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

2018 ◽  
Vol 619 ◽  
pp. A178 ◽  
Author(s):  
B. Barbuy ◽  
L. Muniz ◽  
S. Ortolani ◽  
H. Ernandes ◽  
B. Dias ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
Abundance Ratio ◽  
Mean Value ◽  
Heavy Elements ◽  
Spectroscopic Parameter ◽  
Red Giants ◽  
Abundance Pattern ◽  
Element Abundances

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 Fe I and Fe II. 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 (Sr I, Y I), 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.

scholarly journals Chemical analysis of NGC 6528: one of the most metal-rich bulge globular clusters

2018 ◽  
Vol 620 ◽  
pp. A96 ◽  
Author(s):  
C. Muñoz ◽  
D. Geisler ◽  
S. Villanova ◽  
I. Saviane ◽  
C. C. Cortés ◽  
...  
Keyword(s):  
High Resolution ◽  
Chemical Analysis ◽  
Iron Content ◽  
Globular Clusters ◽  
Chemical Characterization ◽  
Heavy Elements ◽  
High Resolution Spectroscopy ◽  
Origin And Evolution ◽  
Red Giant ◽  
Good Agreement

Context. The bulge globular clusters (GCs) are key tracers of the bulge, a central and ancient component of our Galaxy. It is essential to understand their formation and evolution to study that of the bulge, as well as their relationship with the other Galactic GC systems (halo and disk GCs). High-resolution spectroscopy is a powerful tool for such studies, allowing us to obtain a detailed chemical characterization and kinematics of the clusters and to compare their chemical patterns with those of their halo and disk counterparts. Aims. Our main goals are to obtain detailed abundances for a sample of seven red giant members of NGC 6528 in order to characterize their chemical composition and study the relationship of this GC with the bulge, and with other bulge, halo, and disk GCs. Moreover, we analyze this cluster’s behavior associated with the multiple-populations phenomenon. Methods. We obtained the stellar parameters and chemical abundances of light elements (Na, Al), iron-peak elements (V, Cr, Mn, Fe, Co, Ni, Cu), α-elements (O, Mg, Si, Ca, Ti) and heavy elements (Zr, Ba, Eu) in seven red giant members of NGC 6528 using high-resolution spectroscopy from FLAMES-UVES. Results. In six stars of our sample we obtained a mean iron content of [Fe/H] = − 0.14 ± 0.03 dex, in good agreement with other studies. We found no significant internal iron spread. We detected one candidate variable star, which was excluded from the mean in iron content, and derived a metallicity in this star of [Fe/H] = − 0.55 ± 0.04 dex. Moreover, we found no extended O-Na anticorrelation but instead only an intrinsic Na spread. In addition, NGC 6528 does not exhibit a Mg-Al anticorrelation, and no significant spread in either Mg or Al. The α and iron-peak elements show good agreement with the bulge field star trend. The heavy elements are slightly dominated by the r-process. The chemical analysis suggests an origin and evolution similar to that of typical old Galactic bulge field stars. Finally, we find remarkable agreement in the chemical patterns of NGC 6528 and another bulge GC, NGC 6553, suggesting a similar origin and evolution.

scholarly journals The Chemical Abundances of the Halo Clusters of the Galaxy

1978 ◽  
Vol 80 ◽  
pp. 177-182
Author(s):  
R. Canterna ◽  
R. A. Schommer
Keyword(s):  
Globular Clusters ◽  
Broad Band ◽  
Mean Value ◽  
Red Giants ◽  
Galactocentric Distance ◽  
Chemical Abundances ◽  
Dwarf Spheroidal Galaxies ◽  
The Galaxy ◽  
Ursa Minor ◽  
Metal Abundances

Photometric metal abundances of individual red giants in eight extremely distant halo globular clusters and the Draco and Ursa Minor dwarf spheroidal galaxies have been obtained using the Washington broad-band system, C, M, T1, T2(Canterna 1976). Observations were made at the KPNO 2.1-m and CTIO 1.5-m telescopes. In Table I we list for each system the mean value of [Fe/H], the number of stars observed in each system, n, the Galactocentric distance, RGC, the intrinsic color of the giant branch at the level of the horizontal branch (HB), (B-V)o,g, and the fraction of HB stars bluer than the RR Lyrae gap, fB. Sources for unpublished color-magnitude diagram (CMD) data are: Pal 11 (Canterna and Schommer), Pal 12 (Canterna and Harris), and Ursa Minor (Schommer, Olszewski and Kunkel).

