Spectroscopic study of neutron-capture elements in CEMP and Barium Stars

Abstract

In the quest for understanding the early universe, we have come to a line of thought of looking for Metal-poor stars since they carry the fingerprint of the very first stars formed. The study of the elements produced or preserved in these stars gives a fundamental insight into the chemical evolution on a much larger scale. To understand the composition of such stars and their distribution in the galaxy, there exists a need for High-resolution spectroscopic studies on target stars which show neutron-capture elements enhancement. Therefore, in this work, we present the detailed chemical abundance analysis of objects HD 179832, HD 145777 and HE 2144-1832 using High-resolution spectra of facilities such as FEROS (Fibre-fed Extended Range Optical Spectrograph) and HESP (High-Resolution Echelle Spectrograph). We do a series of reductions procedures using IRAF to obtain final spectra, followed by metallicity estimate and determining model atmosphere parameters such as effective temperature, surface gravity and micro-turbulent velocity of the programme stars. Then we use these to do the chemical analysis of species such as α-elements, Fe-peak elements and neutron-capture process elements using the latest version of spectral analysis code MOOG. We present the mass and age of the stars determined using the up to date models of stellar evolutionary track and isochrones. The object HD 179832, HD 145777 and HE 2144-1832 have [Fe/H] 0.22, - 2.14 and -1.60 respectively. These are classified as Barium star, CEMP-s star and CEMP-r/s star respectively by our analysis. We also report the analysis of more than 15 elements including α elements such as Mg, Ca, Ti; Iron-peak elements such as Co, Ni, and Zn; light neutron-capture elements like Sr, Y and heavy neutron-capture elements Ba, La, Nd, Sm, Eu. At the end of the report, we attempt to classify our results with respect to the large sample of existing literature on the concerned system. Using Kinematic analysis and nucleosynthesis theories we present some conclusions on the galactic distribution of these stars and origin of the elements produced by them