Enhancement of lithium in red clump stars by the additional energy loss induced by new physics

Y Since Li-7 is easily destroyed in low temperatures, the surface lithium abundance decreases as stars evolve. This is supported by the lithium depletion observed in the atmosphere of most red giants. However, recent studies show that almost all of red clump stars have high lithium abundances A(Li) > -0.9, which are not predicted by the standard theory of the low-mass stellar evolution. In order to reconcile the discrepancy between the observations and the model, we consider additional energy loss channels that may come from physics beyond the Standard Model. A(Li) slightly increases near the tip of the red giant branch even in the standard model with thermohaline mixing because of the Be-7 production by the Cameron-Fowler mechanism, but the resultant Li-7 abundance is much lower than the observed values. We find that the production of Be-7 becomes more active if there are additional energy loss channels, because themohaline mixing becomes more efficient and a heavier helium core is formed.

Automated summary

Recent studies have found that most red giants show a decrease in surface lithium abundance as stars evolve, but red clump stars have unexpectedly high lithium abundances. To explain this discrepancy, additional energy loss channels beyond the Standard Model are considered, affecting the production of Be-7 and leading to higher lithium abundances in certain stars.