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321. Abundances of red giants in NGC 6441
ID:
ivo://CDS.VizieR/J/A+A/455/271
Title:
Abundances of red giants in NGC 6441
Short Name:
J/A+A/455/271
Date:
21 Oct 2021
Publisher:
CDS
Description:
The aim of the present work is to determine accurate metallicities for a group of red giant branch stars in the field of the bulge Globular Cluster NGC 6441. This is the third paper in a series resulting from a large project aimed at determining the extent of the Na-O anticorrelation among Globular Cluster stars and exploring its relationship with HB morphology. We present an LTE abundance analysis of these objects, based on data gathered with the FLAMES fiber facility and the UVES spectrograph at VLT2. Results. Five of the thirteen stars observed are members of the cluster. The average Fe abundance for these five stars is [Fe/H]=-0.39+/-0.04+/-0.05dex, where the first error bar includes the uncertainties related to star-to-star random errors, and the second one the systematic effects related to the various assumptions made in the analysis.The overall abundance pattern is quite typical of Globular Clusters, with an excess of the alpha-elements and of Eu. There is evidence that the stars of NGC 6441 are enriched in Na and Al, while they have been depleted of O and Mg by H-burning at high temperatures, analogous with extensive observations of other Globular Clusters: in particular, one star is clearly Na and Al-rich and O and Mg-poor. We also obtained quite high V abundances, but it is possible that this is an artifact of the analysis, since similar high V abundances are also derived for the field stars. These last are all more metal-rich than NGC 6441 and probably belong to the bulge population bulge.
322. Abundances of red giants in NGC 6388
ID:
ivo://CDS.VizieR/J/A+A/464/967
Title:
Abundances of red giants in NGC 6388
Short Name:
J/A+A/464/967
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the LTE abundance analysis of high resolution spectra for red giant stars in the peculiar bulge globular cluster NGC 6388. Spectra of seven members were taken using the UVES spectrograph at the ESO VLT2 and the multiobject FLAMES facility. We exclude any intrinsic metallicity spread in this cluster: on average, [Fe/H]=-0.44+/-0.01+/-0.03dex on the scale of the present series of papers, where the first error bar refers to individual star-to-star errors and the second is systematic, relative to the cluster. Elements involved in H-burning at high temperatures show large spreads, exceeding the estimated errors in the analysis. In particular, the pairs Na and O, Al and Mg are anticorrelated and Na and Al are correlated among the giants in NGC 6388, the typical pattern observed in all galactic globular clusters studied so far. Stars in NGC 6388 shows an excess of alpha-process elements, similar to the one found in the twin bulge cluster NGC 6441. Mn is found underabundant in NGC 6388, in agreement with the average abundance ratio shown by clusters of any metallicity. Abundances of neutron-capture elements are homogeneously distributed within NGC 6388; the [Eu/Fe] ratio stands above the value found in field stars of similar metallicity.
323. Abundances of red giants in NGC 6218
ID:
ivo://CDS.VizieR/J/A+A/464/939
Title:
Abundances of red giants in NGC 6218
Short Name:
J/A+A/464/939
Date:
21 Oct 2021
Publisher:
CDS
Description:
We used the multifiber spectrograph FLAMES on the ESO Very Large Telescope UT2 to derive atmospheric parameters, metallicities and abundances of O and Na for 79 red giant stars in the Galactic globular cluster NGC 6218 (M 12). We analyzed stars in the magnitude range from about 1mag below the bump to the tip of the Red Giant Branch. The average metallicity we derive is [Fe/H]=-1.31+/-0.004+/-0.028dex (random and systematic errors, respectively), with a very small star-to-star scatter (rms=0.033dex), from moderately high-resolution Giraffe spectra. This is the first extensive spectroscopic abundance analysis in this cluster. Our results indicate that NGC 6218 is very homogeneous as far as heavy elements are concerned. On the other hand, light elements involved in the well known proton-capture reactions of H-burning at high temperature, such as O and Na, show large variations, anticorrelated with each other, at all luminosities along the red giant branch. The conclusion is that the Na-O anticorrelation must be established in early times at the cluster formation. We interpret the variation of Na found near the RGB-bump as the effect of two distinct populations having different bump luminosities, as predicted for different He content. To our knowledge, NGC 6218 is the first GC where such a signature has been spectroscopically detected, when combined with consistent and homogeneous data obtained for NGC 6752 to gain in statistical significance.
