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Start Over Subject giant stars Publisher CDS
491. Red giant abundances in NGC 2808
ID:
ivo://CDS.VizieR/J/ApJ/810/148
Title:
Red giant abundances in NGC 2808
Short Name:
J/ApJ/810/148
Date:
21 Oct 2021
Publisher:
CDS
Description:
The chemical composition of multiple populations in the massive globular cluster (GC) NGC 2808 is addressed with the homogeneous abundance reanalysis of 140 red giant branch stars. UVES spectra for 31 stars and GIRAFFE spectra for the other giants were analyzed with the same procedures used for about 2500 giants in 23 GCs in our FLAMES survey, deriving abundances of Fe, O, Na, Mg, Si, Ca, Ti, Sc, Cr, Mn, and Ni. Iron, elements from {alpha} capture, and those in the Fe group do not show intrinsic scatter. On our UVES scale, the metallicity of NGC 2808 is [Fe/H]=-1.29+/-0.005+/-0.034 (+/-statistical+/-systematic error) with {sigma}=0.030 (31 stars). The main features related to proton-capture elements are retrieved, but the improved statistics and the smaller associated internal errors allow us to uncover five distinct groups of stars along the Na-O anticorrelation. We observe large depletions in Mg, anticorrelated with enhancements of Na and also Si, suggestive of unusually high temperatures for proton captures. About 14% of our sample is formed by giants with solar or subsolar [Mg/Fe] ratios. Using the [Na/Mg] ratios, we confirm the presence of five populations with different chemical compositions that we call P1, P2, I1, I2, and E in order of decreasing Mg and increasing Na abundances. Statistical tests show that the mean ratios in any pair of groups cannot be extracted from the same parent distribution. The overlap with the five populations recently detected from UV photometry is good but not perfect, confirming that more distinct components probably exist in this complex GC.
492. Red giant Aluminium abundances in NGC 2808
ID:
ivo://CDS.VizieR/J/A+A/615/A17
Title:
Red giant Aluminium abundances in NGC 2808
Short Name:
J/A+A/615/A17
Date:
21 Oct 2021
Publisher:
CDS
Description:
We observed a sample of 90 red giant branch (RGB) stars in NGC 2808 using FLAMES/GIRAFFE and the high resolution grating with the set up HR21. These stars have previous accurate atmospheric parameters and abundances of light elements. We derived aluminium abundances for them from the strong doublet AlI 8772-8773 Angstrom as in previous works of our group. In addition, we were able to estimate the relative CN abundances for 89 of the stars from the strength of a large number of CN features. When adding self consistent abundances from previous UVES spectra analysed by our team, we gathered [Al/Fe] ratios for a total of 108 RGB stars in NGC 2808. The full dataset of proton-capture elements is used to explore in details the five spectroscopically detected discrete components in this globular cluster. We found that different classes of polluters are required to reproduce the (anti)-correlations among all proton-capture elements in the populations P2, I1, and I2 with intermediate composition. This is in agreement with the detection of lithium in lower RGB second generation stars, requiring at least two kind of polluters. To have chemically homogeneous populations the best subdivision of our sample is into six components, as derived from statistical cluster analysis. By comparing different diagrams [element/Fe] vs [element/Fe] we show for the first time that a simple dilution model is not able to reproduce all the sub-populations in this cluster. Polluters of different masses are required. NGC 2808 is confirmed to be a tough challenge to any scenario for globular cluster formation.
493. Red giant candidates in 10 open clusters
ID:
ivo://CDS.VizieR/J/AN/329/609
Title:
Red giant candidates in 10 open clusters
Short Name:
J/AN/329/609
Date:
21 Oct 2021
Publisher:
CDS
Description:
As part of a long-term project to determine abundances and astrophysical properties of evolved red stars in open clusters, we present high-precision DDO photoelectric observations for a sample of 33 red giant candidates projected in the fields of nine Galactic open clusters. These data are supplemented with UBV photoelectric photometry of 24 of these stars as well as with CORAVEL radial-velocity observations for 13 red giant candidates in four of the clusters. We also present Washington photoelectric photometry of a small sample of red giant candidates of the open cluster Ruprecht 97. The likelihood of cluster membership for each star photometrically observed and for 23 additional red giant candidates with UBV and DDO data available in the literature, is evaluated by using two independent photometric criteria. Nearly 82% of the analysed stars are found to have a high probability of being cluster giants. Photometric membership probabilities show very good agreement with those obtained from CORAVEL radial velocities. While E(B-V) colour excesses were determined from combined B-V and DDO colours, calibrations of the DDO system were used to derive MK spectral types, effective temperatures and metallicities.The derived DDO metallicities range between values typical of moderately metal-poor clusters ([Fe/H]=-0.19) to moderately metal-rich ([Fe/H]=0.25) ones.
