Speaker
Description
The relative variations of the chemical compositions between metal-poor stars ($[\mathrm{F}/\mathrm{H}] < -1$) give the possibility to reveal the pure signature of unique nucleosynthesis processes. The study of the r-process is for instance one of the main goals of stellar archaeology.
In this work we present the atmospheric parameter, the main dynamic properties and the abundances of four metal-poor stars: HE 1523–0901, HD 6268, HD 121135, and HD 195636 ($-1.5 > [\mathrm{Fe}/\mathrm{H}] > -3.0]$).The abundances are derived from spectra obtained with the HRS echelle spectrograph at the Southern African Large Telescope, using both LTE and NLTE approaches, with an average error between $0.10$ and $0.20\,\mathrm{dex}$. The most metal-poor stars in our sample, HE 1523–0901, HD 6268 and HD 195636, show anomalies that are better explained by supernova models from fast-rotating stellar progenitors. If we consider the elements beyond Fe, HE 1523-0901 can be classifed as an r-II star, HD 6268 an r-I candidate, and HD 195636 and HD 121135 show a borderline r-process enrichment between limited-r and r-I star. Significant differences are observed between the r-process signatures in these stars. We discuss those in the light of the current understanding of r-process nucleosynthesis.
