Why the globular cluster NGC 6752 contains no sodium-rich second-generation AGB star

TL;DR

This paper investigates why NGC 6752 lacks sodium-rich second-generation AGB stars, proposing an explanation for the observed absence of these stars along the early asymptotic giant branch in this globular cluster.

Contribution

The study offers a novel explanation for the absence of sodium-rich AGB stars in NGC 6752, addressing a key inconsistency in stellar evolution observations.

Findings

No sodium-rich stars observed on the early AGB in NGC 6752

Proposed explanation accounts for the absence of these stars

Supports revised models of stellar evolution in globular clusters

Abstract

(Abridged) Globular clusters host multiple stellar populations showing different sodium enrichments. These various populations can be observed along the main sequence, red giant and horizontal branch phases. Recently it was shown, however, that at least in the globular cluster NGC 6752, no sodium-rich stars are observed along the early asymptotic giant branch, posing an apparent problem for stellar evolution. We present an explanation for this lack of sodium-rich stars in this region of the colour-magnitude diagram.