scholarly journals The Composition of Warm Giants in M 71 and M 5

1988 ◽  
Vol 126 ◽  
pp. 497-498
Author(s):  
Catherine A. Pilachowski ◽  
Christopher Sneden
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Globular Clusters ◽  
High Dispersion ◽  
High Signal ◽  
Signal To Noise

In 1979 a disturbing controversy arose in the field of globular cluster research when Cohen (1980) and Pilachowski, Canterna, and Wallerstein (1980) announced the results of the first high dispersion studies of the composition of giants in the globular clusters M 71 and 47 Tucanae. In contrast to earlier studies, which found metallicities of typically −0.3 and −0.5 dex, these investigators obtained values of −1.3 and −1.1. Since then, many have attempted to redetermine the abundances of M 71 and 47 Tuc to explain the discrepant results. These efforts have all suffered from the absence of high signal-to-noise, high resolution spectra of stars with temperatures above 4300 K.

scholarly journals Constant light element abundances suggest that the extended P1 in NGC 2808 is not a consequence of CNO-cycle nucleosynthesis

2019 ◽  
Vol 485 (3) ◽  
pp. 4128-4133 ◽  
Author(s):  
I Cabrera-Ziri ◽  
C Lardo ◽  
A Mucciarelli
Keyword(s):  
Mass Fraction ◽  
Globular Clusters ◽  
Light Element ◽  
Complete Characterization ◽  
Alternative Mechanism ◽  
Abundance Pattern ◽  
Element Abundances ◽  
Chemical Enrichment ◽  
Giant Stars ◽  
Cno Cycle

Abstract Recent photometric results have identified a new population among globular cluster stars. This population, referred to as the ‘extended P1', has been suggested to be the manifestation of a new abundance pattern where the initial mass fraction of He changes among cluster stars that share the same CNO values. The current paradigm for the formation of the multiple stellar populations in globular clusters assumes that variations in He are the product of chemical ‘enrichment’ by the ashes of the CNO-cycle (which changes He and other elements like C, N and O simultaneously). We obtained MIKE@Magellan spectra of six giant stars in NGC 2808, a cluster with one of the strongest examples of the extended P1 population. We provide the first complete characterization of the light elements abundances for the stars along a significant range of the extended P1 photometric group. The stars from our sample appear to be homogeneous in C, N, O, Na, Mg and Al. The lack of a significant change in these products of the CNO-cycle suggests that unlike the rest of the populations identified to date, the photometric changes responsible for the extended P1 feature are a consequence of an alternative mechanism. Our measurements are consistent with the interpretations where the changes of the He mass fraction among these stars could be a consequence of p–p chain nucleosynthesis (which could increase the He in stars without affecting heavier elements). Having said that, direct measurements of He are necessary to conclude if variations of this element are present among extended P1 stars.

scholarly journals The peculiar kinematics of the multiple populations in the globular cluster Messier 80 (NGC 6093)

2019 ◽  
Vol 492 (1) ◽  
pp. 966-977 ◽  
Author(s):  
S Kamann ◽  
E Dalessandro ◽  
N Bastian ◽  
J Brinchmann ◽  
M den Brok ◽  
...  
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Evolutionary History ◽  
Hubble Space Telescope ◽  
Light Element ◽  
Nitrogen Enrichment ◽  
Element Abundances ◽  
Angular Momenta ◽  
Uv Photometry ◽  
Two Populations

ABSTRACT We combine MUSE spectroscopy and Hubble Space Telescope ultraviolet (UV) photometry to perform a study of the chemistry and dynamics of the Galactic globular cluster Messier 80 (M80, NGC 6093). Previous studies have revealed three stellar populations that vary not only in their light-element abundances, but also in their radial distributions, with the concentration decreasing with increasing nitrogen enrichment. This remarkable trend, which sets M80 apart from other Galactic globular clusters, points towards a complex formation and evolutionary history. To better understand how M80 formed and evolved, revealing its internal kinematics is key. We find that the most N-enriched population rotates faster than the other two populations at a 2σ confidence level. While our data further suggest that the intermediate population shows the least amount of rotation, this trend is rather marginal (1−2σ). Using axisymmetric Jeans models, we show that these findings can be explained from the radial distributions of the populations if they possess different angular momenta. Our findings suggest that the populations formed with primordial kinematical differences.

