Systematic non-LTE study of the -2.6 < [Fe/H] < 0.2 F and G dwarfs in the solar neighbourhood. II. Abundance patterns from Li to Eu

Zhao, G.; Mashonkina, L.; Yan, H. L.; Alexeeva, S.; Kobayashi, C.; Pakhomov, Yu.; Shi, J. R.; Sitnova, T.; Tan, K. F.; Zhang, H. W.; Zhang, J. B.; Zhou, Z. M.; Bolte, M.; Chen, Y. Q.; Li, X.; Liu, F.; Zhai, M.

For the first time, we present an extensive study of stars with individual non-local thermodynamic equilibrium (NLTE) abundances for 17 chemical elements from Li to Eu in a sample of stars uniformly distributed over the -2.62 < [Fe/H] < +0.24 metallicity range that is suitable for the Galactic chemical evolution research. The star sample has been kinematically selected to trace the Galactic thin and thick disks and halo. We find new and improve earlier results as follows. (i) The element-to-iron ratios for Mg, Si, Ca, and Ti form a MP plateau at a similar height of 0.3~dex, and the knee occurs at common [Fe/H] ~ -0.8. The knee at the same metallicity is observed for [O/Fe], and the MP plateau is formed at [O/Fe] = 0.61. (ii) The upward trend of [C/O] with decreasing metallicity exists at [Fe/H] < -1.2, supporting the earlier finding of Akerman et al. (iii) An underabundance of Na relative to Mg in the [Fe/H] < -1 stars is nearly constant, with the mean [Na/Mg] ~ -0.5. (iv) The K/Sc, Ca/Sc, and Ti/Sc ratios form well-defined trends, suggesting a common site of the K-Ti production. (v) Sr follows the Fe abundance down to [Fe/H] ~ -2.5, while Zr is enhanced in MP stars. (vi) The comparisons of our results with some widely used Galactic evolution models are given. The use of the NLTE element abundances raises credit to the interpretation of the data in the context of the chemical evolution of the Galaxy.

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