EDP Sciences
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Volume 414, Number 3, February II 2004
Page(s) 1071 - 1079
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20034014

A&A 414, 1071-1079 (2004)
DOI: 10.1051/0004-6361:20034014

Heavy elements abundances in turn-off stars and early subgiants in NGC 6752

G. James1, P. François1, P. Bonifacio2, A. Bragaglia3, E. Carretta4, M. Centurión2, G. Clementini3, S. Desidera5, 6, R. G. Gratton4, F. Grundahl7, S. Lucatello4, 6, P. Molaro2, L. Pasquini8, C. Sneden9 and F. Spite1

1  Observatoire de Paris - GEPI, 61 avenue de l'Observatoire, 75014 Paris, France
2  Osservatorio Astronomico di Trieste, via G. B. Tiepolo 11, 34131 Trieste, Italy
3  Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy
4  Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio 5, 35122 Padova, Italy
5  Dipartimento di Fisica, Università di Pisa, Piazza Torricelli 2, 56100 Pisa, Italy
6  Dipartimento di Astronomia, Università di Padova, Vicolo dell'Osservatorio 2, 35122 Padova, Italy
7  Department of Astronomy, University of Aarhus, Bygning 520, 8000 Aarhus C, Denmark
8  European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching bei München, Germany
9  Department of Astronomy, University of Texas at Austin, RLM 15.308, C-1400, Austin, TX, USA

(Received 26 June 2003 / Accepted 28 October 2003)

High resolution spectra ( $R \ge 40\,000$) for 9 main sequence turn-off stars and 9 subgiants in the globular cluster NGC 6752 were acquired with UVES on the VLT-Kueyen (UT2). These data have been used to determine the abundances of some heavy elements (strontium, yttrium, barium and europium). This paper presents for the first time accurate results for heavy elements in this globular cluster. We did not find any systematic effect between the abundances found in turn-off stars, subgiants, and giants. We obtain the following mean abundances for these elements in our sample (turn-off stars and subgiants): $\mathrm{[Sr/Fe]} = 0.06 \pm 0.16$, $\mathrm{[Y/Fe]} = -0.01 \pm 0.12$, $\mathrm{[Ba/Fe]} = 0.18 \pm 0.11$, and $\mathrm{[Eu/Fe]} = 0.41 \pm 0.09$. The dispersion in the abundance ratios of the different elements is low and can be totally explained by uncertainties in their derivation. These ratios are in agreement with the values found in field halo stars with the same metallicity. We did not observe any correlation between the [n-capture/Fe] ratios and the star-to-star variations of the O and Na abundances. The [Ba/Eu] and [Sr/Ba] ratios show clearly that this globular cluster has also been uniformly enriched by r- and s-process synthesis.

Key words: stars: abundances -- Galaxy: globular clusters: individual: NGC 6752

Offprint request: G. James, Gael.James@obspm.fr

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