Manganese abundances in Galactic bulge red giants ^⋆,⋆⋆

¹ Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária, 05508-900 São Paulo, Brazil
e-mail: barbuy@astro.iag.usp.br, nathalia.dutra@usp.br
² Université de Sophia-Antipolis, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, BP4229, 06304 Nice Cedex 4, France
e-mail: vanessa.hill@oca.eu
³ Instituto de Astrofisica, Facultad de Fisica, Pontificia Universidad Catolica de Chile, Casilla 306, 22 Santiago, Chile
e-mail: [mzoccali;dante]@astro.puc.cl
⁴ Vatican Observatory, V 00120 Vatican City State, Italy
⁵ Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122 Padova, Italy
e-mail: alvio.renzini@oapd.inaf.it
⁶ Università di Padova, Dipartimento di Astronomia, Vicolo dell’Osservatorio 2, 35122 Padova, Italy
e-mail: sergio.ortolani@unipd.it
⁷ Observatoire de Paris-Meudon, 92195 Meudon Cedex, France
e-mail: anita.gomez@obspm.fr
⁸ Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas 1758, 12227-010 São José dos Campos, Brazil
e-mail: marinatrevisan@gmail.com

Received: 27 July 2013
Accepted: 18 September 2013

Abstract

Context. Manganese is mainly produced in type II SNe during explosive silicon burning, in incomplete Si-burning regions, and depends on several nucleosynthesis environment conditions, such as mass cut between the matter ejected and falling back onto the remnant, electron and neutron excesses, mixing fallback, and explosion energy. Manganese is also produced in type Ia SNe.

Aims. The aim of this work is the study of abundances of the iron-peak element Mn in 56 bulge giants, among which 13 are red clump stars. Four bulge fields along the minor axis are inspected. The study of abundances of Mn-over-Fe as a function of metallicity in the Galactic bulge may shed light on its production mechanisms.

Methods. High-resolution spectra were obtained using the FLAMES+UVES spectrograph on the Very Large Telescope. The spectra were obtained within a program to observe 800 stars using the GIRAFFE spectrograph, together with the present UVES spectra.

Results. We aim at identifying the chemical evolution of manganese, as a function of metallicity, in the Galactic bulge. We find [Mn/Fe] ~ −0.7 at [Fe/H] ~ −1.3, increasing to a solar value at metallicities close to solar, and showing a spread around − 0.7 ≲ [Fe/H] ≲ −0.2, in good agreement with other work on Mn in bulge stars. There is also good agreement with chemical evolution models. We find no clear difference in the behaviour of the four bulge fields. Whereas [Mn/Fe] vs. [Fe/H] could be identified with the behaviour of the thick disc stars, [Mn/O] vs. [O/H] has a behaviour running parallel, at higher metallicities, compared to thick disc stars, indicating that the bulge enrichment might have proceeded differently from that of the thick disc.