| Abstract : | Metal-poor stars provide an understanding of many aspects of the Galactic chemical evolution. However, many details about the production and evolution of the elements, especially the elements heavier than iron, still remain poorly understood. A comprehensive analysis of the observed abundance peculiarities derived from a significantly large sample of these objects may shed some insight, which is currently lacking. My PhD thesis is aimed at addressing some of these aspects. (i) As a first step towards achieving the goal, we have performed high-resolution spectroscopic analysis of twenty metal-poor stars belonging to different classes of metal-poor stars to provide observational constraints to the theoretical models of neutron (n)-capture nucleosynthesis in terms of elemental abundances. (ii) It is noticed from the chemical abundance studies of CEMP-r/s stars that the abundance patterns of n-capture elements in these stars can neither be reproduced by s- or r- processes alone nor by any combination of s- and r-processes. We have studied the formation scenarios of CEMP-s and CEMP-r/s stars in detail to understand the production channels of these two subclasses of CEMP stars. We have confirmed the recent claims that i-process is responsible for the formation of CEMP-r/s stars. (iii) We have put forward a new classification scheme based on the abundances of Ba, La and Eu to differentiate CEMP-s and CEMP-r/s stars. (iv) We have discovered a carbon-enhanced extremely metal-poor object HE 1005–1439, the peculiar abundance pattern of which was found to be enriched with products of both i- and s-processes. The abundance pattern shown by this object is the first of its kind and possibly forms a new class of objects. (v) We showed that masses of the AGB companions play a dominant role in forming mild and strong Barium stars. |
