English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

The abundance of fluorine in a few Galactic globular clusters is known tostrongly vary from star-to-star. These unexpected chemical properties are anadditional confirmation of the chemical inhomogeneities already found inseveral GC, and probably caused by the first generations of stars formed inthese systems. The aim of this article is to complement our understanding ofthe F-behaviour in GC stars and to look for new constraints on the formationhistories of their multiple stellar populations. We have collected near-IRspectra of 15 RGB stars belonging to GC spanning a wide range of metallicity:47 Tuc, M4, NGC6397 and M30. F, Na and Fe abundances have been estimated byspectral synthesis. No anticorrelation between F and Na abundances are foundfor the most metal-rich cluster of the sample (47 Tuc). In this GC, RGB starsindeed exhibit rather small differences in [F/Fe] unlike the larger ones foundfor the [Na/Fe] ratios. This reveals a rather inhomogeneous stellar system anda complex chemical evolution history for 47 Tuc . In M4, one star of our studyconfirms the previous Na-F distribution reported by another group in 2005. Forthe two very metal-poor GC (NGC6397 and M30), only upper limits of F abundanceshave been derived. We show that F abundances could be estimated in suchmetal-poor GC with current telescopes and spectrographs only if unexpectedF-rich giants are found and/or exceptional observational conditions are met.The distribution of the F and Na abundances in GC reveal that their RGB membersseem to belong to two well-separated regions. All the RGB stars analysed so farin the different GC are indeed found to be either F-rich Na-poor or F-poorNa-rich. Such well-separated bimodal regimes are consistent with the separateformation episodes suspected in most galactic GC.

Fluorine abundances and the puzzle of globular cluster chemical history