Aims. The aim of this paper is to provide the fundamental parameters and abundances for a large sample of local clump giants with a high accuracy. This study is a part of a big project, in which the vertical distribution of the stars in the Galactic disc and the chemical and dynamical evolution of the Galaxy are being investigated. Methods. The selection of clump stars for the sample group was made applying a colour-absolute magnitude window to nearby Hipparcos stars. The effective temperatures were estimated by the line depth ratio method. The surface gravities (log g) were determined by two methods (the first one was the method based on the ionization balance of iron and the second one was the method based on fitting of the wings of the Ca i 6162.17 Å line). The abundances of carbon and nitrogen were obtained from the molecular synthetic spectrum, and the Mg and Na abundances were derived using the non-LTE approximation. The "classical" models of stellar evolution without atomic diffusion and rotation-induced mixing were employed. Results. The atmospheric parameters (T eff , log g, [Fe/H], V t ) and Li, C, N, O, Na, Mg, Si, Ca, and Ni abundances in 177 clump giants of the Galactic disc were determined. The underabundance of carbon, overabundance of nitrogen, and "normal" abundance of oxygen were detected. A small sodium overabundance was found. A possibility of a selection of the clump giants based on their chemical composition and the evolutionary tracks was explored. Conclusions. The theoretical predictions based on the classical stellar evolution models are in good agreement with the observed surface variations of the carbon and nitrogen just after the first dredge-up episode. The giants show the same behaviour of the dependencies of O, Mg, Ca, and Si (α-elements) and Ni (iron-peak element) abundances vs. [Fe/H] as dwarfs do. This allows us to use such abundance ratios to study the chemical and dynamical evolution of the Galaxy.
Aims. The aim of this work is to present and discuss the observations of the iron peak (Fe, Ni) and neutron-capture element (Y, Zr, Ba, La, Ce, Nd, Sm, and Eu) abundances for 276 FGK dwarfs, located in the Galactic disk with metallicity −1 < [Fe/H] < +0.3. Methods. Atmospheric parameters and chemical composition of the studied stars were determined from an high resolution, high signal-to-noise echelle spectra obtained with the echelle spectrograph ELODIE at the Observatoire de Haute-Provence (France). Effective temperatures were estimated by the line depth ratio method and from the H α line-wing fitting. Surface gravities (log g) were determined by parallaxes and the ionization balance of iron. Abundance determinations were carried out using the LTE approach, taking the hyperfine structure for Eu into account, and the abundance of Ba was computed under the NLTE approximation. Results. We are able to assign most of the stars in our sample to the substructures of the Galaxy thick disk, thin disk, or Hercules stream according to their kinematics. The classification of 27 stars is uncertain. For most of the stars in the sample, the abundances of neutron-capture elements have not been measured earlier. For all of them, we provide the chemical composition and discuss the contribution from different nucleosynthesis processes. Conclusions. The [Ni/Fe] ratio shows a flat value close to the solar one for the whole metallicity range, with a small scatter, pointing to a nearly solar Ni/Fe ratio for the ejecta of both core-collapse SN and SNIa. The increase in the [Ni/Fe] for metallicity higher than solar is confirmed, and it is due to the metallicity dependence of 56 Ni ejecta from SNIa. Under large uncertainty in the age determination of observed stars, we verified that there is a large dispersion in the AMR in the thin disk, and no clear trend as in the thick disk. That may be one of the main reasons for the dispersion, observed for the s-process elements in the thin disk (e.g., Ba and La), whereas much narrower dispersion can be seen for r-process elements (e.g., Eu). Within the current uncertainties, we do not see a clear decreasing trend of [Ba/Fe] or [La/Fe] with metallicity in the thin disk, except maybe for super-solar metallicities. We cannot confirm an increase in the mentioned ratios with decreasing stellar age.
In this work we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1 <[Fe/H]< +0.3. The observed stars belong to the substructures of the Galaxy thick and thin discs, and to the Hercules stream. The observations were conducted using the 1.93 m telescope at Observatoire de Haute-Provence (OHP, France) equipped with the echelle type spectrographs ELODIE and SOPHIE. The abundances were derived under the LTE approximation, with an average error for the [Mn/Fe] ratio of 0.10 dex. For most of the stars in the sample Mn abundances are not available in the literature. We obtain an evolution of [Mn/Fe] ratio with the metallicity [Fe/H] consistent with previous data compilations. In particular, within the metallicity range covered by our stellar sample the [Mn/Fe] ratio is increasing with the increase of metallicity. This due to the contribution to the Galactic chemical evolution of Mn and Fe from thermonuclear supernovae. We confirm the baseline scenario where most of the Mn in the Galactic disc and in the Sun is made by thermonuclear supernovae. In particular, the effective contribution from core-collapse supernovae to the Mn in the Solar system is about 10-20%. However, present uncertainties affecting the production of Mn and Fe in thermonuclear supernovae are limiting the constraining power of the observed [Mn/Fe] trend in the Galactic discs on, e.g., the frequency of different thermonuclear supernovae populations. The different production of these two elements in different types of thermonuclear supernovae needs to be disentangled by the dependence of their relative production on the metallicity of the supernova progenitor.
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