Volume 586, February 2016
|Number of page(s)||11|
|Section||Galactic structure, stellar clusters and populations|
|Published online||19 January 2016|
Heavy elements Ba, La, Ce, Nd, and Eu in 56 Galactic bulge red giants⋆
1 Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, Brazil
e-mail: firstname.lastname@example.org; email@example.com
2 Laboratoire Lagrange (UMR 7293), Université de Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, CS 34229, 06304 Nice Cedex 4, France
3 Instituto de Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22, Chile
4 Millennium Institute of Astrophysics, Casilla 306, Santiago 22, Chile
5 Departamento de Ciencias Fisicas, Universidad Andres Bello, Republica 220, Santiago, Chile
6 Vatican Observatory, V00120 Vatican City State, 00120 Vatican City State, Italy
7 Università di Padova, Dipartimento di Astronomia, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
8 Observatoire de Paris-Meudon, 92195 Meudon Cedex, France
Received: 21 January 2015
Accepted: 21 September 2015
Aims. The aim of this work is the study of abundances of the heavy elements Ba, La, Ce, Nd, and Eu in 56 bulge giants (red giant branch and red clump) with metallicities ranging from -1.3 dex to 0.5 dex.
Methods. We obtained high-resolution spectra of our giant stars using the FLAMES-UVES spectrograph on the Very Large Telescope. We inspected four bulge fields along the minor axis.
Results. We measure the chemical evolution of heavy elements, as a function of metallicity, in the Galactic bulge.
Conclusions. The [Ba,La,Ce,Nd/Fe] vs. [Fe/H] ratios decrease with increasing metallicity, in which aspect they differ from disc stars. In our metal-poor bulge stars, La and Ba are enhanced relative to their thick disc counterpart, while in our metal-rich bulge stars La and Ba are underabundant relative to their disc counterpart. Therefore, this contrast between bulge and discs trends indicates that bulge and (solar neighbourhood) thick disc stars could behave differently. An increase in [La,Nd/Eu] with increasing metallicity, for metal-rich stars with [Fe/H] > 0 dex, may indicate that the s-process from AGB stars starts to operate at a metallicity around solar. Finally, [Eu/Fe] follows the [α/ Fe] behaviour, as expected, since these elements are produced by SNe type II.
Key words: stars: abundances / stars: atmospheres / Galaxy: bulge
© ESO, 2016
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