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

Recent work, based on data from the Hubble Space Telescope (HST) UV LegacySurvey of Galactic Globular Clusters (GCs), has revealed that all the analyzedclusters host two groups of first- (1G) and second-generation (2G) stars. Inmost GCs, both 1G and 2G stars host sub-stellar populations with differentchemical composition. We compare multi-wavelength HST photometry with syntheticspectra to determine for the first time the average helium difference betweenthe 2G and 1G stars in a large sample of 57 GCs and the maximum heliumvariation within each of them. We find that in all clusters 2G stars areconsistent with being enhanced in helium with respect to 1G. The maximum heliumvariation ranges from less than 0.01 to more than 0.10 in helium mass fractionand correlates with both the cluster mass and the color extension of thehorizontal branch (HB). These findings demonstrate that the internal heliumvariation is one of the main (second) parameters governing the HB morphology.

The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XVI. The helium abundance of multiple populations