@Article{BarbuyCCDPHCOHZMTBG:2014:HiAbAn,
author = "Barbuy, B. and Chiappini, C. and Cantelli, E. and Depagne, E. and
Pignatari, M. and Hirschi, R. and Cescutti, G. and Ortolani, S.
and Hill, V. and Zoccali, M. and Minniti, D. and Trevisan, Marina
and Bica, E. and G{\'o}mez, A.",
affiliation = "Universidade de S{\~a}o Paulo, IAG, Cidade Universit{\'a}ria,
Rua do Mat{\~a}o 122S{\~a}o Paulo, Brazil and Leibniz-Institut
f{\"u}r Astrophysik Potsdam (AIP), An der Sternwarte 16Potsdam,
Germany and Universidade de S{\~a}o Paulo, IAG, Cidade
Universit{\'a}ria, Rua do Mat{\~a}o 122S{\~a}o Paulo, Brazil
and Leibniz-Institut f{\"u}r Astrophysik Potsdam (AIP), An der
Sternwarte 16Potsdam, Germany and Department of Physics,
University of Basel, Klingelbergstrasse 82Basel, Switzerland and
Astrophysics Group, Keele UniversityKeele, United Kingdom and
Leibniz-Institut f{\"u}r Astrophysik Potsdam (AIP), An der
Sternwarte 16Potsdam, Germany and Dipartimento di Fisica e
Astronomia, Universit{\`a} di PadovaPadova, Italy;
INAF-Osservatorio Astronomico di Padova, Vicolo dell'Osservatorio
5Padova, Italy and Laboratoire Lagrange (UMR7293), Universit{\'e}
de Nice Sophia Antipolis, CNRS, CS 34229Nice Cedex 4, France and
Universidad Catolica de Chile, Instituto de Astrofisica, Casilla
306Santiago, Chile; Millenium Institute of Astrophysics, Av.
Vicuña Mackenna 4860Macul, Santiago, Chile and Millenium Institute
of Astrophysics, Av. Vicuña Mackenna 4860Macul, Santiago, Chile;
Departamento de Ciencias Fisicas, Universidad Andres Bello,
Republica 220Santiago, Chile and {Instituto Nacional de Pesquisas
Espaciais (INPE)} and Universidade Federal Do Rio Grande Do sul,
Departamento de Astronomia, CP 15051, Brazil and Observatoire de
Paris-Meudon, GEPI, France",
title = "High-resolution abundance analysis of red giants in the globular
cluster NGC 6522",
journal = "Astronomy \& Astrophysics",
year = "2014",
volume = "570",
number = "A76",
pages = "21pp",
keywords = "Abundance analysis, Galaxy: bulge, Globular clusters, Globular
clusters: individual, High resolution, Red giants, Stars:
abundances, Stars: atmosphere.",
abstract = "Context. The [Sr/Ba] and [Y/Ba] scatter observed in some galactic
halo stars that are very metal-poor and in a few individual stars
of the oldest known Milky Way globular cluster NGC 6522 have been
interpreted as evidence of early enrichment by massive
fast-rotating stars (spinstars). Because NGC 6522 is a bulge
globular cluster, the suggestion was that not only the very-metal
poor halo stars, but also bulge stars at [Fe/H] ~-1 could be used
as probes of the stellar nucleosynthesis signatures from the
earlier generations of massive stars, but at much higher
metallicity. For the bulge the suggestions were based on early
spectra available for stars in NGC 6522, with a medium resolution
of R ~ 22 000 and a moderate signal-to-noise ratio. Aims. The main
purpose of this study is to re-analyse the NGC 6522 stars reported
previously by using new high-resolution (R ~ 45 000) and high
signal-to-noise spectra (S/N > 100). We aim at re-deriving their
stellar parameters and elemental ratios, in particular the
abundances of the neutron-capture s-process-dominated elements
such as Sr, Y, Zr, La, and Ba, and of the r-element Eu. Methods.
High-resolution spectra of four giants belonging to the bulge
globular cluster NGC 6522 were obtained at the 8m VLT UT2-Kueyen
telescope with the UVES spectrograph in FLAMES-UVES configuration.
The spectroscopic parameters were derived based on the excitation
and ionization equilibrium of Fea i and Fe ii. Results. Our
analysis confirms a metallicity [Fe/H] =-0.95 ± 0.15 for NGC 6522
and the overabundance of the studied stars in Eu (with +0.2 <
[Eu/Fe] < + 0.4) and alpha-elements O and Mg. The neutron-capture
s-element-dominated Sr, Y, Zr, Ba, and La now show less pronounced
variations from star to star. Enhancements are in the range 0.0 <
[Sr/Fe] < +0.4, +0.23 < [Y/Fe] < +0.43, 0.0 < [Zr/Fe] < +0.4, 0.0
< [La/Fe] < +0.35, and 0.05 < [Ba/Fe] < +0.55. Conclusions. The
very high overabundances of [Y/Fe] previously reported for the
four studied stars is not confirmed with the new high-quality
spectra. The moderate enhancement in [Sr/Fe] previously reported
for one of the re-studied stars is confirmed, but the strong
enhancements of this ratio for the other two stars are not
confirmed. Despite the moderate enhancements found for the
neutron-capture s-element-dominated species, none of the four
stars studied here show positive values for all [Sr/Ba], [Y/Ba]
and [Zr/Ba] ratios. The re-studied stars are now compatible not
only with the interpretation that the s-process enhancements in
these very old stars are due to spinstars, but also with
alternative models such as mass transfer from s-process-rich AGB
stars. Note, however, that when our results are interpreted in the
context of more extended datasets from the literature, the
spinstar scenario still seems to be favoured.",
doi = "10.1051/0004-6361/201424311",
url = "http://dx.doi.org/10.1051/0004-6361/201424311",
issn = "0004-6361 and 1432-0746",
label = "scopus 2014-11 BarbuyCCDPHCOHZMTBG:2014:HiAbAn",
language = "en",
targetfile = "1408.2438.pdf",
urlaccessdate = "19 abr. 2024"
}