494. Red giant clump in the Tycho-2 catalog
ID:
ivo://CDS.VizieR/J/PAZh/34/868
Title:
Red giant clump in the Tycho-2 catalog
Short Name:
J/PAZh/34/868
Date:
21 Oct 2021
Publisher:
CDS
Description:
The Tycho-2 proper motions and Tycho-2 and 2MASS photometry are used to select 97348 red giant clump (RGC) stars. The interstellar extinction and photometric distance are calculated for each of the stars. The selected stars are shown to form a selection-unbiased sample of RGC stars within about 350 pc of the Sun with the addition of more distant stars. The distribution of the selected stars in space and their motion are consistent with the assumption that the RGC contains Galactic disk stars with various ages and metallicities, including a significant fraction of stars younger than 1Gyr with masses of more than 2 solar masses. These young stars show differences of their statistical characteristics from those of older RGC stars, including differences in the variations of their distribution density with distance from the Galactic plane and in the dispersion of their velocities found using radial velocities and proper motions. The Sun has been found to rise above the Galactic plane by 13+/-1pc. The distribution density of the stars under consideration in space is probably determined by the Local Spiral Arm and the distribution of absorbing matter in the plane of the Gould Belt. Data are also available at: http://www.geocities.com/orionspiral/
495. Red giants abundances in 4 open clusters
ID:
ivo://CDS.VizieR/J/MNRAS/419/1350
Title:
Red giants abundances in 4 open clusters
Short Name:
J/MNRAS/419/1350
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analysed high-dispersion echelle spectra (R>~50000) of red giant members for four open clusters to derive abundances for many elements. The spread in temperatures and gravities being very small among the red giants nearly the same stellar lines were employed thereby reducing the random errors. The errors of average abundance for the cluster were generally in the range 0.02-0.07dex. Our present sample covers Galactocentric distances of 8.3-10.5kpc. The [Fe/H] values are -0.02+/-0.05 for NGC 752, -0.07+/-0.06 for NGC 2360, -0.11+/-0.05 for NGC 1817 and -0.19+/-0.06 for NGC 2506. Abundances relative to Fe for elements from Na to Eu are equal within measurement uncertainties to published abundances for thin-disc giants in the field. This supports the view that field stars come from disrupted open clusters.
496. Red giants equivalent widths in 4 open clusters
ID:
ivo://CDS.VizieR/J/AJ/137/4753
Title:
Red giants equivalent widths in 4 open clusters
Short Name:
J/AJ/137/4753
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present an analysis of high-dispersion echelle spectra of seven giant stars in the ~1-2Gyr old open clusters NGC 1817, NGC 1883, NGC 2141, and NGC 2158. Abundances were determined relative to the bright, mildly metal-poor disk giant Arcturus.
497. Red giants in NGC 5286
ID:
ivo://CDS.VizieR/J/MNRAS/450/815
Title:
Red giants in NGC 5286
Short Name:
J/MNRAS/450/815
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a high-resolution spectroscopic analysis of 62 red giants in the Milky Way globular cluster (GC) NGC 5286. We have determined abundances of representative light proton-capture, {alpha}, Fe-peak and neutron-capture element groups, and combined them with photometry of multiple sequences observed along the colour-magnitude diagram. Our principal results are: (i) a broad, bimodal distribution in s-process element abundance ratios, with two main groups, the s-poor and s-rich groups; (ii) substantial star-to-star Fe variations, with the s-rich stars having higher Fe, e.g. <[Fe/H]_s-rich_-<[Fe/H]>_s-poor_~0.1dex; and (iii) the presence of O-Na-Al (anti)correlations in both stellar groups. We have defined a new photometric index, c_BVI_=(B-V)-(V-I), to maximize the separation in the colour-magnitude diagram between the two stellar groups with different Fe and s-element content, and this index is not significantly affected by variations in light elements (such as the O-Na anticorrelation). The variations in the overall metallicity present in NGC 5286 add this object to the class of anomalous GCs. Furthermore, the chemical abundance pattern of NGC 5286 resembles that observed in some of the anomalous GCs, e.g. M 22, NGC 1851, M 2, and the more extreme {omega} Centauri, that also show internal variations in s-elements, and in light elements within stars with different Fe and s-elements content. In view of the common variations in s-elements, we propose the term s-Fe-anomalous GCs to describe this sub-class of objects. The similarities in chemical abundance ratios between these objects strongly suggest similar formation and evolution histories, possibly associated with an origin in tidally disrupted dwarf satellites.
