[Rb/Zr] ratio in Ba stars as a diagnostic of the companion AGB stellar mass

Abstract

Understanding nucleosynthesis in and evolution of asymptotic giant branch (AGB) stars is of primary importance as these stars are the main producers of some of the key elements in the Universe. They are the predominant sites for slow-neutron-capture nucleosynthesis (s-process). The exact physical conditions and nucleosynthetic processes occurring in the interior of AGB stars are not clearly understood, and that hinders better understanding of the contribution of these stars to the Galactic chemical enrichment. Extrinsic-variable stars that are known to have received products of AGB phase of evolution via binary mass-transfer mechanisms are vital tools in tracing AGB nucleosynthesis. The [Rb/Zr] ratio is an important diagnostic to understand the average neutron density at the s-process site and provides important clues to the mass of companion AGB stars in binaries. In this work we have presented estimates of [Rb/Zr] ratios based on high-resolution spectroscopic analysis for a sample of Ba stars, and discussed how the ratio can be used to understand the characteristics of the AGB star. Results from an analysis based on a parametric model to confirm the mass of the companion AGB star are also presented.