The Impact of Neutrino Magnetic Moments on the Evolution of the Helium Flash and Lithium-Rich Red Clump Stars

Abstract

The detection of the neutrino magnetic moment (NMM,$\mu_v$) is one of the most significant challenges in physics. The additional energy loss due to NMM can significantly influence the He flash evolution in low-mass stars. Using the MESA code, we investigated the impact of NMM on the He flash evolution in low-mass stars. We found that NMM leads to an increase in both the critical He core mass required for the He flash and the luminosity of TRGB. For a typical $Z = 1 Z_{\odot}$ , $M$ = 1.0 $M_{\odot}$, and $\mu_v = 3 \times 10^{-12} \mu_{\mathrm{B}}$ model, the He core mass increases by $\sim 5\%$, and the TRGB luminosity increases by $\sim 35\%$ compared to the model without NMM. However, contrary to previous conclusions, our model indicates that the He flash occurs earlier, rather than delayed, with increasing NMM values. This is because the additional energy loss from NMM accelerates the contraction of the He core, releases more gravitational energy that heats the H shell and increases the hydrogen burning rate, thereby causing the He core to reach the critical mass faster and advancing the He flash. An increase in NMM results in a higher peak luminosity for the first He flash, a more off-center ignition position, and sub-flashes with higher luminosities, shorter intervals, and higher frequency. We found that the internal gravity wave (IGW) mixing generated by the He flash can induce sufficient mixing in the radiative zone, turning the overshoot region into a low-Dmix bottleneck within the stellar interior. The increase in NMM in the model narrows the overshoot bottleneck region, enabling Li to enter the surface convection zone more quickly, thereby enhancing the enrichment effect of IGW mixing on surface Li. For models incorporating both NMM and IGW mixing, the reduction in the overshoot bottleneck region allows them to effectively produce super Li-rich red clump star samples.