Speaker
Description
The most ancient stars witnessed the assembly of the Galaxy, and they are key for studying the chemical history of the Milky Way. Extremely metal-poor stars offer an opportunity to learn about low-mass star formation, Galactic evolution and supernovae yields. During the last few years we have been exploring the SDSS and LAMOST low-resolution spectroscopic surveys to identify stars at [Fe/H] < -3. Using medium-resolution spectroscopy with ISIS at WHT and OSIRIS at GTC we have followed-up more than 60 promising candidates. Six stars were confirmed to belong to the regime [Fe/H] < -4. We have in particular discovered two very primitive dwarf stars, both with Teff~6200 K: SDSS J0815+4729 at [Fe/H]<-5 and SDSS J0023+0307 at [Fe/H]<-6. The mere existence of these two stars provides new constraints on the properties of first stars and demonstrates that our methodology is highly efficient identifying metal-poor candidates from large spectroscopic surveys.
Affiliation
Instituto de Astrofísica de Canarias
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