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191. Equivalent widths of 9 RGB in Carina dSph
ID:
ivo://CDS.VizieR/J/ApJ/751/102
Title:
Equivalent widths of 9 RGB in Carina dSph
Short Name:
J/ApJ/751/102
Date:
21 Oct 2021
Publisher:
CDS
Description:
The detailed abundances of 23 chemical elements in nine bright red giant branch stars in the Carina dwarf spheroidal galaxy are presented based on high-resolution spectra gathered at the Very Large Telescope (VLT) and Magellan telescopes. A spherical model atmospheres analysis is applied using standard methods (local thermodynamic equilibrium and plane-parallel radiative transfer) to spectra ranging from 380 to 680nm. Stellar parameters are found to be consistent between photometric and spectroscopic analyses, both at moderate and high resolution. The stars in this analysis range in metallicity from -2.9<[Fe/H]<-1.3, and adopting the ages determined by Lemasle et al. (Cat. J/A+A/538/A100), we are able to examine the chemical evolution of Carina's old and intermediate-aged populations.
192. Equivalent widths of RGB stars in NGC 5053
ID:
ivo://CDS.VizieR/J/ApJ/804/109
Title:
Equivalent widths of RGB stars in NGC 5053
Short Name:
J/ApJ/804/109
Date:
21 Oct 2021
Publisher:
CDS
Description:
NGC 5053 provides a rich environment to test our understanding of the complex evolution of globular clusters (GCs). Recent studies have found that this cluster has interesting morphological features beyond the typical spherical distribution of GCs, suggesting that external tidal effects have played an important role in its evolution and current properties. Additionally, simulations have shown that NGC 5053 could be a likely candidate to belong to the Sagittarius dwarf galaxy (Sgr dSph) stream. Using the Wisconsin-Indiana-Yale-NOAO-Hydra multi-object spectrograph, we have collected high quality (signal-to-noise ratio ~75-90), medium-resolution spectra for red giant branch stars in NGC 5053. Using these spectra we have measured the Fe, Ca, Ti, Ni, Ba, Na, and O abundances in the cluster. We measure an average cluster [Fe/H] abundance of -2.45 with a standard deviation of 0.04 dex, making NGC 5053 one of the most metal-poor GCs in the Milky Way (MW). The [Ca/Fe], [Ti/Fe], and [Ba/Fe] we measure are consistent with the abundances of MW halo stars at a similar metallicity, with alpha-enhanced ratios and slightly depleted [Ba/Fe]. The Na and O abundances show the Na-O anti-correlation found in most GCs. From our abundance analysis it appears that NGC 5053 is at least chemically similar to other GCs found in the MW. This does not, however, rule out NGC 5053 being associated with the Sgr dSph stream.
193. Equivalent widths of 18 subgiant of {omega} Cen
ID:
ivo://CDS.VizieR/J/A+A/534/A53
Title:
Equivalent widths of 18 subgiant of {omega} Cen
Short Name:
J/A+A/534/A53
Date:
21 Oct 2021
Publisher:
CDS
Description:
We analyze spectra of 18 stars belonging to the faintest subgiant branch in omega Centauri (the SGB-a), obtained with GIRAFFE@VLT at a resolution of R~=17000 and a S/N ratio between 25 and 50. We measure abundances of Al, Ba, Ca, Fe, Ni, Si, and Ti and we find that these stars have <[Fe/H]>=-0.73+/-0.14dex, similarly to the corresponding red giant branch population (the RGB-a). We also measure <[alpha/Fe]>=+0.40+/-0.16dex, and <[Ba/Fe]>=+0.87+/-0.23dex, in general agreement with past studies. It is very interesting to note that we found a uniform Al abundance, <[Al/Fe]>=+0.32+/-0.14dex, for all the 18 SGB-a stars analysed here, thus supporting past evidence that the usual (anti-)correlations are not present in this population, and suggesting a non globular cluster-like origin of this particular population. In the dwarf galaxy hypothesis for the formation of omega Cen, this population might be the best candidate for the field population of its putative parent galaxy, although some of its properties appear contradictory. It has also been suggested that the most metal-rich population in omega Cen is significantly enriched in helium. If this is true, the traditional abundance analysis techniques, based on model atmospheres with normal helium content, might lead to errors. We have computed helium enhanced atmospheres for three stars in our sample and verified that the abundance errors due to the use of non-enhanced atmospheres are negligible. Additional, indirect support to the enhanced helium content of the SGB-a population comes from our Li upper limits.