498. Red giants in NGC 3680 and IC 4651
ID:
ivo://CDS.VizieR/J/A+A/299/53
Title:
Red giants in NGC 3680 and IC 4651
Short Name:
J/A+A/299/53
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)
499. Red giants in SMC. Abundances
ID:
ivo://CDS.VizieR/J/MNRAS/442/1680
Title:
Red giants in SMC. Abundances
Short Name:
J/MNRAS/442/1680
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present results from the largest Caii triplet line metallicity study of Small Magellanic Cloud (SMC) field red giant stars to date, involving 3037 objects spread across approximately 37.5deg^2^, centred on this galaxy. We find a median metallicity of [Fe/H]=-0.99+/-0.01, with clear evidence for an abundance gradient of -0.075+/-0.011dex/deg over the inner 5{deg}. We interpret the abundance gradient to be the result of an increasing fraction of young stars with decreasing galactocentric radius, coupled with a uniform global age-metallicity relation. We also demonstrate that the age-metallicity relation for an intermediate-age population located 10kpc in front of the north-east of the cloud is indistinguishable from that of the main body of the galaxy, supporting a prior conjecture that this is a stellar analogue of the Magellanic Bridge. The metal-poor and metal-rich quartiles of our red giant branch star sample (with complementary optical photometry from the Magellanic Clouds Photometric Survey) are predominantly older and younger than approximately 6Gyr, respectively. Consequently, we draw a link between a kinematical signature, tentatively associated by us with a disc-like structure, and the upsurges in stellar genesis imprinted on the star formation history of the central regions of the SMC. We conclude that the increase in the star formation rate around 5-6Gyr ago was most likely triggered by an interaction between the SMC and Large Magellanic Cloud.
500. Red giant star sample from SDSS
ID:
ivo://CDS.VizieR/J/ApJ/795/52
Title:
Red giant star sample from SDSS
Short Name:
J/ApJ/795/52
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have obtained a sample of ~22000 red giant branch (RGB) stars based on stellar parameters, provided by the ninth data release of the Sloan Digital Sky Survey (Cat. V/139), and the CH(G)/MgH indices, measured from the included spectra. The Galactic rest-frame velocity of V_gsr_ versus longitude for the sample shows the existence of several groups of stars from globular clusters and known streams. Excluding these substructures, a sample of ~16000 RGB stars from the general field is used to investigate the properties of the thick disk, the inner halo, and the outer halo of our Galaxy. The metallicity and rotational velocity distributions are investigated for stars at 0 kpc<|Z|<10 kpc. It is found that the canonical thick disk dominates at 0 kpc<|Z|<2 kpc and its contribution becomes negligible at |Z|>3 kpc. The MWTD is present and overlaps with the inner halo at 1 kpc<|Z|<3 kpc. The inner halo starts at 2 kpc<|Z|<3 kpc and becomes the dominated population for 4 kpc<|Z|<10 kpc. For halo stars with |Z|>5 kpc, bimodal metallicity distributions are found for 20 kpc<|Z|<25 kpc and 35 kpc<RR<45 kpc, which suggests a dual halo, the inner and the outer halo, as reported in Carollo et al. (2007Natur.450.1020C) at low|Z| values. The peak of metallicity for the inner halo is at [Fe/H]~-1.6 and appears to be at [Fe/H]~-2.3 for the outer halo. The transition point from the inner to the outer halo is located at|Z|~20 kpc and RR~35 kpc.

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