- ID:
- ivo://CDS.VizieR/J/AJ/136/375
- Title:
- Chemical composition of LMC red giants
- Short Name:
- J/AJ/136/375
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the chemical abundance analysis of a sample of 27 red giant stars located in four populous intermediate-age globular clusters in the Large Magellanic Cloud, namely NGC 1651, 1783, 1978, and 2173. This analysis is based on high-resolution (R~47000) spectra obtained with the UVES@VLT spectrograph. For each cluster we derived up to 20 abundance ratios sampling the main chemical elemental groups, namely light odd-Z, {alpha} iron-peak, and neutron-capture elements.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/709/447
- Title:
- Chemical composition of OGLE-2007-BLG-514S
- Short Name:
- J/ApJ/709/447
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present a high-resolution spectrum of a microlensed G dwarf in the Galactic bulge with spectroscopic temperature T_eff_=5600+/-180K. This I~21mag star was magnified by a factor ranging from 1160 to 1300 at the time of observation. Its high metallicity ([Fe/H]=0.33+/-0.15dex) places this star at the upper end of the bulge giant metallicity distribution. Using a Kolmogorov-Smirnov test, we find a 1.6% probability that the published microlensed bulge dwarfs share an underlying distribution with bulge giants, properly accounting for a radial bulge metallicity gradient. We obtain abundance measurements for 15 elements and perform a rigorous error analysis that includes covariances between parameters. This star, like bulge giants with the same metallicity, shows no alpha enhancement. It confirms the chemical abundance trends observed in previously analyzed bulge dwarfs. At supersolar metallicities, we observe a discrepancy between bulge giant and bulge dwarf Na abundances.
- ID:
- ivo://CDS.VizieR/J/ApJ/717/277
- Title:
- Chemical composition of old LMC clusters
- Short Name:
- J/ApJ/717/277
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- This paper presents the chemical abundance analysis of a sample of 18 giant stars in three old globular clusters in the Large Magellanic Cloud (LMC), NGC 1786, NGC 2210, and NGC 2257. The derived iron content is [Fe/H]=-1.75+/-0.01dex ({sigma}=0.02dex), -1.65+/-0.02dex ({sigma}=0.04dex), and -1.95+/-0.02dex ({sigma}=0.04dex) for NGC 1786, NGC 2210, and NGC 2257, respectively. All the clusters exhibit similar abundance ratios, with enhanced values (~+0.30dex) of [{alpha}/Fe], consistent with the Galactic halo stars, thus indicating that these clusters have formed from a gas enriched by Type II supernovae. We also found evidence that r-process is the main channel of production of the measured neutron capture elements (Y, Ba, La, Nd, Ce, and Eu). In particular, the quite large enhancement of [Eu/Fe] (~+0.70dex) found in these old clusters clearly indicates a relevant efficiency of the r-process mechanism in the LMC environment.
- ID:
- ivo://CDS.VizieR/J/AJ/161/128
- Title:
- Chemical composition of 15 red giant stars with HPF
- Short Name:
- J/AJ/161/128
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used the Habitable Zone Planet Finder (HPF) to gather high-resolution, high signal-to-noise near-infrared spectra of 13 field red horizontal branch (RHB) stars, one open cluster giant, and one very metal-poor halo red giant. The HPF spectra cover the 0.81-1.28{mu}m wavelength range of the zyJ bands, partially filling the gap between the optical (0.4-1.0{mu}m) and infrared (1.5-2.4{mu}m) spectra already available for the program stars. We derive abundances of 17 species from LTE-based computations involving equivalent widths and spectrum syntheses, and estimate abundance corrections for the species that are most affected by departures from LTE in RHB stars. Generally good agreement is found between HPF-based metallicities and abundance ratios and those from the optical and infrared spectral regions. Light element transitions dominate the HPF spectra of these red giants, and HPF data can be used to derive abundances from species with poor or no representation in optical spectra (e.g., C i, P i, S i, K i). Attention is drawn to the HPF abundances in two field solar-metallicity RHB stars of special interest: one with an extreme carbon isotope ratio, and one with a rare, very large lithium content. The latter star is unique in our sample in exhibiting very strong He i 10830{AA} absorption. The abundances of the open cluster giant concur with those derived from other wavelength regions. Detections of CI and SI in HD122563 are reported, yielding the lowest metallicity determination of [S/Fe] from more than one multiplet.
- ID:
- ivo://CDS.VizieR/J/A+A/619/A176
- Title:
- Chemical composition of Ruprecht 147
- Short Name:
- J/A+A/619/A176
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Ruprecht 147 (NGC 6774) is the closest old open cluster, with a distance of less than 300pc and an age of about 2.5Gyr. It is therefore well suited for testing stellar evolution models and for obtaining precise and detailed chemical abundance information. We combined photometric and astrometric information coming from literature and the Gaia mission with very high-resolution optical spectra of stars in different evolutionary stages to derive the cluster distance, age, and detailed chemical composition. We obtained spectra of six red giants using HARPS-N at the Telescopio Nazionale Galileo (TNG). We also used European Southern Observatory (ESO) archive spectra of 22 main sequence (MS) stars, observed with HARPS at the 3.6m telescope. The very high resolution (115000) and the large wavelength coverage (about 380-680nm) of the twin instruments permitted us to derive atmospheric parameters, metallicity, and detailed chemical abundances of 23 species from all nucleosynthetic channels. We employed both equivalent widths and spectrum synthesis. We also re-derived the cluster distance and age using Gaia parallaxes, proper motions, and photometry in conjunction with the PARSEC stellar evolutionary models. We fully analysed those stars with radial velocity and proper motion/parallax in agreement with the cluster mean values. We also discarded one binary not previously recognised, and six stars near the MS turn-off because of their high rotation velocity. Our final sample consists of 21 stars (six giants and 15 MS stars). We measured metallicity (the cluster average [Fe/H] is +0.08, rms=0.07) and abundances of light, alpha, Fe-peak, and neutron-capture elements. The Li abundance follows the expectations, showing a tight relation between temperature and abundance on the MS, at variance with M67, and we did not detect any Li-rich giant.
