Abstract Details
| Name: Drisya K Affiliation: Indian Institute of Astrophysics Conference ID: ASI2016_465 Title : Studies on Carbon-Enhanced Metal-Poor (CEMP) stars Authors and Co-Authors : Prof. Aruna Goswami. Indian Institute of Astrophysics Abstract Type : Oral Abstract Category : Thesis Abstract : Thesis Title: Studies on Carbon-Enhanced Metal-Poor (CEMP) stars Supervisor: Prof. Aruna Goswami Carbon-Enhanced Metal-poor (CEMP) stars are an important class of chemically peculiar stars; a large fraction of them show enhancement of carbon and heavy elements and are known to populate the halo of the Galaxy. They are population II objects formed from the ejecta of more massive population III stars. Hence chemical composition studies of CEMP stars are crucial to develop an understanding of the nature of the earliest stars formed in the universe, the nucleosynthesis events associated with them, as well as, to redefine the models of galaxy formation. Elements heavier than the iron peak are made via two principal processes: the rapid neutron-capture process (r-process) and the slow neutron-capture process (s-process). Among the CEMP stars, CEMP-s stars exhibit the presence of strongly enhanced s-process elements and CEMP-r stars are with strong enhancement of r-process elements. A number of CEMP stars, CEMP-r/s stars, exhibit enhancement of both r- and s-process elements. Insight into the astrophysical sites and the production mechanisms of neutron-capture elements can be obtained by studying chemical composition of stars that exhibit large enhancement of neutron-capture elements such as CEMP stars. According to certain spectral criteria carbon stars are again classified into different groups such as C-R, C-N, CH and C-J. Among these CH stars are most important because they are identified as the more metal-poor counter parts of CEMP-s stars and are believed to have a similar origin. The main goal of this thesis was to conduct detailed chemical composition study of a large sample of CEMP stars to understand the nucleosynthetic origin of the observed abundance patterns. We have carried out low-resolution spectroscopic analysis of a group of hundred and twelve CEMP stars to find potential CH (or CEMP-s) stars. High resolution spectroscopic analysis of a group of twenty two CH stars are also carried out to determine the detailed chemical abundances. A parametric model based study is conducted to understand the origin of the anomalous abundance patterns in them. From the high resolution spectroscopic analysis, we find eleven objects that exhibit enhancement of heavy elements also show radial velocity variations indicating their binary nature. Among these, seven objects show the characteristics of CEMP-s stars. The enhancement in heavy elements shown by the binaries are distinctly more compared to the other objects which do not belong to binary system. We have also noted an increasing trend of heavy element abundances with decreasing metallicity. In this talk, I will highlight some of these results and important conclusions drawn from this thesis work. |