324. Abundances of red giants in NGC 6441
ID:
ivo://CDS.VizieR/J/A+A/464/953
Title:
Abundances of red giants in NGC 6441
Short Name:
J/A+A/464/953
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of FLAMES-Giraffe spectra for several bright giants in NGC 6441, to investigate the presence and extent of the Na-O anticorrelation in this anomalous globular cluster. The field of NGC 6441 is very crowded, with severe contamination by foreground (mainly bulge) field stars. Appropriate membership criteria were devised to identify a group of 25 likely cluster members among the about 130 stars observed. Combined with the UVES data obtained with the same observations (Gratton et al., 2006, Cat. <J/A+A/455/271>), high dispersion abundance analyses are now available for a total of 30 stars in NGC 6441, 29 of them having data for both O and Na. The spectra were analyzed by a standard line analysis procedure; care was taken to minimize the impact of the differential interstellar reddening throughout the cluster, and to extract reliable information from crowded, and moderately high S/N (30-70), moderately high resolution (R~23000) spectra.
325. Abundances of red giants in NGC 6752
ID:
ivo://CDS.VizieR/J/A+A/464/927
Title:
Abundances of red giants in NGC 6752
Short Name:
J/A+A/464/927
Date:
21 Oct 2021
Publisher:
CDS
Description:
We are studying the Na-O anticorrelation in several globular clusters of different Horizontal Branch (HB) morphology in order to derive a possible relation between (primordial) chemical inhomogeneities and morphological parameters of the cluster population. We used the multifiber spectrograph FLAMES on the ESO Very Large Telescope UT2 and derived atmospheric parameters and elemental abundances of Fe, O and Na for about 150 red giant stars in the Galactic globular cluster NGC 6752. The average metallicity we derive is [Fe/H]=-1.56, in agreement with other results from red giants, but lower than obtained for dwarfs or early subgiants. In NGC 6752 there is not much space for an intrinsic spread in metallicity: on average, the rms scatter in [Fe/H] is 0.037+/-0.003dex, while the scatter expected on the basis of the major error sources is 0.039+/-0.003dex. The distribution of stars along the Na-O anticorrelation is different to what was found in the first paper of this series for the globular cluster NGC 2808: in NGC 6752 it is skewed toward more Na-poor stars, and it resembles more the one in M 13. Detailed modeling is required to clarify whether this difference may explain the very different distributions of stars along the HB.
326. Abundances of red giants in {omega} Cen
ID:
ivo://CDS.VizieR/J/ApJ/698/2048
Title:
Abundances of red giants in {omega} Cen
Short Name:
J/ApJ/698/2048
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present abundances of several light, {alpha}, Fe-peak, and neutron-capture elements for 66 red giant branch (RGB) stars in the Galactic globular cluster Omega Centauri ({omega} Cen). Our observations lie in the range 12.0<V<13.5 and focus on the intermediate and metal-rich RGBs. Abundances were determined using equivalent width measurements and spectrum synthesis analyses of moderate resolution (R~18000) spectra obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. Combining these data with previous work, we find that there are at least four peaks in the metallicity distribution function at [Fe/H]=-1.75, -1.45, -1.05, and -0.75, which correspond to about 55%, 30%, 10%, and 5% of our sample, respectively. We conclude that the metal-rich population must be at least 1-2Gyr younger than the metal-poor stars, owing to the long timescales needed for strong s-process enrichment and the development of a large contingent of mass transfer binaries.
327. Abundances of red giants in {omega} Cen
ID:
ivo://CDS.VizieR/J/ApJ/681/1505
Title:
Abundances of red giants in {omega} Cen
Short Name:
J/ApJ/681/1505
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radial velocities and Fe and Al abundances for 180 red giant branch (RGB) stars in the Galactic globular cluster Omega Centauri ({omega} Cen). The majority of our data lie in the range 11.0<V<13.5, which covers the RGB from about 1mag above the horizontal branch to the RGB tip. The selection procedures are biased toward preferentially observing the more metal-poor and luminous stars of {omega} Cen. Abundances were determined using equivalent width measurements and spectrum synthesis analyses of moderate resolution spectra (R~13000) obtained with the Blanco 4m telescope and Hydra multifiber spectrograph. Our results are in agreement with previous studies as we find at least four different metallicity populations with [Fe/H]=-1.75, -1.45, -1.05, and -0.75, with a full range of -2.20<~[Fe/H]<~-0.70. Results seem to fit in the adopted scheme that star formation occurred in {omega} Cen over >1Gyr.
