Mass Matters: No Evidence for Ubiquitous Lithium Production in Low-mass Clump Giants

Known sources of lithium (Li) in the universe include the Big Bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. During their longer-lived evolutionary phases, stars are not expected to add to the Li budget of the Galaxy, but to largely deplete it. In this context, recent analyse...

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Published in:The Astrophysical journal 2022-07, Vol.933 (1), p.58
Main Authors: Chanamé, Julio, Pinsonneault, Marc H., Aguilera-Gómez, Claudia, Zinn, Joel C.
Format: Article
Language:English
Subjects:
Abundance
Asteroseismology
Astronomical models
Astrophysics
Asymptotic giant branch stars
Big bang cosmology
Chemical abundances
Cosmic rays
Cosmology
Evolved stars
Galaxies
Helium
Lithium
Low mass stars
Novae
Red giant clump
Red giant stars
Sky surveys
Spallation
Stellar evolution
Stellar interiors
Stellar populations
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Summary:Known sources of lithium (Li) in the universe include the Big Bang, novae, asymptotic giant branch stars, and cosmic-ray spallation. During their longer-lived evolutionary phases, stars are not expected to add to the Li budget of the Galaxy, but to largely deplete it. In this context, recent analyses of Li data from GALAH and LAMOST for field red clump (RC) stars have concluded that there is the need for a new production channel of Li, ubiquitous among low-mass stars, and that would be triggered on the upper red giant branch (RGB) or at helium ignition. This is distinct from the Li-rich giant problem and reflects bulk RC star properties. We provide an analysis of the GALAH Li data that accounts for the distribution of progenitor masses of field RC stars observed today. Such progenitors are different than today’s field RGB stars. Using standard post-main-sequence stellar evolution, we show that the distribution of Li among field RC giants as observed by GALAH is consistent with standard model predictions, and does not require new Li production mechanisms. Our model predicts a large fraction of very low Li abundances from low-mass progenitors, with higher abundances from higher mass ones. Moreover, there should be a large number of upper limits for RC giants, and higher abundances should correspond to higher masses. The most recent GALAH data indeed confirm the presence of large numbers of upper limits, and a much lower mean Li abundance in RC stars, in concordance with our interpretation.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac70c8