Based on the Sewan Digital Sky Survey Data Release 12 (SDSS DR12) database, an international team of researchers chemically investigated six new candidates for metal deprived stars. The new study, published Aug.29 in the arXiv pre-print repository, could help scientists better understand the early stages of the galaxy's chemical evolution.
Extremely metal-poor stars (EMPs) are generally perceived by astronomers as relics of the early chemical evolution of the Milky Way galaxy. They may be critical in increasing knowledge about the nature of the first stars formed in the universe, since their chemical composition is an important tool for limiting nucleosynthesis in the first generation of stars.
Thus, a team of scientists led by Patrick François of the Paris Observatory in France performed a chemical analysis of a sample of new EMP candidates from SDSS DR12. They selected six stars from a database and obtained medium-resolution spectra of these objects using the X-Shooter spectrograph at ESO's very large telescope (VLT) in Chile. The observations made it possible to determine the chemical composition of these stars.
'The latest analysis of SDSS DR12 data has allowed us to discover new extremely weak metal candidates that have never been observed at high resolution. In this article, we report a detailed analysis of six new metal-deprived candidates, ”the researchers report.
The metallicity of the six studied stars ranges from -5.0 to -3.5 [Fe / H], and their effective temperature ranges from 6050 to 6530 K. The researchers found that three of the six stars described in the article contain calcium (Ca ). They noted that the ratio of magnesium to iron (Fe) of this trio is also quite low.
The authors report that the five stars in the sample exhibit abundance ratios for stars with poor metals in the -3.5 to -2.0 metallicity range. However, there is one dwarf star in the sample, designated SDSS J002314.00 + 030758.0 (or SDSS J0023 + 0307 for short), showing anomalies in iron abundance. In doing so, scientists have found that it is extremely high in magnesium (Mg) and calcium.
'We see that the star SDSS J002314.00 + 030758.0 stands out in that it has an obvious abundance of Mg and Ca, sharing this feature with the Keller star (SMSS J031300-670839.3) and, to a lesser extent, with the Depagne star (CS 22949-037) '.
According to the researchers, the anomalies found in SDSS J0023 + 0307 suggest different channels for the enrichment of the gas that forms most non-metal stars.
As a result, scientists concluded that several different astrophysical processes could be behind such anomalies in SDSS J0023 + 0307, which include supernova explosions and very fast rotation of stars. However, to determine the most plausible hypothesis, more detailed chemical studies of metal-depleted stars are needed.
