T. V. Mishenina

NLTE barium abundance in thin and thick disks of the Galaxy

We present the determinations of the barium abundance takin g into account the non-LTE (NLTE) effects in 173 dwarf stars belonging to the thin and thick dis ks. The NLTE profiles of the unblended Ba II lines (4554, 5853, 6496 ÅÅ) have been computed a nd compared to the observed profiles. The line 6141 Å was also used, but taking into accoun t an influence of iron line. We used a modified version of the MULTI code and atomic model of Ba atom with 31 levels of Ba I, and 101 levels of Ba II. Atmosphere models of investigated stars h ve been calculated with ATLAS9 code (modified using the New Opacity distribution functions by Castelli & Kurucz). The obtained trend in the Ba abundance vs. [Fe/H] suggests a complex proce ss f the Ba production in the thin and thick disks.

Li abundances and chromospheric activity of BY Dra type stars

Atmospheric parameters and Li abundances have been determined for 162 stars observed at high resolution, high signal to noise ratio with the ELODIE echelle spectrograph (OHP, France). Among them, about 70 stars are active stars with a large fraction of BY Dra type stars. For all stars, rotational velocities were obtained with a calibration of the cross-correlation function, effective temperatures by the line depth ratio method, surface gravities by the parallaxe method and by the ionization balance of iron. The frequency of stars with observed lithium is significantly higher in active stars than in non active stars. Among active stars, no clear correlation has been found between different indicators of activity for our sample stars, but some correlation of an index R′ H K and v sin i is observed.