The non-local thermodynamic equilibrium barium abundance in dwarf stars in the metallicity range of

Abstract

We present the results of determination of the barium abundance considering the non-local thermodynamic equilibrium (NLTE) effects in 172 dwarf stars in the metallicity range of −1 < [Fe/H] < +0.3, assigned to different Galactic substructures by kinematic criteria. We used a model of the Ba atom with 31 levels of Ba i and 101 levels of Ba ii. The atmosphere models for the investigated stars were computed using the atlas9 code modified by new opacity distribution functions by Castelli & Kurucz. The NLTE profiles of the unblended Ba ii (4554, 5853, 6496 Å) were computed and then compared to those observed. The line 6141 Å was also used, but with an allowance for its correlation with the iron line. The average barium abundances in the thin and thick discs are 0.01 ± 0.08 and −0.03 ± 0.07, respectively. The comparison to the calculations of the Galactic chemical evolution by Serminato et al. was conducted. The trend obtained for the Ba abundance versus [Fe/H] suggests a complex barium production process in the thin and thick discs.