scholarly journals Globular Cluster Formation in Galaxy Mergers

2005 ◽  
Vol 13 ◽  
pp. 205-205
Author(s):  
Yuexing Li ◽  
Mordecai-Mark Mac Low ◽  
Ralf S. Klessen
Keyword(s):  
High Resolution ◽  
Equation Of State ◽  
Globular Cluster ◽  
Orbital Period ◽  
Globular Clusters ◽  
Cluster Formation ◽  
Galaxy Mergers ◽  
Barotropic Equation ◽  
Tidal Tails ◽  
Resolution Simulation

AbstractWe present preliminary results of a high resolution simulation of globular cluster formation in a galaxy merger using GADGET (Springel et al. 2001). A barotropic equation of state (Li et al 2003) is implemented to include effects of cooling and heating. After one orbital period, a dozen proto-globular clusters are identified in the tidal tails.

scholarly journals A nitrogen-enhanced metal-poor star discovered in the globular cluster ESO280−SC06

2019 ◽  
Vol 490 (1) ◽  
pp. 741-751 ◽  
Author(s):  
Jeffrey D Simpson ◽  
Sarah L Martell
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Binary Systems ◽  
Asymptotic Giant Branch ◽  
Red Giants ◽  
Horizontal Branch ◽  
Term Survival ◽  
Abundance Patterns ◽  
Metal Poor Star

ABSTRACT We report the discovery of the only very nitrogen-enhanced metal-poor star known in a Galactic globular cluster. This star, in the very metal-poor cluster ESO280−SC06 , has $[\textrm{N}/\textrm{Fe}]\, \gt +2.5$, while the other stars in the cluster show no obvious enhancement in nitrogen. Around 80 NEMP stars are known in the field, and their abundance patterns are believed to reflect mass transfer from a binary companion in the asymptotic giant branch phase. The dense environment of globular clusters is detrimental to the long term survival of binary systems, resulting in a low observed binary fraction among red giants and the near absence of NEMP stars. We also identify the first known horizontal branch members of ESO280−SC06 , which allow for a much better constraint on its distance. We calculate an updated orbit for the cluster based on our revised distance of 20.6 ± 0.5 kpc, and find no significant change to its orbital properties.

High-resolution spectroscopy of red giants and ‘yellow stragglers’ in the southern open cluster NGC 2539

2020 ◽  
Vol 494 (1) ◽  
pp. 1470-1489
Author(s):  
Cintia F Martinez ◽  
N Holanda ◽  
C B Pereira ◽  
N A Drake
Keyword(s):  
High Resolution ◽  
Open Cluster ◽  
Open Clusters ◽  
Solar Neighborhood ◽  
Spectroscopic Binaries ◽  
High Resolution Spectroscopy ◽  
Red Giants ◽  
Light Elements ◽  
Abundance Pattern ◽  
Solar Metallicity

ABSTRACT We present a detailed high-resolution spectroscopic analysis of 12 red giant stars, in single and binaries or multiples systems, classified as members of the intermediate-age (631 Myr) open cluster NGC 2539. We used FEROS echelle spectra and the standard LTE analysis to derive the atmospheric parameters for the stars and the abundance ratios of light elements (Li, C, N), light odd-Z elements (Na, Al), α-elements (Mg, Si, Ca, Ti), Fe-group elements (Cr, Fe, Ni), and n-capture elements (Y, Zr, Ce, Nd, Eu). Our results show that the sample star of NGC 2539 has low projected rotational velocities and an almost solar metallicity, with a mean of [Fe/H] = −0.03 ± 0.07 dex. The abundance pattern displays for the analyzed stars are, in general, similar to those presented by solar neighborhood stars, including giant members of others open clusters. In particular, light elements and Na abundance pattern shows anomalies resulting from the appearance of enriched material on the stellar surface, produced by mechanisms like the first dredge-up and/or thermohaline and rotation-induced mixing. We also identified two of the spectroscopic binaries of our sample as ‘yellow stragglers’ and we determined the nature of their companions.

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