- 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.
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- 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.
- ID:
- ivo://CDS.VizieR/J/ApJ/780/94
- Title:
- Abundances of red giants in 47 Tuc
- Short Name:
- J/ApJ/780/94
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 47 Tuc is an ideal target to study chemical evolution and globular cluster (GC) formation in massive more metal-rich GCs, as it is the closest massive GC. We present chemical abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu in 164 red giant branch stars in the massive GC 47 Tuc using spectra obtained with both the Hydra multifiber spectrograph at the Blanco 4m telescope and the FLAMES multiobject spectrograph at the Very Large Telescope. We find an average [Fe/H]=-0.79+/-0.09dex, consistent with literature values, as well as overabundances of alpha-elements ([{alpha}/Fe]~0.3dex). The n-capture process elements indicate that 47 Tuc is r process-dominated ([Eu/La]=+0.24), and the light elements O, Na, and Al exhibit star-to-star variations. The Na-O anticorrelation, a signature typically seen in Galactic GCs, is present in 47 Tuc, and extends to include a small number of stars with [O/Fe]~-0.5. Additionally, the [O/Na] ratios of our sample reveal that the cluster stars can be separated into three distinct populations. A Kolmogorov-Smirnov test demonstrates that the O-poor/Na-rich stars are more centrally concentrated than the O-rich/Na-poor stars. The observed number and radial distribution of 47 Tuc's stellar populations, as distinguished by their light element composition, agrees closely with the results obtained from photometric data. We do not find evidence supporting a strong Na-Al correlation in 47 Tuc, which is consistent with current models of asymptotic giant branch nucleosynthesis yields.
- ID:
- ivo://CDS.VizieR/J/A+A/600/A118
- Title:
- Abundances of red giant stars in NGC6093 (M80)
- Short Name:
- J/A+A/600/A118
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Homogeneous abundances of light elements, alpha-elements, Fe-group elements and neutron-capture elements from high-resolution FLAMES spectra are presented for stars in the globular cluster NGC 5634, associated to the Sagittarius dwarf spheroidal galaxy. In particular we present detailed chemical abundance of 22 species for the seven stars observed with UVES-FLAMES, and the abundance of six elements for stars observed with GIRAFFE. We derived a metallicity [Fe/H]=-1.867+/-0.019+/-0.065dex (+/-statistical+/-systematic error) with sigma=0.050dex (7 stars). We found the normal anti-correlations between light elements (Na and O, Mg and Al), signature of multiple populations typical of massive and old GCs. We confirm the associations of NGC 5634 to the Sgr dSph, from which the cluster was lost a few Gyr ago, on the basis of its velocity and position, and the abundance ratios of {alpha} and neutron capture elements.
- ID:
- ivo://CDS.VizieR/J/A+A/578/A116
- Title:
- Abundances of red giant stars in NGC6093 (M80)
- Short Name:
- J/A+A/578/A116
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Homogeneous abundances of light elements, alpha-elements, and Fe-group elements from high-resolution FLAMES spectra are presented for 82 red giant stars in NGC 6093 (M 80), a dense, metal-poor globular cluster (GC). M 80 shows star to star variations in proton-capture elements, and the extension of the Na-O anticorrelation perfectly fit the relations with (i) total cluster mass, (ii) horizontal branch morphology, and (iii) cluster concentration previously found by our group. The chemistry of multiple stellar populations in M 80 does not look extreme. The cluster is also a typical representative of halo globular clusters for what concerns the pattern of alpha-capture and Fe-group elements. However we found that a significant contribution from the s-process is required to account for the distribution of neutron-capture elements.
- ID:
- ivo://CDS.VizieR/J/AJ/157/154
- Title:
- Abundances of RGs in Galactic globular clusters
- Short Name:
- J/AJ/157/154
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Among stars in Galactic globular clusters the carbon abundance tends to decrease with increasing luminosity on the upper red giant branch, particularly within the lowest metallicity clusters. While such a phenomena is not predicted by canonical models of stellar interiors and evolution, it is widely held to be the result of some extra mixing operating during red giant branch ascent which transports material exposed to the CN(O)-cycle across the radiative zone in the stellar interior and into the base of the convective envelope, whereupon it is brought rapidly to the stellar surface. Here we present measurements of [C/Fe] abundances among 67 red giants in 19 globular clusters within the Milky Way. Building on the work of Martell et al. (2008AJ....136.2522M), we have concentrated on giants with absolute magnitudes of M_V_~-1.5 within clusters encompassing a range of metallicity (-2.4<[Fe/H]<-0.3). The Kitt Peak National Observatory (KPNO) 4 m and Southern Astrophysical Research (SOAR) 4.1 m telescopes were used to obtain spectra covering the {lambda}4300 CH and {lambda}3883 CN bands. The CH absorption features in these spectra have been analyzed via synthetic spectra in order to obtain [C/Fe] abundances. These abundances and the luminosities of the observed stars were used to infer the rate at which C abundances change with time during upper red giant branch evolution (i.e., the mixing efficiency). By establishing rates over a range of metallicity, the dependence of deep mixing on metallicity is explored. We find that the inferred carbon depletion rate decreases as a function of metallicity, although our results are dependent on the initial [C/Fe] composition assumed for each star.
