New ultra metal-poor stars from SDSS: Follow-up GTC medium-resolution spectroscopy

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Abstract

Context. The first generation of stars formed in the Galaxy left behind the chemical signatures of their nucleosynthesis in the interstellar medium, visible today in the atmospheres of low-mass stars that formed afterwards. Sampling the chemistry of those low-mass provides insight into the first stars. Aims. We aim to increase the samples of stars with extremely low metal abundances, identifying ultra metal-poor stars from spectra with modest spectral resolution and signal-to-noise ratio (S/N). Achieving this goal involves deriving reliable metallicities and carbon abundances from such spectra. Methods. We carry out follow-up observations of faint, V > 19, metal-poor candidates selected from SDSS spectroscopy and observed with the Optical System for Imaging and low-Intermediate-Resolution Integrated Spectroscopy (OSIRIS) at GTC. The SDSS and follow-up OSIRIS spectra were analyzed using the FERRE code to derive effective temperatures, surface gravities, metallicities and carbon abundances. In addition, a well-known extremely metal-poor star has been included in our sample to calibrate the analysis methodology. Results. We observed and analyzed five metal-poor candidates from modest-quality SDSS spectra. All stars in our sample have been confirmed as extremely metal-poor stars, in the [Fe/H]

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Aguado, D. S., Allende Prieto, C., González Hernández, J. I., Rebolo, R., & Caffau, E. (2017). New ultra metal-poor stars from SDSS: Follow-up GTC medium-resolution spectroscopy. Astronomy and Astrophysics, 604. https://doi.org/10.1051/0004-6361/201731320

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