Francesca Primas (ESO, Garching)

Sodium abundances in GC AGB stars: what do they tell us?
When Apr 21, 2016 from 02:30 PM to 03:30 PM
What
  • Colloquium
Where SH Lecture Hall
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Both photometry and spectroscopy have clearly shown that most, if not all, Galactic globular clusters host at least two (likely more) stellar populations, which are characterized by specific chemical features. One of the most documented ones is the anti-correlation observed between sodium (Na) and oxygen (O), which implies the existence of at least a first (Na-poor, O-rich) and second (Na-rich, O-poor) stellar populations, co-existing in the same cluster. Although these features differ among the globular clusters, they have been detected at all evolutionary stages from the Main Sequence/Turn–Off up to the tip of the Red Giant Branch. The only stage at which contrasting results have been reported in the literature is the Asymptotic Giant Branch. Understanding this is key to our attempts to identify the nature of the polluters.

 

I will present the results of a new spectroscopic analysis of Na abundances in globular clusters. Our focus is on the comparison of the Na distributions in Asymptotic vs Red Giant Branch stars, in order to verify the presence or lack thereof of Na-rich (second population) stars on the AGB and how they compare to the RGB phase. Our results will be discussed in light of different theoretical predictions.