Binary interactions as a possible scenario for the formation of multiple stellar populations in globular clusters

TL;DR

This paper proposes that binary star interactions, leading to merged and accretor stars, could explain the multiple stellar populations and observed abundance variations in globular clusters.

Contribution

It introduces a new scenario where binary interactions produce rapidly rotating stars that account for multiple populations in GCs, aligning with observations.

Findings

Binary interactions produce stars with different surface abundances.

The model reproduces Na-O anticorrelation.

Multiple sequences in HR diagram are explained.

Abstract

Observations revealed the presence of multiple stellar populations in globular clusters (GCs) that exhibit wide abundance variations and multiple sequences in Hertzsprung-Russell (HR) diagram. We present a scenario for the formation of multiple stellar populations in GCs. In this scenario, initial GCs are single-generation clusters, and our model predicts that the abundance anomalous stars observed in GCs are the merged stars and the accretor stars produced by binary interactions, which are rapidly rotating stars at the moment of their formation and are more massive than normal single stars in the same evolutionary stage. We find that due to their own evolution, these rapidly rotating stars have different surface abundances, effective temperatures and luminosities from normal single stars in the same evolutionary stage. The stellar population with binaries can reproduce two important observational evidences of multiple stellar populations, the Na-O anticorrelation and the multiple sequences in HR diagram. This suggests that binary interactions may be a possible scenario for the formation of multiple stellar populations in GCs.