2018A&A...619A.178B


C.D.S. - SIMBAD4 rel 1.7 - 2019.11.13CET07:06:29

2018A&A...619A.178B - Astronomy and Astrophysics, volume 619A, 178-178 (2018/11-1)

High-resolution abundance analysis of four red giants in the globular cluster NGC 6558.

BARBUY B., MUNIZ L., ORTOLANI S., ERNANDES H., DIAS B., SAVIANE I., KERBER L., BICA E., PEREZ-VILLEGAS A., ROSSI L. and HELD E.V.

Abstract (from CDS):


Context. NGC 6558 is a bulge globular cluster with a blue horizontal branch (BHB), combined with a metallicity of [Fe/H]~=-1.0.It is similar to HP 1 and NGC 6522, which could be among the oldest objects in the Galaxy. Element abundances in these clusters could reveal the nature of the first supernovae.
Aims. We aim to carry out detailed spectroscopic analysis for four red giants of NGC 6558, in order to derive the abundances of the light elements C, N, O, Na, Al, the α-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu.
Methods. High-resolution spectra of four stars with FLAMES-UVES at VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of FeI and FeII.
Results. This analysis results in a metallicity of [Fe/H]=-1.17±0.10 for NGC 6558. We find the expected α-element enhancements in O and Mg with [O/Fe]=+0.40, [Mg/Fe]=+0.33, and low enhancements in Si and Ca. Ti has a moderate enhancement of [Ti/Fe]=+0.22. The r-element Eu appears very enhanced with a mean value of [Eu/Fe]=+0.63. The first peak s-elements Y and Sr are also enhanced, these results have however to be treated with caution, given the uncertainties in the continuum definition; the use of neutral species (SrI, YI), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe.
Conclusions. NGC 6558 shows an abundance pattern that could be typical of the oldest inner bulge globular clusters, together with the pattern in the similar clusters NGC 6522 and HP 1. They show low abundances of the odd-Z elements Na and Al, and of the explosive nucleosynthesis α-elements Si, Ca, and Ti. The hydrostatic burning α-elements O and Mg are normally enhanced as expected in old stars enriched with yields from core-collapse supernovae, and the iron-peak elements Mn, Cu, Zn show low abundances, which is expected for Mn and Cu, but not for Zn. Finally, the cluster trio NGC 6558, NGC 6522, and HP 1 have relatively high abundances of first-peak heavy elements, variable second-peak element Ba, and the r-element Eu is enhanced. The latter is particularly high in NGC 6558.

Abstract Copyright: © ESO 2018

Journal keyword(s): stars: abundances - Galaxy: bulge - globular clusters: individual: NGC 6558

VizieR on-line data: <Available at CDS (J/A+A/619/A178): stars.dat tablea1.dat tablea2.dat>

CDS comments: Stars #5 and #11 from Davidge et al. 2004AJ....128..300D are not in SIMBAD (<Cl* NGC 6568 DLP NN>).

Simbad objects: 16

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Number of rows : 16

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 NAME Reticulum II G 03 35 42.1 -54 02 57           ~ 151 0
2 GrW 170817 GWE 13 09 48.0850 -23 22 53.343           ~ 547 0
3 * alf Boo RG* 14 15 39.67207 +19 10 56.6730 2.46 1.18 -0.05 -1.03 -1.68 K1.5IIIFe-0.5 2095 0
4 NGC 5986 GlC 15 46 03.00 -37 47 11.1     6.92     ~ 291 0
5 M 4 GlC 16 23 35.22 -26 31 32.7           ~ 1635 0
6 M 62 GlC 17 01 12.60 -30 06 44.5   8.55 7.39     ~ 490 0
7 ESO 455-11 GlC 17 31 05.20 -29 58 54.0           ~ 119 0
8 NAME Gal Center reg 17 45 40.04 -29 00 28.1           ~ 11035 0
9 NGC 6522 GlC 18 03 34.08 -30 02 02.3   10.68 9.48     ~ 437 1
10 Cl* NGC 6558 BZO F97 * 18 10 15.20 -31 46 01.5     16.037   14.467 ~ 5 0
11 2MASS J18101768-3145246 IR 18 10 17.68464 -31 45 24.6636           ~ 2 0
12 NGC 6558 GlC 18 10 18.38 -31 45 48.6   12.39 11.29     ~ 169 0
13 Cl* NGC 6558 BZO B73 * 18 10 21.5037029738 -31 45 26.770206814     15.709   14.187 ~ 8 0
14 2MASS J18102223-3145435 IR 18 10 22.23432 -31 45 43.5132           ~ 2 0
15 NAME Galactic Bulge reg ~ ~           ~ 3242 0
16 NAME Galactic Bar reg ~ ~           ~ 824 0

    Equat.    Gal    SGal    Ecl

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2019.11.13-07:06:29

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