S316p.114 — Are Galactic globular cluster AGB stars rich or poor in Sodium?

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Aug 10th at 6:00 PM until 7:30 PM




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Author(s): Yue Wang1, Francesca Primas1, Corinne Charbonnel2, William Chantereau2

Institution(s): 1. European Southern Observatory, 2. University of Geneva

In recent years, multiple stellar populations have been identified in Galactic globular clusters (GCs),
with different scenarios being debated for their origin (e.g., the AGB and the Fast Rotating Massive Stars scenario, which are the most developed in the literature). These populations are currently identified thanks to their chemical properties. In particular stars with sodium overabundances have been found at different evolution stages, from the main sequence turnoff up to the tip of the red giant branch. Surprisingly however, no sodium-rich AGB stars has been found in NGC 6752. This apparent difficulty for stellar evolution could be relieved within the FRMS scenario, which predicts that above a certain cutoff in initial helium and sodium content, stars do miss the AGB.
Here we present the results of the chemical analysis of our new AGB star samples observed at the ESO/VLT with FLAMES in three GCs that span a large range in metallicity. Our aim is to investigate which kind of GCs host Na-rich second-generation AGB stars, and to probe the FRMS scenario. We compare the results with theoretical evolution features based on the FRMS model at various metallicities. This study provides a new and original insight onto the GC pollution scenarios.