Novae: An Important Source of Lithium in the Galaxy

The source of the Galactic lithium (Li) has long been a puzzle. With the discovery of Li in novae, extensive research has been conducted. However, there still exists a significant disparity between the observed abundance of Li in novae and the existing theoretical predictions. Using the Modules for Experiments in Stellar Astrophysics, we simulate the evolution of novae with element diffusion and appropriately increase the amount of ³He in the mixtures. Element diffusion enhances the transport efficiency between the nuclear reaction zone and the convective region on the surface of the white dwarf (WD) during nova eruptions, which results in more ⁷Be being transmitted to the WD surface and ultimately ejected. Compared to the previous predictions, the abundance of ⁷Be in novae simulated in our model significantly increases. The result is able to explain almost all observed novae. Using the method of population synthesis, we calculate Li yield in the Galaxy. We find that the Galactic occurrence rate of novae is about 130 yr^‑1, and about 110 M _⊙ Li produced by nova eruption is ejected into the interstellar medium (ISM). About 73% of Li in the Galactic ISM originates from novae and approximately 15%–20% of the entire Galaxy. This means that novae are the important source of Li in the Galaxy.