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Communication Dans Un Congrès Année : 2007

Chemical composition of the clump giants

Résumé

The atmospheric parameters (T_{eff}, log g, [Fe/H], V_{t}) and Li, C, N, O, Na, Mg, Si, Ca, Ni, Y, Ba, La, Ce, Pr, Nd, and Eu abundances in 177 clump giants of the Galactic disc were determined. The selection of the clump stars 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 ionization balance of iron and the method based on fitting of the wings of the Ca I 6162.17 A line. The abundances of carbon and nitrogen were obtained from the molecular spectral synthesis, Mg and Na abundances were derived using non-LTE approximation. For Ba and Eu, the hyperfine structure was taken into account. 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 temperature, chemical composition and the evolutionary tracks was explored. 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 (?-elements) and Ni (iron-peak element) abundances vs. [Fe/H] as dwarfs do. Clump giants and giants of the ascending branch do not show an essential difference between n-capture element abundances.
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Dates et versions

hal-00256888 , version 1 (18-02-2008)

Identifiants

Citer

T. V. Mishenina, O. Bienaymé, T. I. Gorbaneva, Corinne Charbonnel, C. Soubiran, et al.. Chemical composition of the clump giants. Spectroscopic methods in modern astrophysics., 2006, Moscow, Russia. pp.131-151. ⟨hal-00256888⟩
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