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31. Abundances for 79 Sun-like stars within 100pc
ID:
ivo://CDS.VizieR/J/ApJ/865/68
Title:
Abundances for 79 Sun-like stars within 100pc
Short Name:
J/ApJ/865/68
Date:
21 Oct 2021
Publisher:
CDS
Description:
The compositions of stars are a critical diagnostic tool for many topics in astronomy such as the evolution of our Galaxy, the formation of planets, and the uniqueness of the Sun. Previous spectroscopic measurements indicate a large intrinsic variation in the elemental abundance patterns of stars with similar overall metal content. However, systematic errors arising from inaccuracies in stellar models are known to be a limiting factor in such studies, and thus it is uncertain to what extent the observed diversity of stellar abundance patterns is real. Here we report the abundances of 30 elements with precisions of 2% for 79 Sun-like stars within 100pc. Systematic errors are minimized in this study by focusing on solar twin stars and performing a line-by-line differential analysis using high-resolution, high-signal-to-noise spectra. We resolve [X/Fe] abundance trends in galactic chemical evolution at precisions of 10^-3^dex/Gyr and reveal that stars with similar ages and metallicities have nearly identical abundance patterns. Contrary to previous results, we find that the ratios of carbon-to-oxygen and magnesium-to-silicon in solar-metallicity stars are homogeneous to within 10% throughout the solar neighborhood, implying that exoplanets may exhibit much less compositional diversity than previously thought. Finally, we demonstrate that the Sun has a subtle deficiency in refractory material relative to >80% of solar twins (at 2{sigma} confidence), suggesting a possible signpost for planetary systems like our own.
32. Abundances from Gaia-ESO Survey
ID:
ivo://CDS.VizieR/J/A+A/572/A33
Title:
Abundances from Gaia-ESO Survey
Short Name:
J/A+A/572/A33
Date:
21 Oct 2021
Publisher:
CDS
Description:
Most high-resolution spectroscopic studies of the Galactic discs were mostly confined to objects in the solar vicinity. Here we aim at enlarging the volume in which individual chemical abundances are used to characterise both discs, using the first internal data release of the Gaia-ESO survey. We derive and discuss the abundances of eight elements (Mg, Al, Si, Ca, Ti, Fe, Cr, Ni, and Y). The trends of these elemental abundances with iron are very similar to those in the solar neighbourhood. We find a natural division between {alpha}-rich and {alpha}-poor stars, best seen in the bimodality of the [Mg/M] distributions in bins of metallicity, which we attribute to thick- and thin-disc sequences, respectively. With the possible exception of Al, the observed dispersion around the trends is well described by the expected errors, leaving little room for astrophysical dispersion. Using previously derived distances from Recio-Blanco et al. (2014A&A...567A...5R), we further find that the thick-disc is more extended vertically and is more centrally concentrated towards the inner Galaxy than the thin-disc, which indicates a shorter scale-length. We derive the radial and vertical gradients in metallicity, iron, four {alpha}-element abundances, and Al for the two populations, taking into account the identified correlation between R_GC_ and |Z|. Radial metallicity gradient is found in the thin disc. The positive radial individual [{alpha}/M] gradients found are at variance from the gradients observed in the RAVE survey. The thin disc also hosts a negative vertical metallicity gradient, accompanied by positive individual [{alpha}/M] and [Al/M] gradients. The thick-disc, presents no radial metallicity gradient, a shallower vertical metallicity gradient than the thin-disc, an {alpha}-elements-to-iron radial gradient in the opposite sense than that of the thin disc, and positive vertical individual [{alpha}/M] and [Al/M] gradients.
