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

Regions of rapid variation in the internal structure of a star are oftenreferred to as acoustic glitches since they create a characteristic periodicsignature in the frequencies of p modes. Here we examine the localizeddisturbance arising from the helium second ionization zone in red giant branchand clump stars. More specifically, we determine how accurately and preciselythe parameters of the ionization zone can be obtained from the oscillationfrequencies of stellar models. We use models produced by three differentgeneration codes that not only cover a wide range of stages of evolution alongthe red giant phase but also incorporate different initial helium abundances.We discuss the conditions under which such fits robustly and accuratelydetermine the acoustic radius of the second ionization zone of helium. Thedetermined radii of the ionization zones as inferred from the mode frequencieswere found to be coincident with the local maximum in the first adiabaticexponent described by the models, which is associated with the outer edge ofthe second ionization zone of helium. Finally, we consider whether this methodcan be used to distinguish stars with different helium abundances. Although adefinite trend in the amplitude of the signal is observed any distinction wouldbe difficult unless the stars come from populations with vastly differenthelium abundances or the uncertainties associated with the fitted parameterscan be reduced. However, application of our methodology could be useful fordistinguishing between different populations of red giant stars in globularclusters, where distinct populations with very different helium abundances havebeen observed.

Prospects for asteroseismic inference on the envelope helium abundance in red giant stars