Asteroseismology of Red Giants: Discovering the Origins of Li-rich Giants

Le résumé fourni par la source

Lithium is a sensitive element commonly used to trace the internal structure of stars and is expected to dramatically decrease as stars evolve up the red giant branch. The actual distribution of lithium abundances on the red giant branch, including the so-called lithium-rich giants, have therefore long been a challenge to explain with standard evolution models. For 99% of red giants, the observed surface lithium abundance is A(Li) < 1.5 dex, but for almost 1% of RGB stars we observe higher abundances. Confirming masses can be used to separate the different mechanisms for lithium enrichment. Suggesting that large, homogeneous samples of asteroseismically characterized stars are likely to help illuminate the true origin of the Li-rich red giants. In order to characterize the masses, evolutionary states, and therefore the evolutionary history of these lithium-rich giants compared to other stars in the field, we use a tool that will work for large samples. Using TESS asteroseismology for a simply selected sample of 15,016 stars with lithium abundances from GALAH, we are able to confirm previous indications that over 95% of lithium rich red giants are in the clump phase. Most lithium rich stars are in the clump, with many indications that they are likely related to stellar binarity, but the rate is not high enough and trends are not steep enough for this relationship to be simple.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.