Ba stars and other binaries in first and second generation stars in globular clusters

Valentina D'Orazi*, Raffaele Gratton, Sara Lucatello, Eugenio Carretta, Angela Bragaglia, Anna F. Marino

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

70 Citations (Scopus)


The determination of the Ba abundance in globular cluster (GC) stars is a very powerful test to address several issues in the framework of multiple population scenarios. We measured the Ba content for a sample of more than 1200 stars in 15 Galactic GCs, using high-resolution FLAMES/Giraffe spectra. We found no variation in [Ba/Fe] ratios for different stellar populations within each cluster; this means that low-mass asymptotic giant branch stars do not significantly contribute to the intracluster pollution. Very interestingly, we found that the fraction of Ba stars in first generation (FG) stars is close to the values derived for field stars (∼2%); on the other hand, second generation (SG) stars present a significantly lower fraction. An independent and successful test, based on radial velocity variations among giant stars in NGC 6121, confirms our finding: the binary fraction among FG stars is about ∼12%, to be compared with ∼1% of SG stars. This is an evidence that SG stars formed in a denser environment, where infant mortality of binary systems was particularly efficient.

Original languageEnglish
Pages (from-to)L213-L217
Number of pages5
JournalAstrophysical Journal Letters
Issue number2
Publication statusPublished - 20 Aug 2010
Externally publishedYes


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