328. Abundances of red giants in open clusters
ID:
ivo://CDS.VizieR/J/MNRAS/431/3338
Title:
Abundances of red giants in open clusters
Short Name:
J/MNRAS/431/3338
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analysed high-resolution echelle spectra of red giant members for seven open clusters in the Galactic anticentre direction to explore their chemical compositions. Cluster membership has been confirmed by radial velocity. The spread in temperatures and gravities being very small among the red giants, nearly the same stellar lines were employed for all stars thereby reducing the abundance errors: the errors of the average abundance for a cluster were generally in the 0.02-0.05dex range. Our present sample covers Galactocentric distances of 8.3-11.3kpc and an age range of 0.2-4.3Gyr. A careful comparison of our results for the cluster NGC 2682 (M67) to other high-resolution abundance studies in the literature shows general good agreement for almost all elements in common.
329. Abundances of 4 red giants in Pal 1
ID:
ivo://CDS.VizieR/J/ApJ/740/106
Title:
Abundances of 4 red giants in Pal 1
Short Name:
J/ApJ/740/106
Date:
21 Oct 2021
Publisher:
CDS
Description:
Detailed chemical abundances for 21 elements are presented for four red giants in the anomalous outer halo globular cluster Palomar 1 (R_GC_=17.2kpc, Z=3.6kpc) using high-resolution (R=36000) spectra from the High Dispersion Spectrograph on the Subaru Telescope. Pal 1 has long been considered unusual because of its low surface brightness, sparse red giant branch, young age, and its possible association with two extragalactic streams of stars. This paper shows that its chemistry further confirms its unusual nature. The mean metallicity of the four stars, [Fe/H]=-0.60+/-0.01, is high for a globular cluster so far from the Galactic center, but is low for a typical open cluster. The [{alpha}/Fe] ratios, though in agreement with the Galactic stars within the 1{sigma} errors, agree best with the lower values in dwarf galaxies. No signs of the Na/O anticorrelation are detected in Pal 1, though Na appears to be marginally high in all four stars. Pal 1's neutron-capture elements are also unusual: its high [Ba/Y] ratio agrees best with dwarf galaxies, implying an excess of second-peak over first-peak s-process elements, while its [Eu/{alpha}] and [Ba/Eu] ratios show that Pal 1's contributions from the r-process must have differed in some way from normal Galactic stars. Therefore, Pal 1 is unusual chemically, as well in its other properties. Pal 1 shares some of its unusual abundance characteristics with the young clusters associated with the Sagittarius dwarf galaxy remnant and the intermediate-age LMC clusters, and could be chemically associated with the Canis Majoris overdensity; however, it does not seem to be similar to the Monoceros/Galactic Anticenter Stellar Stream.
330. Abundances of red giants in the Galactic bulge
ID:
ivo://CDS.VizieR/J/ApJ/765/157
Title:
Abundances of red giants in the Galactic bulge
Short Name:
J/ApJ/765/157
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present radial velocities and chemical abundance ratios of [Fe/H], [O/Fe], [Si/Fe], and [Ca/Fe] for 264 red giant branch stars in three Galactic bulge off-axis fields located near (l,b)=(-5.5,-7), (-4,-9), and (+8.5,+9). The results are based on equivalent width and spectrum synthesis analyses of moderate resolution (R{approx}18000), high signal-to-noise ratio (S/N~75-300pixel^-1^) spectra obtained with the Hydra spectrographs on the Blanco 4m and WIYN 3.5m telescopes. The targets were selected from the blue side of the giant branch to avoid cool stars that would be strongly affected by CN and TiO; however, a comparison of the color-metallicity distribution in literature samples suggests that our selection of bluer targets should not present a significant bias against metal-rich stars.

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