| Abstract : | Understanding the formation of heavier elements is one of the key topics in stellar astronomy. The rapid neutron capture process (r-process) is the prime nucleosynthesis mechanism for producing heavy elements. Several sites have been proposed for the r-process nucleosynthesis, such as core-collapse supernovae, neutron star mergers, etc., but none of them is well constrained. Studying heavier elements in the metal-poor stars is the pristine tool to investigate the sites of r-process nucleosynthesis. But, the rarity of r-process enhanced metal-poor stars in the Galaxy makes us difficult to understand its formation sites. So, a large sample of r-process rich stars will help us understand the nucleosynthesis history of these populations. Here, we have presented the detailed abundance analysis of four r-process enhanced metal-poor stars. These stars were selected from SDSS/MARVEL survey and reobserved with the 10-m class telescope Gran Telescopio CANARIAS (GTC), Spain. The high signal-to-noise ratio at R~25000 spectral resolution of GTC has allowed us to detect 21 neutron-capture elements in four of our program stars. Among these elements, we could detect thorium (Th) in two of our target stars, which we used to estimate their ages. The r-process element abundances of our target stars also matched with the scaled-Solar abundances, confirming the universality of the main r-process pattern (second peak elements), along with the usual scatter for the first and third r-process elements. We have also used our target stars together with already identified r-process rich stars in literature to constraint the nature and origin of the r-process at early times. |
