Speaker
Description
Several enigmatic questions have come up on the formation and chemical evolution of the Milky Way over the last decade. The detailed chemical abundances of the old, long-lived, metal-poor halo stars provide insights into the nature of the early chemical enrichment events leading to the formation of the metals as we see them now in the universe. In this talk, I will present a study on the detailed chemical abundances of very faint and extremely metal-poor stars from the R-process Alliance using the GTC. Here, we discuss the detailed abundances of light, alpha, Fe-peak and r-process elements of the faintest RPA sample of stars. The over-abundance of carbon for the most metal-poor stars indicates mixing and fallback type of supernova as the primary progenitor. We use the alpha elements to demonstrate that massive stars were the most likely progenitors at the lowest metallicities. We also identify stars of globular cluster origin at very low metallicities (Fe/H ~ -3.0) using the light element anticorrelation, which suggests further lowering the metallicity floor of GCs and revisiting the Galactic chemical evolutionary models. The neutron capture elements (Sr, Ba and Eu) could be measured, and several new R-process Enhanced stars have been identified for follow-up studies. We have also used the astrometric parameters from Gaia to obtain the kinematics of all the stars to understand the nature of their origin in the Galaxy. Thus we derive the complete chemo dynamical history of the stellar population in this study.
