1D non-LTE corrections for chemical abundance analyses of very metal-poor stars

Detailed chemical abundances of very metal-poor (VMP; [Fe/H] < -2) stars are important for better understanding the first stars, early star formation, and chemical enrichment of galaxies. Big on-going and coming high-resolution spectroscopic surveys provide a wealth of material that needs to be carefully analysed. For VMP stars, their elemental abundances should be derived based on the non-local thermodynamic equilibrium (non-LTE = NLTE) line formation because low metal abundances and low electron number density in the atmosphere produce the physical conditions favourable for the departures from LTE. The galactic archaeology research requires homogeneous determinations of chemical abundances. For this purpose, we present grids of the 1D-NLTE abundance corrections for lines of Na i, Mg i, Ca i, Ca ii, Ti ii, Fe i, Zn i, Zn ii, Sr ii, and Ba ii in the range of atmospheric parameters that represent VMP stars on various evolutionary stages and cover effective temperatures from 4000 to 6500 K, surface gravities from $\rm log g$ = 0.5 to 5.0, and metallicities -5.0 = [Fe/H] = -2.0. The data is publicly available, and we provide the tools for interpolating in the grids online.

Automated summary

NLTE line formation is crucial for deriving elemental abundances of VMP stars, which is essential for understanding the first stars, early star formation, and chemical enrichment of galaxies. In this study, we present grids of 1D-NLTE abundance corrections and provide online tools for interpolation.