- ID:
- ivo://CDS.VizieR/J/AZh/82/601
- Title:
- Abundances of 4 red giants
- Short Name:
- J/AZh/82/601
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We analyze the Na, Mg, Al, and Si abundances in the atmospheres of more than 40 stars, including red giants of different spectral subgroups (normal red giants, mild and classical barium stars) and several supergiants. All these elements exhibit abundance excesses, with the overabundance increasing with the star's luminosity. The dependence of the overabundances for each of these elements on the luminosity (or logg) is the same for all the spectral subgroups, testifying to a common origin: they are all products of hydrogen burning in the NeNa and MgAl cycles that have been dredged up from the stellar interiors to the outer atmospheric layers by convection that gradually develops during the star's evolution from the main sequence to the red-giant stage. The sodium abundances derived for several stars are lower than for other stars with similar atmospheric parameters. The ages and kinematic characteristics of these two groups of stars suggest that they probably belong to different stellar generations.
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- ID:
- ivo://CDS.VizieR/J/AJ/149/153
- Title:
- Abundances of red giants in 10 globular clusters
- Short Name:
- J/AJ/149/153
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigate the light-element behavior of red giant stars in northern globular clusters (GCs) observed by the SDSS-III Apache Point Observatory Galactic Evolution Experiment. We derive abundances of 9 elements (Fe, C, N, O, Mg, Al, Si, Ca, and Ti) for 428 red giant stars in 10 GCs. The intrinsic abundance range relative to measurement errors is examined, and the well-known C-N and Mg-Al anticorrelations are explored using an extreme-deconvolution code for the first time in a consistent way. We find that Mg and Al drive the population membership in most clusters, except in M107 and M71, the two most metal-rich clusters in our study, where the grouping is most sensitive to N. We also find a diversity in the abundance distributions, with some clusters exhibiting clear abundance bimodalities (for example M3 and M53) while others show extended distributions. The spread of Al abundances increases significantly as cluster average metallicity decreases as previously found by other works, which we take as evidence that low metallicity, intermediate mass AGB polluters were more common in the more metal-poor clusters. The statistically significant correlation of [Al/Fe] with [Si/Fe] in M15 suggests that ^28^Si leakage has occurred in this cluster. We also present C, N, and O abundances for stars cooler than 4500K and examine the behavior of A(C+N+O) in each cluster as a function of temperature and [Al/Fe]. The scatter of A(C+N+O) is close to its estimated uncertainty in all clusters and independent of stellar temperature. A(C+N+O) exhibits small correlations and anticorrelations with [Al/Fe] in M3 and M13, but we cannot be certain about these relations given the size of our abundance uncertainties. Star-to-star variations of {alpha}-element (Si, Ca, Ti) abundances are comparable to our estimated errors in all clusters.
- ID:
- ivo://CDS.VizieR/J/A+A/505/117
- Title:
- Abundances of red giants in 15 globular clusters
- Short Name:
- J/A+A/505/117
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present abundances of Fe, Na and O for 1409 red giant stars in 15 galactic globular clusters (GCs), derived from the homogeneous analysis of high resolution FLAMES/GIRAFFE spectra. The program clusters cover a range in metallicity from [Fe/H]=-2.4dex to [Fe/H]=-0.4dex, with a wide variety of global parameters (morphology of the horizontal branch, mass, concentration, etc.). For all clusters we find the Na-O anticorrelation, classical signature of the operation of proton-capture reactions in H burning at high temperature in a previous generation of more massive stars now extinct. Using quantitative criteria (from the morphology and extension of the Na-O anticorrelation), we can define three different components of the stellar population in GCs.
- ID:
- ivo://CDS.VizieR/J/A+A/505/139
- Title:
- Abundances of red giants in 17 globular clusters
- Short Name:
- J/A+A/505/139
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present homogeneous abundance determinations for iron and some of the elements involved in the proton-capture reactions (O, Na, Mg, Al, and Si) for 202 red giants in 17 Galactic globular clusters (GCs) from the analysis of high-resolution UVES spectra obtained with the FLAMES facility at the ESO VLT2 telescope. Our programme clusters span almost the whole range of the metallicity distribution of GCs and were selected to sample the widest range of global parameters (horizontal-branch morphology, masses, concentration, etc). In this paper we focus on the discussion of the Na-O and Mg-Al anticorrelations and related issues. Our study finds clear Na and O star-to-star abundance variations, exceeding those expected from the error in the analysis, in all clusters. Variations in Al are present in all but a few GCs. Finally, a spread in abundances of Mg and Si are also present in a few clusters. Mg is slightly less overabundant and Si slightly more overabundant in the most Al-rich stars.
