica@if.ufrgs.br
⁸ UCLA, Department of Physics & Astronomy, 8979 Math-Sciences Building, Los Angeles, CA 90095-1562, USA e-mail: rmr@astro.ucla.edu
⁹ Australian National University, Australia e-mail: jorge@mso.anu.edu.au

Received: 24 April 2006
Accepted: 10 August 2006

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 échelle spectra obtained with UVES at the ESO VLT-UT2 Kueyen telescope.

Results.A metallicity [Fe/H] = -0.20 dex is derived, together with α-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.