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

Abstract

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.

10 pages, 6 figures; replaced with version accepted in ApJ

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Cited by in corpus (10)

• Search for lithium-rich giants in 32 open clusters with high-resolution spectroscopy
• A close-in giant planet escapes engulfment by its star
• Many Roads Lead to Lithium: Formation Pathways For Lithium-Rich Red Giants
• Evidence of extra-mixing in field giants as traced by lithium and carbon isotope ratio
• Lithium abundances in giants as a function of stellar mass: An evidence for He-flash as the source of Li enhancement in low mass giants
• Are Lithium-Rich Giants Binaries? A Radial Velocity Variability Analysis of 1,400 Giants
• Distribution and evolution of Li abundance in red clump stars can be explained by the internal gravity waves
• Convective Mixing: The Formation Channel of Li-rich Giants
• Angular momentum and lithium transport from main sequence to sub-giant and red giant low-mass stars
• Discovery of a Metal-Poor Red Giant Star with the Highest Ultra-Lithium Enhancement