- ID:
- ivo://CDS.VizieR/J/A+A/480/379
- Title:
- Abundances of 59 red giants in LMC
- Short Name:
- J/A+A/480/379
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used FLAMES (the Fibre Large Array Multi Element Spectrograph) at the VLT-UT2 telescope to obtain spectra of a large sample of red giant stars from the inner disk of the LMC, ~2kpc from the center of the galaxy. We investigate the chemical abundances of key elements to understand the star formation and evolution of the LMC disk: heavy and light [s-process/Fe] and [alpha/Fe] give constraints on the time scales of formation of the stellar population. Cu, Na, Sc, and the iron-peak elements are also studied aiming to better understand the build up of the elements of this population and the origin of these elements. We aim to provide a more complete picture of the LMC's evolution by compiling a large sample of field star abundances. LTE abundances were derived using line spectrum synthesis or equivalent width analysis. We used OSMARCS model atmospheres and an updated line list.
- ID:
- ivo://CDS.VizieR/J/A+A/520/A95
- Title:
- Abundances of red giants in M54 and Sgr dSph
- Short Name:
- J/A+A/520/A95
- 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 76 red giant stars in NGC 6715 (M 54), a massive globular cluster (GC) lying in the nucleus of the Sagittarius dwarf galaxy. We also derived detailed abundances for 27 red giants belonging to the Sgr nucleus. Our abundances assess the intrinsic metallicity dispersion (~0.19dex, rms scatter) of M 54, with the bulk of stars peaking at [Fe/H]~-1.6 and a long tail extending to higher metallicities, similar to {omega} Cen. The spread in these probable nuclear star clusters exceeds those of most GCs: these massive clusters are located in a region intermediate between normal GCs and dwarf galaxies. M 54 shows the Na-O anticorrelation, typical signature of GCs, which is instead absent in the Sgr nucleus. The light elements (Mg, Al, Si) participating to the high temperature Mg-Al cycle show that the entire pattern of (anti)correlations produced by proton-capture reactions in H-burning is clearly different between the most metal-rich and most metal-poor components in the two most massive GCs in the Galaxy, confirming early result based on the Na-O anticorrelation. As in {omega} Cen, stars affected by most extreme processing, i.e. showing the signature of more massive polluters, are those of the metal-rich component. These observations can be understood if the burst of star formation giving birth to the metal-rich component was delayed by as much as 10-30Myr with respect to the metal-poor one. The evolution of these massive GCs can be easily reconciled in the general scenario for the formation of GCs recently sketched in Carretta et al.(2010a) taking into account that {omega} Cen could have already incorporated the surrounding nucleus of its progenitor and lost the rest of the hosting galaxy while the two are still observable as distinct components in M 54 and the surrounding field.
- ID:
- ivo://CDS.VizieR/J/A+A/550/A34
- Title:
- Abundances of red giants in M4 and 47 Tuc
- Short Name:
- J/A+A/550/A34
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present aluminium abundances for a sample of about 100 red giant stars in each of the Galactic globular clusters 47 Tuc (NGC 104) and M 4 (NGC 6121). We have derived homogeneous abundances from intermediate-resolution FLAMES/GIRAFFE spectra. Aluminium abundances are from the strong doublet AlI 8772-8773{AA}, as in previous works done for giants in NGC 6752 and NGC 1851, and nitrogen abundances are extracted from a large number of features of the CN molecules by assuming a suitable carbon abundance. We added previous homogeneous abundances of O and Na and newly derived abundances of Mg and Si for our samples of 83 stars in M 4 and 116 stars in 47 Tuc to obtain the full set of elements from proton-capture reactions produced by different stellar generations in these clusters.