194. Equivalent widths of thick-disk red giants
ID:
ivo://CDS.VizieR/J/PAZh/39/58
Title:
Equivalent widths of thick-disk red giants
Short Name:
J/PAZh/39/58
Date:
21 Oct 2021
Publisher:
CDS
Description:
The atmospheric parameters and elemental abundances for ten thick-disk red giants have been determined from high-resolution spectra by the method of model stellar atmospheres. The results of a comparative analysis of the [Na/Fe] abundances in the atmospheres of the investigated stars and thindisk red giants are presented. Sodium in the atmospheres of thick-disk red giants is shown to have no overabundances typical of thin-disk red giants.
195. ESPRESSO radial velocities of HE0107-5240
ID:
ivo://CDS.VizieR/J/A+A/633/A129
Title:
ESPRESSO radial velocities of HE0107-5240
Short Name:
J/A+A/633/A129
Date:
21 Oct 2021
Publisher:
CDS
Description:
The vast majority of the known stars of ultra low metallicity ([Fe/H]<-4.5) are known to be enhanced in carbon, and belong to the 'low-carbon band' (A(C)=log(C/H)+12~7.6). It is generally, although not universally, accepted that this peculiar chemical composition reflects the chemical composition of the gas cloud out of which these stars were formed. The first ultra-metal-poor star discovered, HE 0107-5240, is also enhanced in carbon and belongs to the 'low-carbon band'. It has recently been claimed to be a long-period binary, based on radial velocity measurements. It has also been claimed that this binarity may explain its peculiar composition as being due to mass transfer to a former AGB companion. Theoretically, low-mass ratios in binary systems are much more favoured amongst Pop III stars than they are amongst solar-metallicity stars. Any constraint on the mass ratio of a system of such low metallicity would shed light on the star formation mechanisms in this metallicity regime. We acquired one high precision spectrum with ESPRESSO in order to check the reality of the radial velocity variations. In addition we analysed all the spectra of this star in the ESO archive obtained with UVES to have a set of homogenously measured radial velocities. The radial velocities were measured using cross correlation against a synthetic spectrum template. Due to the weakness of metallic lines in this star, the signal comes only from the CH molecular lines of the G-band. The measurement obtained in 2018 from an ESPRESSO spectrum demonstrates unambiguously that the radial velocity of HE 0107-5240 has increased from 2001 to 2018. Closer inspection of the measurements based on UVES spectra in the interval 2001-2006 show that there is a 96% probability that the radial velocity correlates with time, hence the radial velocity variations can already be suspected from the UVES spectra alone. We confirm the earlier claims of radial velocity variations in HE 0107-5240. The simplest explanation of such variations is that the star is indeed in a binary system with a long period. The nature of the companion is unconstrained and we consider it is equally probable that it is an unevolved companion or a white dwarf. Continued monitoring of the radial velocities of this star is strongly encouraged.
196. Evidence for two distinct giant planet population
ID:
ivo://CDS.VizieR/J/A+A/603/A30
Title:
Evidence for two distinct giant planet population
Short Name:
J/A+A/603/A30
Date:
21 Oct 2021
Publisher:
CDS
Description:
Analysis of the statistical properties of exoplanets, together with those of their host stars, are providing a unique view into the process of planet formation and evolution. In this paper we explore the properties of the mass distribution of giant planet companions to solar-type stars, in a quest for clues about their formation process. With this goal in mind we studied, with the help of standard statistical tests, the mass distribution of giant planets using data from the exoplanet.eu catalog and the SWEET-Cat database of stellar parameters for stars with planets. We show that the mass distribution of giant planet companions is likely to present more than one population with a change in regime around 4M_{Jup}_. Above this value host stars tend to be more metal poor and more massive and have [Fe/H] distributions that are statistically similar to those observed in field stars of similar mass. On the other hand, stars that host planets below this limit show the well-known metallicity-giant planet frequency correlation. We discuss these results in light of various planet formation models and explore the implications they may have on our understanding of the formation of giant planets. In particular, we discuss the possibility that the existence of two separate populations of giant planets indicates that two different processes of formation are at play.
