- ID:
- ivo://CDS.VizieR/J/MNRAS/365/1357
- Title:
- Absolute magnitude of Globular Cluster
- Short Name:
- J/MNRAS/365/1357
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We test whether the peak absolute magnitude MV(TO) of the Globular Cluster Luminosity Function (GCLF) can be used for reliable extragalactic distance determination. Starting with the luminosity function of the Galactic Globular Clusters listed in Harris (Cat. <VII/202>) catalogue, we determine MV(TO) either using current calibrations of the absolute magnitude MV(RR) of RR Lyrae stars as a function of the cluster metal content [Fe/H] and adopting selected cluster samples.
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- ID:
- ivo://CDS.VizieR/J/A+A/537/A83
- Title:
- Abunbances of 9 red giants of Pal 14
- Short Name:
- J/A+A/537/A83
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundances of 25 elements, which include {alpha}-, iron peak-, and neutron-capture elements, in the outer halo globular cluster Palomar 14 have been determined for the nine red giants observed with the FLAMES/UVES spectrograph. The abundance pattern of Pal 14 is similar to the inner halo GCs, halo field stars, and GCs of recognized extragalactic origin, but differs from what is customarily found in dSphs field stars. The abundance properties of Pal 14 as well as those of the other outer halo GCs are thus compatible with an accretion origin from dSphs. The neutron-capture elements show an r-process signature.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A178
- Title:
- Abundance analysis of 4 red giants in NGC 6558
- Short Name:
- J/A+A/619/A178
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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. 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 {alpha}-elements Mg, Si, Ca, Ti, and the heavy elements Y, Ba, and Eu. High-resolution spectra of four stars with FLAMES-UVES@VLT UT2-Kueyen were analysed. Spectroscopic parameter-derivation was based on excitation and ionization equilibrium of FeI and FeII. This analysis results in a metallicity of [Fe/H]=-1.17+/-0.10 for NGC 6558. We find the expected {alpha}-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, YI), instead of the dominant ionized species is another source of uncertainty. Ba appears to have a solar abundance ratio relative to Fe. 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 {alpha}-elements Si, Ca, and Ti. The hydrostatic burning {alpha}-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 forMn 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.
- ID:
- ivo://CDS.VizieR/J/A+A/656/A67
- Title:
- Abundance of Ba in 47 Tuc
- Short Name:
- J/A+A/656/A67
- Date:
- 22 Feb 2022
- Publisher:
- CDS
- Description:
- While most (if not all) Type I Galactic globular clusters (GGCs) are characterised by spreads in the abundances of light chemical elements (e.g. Li, N, O, Na, Mg, Al), it is not yet well established whether similar spreads may exist in s-process elements as well. We investigated the possible difference in Ba abundance between the primordial (1P) and polluted (2P) stars in the Galactic globular cluster (GGC) 47 Tuc (NGC 104). For this purpose, we obtained homogeneous abundances of Fe, Na, and Ba in a sample of 261 red giant branch (RGB) stars. Abundances of Na and Ba were determined using archival GIRAFFE/VLT spectra and 1D non-local thermodynamic equilibrium (NLTE) abundance analysis methodology. Contrary to the finding of Gratton et al. (2013A&A...549A..41G), we did not detect any significant Ba-Na correlation or 2P-1P Ba abundance difference in the sample of 261 RGB stars in 47 Tuc. This corroborates the result of D'Orazi et al. (2010ApJ...719L.213D), who found no statistically significant Ba-Na correlation in 110 RGB stars in this GGC. The average barium-to-iron ratio obtained in the sample of 261 RGB stars, <[Ba/Fe]_1DNLTE_>=-0.01+/-0.06, agrees well with those determined in Galactic field stars at this metallicity and may therefore represent the abundance of primordial proto-cluster gas that has not been altered during the subsequent chemical evolution of the cluster.
- ID:
- ivo://CDS.VizieR/J/AJ/142/63
- Title:
- Abundance of five stars in NGC 6397
- Short Name:
- J/AJ/142/63
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present chemical abundances in three red giants and two turnoff (TO) stars in the metal-poor Galactic globular cluster (GC) NGC 6397 based on spectroscopy obtained with the Magellan Inamori Kyocera Echelle high-resolution spectrograph on the Magellan 6.5m Clay telescope. Our results are based on a line-by-line differential abundance analysis relative to the well-studied red giant Arcturus and the Galactic halo field star HIP 66815.