33. Abundance signature of M dwarf stars
ID:
ivo://CDS.VizieR/J/A+A/644/A68
Title:
Abundance signature of M dwarf stars
Short Name:
J/A+A/644/A68
Date:
21 Oct 2021
Publisher:
CDS
Description:
Most of our current knowledge on planet formation is still based on the analysis of main-sequence, solar-type stars. Conversely, detailed chemical studies of large samples of M-dwarf planet hosts are still missing. We aim to test whether the correlations between the metallicity, individual chemical abundances, and mass of the star and the presence of different type of planets found for FGK stars still holds for the less massive M dwarf stars. Methods to determine in a consistent way stellar abundances of M dwarfs from high-resolution optical spectra are still missing. The present work is a first attempt to fill this gap. We analyse in a coherent and homogeneous way a large sample of M dwarfs with and without known planetary companions. We develop for the first time a methodology to determine stellar abundances of elements others than iron for M dwarf stars from high-resolution, optical spectra. Our methodology is based on the use of principal component analysis and sparse Bayesian's methods. We made use of a set of M dwarfs orbiting around an FGK primary with known abundances to train our methods. We applied our methods to derive stellar metallicities and abundances of a large sample of M dwarfs observed within the framework of current radial velocity surveys. We then used a sample of nearby FGK stars to cross-validate our technique by comparing the derived abundance trends in the M dwarf sample with those found on the FGK stars. The metallicity distribution of the different subsamples shows that M dwarfs hosting giant planets show a planet-metallicity correlation as well as a correlation with the stellar mass. M dwarfs hosting low-mass planets do not seem to follow the planet-metallicity correlation. We also found that the frequency of low-mass planets does not depend on the mass of the stellar host. These results seem in agreement with previous works. However, we note that for giant planet hosts our metallicities predict a weaker planet metallicity correlation but a stronger mass-dependency than photometric values. We show, for the first time, that there seems to be no differences in the abundance distribution of elements different from iron between M dwarfs with and without known planets. Our data shows that low-mass stars with planets follow the same metallicity, mass, and abundance trends than their FGK counterparts, which are usually explained within the framework of core-accretion models.
34. Abundances in dwarfs, subgiants, and giants
ID:
ivo://CDS.VizieR/J/A+A/580/A24
Title:
Abundances in dwarfs, subgiants, and giants
Short Name:
J/A+A/580/A24
Date:
21 Oct 2021
Publisher:
CDS
Description:
We have analyzed high-resolution and high signal-to-noise ratio optical spectra of nearby FGK stars with and without detected giant planets in order to homogeneously measure their photospheric parameters, mass, age, and the abundances of volatile (C, N, and O) and refractory (Na, Mg, Si, Ca, Ti, V, Mn, Fe, Ni, Cu, and Ba) elements. Our sample contains 309 stars from the solar neighborhood (up to the distance of 100pc), out of which 140 are dwarfs, 29 are subgiants, and 140 are giants. The photospheric parameters are derived from the equivalent widths (EWs) of FeI and FeII lines. Masses and ages come from the interpolation in evolutionary tracks and isochrones on the HR diagram. The abundance determination is based on the equivalent widths of selected atomic lines of the refractory elements and on the spectral synthesis of C_2_, CN, CI, OI, and NaI features. We apply a set of statistical methods to analyze the abundances derived for the three subsamples. Our results show that: i) giant stars systematically exhibit underabundance in [C/Fe] and overabundance in [N/Fe] and [Na/Fe] in comparison with dwarfs, a result that is normally attributed to evolution-induced mixing processes in the envelope of evolved stars; ii) for solar analogs only, the abundance trends with the condensation temperature of the elements are correlated with age and anticorrelated with the surface gravity, which is in agreement with recent studies; iii) as in the case of [Fe/H], dwarf stars with giant planets are systematically enriched in [X/H] for all the analyzed elements, except for O and Ba (the former due to limitations of statistics), confirming previous findings in the literature that not only iron has an important relation with the planetary formation; and iv) giant planet hosts are also significantly overabundant for the same metallicity when the elements from Mg to Cu are combined together.
35. Abundances in eta Psc
ID:
ivo://CDS.VizieR/J/AZh/72/855
Title:
Abundances in eta Psc
Short Name:
J/AZh/72/855
Date:
21 Oct 2021
Publisher:
CDS
Description:
CCD observations are used to analyse the atmosphere of the G7 IIIa giant Eta Piscium. The following atmospheric parameters were obtained: T(eff)=4930K, logg=2.1, and microturbulence v(t)=1.7km/s. The abundances of 21 elements in the atmosphere of eta Psc were determined.
