For the first time, we present an extensive study of stars with individual non-LTE (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 results and improve earlier ones as follows: (i) the element-to-iron ratios for Mg, Si, Ca, and Ti form a metal-poor (MP) plateau at a similar height of 0.3 dex, and the knee occurs at common

About one percent of giants[1] are detected to have anomalously high lithium (Li) abundances in their atmospheres, conflicting directly with the prediction of the standard stellar evolution models [2] , and making the production and evolution of Li more intriguing, not only in the sense of the Big Bang nucleosynthesis [3,4] or the Galactic medium [5] , but also the evolution of stars. [6,7,8] , yet the origins of Li-rich giants are still being debated. Here we report the discovery of the most Li-rich giant known to date, with a super-high Li abundance of 4.51. This rare phenomenon was snapshotted together with another short-term event that the star is experiencing its luminosity bump on the red giant branch. Such high Li abundance indicates that the star might be at the very beginning of its Li-rich phase, which provides a great opportunity to investigate the origin and evolution of Li in the Galaxy. A detailed nuclear simulation is presented with up-to-date reaction rates to recreate the Li enriching process in this star. Our results provide tight constraints on both observational and theoretical points of view, suggesting that low-mass giants can produce Li inside themselves to a super high level via 7 Be transportation during the red giant phase. Decades of efforts have been put into explaining why such outliers existLithium is too fragile to survive in deeper layers of a stellar atmosphere due to the high temperature. Thus the first dredge up (FDU) process can sharply dilute the surface Li abundance in red giants. That explains why the first discovery [9] of a Li-rich giant evoked great interests on exploring and understanding the Li-rich objects. However, only about 150 Li-rich giants have been found [1,10,11,12,13,14] in the past three decades, and ∼ 20 of them were found to be super Li-rich with Li abundances higher than 3.3. Considering the NLTE corrections, three [12,15,16] stars were found to be at a level of A(Li) > 4.0. Such rare objects could provide a great opportunity to reveal the nature of the phenomenon of Li-richness because high Li abundance cannot be maintained for a long time due to frequent convection activity. Taking advantage of the powerful ability for spectral collection with the Large Sky Area Multi-Object * sjr@nao.cas.cn † gzhao@nao.cas.cn 1 Fiber Spectroscopy Telescope (LAMOST), we have obtained a large sample of Li-rich candidates by measuring the equivalent width of the Li I line at λ = 6707.8 Å. One of our candidates, TYC 429-2097-1, has a super strong Li absorption line (see Fig. 1, panel a). We then made a follow-up high-resolution observation with the 2.4-m Automated Planet Finder Telescope (APF) located at Lick Observatory on June 23, 2015. The spectrum covers a wavelength range of 374 nm − 970 nm with a resolution of ∼ 80, 000. The total integration time was 1.5 hours and was divided into three single exposures (30 minutes each) for a better subtraction of cosmic-rays. The spectrum of TYC 429-2097-1 obtained from APF is presented in Fig. 1, panels (b) and (e), where the spec...

The copper abundances of 29 metal-poor stars are determined based on the high resolution, high signalto-noise ratio spectra from the UVES spectragraph at the ESO VLT telescope. Our sample consists of the stars of the Galactic halo, thick-and thin-disk with [Fe/H] ranging from ∼ −3.2 to ∼ 0.0 dex. The non-local thermodynamic equilibrium (NLTE) effects of Cu I lines are investigated, and line formation calculations are presented for an atomic model of copper including 97 terms and 1089 line transitions. We adopted the recently calculated photo-ionization cross-sections of Cu I, and investigated the hydrogen collision by comparing the theoretical and observed line profiles of our sample stars. The copper abundances are derived for both local thermodynamic equilibrium (LTE) and NLTE based on the spectrum synthesis methods. Our results show that the NLTE effects for Cu I lines are important for metal-poor stars, in particular for very metal-poor stars, and these effects depend on the metallicity. For very metal-poor stars, the NLTE abundance correction reaches as large as ∼ +0.5 dex compared to standard LTE calculations. Our results indicate that [Cu/Fe] is under-abundant for metal-poor stars (∼ −0.5 dex) when the NLTE effects are included.

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