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 Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

We derive age constraints for 1639 red giants in the APOKASC sample for whichseismic parameters from Kepler, as well as effective temperatures,metallicities and [alpha/Fe] values from APOGEE DR12 are available. Weinvestigate the relation between age and chemical abundances for these stars,using a simple and robust approach to obtain ages. We first derive stellarmasses using standard seismic scaling relations, then determine the maximumpossible age for each star as function of its mass and metallicity,independently of its evolutionary stage. While the overall trend betweenmaximum age and chemical abundances is a declining fraction of young stars withincreasing [alpha/Fe], at least 14 out of 241 stars with [alpha/Fe]>0.13 areyounger than 6 Gyr. Five stars with [alpha/Fe]>0.2 have ages below 4 Gyr. Weexamine the effect of modifications in the standard seismic scaling relations,as well as the effect of very low helium fractions, but these changes are notenough to make these stars as old as usually expected for alpha-rich stars(i.e., ages greater than 8-9 Gyr). Such unusual alpha-rich young stars havealso been detected by other surveys, but defy simple explanations in a galaxyevolution context.

Young alpha-enriched giant stars in the solar neighbourhood