Issue |
A&A
Volume 640, August 2020
|
|
---|---|---|
Article Number | A89 | |
Number of page(s) | 16 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361/202037869 | |
Published online | 17 August 2020 |
Cobalt and copper abundances in 56 Galactic bulge red giants★
1
Universidade de São Paulo, IAG, Rua do Matão 1226, Cidade Universitária,
São Paulo
05508-900, Brazil
e-mail: b.barbuy@iag.usp.br
2
UK Astronomy Technology Centre, Royal Observatory, Blackford Hill,
Edinburgh,
EH9 3HJ, UK
3
IfA, University of Edinburgh, Royal Observatory,
Blackford Hill,
Edinburgh,
EH9 3HJ, UK
4
Université de Sophia-Antipolis, Observatoire de la Côte d’Azur, CNRS UMR 6202,
BP4229,
06304
Nice Cedex 4, France
5
Universidad Catolica de Chile, Departamento de Astronomia y Astrofisica, Casilla 306,
Santiago 22, Chile
6
Millennium Institute of Astrophysics,
Av. Vicuna Mackenna 4860,
782-0436
Santiago, Chile
7
Departamento de Ciencias Fisicas, Facultad de Ciencias Exactas, Universidad Andres Bello,
Av. Fernandez Concha 700,
Las Condes,
Santiago, Chile
8
Vatican Observatory,
V00120
Vatican City State, Italy
9
Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova, Italy
10
Università di Padova, Dipartimento di Fisica e Astronomia,
Vicolo dell’Osservatorio 2,
35122
Padova, Italy
11
INAF-Osservatorio Astronomico di Padova,
Vicolo dell’Osservatorio 5,
35122
Padova, Italy
Received:
3
March
2020
Accepted:
15
June
2020
Context. The Milky Way bulge is an important tracer of the early formation and chemical enrichment of the Galaxy. The abundances of different iron-peak elements in field bulge stars can give information on the nucleosynthesis processes that took place in the earliest supernovae. Cobalt (Z = 27) and copper (Z = 29) are particularly interesting.
Aims. We aim to identify the nucleosynthesis processes responsible for the formation of the iron-peak elements Co and Cu.
Methods. We derived abundances of the iron-peak elements cobalt and copper in 56 bulge giants, 13 of which were red clump stars. High-resolution spectra were obtained using FLAMES-UVES at the ESO Very Large Telescope by our group in 2000–2002, which appears to be the highest quality sample of optical high-resolution data on bulge red giants obtained in the literature to date. Over the years we have derived the abundances of C, N, O, Na, Al, Mg; the iron-group elements Mn and Zn; and neutron-capture elements. In the present work we derive abundances of the iron-peak elements cobalt and copper. We also compute chemodynamical evolution models to interpret the observed behaviour of these elements as a function of iron.
Results. The sample stars show mean values of [Co/Fe] ~ 0.0 at all metallicities, and [Cu/Fe] ~ 0.0 for [Fe/H] ≥−0.8 and decreasing towards lower metallicities with a behaviour of a secondary element.
Conclusions. We conclude that [Co/Fe] varies in lockstep with [Fe/H], which indicates that it should be produced in the alpha-rich freezeout mechanism in massive stars. Instead [Cu/Fe] follows the behaviour of a secondary element towards lower metallicities, indicating its production in the weak s-process nucleosynthesis in He-burning and later stages. The chemodynamical models presented here confirm the behaviour of these two elements (i.e. [Co/Fe] vs. [Fe/H] ~constant and [Cu/Fe] decreasing with decreasing metallicities).
Key words: stars: abundances / Galaxy: bulge / Galaxy: abundances / nuclear reactions, nucleosynthesis, abundances / stars: late-type
© ESO 2020
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