36. Abundances in gamma Sge
ID:
ivo://CDS.VizieR/J/AZh/72/864
Title:
Abundances in gamma Sge
Short Name:
J/AZh/72/864
Date:
21 Oct 2021
Publisher:
CDS
Description:
CCD spectra are used to analyse the abundances of chemical elements in the atmosphere of the MOIII giant gamma Sagittae. Its atmospheric atmospheric parameters were determined to be T(eff)=3970K, logg=1.3, and microturbulence v(t)=1.65km/s.
37. Abundances in Hyades red giants
ID:
ivo://CDS.VizieR/J/AZh/77/96
Title:
Abundances in Hyades red giants
Short Name:
J/AZh/77/96
Date:
21 Oct 2021
Publisher:
CDS
Description:
CCD spectra are obtained in 1994-1997 on the 2.6-m telescope of the Crimean Astrophysical observatory in the first chamber of the Coude focus. The dispersion was 3{AA}/mm and the signal-to-noise ratios were 100-300.
38. Abundances in Magellanic Cloud planetary nebulae
ID:
ivo://CDS.VizieR/J/MNRAS/234/583
Title:
Abundances in Magellanic Cloud planetary nebulae
Short Name:
J/MNRAS/234/583
Date:
21 Oct 2021
Publisher:
CDS
Description:
Optical spectroscopic data for 71 Planetary Nebulae (PN) in the Large and Small Magellanic Clouds have been analysed. The line fluxes have been used to determine nebular temperatures, densities, and the abundances of He, N, O, Ne and Ar, relative to H. In our sample there are 12 nebulae with N/O>=0.5, resembling Peimbert's Type I PN; six low-excitation objects [1<=I(5007)/I(H{beat})<=4], and four very-low excitation (VLE) nebulae [I(H{beta})>I(5007)], similar to the Galactic VLE class. Mean abundances have been calculated for the nebulae not in these special groups. After correction for collisional excitation contributions to the nebular He I lines, PN in the SMC and LMC yield mass fractions of Y=0.249+/-0.025 and Y=0.258+/-0.012, respectively.
39. Abundances in 6 metal-poor stars
ID:
ivo://CDS.VizieR/J/ApJ/857/2
Title:
Abundances in 6 metal-poor stars
Short Name:
J/ApJ/857/2
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present new abundances derived from CuI, CuII, ZnI, and ZnII lines in six warm (5766<=T_eff_<=6427K), metal-poor (-2.50<=[Fe/H]<=-0.95) dwarf and subgiant (3.64<=logg<=4.44) stars. These abundances are derived from archival high-resolution ultraviolet spectra from the Space Telescope Imaging Spectrograph on board the Hubble Space Telescope and ground-based optical spectra from several observatories. Ionized Cu and Zn are the majority species, and abundances derived from CuII and ZnII lines should be largely insensitive to departures from local thermodynamic equilibrium (LTE). We find good agreement between the [Zn/H] ratios derived separately from ZnI and ZnII lines, suggesting that departures from LTE are, at most, minimal (<~0.1dex). We find that the [Cu/H] ratios derived from CuII lines are 0.36+/-0.06dex larger than those derived from CuI lines in the most metal-poor stars ([Fe/H]{<}-1.8), suggesting that LTE underestimates the Cu abundance derived from CuI lines. The deviations decrease in more metal-rich stars. Our results validate previous theoretical non-LTE calculations for both Cu and Zn, supporting earlier conclusions that the enhancement of [Zn/Fe] in metal-poor stars is legitimate, and the deficiency of [Cu/Fe] in metal-poor stars may not be as large as previously thought.
40. Abundances in NGC 2243 and Mel 66
ID:
ivo://CDS.VizieR/J/A+A/283/911
Title:
Abundances in NGC 2243 and Mel 66
Short Name:
J/A+A/283/911
Date:
21 Oct 2021
Publisher:
CDS
Description:
(no description available)

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