- ID:
- ivo://CDS.VizieR/J/A+A/324/435
- Title:
- Chemical composition of six K supergiants in the SMC
- Short Name:
- J/A+A/324/435
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- A sample of six SMC cool stars (K supergiants) are analysed by high resolution spectroscopy in order to investigate their chemical content, which should reflect that of the current interstellar medium within the SMC. The abundance of Na, Al, {alpha}-elements, Fe peak and heavy elements are derived through an LTE analysis of the lines, compared to a Galactic "standard" (the well-studied K giant Arcturus) and discussed in terms of chemical evolution of the SMC. The following results were obtained: 1. All the stars from this sample are metal deficient ([Fe/H] ranges from -0.59 to -0.89dex). The abundance varies little from star-to-star (0.10dex rms, comparable with the expected error due to uncertainties on the effective parameters of the stars), in agreement with the very small chemical composition variations among the H II regions within the SMC found by Pagel et al. (1978MNRAS.184..569P). 2. Sodium is not strongly enhanced in these stars, and the star-to-star scatter is larger than expected. 3. At variance with metal-poor stars in our Galaxy, the so-called {alpha}-elements do not seem to be enhanced. 4. Nickel displays a noticeable depletion with respect to iron ([Ni/Fe]=~-0.3dex), at variance with what is found in the SMC F supergiants and in Arcturus. 5. Except for PMMR 144, the s and r process elements heavier than Ba are enhanced in all of our stars by =~+0.4dex.
- ID:
- ivo://CDS.VizieR/J/A+A/305/551
- Title:
- Chemical composition of the s-Cepheids
- Short Name:
- J/A+A/305/551
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- On the base of photographic, Reticon and CCD spectra analysis we have derived the abundances for 8 s-Cepheids and V1162 Aql (before classified as s-Cepheid). The following results have been obtained: 1) all Cepheids (excluding only EU Tau) have solar-like abundances of {alpha}- and iron-group elements, 2) Na is over abundant for all program stars, 3) the carbon deficiency found for EU Tau, DT Cyg, V440 Per and nitrogen overabundance (DT Cyg), show that these s-Cepheids are not crossing the instability strip for first time, 4) s-process elements are slightly enhanced in the program stars, 5) V1162 Aql does not show any changes in C and N abundances. The most plausible explanation is that this star is a normal Cepheid (C{delta}), but it is firstly crossing the instability strip toward the giant branch. This conclusion is also confirmed by its position on the evolutionary diagram.
- ID:
- ivo://CDS.VizieR/J/AJ/134/926
- Title:
- Chemical composition of V2314 Oph
- Short Name:
- J/AJ/134/926
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We investigated V2314 Oph using high-resolution (R=45000) spectral observations. The atmospheric parameters were determined using iron-line abundance analysis. We derived a mean effective temperature of Teff=7510K, mean surface gravity of logg=3.30, metallicity of [Fe/H]=-0.59, and rotation velocity of vsini=38km/s. The abundances of 19 chemical elements were determined.
- ID:
- ivo://CDS.VizieR/J/A+A/397/257
- Title:
- Chemical compositions of four barium stars
- Short Name:
- J/A+A/397/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical compositions of four barium stars are studied. We obtain their {alpha}, iron peak and neutron-capture (n-capture) process element abundances. The atomic data and measured equivalent widths (EWs) of the related spectral lines are given. The abundance errors caused by the combined effects of the uncertainties in oscillator strengths loggf-values, equivalent widths (EWs) and stellar atmospheric parameters (e.g. effective temperature Teff, surface gravity logg, and microturbulent velocity {xi_t_}) are the total abundance uncertainties. The individual and total abundance uncertainties caused by these factors are given.
- ID:
- ivo://CDS.VizieR/J/ApJ/706/1095
- Title:
- Chemical compositions of 26 outer halo stars
- Short Name:
- J/ApJ/706/1095
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Chemical abundances of 26 metal-poor dwarfs and giants are determined from high-resolution and high signal-to-noise ratio spectra obtained with the Subaru/High Dispersion Spectrograph. The sample is selected so that most of the objects have outer-halo kinematics. Self-consistent atmospheric parameters were determined by an iterative procedure based on spectroscopic analysis. Abundances of 13 elements, including {alpha}-elements (Mg, Si, Ca, Ti), odd-Z light elements (Na, Sc), iron-peak elements (Cr, Mn, Fe, Ni, Zn), and neutron-capture elements (Y, Ba), are determined by two independent data reduction and local thermodynamic equillibrium analysis procedures, confirming the consistency of the stellar parameters and abundances results.
