- ID:
- ivo://CDS.VizieR/J/AZh/78/807
- Title:
- Chemical composition of eta Ser
- Short Name:
- J/AZh/78/807
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table2 contains the results of an analysis of elemental abundances in the atmosphere of eta Ser - a red giant of spectral type K2IIIabCN1. The resulting atmosphere parameters correspond to a K0 giant, and the peculiarities of the star chemical composition provide evidence that the assignment of Eta Ser to a class of CN stars was erroneous.
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- ID:
- ivo://CDS.VizieR/J/A+A/599/A97
- Title:
- Chemical composition of globular cluster NGC 6426
- Short Name:
- J/A+A/599/A97
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present our detailed spectroscopic analysis of the chemical composition of four red giant stars in the halo globular cluster NGC 6426. We obtained high-resolution spectra using the Magellan2/MIKE spectrograph, from which we derived equivalent widths and subsequently computed abundances of 24 species of 22 chemical elements. For the purpose of measuring equivalent widths, we developed a new semi-automated tool, called EWCODE. We report a mean Fe content of [Fe/H]=-2.34+/-0.05dex (stat.) in accordance with previous studies. At a mean {alpha}-abundance of [(Mg,Si,Ca)/3Fe]=0.39+/-0.03dex, NGC 6426 falls on the trend drawn by the Milky Way halo and other globular clusters at comparably low metallicities. The distribution of the lighter {alpha}-elements as well as the enhanced ratio [Zn/Fe]=0.39dex could originate from hypernova enrichment of the pre-cluster medium. We find tentative evidence for a spread in the elements Mg, Si, and Zn, indicating an enrichment scenario, where ejecta of evolved massive stars of a slightly older population polluted a newly born younger one. The heavy element abundances in this cluster fit well into the picture of metal-poor globular clusters, which in that respect appear to be remarkably homogeneous. The pattern of the neutron-capture elements heavier than Zn point towards an enrichment history governed by the r-process with only little - if any - sign of s-process contributions. This finding is supported by the striking similarity of our program stars to the metal-poor field star HD 108317.
- ID:
- ivo://CDS.VizieR/J/A+AS/141/491
- Title:
- Chemical composition of halo and disk stars
- Short Name:
- J/A+AS/141/491
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 3. Atmospheric parameters, space velocities, distances, masses and ages of the program stars. Table 4. Atomic line data including wavelength, excitation energy of the lower level, the logarithm of the oscillator strength (the experimental or theoretical value, the corrected value and the differential value from standard stars) and the adopted enhancement factor of the Unsold approximation to the van der Waals damping constant. The last column gives the equivalent width in the spectrum of HD 142373 representing a typical metallicity of the sample of stars. Uncertain EWs marked by (:) and strong lines with EW>100m{AA} are not used in the abundance determination for this star. Table 5. Abundance ratios for the program stars. The oxygen abundance is derived from the 7774{AA} triplet but scaled to results from the forbidden [OI] line at 6300{AA}.
- ID:
- ivo://CDS.VizieR/J/A+A/326/751
- Title:
- Chemical composition of halo and disk stars
- Short Name:
- J/A+A/326/751
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table A1 lists the Stromgren photometry together with color excesses, E(b-y), photometric metallicities, [Fe/H] , calculated from the calibrations of Schuster & Nissen (1989A&A...221...65S), and absolute magnitudes, M(V), and distances derived with the equations of Nissen & Schuster (1991A&A...251..457N) using the photometric metallicities. Table A2 contains coordinates, proper motions and radial velocities for the program stars as well as distances calculated from the calibrations Nissen & Schuster (1991A&A...251..457N) using the spectroscopic metallicities scaled to our photometric [Fe/H] system. Table A3 gives a list of the 209 spectral lines, which were analyzed, arranged element by element. The table contains the wavelength, the excitation potential of the lower level corresponding to the line, the gf-value, the enhancement factor of the classical van der Waals damping constant, the statistical weight of the upper level, and the equivalent widths measured for the two "standard" stars, HD 22879 and HD 76932. Table A4 contains the measured equivalent widths for all program stars. Table A5 gives abundance ratios and kinematical as well as orbital parameters for the program stars. First are given the data for the 16 disk stars, then follows the 14 halo stars.
- 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.
- 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.