- ID:
- ivo://CDS.VizieR/J/AJ/131/1766
- Title:
- Abundances and equivalent widths in NGC 2808
- Short Name:
- J/AJ/131/1766
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the abundance analysis of stars from the tip of the red giant branch (RGB) to below the RGB bump in the globular cluster NGC 2808 based on high-resolution echelle spectra. We derive abundances of Al, {alpha}-process elements (SiI, CaI, TiI, and TiII), and Fe-group elements (ScII, VI, CrI, CrII, MnI, CoI, and NiI). Apart from Mg being somewhat reduced, likely because it has been depleted at the expense of Al in the MgAl cycle, the other {alpha}-element ratios show the overabundance typical of halo stars of similar metallicity.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/L38
- Title:
- Abundances and radial velocities of M13 giants
- Short Name:
- J/ApJ/754/L38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present O, Na, and Fe abundances, as well as radial velocities, for 113 red giant branch (RGB) and asymptotic giant branch (AGB) stars in the globular cluster M13. The abundances and velocities are based on spectra obtained with the WIYN-Hydra spectrograph, and the observations range in luminosity from the horizontal branch (HB) to RGB tip. The results are examined in the context of recent globular cluster formation scenarios. We find that M13 exhibits many key characteristics that suggest its formation and chemical enrichment are well described by current models. Some of these observations include the central concentration of O-poor stars, the notable decrease in [O/Fe] (but small increase in [Na/Fe]) with increasing luminosity that affects primarily the "extreme" population, the small fraction of stars with halo-like composition, and the paucity of O-poor AGB stars. In agreement with recent work, we conclude that the most O-poor M13 giants are likely He-enriched and that most (all?) O-poor RGB stars evolve to become extreme HB and AGB-manqu\'e stars. In contrast, the "primordial" and "intermediate" population stars appear to experience standard HB and AGB evolution.
- ID:
- ivo://CDS.VizieR/J/A+AS/113/299
- Title:
- Abundances and velocities for cluster giants
- Short Name:
- J/A+AS/113/299
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a large dataset consisting of giants in the field, and in open and globular clusters. A total of 122 giants were observed in the fields of 8 open clusters. A total of 342 giants were observed in the fields of 25 globular clusters. A total of 36 field stars with well known abundances and luminosities were also observed. Table 8 lists the spectral indices measured for the giants observed with the Argus and Red Channel spectrographs during 1991 and 1992. The central and continuum passbands for these indices are defined in Table 6.
- ID:
- ivo://CDS.VizieR/J/AJ/130/2140
- Title:
- Abundances and velocities in globular clusters
- Short Name:
- J/AJ/130/2140
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have compiled a sample of globular clusters with high-quality stellar abundances from the literature to compare to the chemistries of stars in the Galaxy and in dwarf spheroidal galaxies. Of the 45 globular clusters examined, 29 also have kinematic information. Most of the globular clusters belong to the Galactic halo; however, a significant number have disk kinematics or belong to the bulge.
- ID:
- ivo://CDS.VizieR/J/ApJ/754/91
- Title:
- Abundances and velocities of NGC 6397 stars
- Short Name:
- J/ApJ/754/91
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We used three sets of high-resolution spectra acquired with the multifiber facility FLAMES at the Very Large Telescope of the European Southern Observatory to investigate the chemical and kinematical properties of a sample of 42 horizontal branch (HB) stars, 18 blue straggler stars (BSSs), and 86 main-sequence (MS) turnoff (TO) and sub-giant branch stars in the nearby globular cluster NGC 6397. We measured rotational velocities and Fe, O, and Mg abundances. All of the unevolved stars in our sample have low rotational velocites (vsin i<10km/s), while the HB stars and BSSs show a broad distribution, with values ranging from 0 to ~70km/s. For HB stars with T<10500K there is a clear temperature-oxygen anticorrelation that can be understood if the star position along the HB is mainly determined by the He content. The hottest BSSs and HB stars (with temperatures T>8200K and T>10500K, respectively) also show significant deviations in their iron abundance with respect to the cluster metallicity (as traced by the unevolved stars, [Fe/H]=-2.12). While similar chemical patterns have already been observed in other hot HB stars, this is the first evidence ever collected for BSSs. We interpret these abundance anomalies as due to the metal radiative levitation, occurring in stars with shallow or no convective envelopes.