- ID:
- ivo://CDS.VizieR/J/MNRAS/446/3562
- Title:
- Abundances of red giants in NGC752
- Short Name:
- J/MNRAS/446/3562
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present detailed chemical compositions of 10 red giant star members of the Galactic (open) cluster NGC 752, derived from high-resolution (R~60000), high signal-to-noise (S/N>=140) spectra. We confirmed cluster memberships by measuring the stellar radial velocities, and by deriving model atmosphere parameters (Teff, logg, [Fe/H] and {xi}t) from equivalent widths of FeI, FeII, TiI, and TiII lines. The metallicity we obtained for NGC 752 ([Fe/H]=-0.02+/-0.05) is in good agreement with previous studies. We derived abundances of alpha (Mg, Si, Ca), light odd-Z (Na, Al), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), n-capture (Y, La, Nd, Eu), and p-capture (Li, C, N, O) species for each star. Furthermore, we also derived abundances of the LiCNO p-capture element group and carbon isotopic ratios, using synthetic spectrum analyses of the LiI 6707{AA} resonance doublet, the [OI] line at 6300{AA}, the CH G-band features near 4311 and 4325{AA}, the C_2_ bandheads at 5160 and 563{AA}, and ^12,13^CN red system lines in the 7995-8040{AA} region. By applying recent isochrones to NGC 752 photometry, and comparing the colour-magnitude diagram information to our Li abundances and 12C/13C ratios, we suggest that the 10 observed red giants can be separated into three first-ascent, six red-clump and one red horizontal branch star.
- ID:
- ivo://CDS.VizieR/J/MNRAS/463/580
- Title:
- Abundances of red giants in NGC6940
- Short Name:
- J/MNRAS/463/580
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the high-resolution (R~=60000), high signal-to-noise ratio (S/N~=120) spectroscopic analysis of 12 red giant members of the Galactic open cluster NGC 6940. We applied Yonsei-Yale isochrones to the colour-magnitude diagram, which suggested an age of 1.1Gyr for the cluster with a turn-off mass of 2 M_{sun}_. Atmospheric parameters (T_eff_, logg, [Fe/H], and {xi}_t_) were determined via equivalent widths of FeI, FeII, TiI, and TiII lines. Calculated mean metallicity of the cluster is <[Fe/H]>=0.04+/-0.02. We derived abundances of {alpha} (Mg, Si, Ca), Fe-group (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn), and n-capture (Y, La, Nd, Eu) elements to be about solar. Light odd-Z elements Na and Al are slightly enhanced in MMU 108 and MMU 152 by ~0.34 and ~0.16dex, respectively. Abundances of light elements Li, C, N, O, and ^12^C/^13^C ratios were derived from spectrum syntheses of the LiI resonance doublet at 6707{AA}, [OI] line at 6300{AA}, C_2_ Swan bandheads at 5164 and 5635{AA}, and strong ^12,13^CN system lines in the 7995-8040{AA} region. Most carbon isotopic ratios are similar to those found in other solar-metallicity giants, but MMU 152 has an unusual value of ^12^C/^13^C=6. Evaluation of the LiCNO abundances and ^12^C/^13^C ratios along with the present theoretical models suggests that all the red giants in our sample are core-helium-burning clump stars.
- ID:
- ivo://CDS.VizieR/J/ApJ/750/L14
- Title:
- Abundances of red giants in NGC 6752
- Short Name:
- J/ApJ/750/L14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present aluminum, magnesium, and silicon abundances in the metal-poor globular cluster NGC 6752 for a sample of more than 130 red giants with homogeneous oxygen and sodium abundances. We find that [Al/Fe] shows a spread of about 1.4 dex among giants in NGC 6752 and is anticorrelated with [Mg/Fe] and [O/Fe] and correlated with [Na/Fe] and [Si/Fe]. These relations are not continuous in nature, but the distribution of stars is clearly clustered around three distinct Al values, low, intermediate, and high. These three groups nicely correspond to the three distinct sequences previously detected using Stromgren photometry along the red giant branch. These two independent findings strongly indicate the existence of three distinct stellar populations in NGC 6752. Comparing the abundances of O and Mg, we find that the population with intermediate chemical abundances cannot originate from material with the same composition of the most O- and Mg-poor population, diluted by material with that of the most O- and Mg-rich one. This calls for different polluters.
