Enhancement of Lithium in Red Clump Stars by the Additional Energy Loss Induced by New Physics

TL;DR

This paper investigates how new physics introducing additional energy loss channels can explain the unexpectedly high lithium abundances in red clump stars, which standard stellar evolution models cannot account for.

Contribution

It proposes a novel mechanism where additional energy loss enhances 7Be production, leading to increased lithium in red clump stars, reconciling observations with theory.

Findings

Additional energy loss channels increase 7Be production.

Thermohaline mixing becomes more efficient with extra energy loss.

Heavier helium cores form due to enhanced mixing.

Abstract

Since 7Li 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 which 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 7Be production by the Cameron-Fowler mechanism, but the resultant 7Li abundance is much lower than the observed values. We find that the production of 7Be becomes more active if there are additional energy loss channels, because themohaline mixing becomes more efficient and a heavier helium core is formed.