Heavy elements Ba, La, Ce, Nd, and Eu in 56 Galactic bulge red giants

Author(s)

Van der Swaelmen, M. ^[1] ; Barbuy, B. ^[1] ; Hill, V. ^[2] ; Zoccali, M. ^{[3, 4]} ; Minniti, D. ^{[4, 5, 6]} ; Ortolani, S. ^[7] ; Gomez, A. ^[8]

Affiliation

^[1] Univ Sao Paulo, IAG, Rua Matao 1226, Cidade Univ, BR-05508900 Sao Paulo - Brazil

^[2] Univ Nice Sophia Antipolis, CNRS, Observ Cote Azur, Lab Lagrange, UMR 7293, CNRS, CS 34229, F-06304 Nice 4 - France

^[3] Pontificia Univ Catolica Chile, Fac Fis, Inst Astrofis, Casilla 306, Santiago 22 - Chile

^[4] Millennium Inst Astrophys, Casilla 306, Santiago 22 - Chile

^[5] Univ Andres Bello, Dept Ciencias Fis, Republ 220, Santiago - Chile

^[6] Vatican Observ, V00120 Vatican City State, I-00120 Vatican City - Vatican

^[7] Univ Padua, Dipartimento Astron, Vicolo Osservatorio 2, I-35122 Padua - Italy

^[8] Observ Paris, F-92195 Meudon - France

• Document type: Journal article
• Source: Astronomy & Astrophysics; v. 586, FEB 2016.
• Web of Science Citations: 21

Abstract

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 left perpendicularLa; Nd = Euright perpendicular 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 {[}alpha = Fe] behaviour, as expected, since these elements are produced by SNe type II. (AU)

• FAPESP's process: 13/50361-0 - Heavy elements in galactic bulge stars
• Grantee: Mathieu van der Swaelmen
• Support Opportunities: Scholarships in Brazil - Post-Doctoral