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

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 formed afterwards. Sampling the chemistry of 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 OSIRIS at GTC. The SDSS and follow-up OSIRIS spectra have been 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 have 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]<-3.3 regime. We report the recognition of J173403+644632, a carbon-enhanced ultra metal-poor dwarf star with [Fe/H]=-4.3 and [C/Fe]=+3.1.

Accepted for publication in A&A

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Cited by in corpus (15)

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• The Pristine survey III: Spectroscopic confirmation of an efficient search for extremely metal-poor stars
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• J0815+4729: A chemically primitive dwarf star in the Galactic Halo observed with Gran Telescopio Canarias
• The chemical abundance pattern of the extremely metal-poor thin disk star 2MASS J1808-5104 and its origins
• On the 12C/13C isotopic ratio at the dawn of chemical evolution
• The Pristine survey XIV: chemical analysis of two ultra-metal-poor stars
• Espresso observations of HE 0107$-$5240 and other CEMP-no stars with $[Fe/H]\le -4.5$
• On the dearth of C-enhanced metal-poor stars in the Galactic bulge
• The Pristine survey -- XX: GTC follow-up observations of extremely metal-poor stars identified from Pristine and LAMOST
• Stellar Loci VI: An Updated Catalog of the Best and Brightest Metal-poor Stars
• A second-generation star in a relic dwarf galaxy
• Searching for Low-mass Population III Stars Disguised as White Dwarfs
• When did the initial mass function become bottom-heavy?