- ID:
- ivo://CDS.VizieR/J/A+A/465/815
- Title:
- Abundances of Sgr dSph stars
- Short Name:
- J/A+A/465/815
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The Sagittarius dwarf spheroidal galaxy is the nearest neighbor of the Milky Way. Moving along a short period quasi-polar orbit within the Halo, it is being destroyed by the tidal interaction with our Galaxy, losing its stellar content along a huge stellar stream. We study the detailed chemical composition of 12 giant stars in the Sagittarius dwarf Spheroidal main body, together with 5 more in the associated globular cluster Terzan 7, by means of high resolution VLT-UVES spectra. Abundances are derived for up to 21 elements from O to Nd, by fitting lines EW or line profiles against ATLAS 9 model atmospheres and SYNTHE spectral syntheses calculated ad-hoc. Temperatures are derived from (V-I)_0_ or (B-V)_0_ colors and gravities from FeI-FeII ionization equilibrium. The metallicity of the observed stars is between [Fe/H]=-0.9 and 0. We detected a highly peculiar "chemical signature", with undersolar alpha elements, Na, Al , Sc, V, Co, Ni, Cu, and Zn, among others, and overabundant La, Ce, and Nd. Many of these abundance ratios (in particular light-odd elements and iron peak ones) are strongly at odds with what is observed within the Milky Way, so they may be a very useful tool for recognizing populations originating within the Sagittarius dwarf. This can be clearly seen in the case of the globular Palomar 12, which is believed to have been stripped from Sagittarius: the cluster shows precisely the same chemical "oddities", thus finally confirming its extragalactic origin.
- ID:
- ivo://CDS.VizieR/J/ApJ/742/37
- Title:
- Abundances of six RGB stars in M22
- Short Name:
- J/ApJ/742/37
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present an empirical s-process abundance distribution derived with explicit knowledge of the r-process component in the low-metallicity globular cluster M22. We have obtained high-resolution, high signal-to-noise spectra for six red giants in M22 using the Magellan Inamori Kyocera Echelle spectrograph on the Magellan-Clay Telescope at Las Campanas Observatory. In each star we derive abundances for 44 species of 40 elements, including 24 elements heavier than zinc (Z=30) produced by neutron-capture reactions. Previous studies determined that three of these stars (the "r+s group") have an enhancement of s-process material relative to the other three stars (the "r-only group"). We confirm that the r+s group is moderately enriched in Pb relative to the r-only group. Both groups of stars were born with the same amount of r-process material, but s-process material was also present in the gas from which the r+s group formed. The s-process abundances are inconsistent with predictions for asymptotic giant branch (AGB) stars with M<=3M_{sun}_ and suggest an origin in more massive AGB stars capable of activating the ^22^Ne({alpha},n)^25^Mg reaction. We calculate the s-process "residual" by subtracting the r-process pattern in the r-only group from the abundances in the r+s group. In contrast to previous r- and s-process decompositions, this approach makes no assumptions about the r- and s-process distributions in the solar system and provides a unique opportunity to explore s-process yields in a metal-poor environment.
- ID:
- ivo://CDS.VizieR/J/AJ/129/303
- Title:
- Abundances of stars in M3 and M13
- Short Name:
- J/AJ/129/303
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have carried out a detailed abundance analysis for 21 elements in a sample of 27 stars with a wide range in luminosity from luminous giants to stars near the main-sequence turnoff in the globular cluster M13 ([Fe/H]=-1.50dex) and in a sample of 13 stars distributed from the tip to the base of the red giant branch (RGB) in the globular cluster M3 ([Fe/H]=-1.39dex). The analyzed spectra, obtained with HIRES at the Keck Observatory, are of high dispersion (R={lambda}/{Delta}{lambda}=35000).
- ID:
- ivo://CDS.VizieR/J/AJ/135/1551
- Title:
- Abundances of stars in 47 Tuc
- Short Name:
- J/AJ/135/1551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances for O, Na, Mg, Al, Si, Ca, Ti, and Fe in eight red giants and one turnoff star in the metal-rich globular cluster 47 Tuc, based on spectroscopy with the Magellan Inamori Kyocera Echelle high-resolution spectrograph on the Magellan 6.5m Clay telescope. A robust line by a line differential abundance analysis technique, relative to the K-giant Arcturus, was used to reduce systematic errors from atmospheric and atomic parameters.
