Characterizing the companion AGBs using surface chemical composition of barium stars

Abstract

Barium stars are one of the important probes to understand the o rigin and evolution of slow neutron-capture process elements in the Galaxy. These are e xtrinsic stars, where the observed s-process element abundances are believed to have an origin in the now invisible companions that produced these elements at their Asympto tic Giant Branch phase of evolution. We have attempted to understand the s-proc ess nucleosynthesis, as well as the physical properties of the companion stars through a detailed compar- ison of observed elemental abundances of 10 barium stars with the predictions from AGB nucleosynthesis models, FRUITY. For these stars, we have pr esented estimates of abundances of several elements, C, N, O, Na, Al, α -elements, Fe-peak elements and neutron-capture elements Rb, Sr, Y, Zr, Ba, La, Ce, Pr, Nd, Sm and Eu. The abundance estimates are based on high resolution spectral analys is. Observations of Rb in four of these stars have allowed us to put a limit to the mass of th e companion AGB stars. Our analysis clearly shows that the former companions r esponsible for the surface abundance peculiarities of these stars are low-mass A GB stars. Kinematic analysis have shown the stars to be members of Galactic disk populat ion.