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Spectroscopic analysis of metal-poor stars from LAMOST: early results

Metal-poor stars preserve the information of very early stage of the Milky Way and the universe, and thus are very important to understanding the formation and evolution of the Galaxy. Using LAMOST survey data, we have measured the stellar parameters based on the low-resolution spectra, and selected more than 100 candidates of extremely metal-poor stars. With the help of Magellan/MIKE supported by the TAP project, follow-up observations have been carried out on eight candidates, identifying five extremely metal-poor stars with [Fe/H] < -3.0. Expect one standard star, four are new discoveries (with one first-time high-resolution confirmation). Besides, a carbon and nitrogen enhanced metal-poor turnoff stars is discovered, while only two other similar objects are known to day with their origins still uncertain. As a pilot project for the metal-poor star survey with LAMOST, this work proves the capability of LAMOST being an important resource for such rare stars, and also provide valuable experiences for future investigations with LAMOST. The work has been publish in ApJ (2015, 798, 110).