Abundances of neutron-capture elements in stars of the galactic disk substructures

Autor: Corinne Charbonnel, Caroline Soubiran, N. Yu. Basak, Friedrich-Karl Thielemann, T. V. Mishenina, S. A. Korotin, T. I. Gorbaneva, Marco Pignatari
Přispěvatelé: Astronomical observatory of Odessa National University [Odessa], Odessa National I.I.Mechnikov University, M2A 2013, Laboratoire d'astrodynamique, d'astrophysique et d'aéronomie de bordeaux (L3AB), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Observatoire aquitain des sciences de l'univers (OASU), Université Sciences et Technologies - Bordeaux 1-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Centre National de la Recherche Scientifique (CNRS)-Laboratoire d'Astrophysique de Bordeaux [Pessac] (LAB), Université de Bordeaux (UB)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université de Bordeaux (UB), Université de Genève (UNIGE)
Jazyk: angličtina
Rok vydání: 2013
Předmět:
Zdroj: Astronomy and Astrophysics-A&A
Astronomy and Astrophysics-A&A, EDP Sciences, 2013, 552, pp.id.A128. ⟨10.1051/0004-6361/201220687⟩
Astronomy and Astrophysics
Astronomy & Astrophysics
ASTRONOMY & ASTROPHYSICS
ISSN: 0004-6361
Popis: 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 a 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 56Ni 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. © 2013 ESO.
Databáze: OpenAIRE
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