# First evidence of multiple populations along the AGB from Str\"omgren photometry

## TL;DR

This study demonstrates that Str"omgren photometry can effectively identify multiple stellar populations along the AGB in globular clusters, revealing complexities previously unconfirmed and providing a basis for future spectroscopic analysis.

## Contribution

First evidence showing multiple populations along the AGB using Str"omgren photometry, expanding understanding of stellar population distributions in globular clusters.

## Key findings

- AGB stars in several clusters are not consistent with a single population.
- Str"omgren photometry effectively identifies multiple populations along the AGB.
- In NGC6752, only two AGB populations are present despite three in other evolutionary stages.

## Abstract

Spectroscopic studies have demonstrated that nearly all Galactic globular clusters (GCs) harbour multiple stellar populations with different chemical compositions. Moreover, colour-magnitude diagrams based exclusively on Str\"omgrem photometry have allowed us to identify and characterise multiple populations along the RGB of a large number of clusters. In this paper we show for the first time that Str\"omgren photometry is also very effcient at identifying multiple populations along the AGB, and demonstrate that the AGB of M3, M92, NGC362, NGC1851, and NGC6752 are not consistent with a single stellar population. We also provide a catalogue of RGB and AGB stars photometrically identified in these clusters for further spectroscopic follow-up studies.We combined photometry and elemental abundances from the literature for RGB and AGB stars in NGC6752 where the presence of multiple populations along the AGB has been widely debated. We find that, while the MS, SGB, and RGB host three stellar populations with different helium and light element abundances, only two populations of AGB stars are present in the cluster. These results are consistent with standard evolutionary theory.