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 Tools annual

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 monthly

Global: Zendy Plus monthly

Presents the access of premium content as premium feature

Premium Content

Global: Zendy Plus annual

Global: Zendy Free Plan

Galactic Globular clusters (GCs) are now known to harbour multiple stellarpopulations, which are chemically distinct in many light element abundances. Itis becoming increasingly clear that asymptotic giant branch (AGB) stars in GCsshow different abundance distributions in light elements compared to those inthe red giant branch (RGB) and other phases, skewing toward more primordial,field-star-like abundances, which we refer to as subpopulation one (SP1). Aspart of a larger program targeting giants in GCs, we obtained high-resolutionspectra for a sample of 106 RGB and 15 AGB stars in Messier 4 (NGC 6121) usingthe 2dF+HERMES facility on the Anglo-Australian Telescope. In this Letter wereport an extreme paucity of AGB stars with [Na/O] > -0.17 in M4, whichcontrasts with the RGB that has abundances up to [Na/O] =0.55. The AGBabundance distribution is consistent with all AGB stars being from SP1. Thisresult appears to imply that all subpopulation two stars (SP2; Na-rich, O-poor)avoid the AGB phase. This is an unexpected result given M4's horizontal branchmorphology -- it does not have an extended blue horizontal branch. This is thefirst abundance study to be performed utilising the HERMES spectrograph.

An extreme paucity of second population AGB stars in the normal globular cluster M4