197. Evolution state of red giants from seismology
ID:
ivo://CDS.VizieR/J/A+A/572/L5
Title:
Evolution state of red giants from seismology
Short Name:
J/A+A/572/L5
Date:
21 Oct 2021
Publisher:
CDS
Description:
The detection of oscillations with a mixed character in subgiants and red giants allows us to probe the physical conditions in their cores. With these mixed modes, we aim at determining seismic markers of stellar evolution. Kepler asteroseismic data were selected to map various evolutionary stages and stellar masses. Seismic evolutionary tracks were then drawn with the combination of the frequency and period spacings.
198. Evolved GK stars near the Sun. II.
ID:
ivo://CDS.VizieR/J/AJ/107/594
Title:
Evolved GK stars near the Sun. II.
Short Name:
J/AJ/107/594
Date:
21 Oct 2021
Publisher:
CDS
Description:
From a sample of nearly 2000 GK giants a group of young disk stars with well determined space motions has been selected. The zero point of the luminosity calibrations, both from the ultraviolet flux (modified Stromgren system) and that in the region of 4200 to 4900A (DDO system), show a discontinuity of about a half magnitude at the border of the young disk and old disk domains. The population separation is based on the space velocity components, which are also an age discriminants with the population interface near 2x10^9yr, based on models with convective overshoot at the core. This age corresponds to giant masses near 1.7M_{sun}_, near the critical mass separating the young stars that do not burn helium in degenerate cores from older stars that do. Ten percent of both populations show CN anomalies in that the derived value of P[Fe/H] from CN(C_m_) and from Fe(M_1_) differ by more than 0.1dex and the weak and strong CN stars occur equally in the old disk but the weak CN stars predominate in the young disk. Peculiar stars, where flux distortions affect the luminosity calibrations, are of the CH+ (Ba II) and CH- (weak G band) variety and represent less than 1% of the stars in both populations. The young disk giants are restricted to ages greater than about 10^9^yr, because younger stars are bright giants or supergiants (luminosity class II or I), and younger than about 2x10^9yr, because the old disk-young disk boundary occurs near 1.7M_{sun}_. The distribution of heavy element abundances, P[Fe/H], for young disk giants is both more limited in range (+/-0.4dex) and is skewed toward higher abundances, compared with the nearly normal distribution for old disk giants. The distribution of (U,V) velocity vectors gives (U,V,W) and their dispersions =(+17.6+/-18.4, -14.8+/-8.4, -6.9+/-13.0) and (+3.6+/-38.4, -20.7+/-27.5, -6.7+/-17.3) km/s for young and old disk giants, respectively. For a description of the DDO and RI Eggen photometric system, see e.g. <GCPD/12> and <GCPD/17> , respectively.
199. Evolved stars in M13
ID:
ivo://CDS.VizieR/J/AJ/139/2374
Title:
Evolved stars in M13
Short Name:
J/AJ/139/2374
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analyzed photometry from space- and ground-based cameras to identify all bright red giant branch (RGB), horizontal branch (HB), and asymptotic giant branch (AGB) stars within 10' of the center of the globular cluster M13.
200. EW and [Fe/H] for 30000 globular cluster RGB stars
ID:
ivo://CDS.VizieR/J/A+A/635/A114
Title:
EW and [Fe/H] for 30000 globular cluster RGB stars
Short Name:
J/A+A/635/A114
Date:
21 Oct 2021
Publisher:
CDS
Description:
The CaII triplet in the near-infrared at 8498, 8542, and 8662{AA} is visible in stars with spectral types between F and M and can be used to determine their metallicities. We calibrated the relation using average cluster metallicities from literature and MUSE spectra, and extend it below the horizontal branch - a cutoff that has traditionally been made to avoid a non-linear relation - using a quadratic function. In addition to the classic relation based on V-\vhb$ we used calibrations based on absolute magnitude and luminosity and used it for those cluster, for which no HB brightness was available. The obtained relations are then used to calculate metallicities for all the stars in the sample.

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