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

Multiple stellar populations in globular clusters (GCs) are distinct by theirdifferent abundances of light elements. The abundance anti-correlations pointtowards a nucleosynthesis origin due to high-temperature H burning, but itremains to be assessed which type of stars altered primordial abundances inGCs. In particular, the regime at very high temperature that shapes thevariations in potassium as well as calcium and scandium, which has beendetected in a few notable cases such as NGC 2419 and NGC 2808, is still poorlyexplored. We started a systematic search for excess of Ca (and Sc) in GC starswith respect to the level of unmodified field stars. Statistically robustevidence of such excess was found in a small number of GCs (NGC 4833, NGC 6715,NGC 6402, NGC 5296, NGC 5824, and NGC 5139/omega Centauri) that join thepreviously known two clusters. For the first time we show that NGC 4833 islikely to host anti-correlated K and Mg abundances. All these GCs are among themost massive ones in the Galaxy. We found that the fraction of stars with Caenhancement at 3sigma above the field star distribution is a multivariatefunction of the GC mass and metallicity, as in other manifestations of themultiple population phenomenon in GCs. We argue that these alterations in onlya few GCs can be reproduced by two different channels: either a class ofordinary stars, that is common to all GCs, acts only in particularenvironments, or an on-off mechanism is generated by the occurrence of apeculiar type of stars (or lack of such stars). Hot bottom burning inasymptotic giant branch stars in the low-metallicity regime is a good candidatefor the first class. Alternatively, a metallicity dependence is also expectedfor supermassive stars, which are predicted to preferentially form in massiveGCs. (abridged).

Excess of Ca (and Sc) produced in globular cluster multiple populations: a first census in 77 Galactic globular clusters