V. V. Kovtyukh

On the correlation of elemental abundances with kinematics among galactic disk stars

We have performed the detailed analysis of 174 high-resolution spectra of FGK dwarfs obtained with the ELODIE echelle spectrograph at the Observatoire de Haute-Provence. Abundances of Fe, Si and Ni have been determined from equiv- alent widths under LTE approximation, whereas abundances of Mg have been determined under NLTE approximation using equivalent widths of 4 lines and profiles of 5 lines. Spatial velocities with an accuracy better than 1 km s −1 , as well as orbits, have been computed for all stars. They have been used to define 2 subsamples kinematically representative of the thin disk and the thick disk in order to highlight their respective properties. A transition occurs at (Fe/H) = −0.3. Stars more metal-rich than this value have a flat distribution with Zmax < 1 kpc and σW < 20 km s −1 , and a narrow distribution of (α/Fe). There exist stars in this metallicity regime which cannot belong to the thin disk because of their excentric orbits, neither to the thick disk because of their low scale height. Several thin disk stars are identified down to (Fe/H) = −0.80. Their Mg enrichment is lower than thick disk stars with the same metallicity. We confirm from a larger sample the results of Feltzing et al. (2003) and Bensby et al. (2003) showing a decrease of (α/Fe) with (Fe/H) in the thick disk interpreted as the signature of the SNIa which have progressively enriched the ISM with iron. However our data suggest that the star formation in the thick disk stopped when the enrichment was (Fe/H) = −0.30, (Mg/Fe) =+ 0.20, (Si/Fe) =+ 0.17. A vertical gradient in (α/Fe) may exist in the thick disk but should be confirmed with a larger sample. Finally we have identified 2 new candidates of the HR1614 moving group.

Abundances of Cu and Zn in metal-poor stars: Clues for Galaxy evolution

We present new observations of copper and zinc abundances in 90 metal-poor stars, belonging to the metallicity range −3 100). The trend of Cu and Zn abundances as a function of the metallicity (Fe/H) is discussed and compared to that of other heavy elements beyond iron. We also estimate spatial velocities and galactic orbital parameters for our target stars in order to disentangle the population of disk stars from that of halo stars using kinematic criteria. In the absence of a firm a priori knowledge of the nucleosynthesis mechanisms controlling Cu and Zn production, and of the relative stellar sites, we derive constraints on these last from the trend of the observed ratios (Cu/Fe) and (Zn/Fe) throughout the history of the Galaxy, as well as from a few well established properties of basic nucleosynthesis processes in stars. We thus confirm that the production of Cu and Zn requires a number of different sources (neutron captures in massive stars, s-processing in low and intermediate mass stars, explosive nucleosynthesis in various supernova types). We also attempt a ranking of the relative roles played by different production mechanisms, and verify these hints through a simple estimate of the galactic enrichment in Cu and Zn. In agreement with suggestions presented earlier, we find evidence that type Ia Supernovae must play a relevant role, especially for the production of Cu.

Elemental abundances in the atmosphere of clump giants

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 (

High precision effective temperatures for 181 F-K dwarfs from line-depth ratios

log,{g}

Galactic abundance gradients from Cepheids: α and heavy elements in the outer disk

) 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

Vertical distribution of Galactic disk stars - III. The Galactic disk surface mass density from red clump giants

ion{Ca}{i}

Activity and the Li abundances in the FGK dwarfs

6162.17 Au2000line). 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 (

A new Böhm-Vitense gap in the temperature range 5560 to 5610 K in the main sequence ,

{T_{rm eff}}

Oxygen abundance distribution in the Galactic disc

,

Oxygen, α-element and iron abundance distributions in the inner part of the Galactic thin disc

log,{g}