VLT-UVES analysis of 5 giants in 47 Tucanae

Free access article

Issue		A&A Volume 435, Number 2, May IV 2005


Page(s)		657 - 667
Section		Stellar atmospheres
DOI		http://dx.doi.org/10.1051/0004-6361:20041634

A&A 435, 657-667 (2005)
DOI: 10.1051/0004-6361:20041634

VLT-UVES analysis of 5 giants in 47 Tucanae

A. Alves-Brito¹, B. Barbuy¹, S. Ortolani², Y. Momany², V. Hill³, M. Zoccali^{4, 5}, A. Renzini⁶, D. Minniti⁴, L. Pasquini⁶, E. Bica⁷ and R. M. Rich⁸

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 Università di Padova, Dipartimento di Astronomia, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
    e-mail: ortolani@pd.astro.it
³ Observatoire de Paris-Meudon, 92195 Meudon Cedex, France
    e-mail: Vanessa.Hill@obspm.fr
⁴ Universidad Catolica de Chile, Department of Astronomy & Astrophysics, Casilla 306, Santiago 22, Chile
    e-mail: [dante;mzoccali]@astro.puc.cl
⁵ Princeton University Observatory, Peyton Hall, Princeton, NJ 08544, USA
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

(Received 10 July 2004 / Accepted 10 January 2005)

Abstract
High resolution spectra of 5 giants, including a horizontal branch star, of the metal-rich globular cluster 47 Tucanae were obtained with the UVES spectrograph at the 8 m VLT UT2-Kueyen telescope. The atmospheric parameters ( $T_{\rm eff}$ , log g, [Fe/H], $v_{\rm t}$ ) were derived from VIJK photometry and spectroscopic data based on Fe I and Fe II lines. Fe I and Fe II iron abundances and respective total errors [Fe I/H] = - $0.66 \pm0.12$ and [Fe II/H] = - $0.69 \pm 0.24$ are found. Abundances of $\alpha$ (O, Mg, Ca, Si, Ti), odd-Z (Na, Al), s- (Ba, La, Zr), and r-process (Eu) elements were determined by means of spectrum synthesis. The main results are $\rm [O/Fe] = +0.35 \pm 0.11$ , [Mg/Fe] $\approx$ [Si/Fe] $\approx$ [Ti/Fe] = + $0.23 \pm 0.17$ , $\rm [Ca/Fe] = 0.0 \pm 0.15$ , $\rm [Ba/Fe] = +0.31 \pm 0.22$ and $\rm [Eu/Fe] = +0.33 \pm 0.10$ . Overabundances of the $\alpha$ -elements O, Mg, Si and Ti, and of Eu are similar to those seen in halo metal-poor stars, whereas a solar Ca-to-Fe ratio resembles the values found in bulge stars. An overall metallicity Z=0.006 or [M/H] = -0.45 is thus obtained, as is a mean heliocentric radial velocity $v_{\rm r}^{\rm hel}\,=\,-22.43 \pm 1.99$ km s^-1.

Key words: globular clusters: individual: 47 Tucanae -- globular clusters: general -- stars: abundances

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