Viability of novae as sources of Galactic lithium

TL;DR

This study evaluates whether novae can explain the observed lithium abundance in the Milky Way, finding observationally-derived yields align well with proto-solar levels, unlike theoretical yields.

Contribution

It presents the most comprehensive galactic chemical evolution model incorporating nova Li yields, demonstrating observational data better explains lithium evolution than theoretical predictions.

Findings

Observationally-derived nova Li yields match proto-solar Li abundance.

Theoretical nova yields fail to reproduce proto-solar Li levels.

Uncertainties in Li yields are mainly due to observational scatter.

Abstract

Of all the light elements, the evolution of lithium (Li) in the Milky Way is perhaps the most difficult to explain. Li is difficult to synthesize and is easily destroyed, making most stellar sites unsuitable for producing Li in sufficient quantities to account for the proto-solar abundance. For decades, novae have been proposed as a potential explanation to this 'Galactic Li problem', and the recent detection of 7Be in the ejecta of multiple nova eruptions has breathed new life into this theory. In this work, we assess the viability of novae as dominant producers of Li in the Milky Way. We present the most comprehensive treatment of novae in a galactic chemical evolution code to date, testing theoretical- and observationally-derived nova Li yields by integrating metallicity-dependent nova ejecta profiles computed using the binary population synthesis code binary c with the galactic chemical evolution code OMEGA+. We find that our galactic chemical evolution models which use observationally-derived Li yields account for the proto-solar Li abundance very well, while models relying on theoretical nova yields cannot reproduce the proto-solar observation. A brief exploration of physical uncertainties including single-stellar yields, the metallicity resolution of our nova treatment, common-envelope physics, and nova accretion efficiencies indicates that this result is robust to physical assumptions. Scatter within the observationally-derived Li yields in novae is identified as the primary source of uncertainty, motivating further observations of 7Be in nova ejecta.