Sergei M. Andrievsky

Non-LTE abundances of Mg and K in extremely metal-poor stars and the evolution of [O/Mg], [Na/Mg], [Al/Mg], and [K/Mg] in the Milky Way

Aims. LTE abundances of light elements in extremely metal-poor (EMP) stars have been previously derived from high quality spectra. New derivations, free from the NLTE effects, will better constrain the models of the Galactic chemical evolution and the yields of the very first supernovae. Methods. The NLTE profiles of the magnesium and potassium lines have been computed in a sample of 53 extremely metal-poor stars with a modified version of the program MULTI and adjusted to the observed lines in order to derive the abundances of these elements. Results. The NLTE corrections for magnesium and potassium are in good agreement with the works found in the literature. The abundances are slightly changed, reaching a better precision: the scatter around the mean of the abundance ratios has decreased. Magnesium may be used with confidence as reference element. Together with previously determined NLTE abundances of sodium and aluminum, the new ratios are displayed, for comparison, along the theoretical trends proposed by some models of the chemical evolution of the Galaxy, using different models of supernovae.

Evolution of the Barium abundance in the early Galaxy from a NLTE analysis of the Ba lines in a homogeneous sample of EMP stars.

Context. Barium is a key element in constraining the evolution of the (not well understood) r-process in the first galactic stars and currently the Baxa0abundances in these very metal-poor stars were mostly measured under the Local Thermodynamical Equilibrium (LTE) assumption, which may lead in general to an underestimation ofxa0Ba. Aims. We present here determinations of the barium abundance taking into account the non-LTE (NLTE) effects in a sample of extremely metal-poor stars (EMP stars): 6xa0turnoff stars and 35xa0giants. Methods. The NLTE profiles of the three unblended

NLTE strontium abundance in a sample of extremely metal poor stars and the Sr/Ba ratio in the early Galaxy

ion{Ba}{ii}

NLTE determination of the calcium abundance and 3D corrections in extremely metal-poor stars

lines (4554u2009A, 5853u2009A, 6496u2009A) have been computed. The computations were made with a modified version of the MULTIxa0code, applied to an atomic model of the Baxa0atom with 31xa0levels of

First stars - XIV. Sulfur abundances in extremely metal-poor stars

ion{Ba}{i}

Oxygen abundance distribution in the Galactic disc

, 101xa0levels of

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

ion{Ba}{ii}

The chemical composition of red giants in 47 Tucanae: I. Fundamental parameters and chemical abundance patterns

, and compared to the observations. Results. The ratios of the NLTE abundances of barium relative toxa0Fe are slightly shifted towards the solar ratio. In the plot of [Ba/Fe] versus [Fe/H], the slope of the regression line is slightly reduced as is the scatter. In the interval

GIANO Y-band spectroscopy of dwarf stars: Phosphorus, sulphur, and strontium abundances

rm -3.3 <[Fe/H] < -2.6

A critical reassessment of the fundamental properties of GJ 504: chemical composition and age

, [Ba/Fe] decreases with a slope of about 1.4 and a scatter close toxa00.44. For