Analysis of Six extremely metal-poor star candidates

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https://phys.org/news/2018-09-chemical-analysis-extremely-metal-poor-star.html

Researchers conduct chemical analysis of six extremely metal-poor star candidates

September 11, 2018 by Tomasz Nowakowski, Phys.org

An international team of researchers has conducted a chemical study of six new very metal-poor star candidates in the Sloan Digital Sky Survey Data Release 12 (SDSS DR12). The new research, available in a paper published August 29 on the arXiv pre-print repository, could help researchers better understand the early stages of chemical evolution of the galaxy.

Extremely metal-poor stars (EMPs) are generally perceived by astronomers as the relics of the early chemical evolution of the Milky Way galaxy. They can be crucial in advancing the knowledge of the nature of the first stars that formed in the universe as their chemical composition is an important tool for constraining the nucleosynthesis in the first generation of stars.

Read more at: https://phys.org/news/2018-09-chemical-analysis-extremely-metal-poor-star.html#jCp

 

the paper:

arxiv.org/abs/1808.09918

Abstract 
The most metal-poor stars are the relics of the early chemical evolution of the Galaxy. Their chemical composition is an important tool to constrain the nucleosynthesis in the first generation of stars. The aim is to observe a sample of extremely metal-poor star (EMP stars) candidates selected from the Sloan Digital Sky Survey Data Release 12 (SDSS DR12) and determine their chemical composition. We obtain medium resolution spectra of a sample of six stars using the X-Shooter spectrograph at the Very Large Telescope (VLT) and we used ATLAS models to compute the abundances. Five stars of the sample have a metallicity [Fe/H] between -2.5 dex and -3.2 dex. We confirm the recent discovery of SDSS J002314.00+030758.0. As a star with an extremely low [Fe/H] ratio. Assuming the alpha-enhancement [Ca/Fe]=+0.4 dex, we obtain [Fe/H]=-6.1 dex. We could also determine its magnesium abundance and found that this star exhibits a very high ratio [Mg/Fe] >= +3.60~dex assuming [Fe/H] = -6.13 dex. We determined the carbon abundance and found A(C)=6.4 dex. From this carbon abundance, this stars belongs to the lower band of the A(C)-[Fe/H] diagram.

Read more at: https://phys.org/news/2018-09-chemical-analysis-extremely-metal-poor-star.html#jCp