Abstract Details

Name: Partha Pratim Goswami
Affiliation: Indian Institute of Astrophysics
Conference ID: ASI2020_483
Title : Metal-poor stars and neutron-capture nucleosynthesis
Authors and Co-Authors : Author: Partha Pratim Goswami, Co-Author: Aruna Goswami
Abstract Type : Oral
Abstract Category : Stars, ISM and Galaxy
Abstract : The elements heavier than iron (Fe) are believed to be produced by slow ('s') and rapid ('r') neutron-capture processes. The surface chemical compositions of a large fraction of metal-poor stars show enhancement of s-process elements (CH/CEMP-s stars), a few exhibit enhancement of r-process elements (CEMP-r stars), and a sizeable fraction shows enhancement of both s- and r-process elements (CEMP-r/s stars). While the production sites of s-process elements are believed to be the inter-pulse phases of low- and intermediate-mass AGB stars, the r-process is expected to occur during supernova explosions and neutron star mergers. These two processes produce distinct abundance patterns. Recent chemical composition studies on CEMP-r/s stars have revealed that in many cases the observed heavy element abundances cannot be explained either by s-process or r-process nucleosynthesis alone. As s- and r- process occurs at completely different stellar environment and sites, the observed enhancement of surface chemical composition of these stars seems a mystery. There are several proposed scenarios for the production mechanism of CEMP-r/s stars, a recent suggestion is 'i-process (intermediate process) nucleosynthesis'. Here, we'll present the results of detailed spectroscopic analysis of a few CEMP (s and -r/s) stars based on high resolution spectra obtained using HESP attached to HCT, FEROS/ESO and SUBARU/HDS. On the basis of existing nucleosynthesis theories and models we have examined whether i-process could explain the abundance patterns observed in the CEMP-r/s stars. It is seen that most of the existing classifiers overlap and fail to successfully classify them in different CEMP subclasses. We have examined if [hs/ls] ratios can be used to distinguish CEMP-s and CEMP-r/s stars. Some results of these studies will be discussed here.