The effect of intermediate mass close binaries on the chemical evolution of Globular Clusters

TL;DR

This paper explores how intermediate mass close binaries influence the chemical evolution of globular clusters, particularly in providing pristine matter necessary for explaining observed stellar abundance patterns.

Contribution

It introduces a population synthesis approach to quantify binary mass loss and its role in globular cluster chemical enrichment, extending single star AGB models.

Findings

Binary mass loss contributes significantly to pristine matter in clusters.

Combined binary and single star models better reproduce observed chemical patterns.

Binary interactions help explain multiple stellar populations in globular clusters.

Abstract

Context. The chemical processes during the Asymptotic Giant Branch (AGB) evolution of intermediate mass single stars predict most of the observations of the different populations in globular clusters although some important issues still need to be further clarified. In particular, to reproduce the observed anticorrelations of Na-O and Al-Mg, chemically enriched gas lost during the AGB phase of intermediate mass single stars must be mixed with matter with a pristine chemical composition. The source of this matter is still a matter of debate. Furthermore, observations reveal that a significant fraction of the intermediate mass and massive stars are born as components of close binaries. Aims. We will investigate the effects of binaries on the chemical evolution of Globular Clusters and on the origin of matter with a pristine chemical composition that is needed for the single star AGB scenario to work Methods. We use a population synthesis code that accounts for binary physics in order to estimate the amount and the composition of the matter returned to the interstellar medium of a population of binaries. Results. We demonstrate in the present paper that the mass lost by a significant population of intermediate mass close binaries in combination with the single star AGB pollution scenario may help to explain the chemical properties of the different populations of stars in Globular Clusters.