Evolution of lithium in the disc of the Galaxy and the role of novae

TL;DR

This study investigates the sources of lithium in the Milky Way, finding that novae are likely the main contributors to lithium enrichment, while AGB stars are insufficient to explain observed abundances.

Contribution

It provides a comparative analysis of AGB stars and novae as lithium sources using advanced chemical evolution models and observational data.

Findings

AGB stars cannot account for meteoritic Li abundance.

Novae are promising Li producers consistent with observations.

Radial migration influences Li evolution across the Galaxy.

Abstract

Lithium plays a crucial role in probing stellar physics and stellar and primordial nucleosynthesis, as well as the chemical evolution of our Galaxy. Stars are considered to be the main source of Li, still the identity of its primary stellar producer has long been a matter of debate. In light of recent theoretical and observational results, we investigate in this study the role of two candidate sources of Li enrichment in the Milky Way, namely AGB stars and, in particular, novae. We utilize a one-zone Galactic chemical evolution model to assess the viability of AGB stars and novae as stellar sources of Li. We use recent theoretical Li yields for AGB stars, while for novae we adopt observationally inferred Li yields and recently derived Delay Time Distributions (DTDs). Subsequently, we extend our analysis using a multi-zone model with radial migration to investigate spatial variations in the evolution of Li across the Milky Way disc and compare the results with observational data for field stars and open clusters. Our analysis shows that AGB stars fail by far to reproduce the meteoritic Li abundance. In contrast, novae appear as promising candidates within the adopted framework, allowing us to quantify the contribution of each Li source at Sun's formation and today. Our multi-zone model reveals the role of the differences in the DTDs of SN Ia and novae in shaping the evolution of Li in the various galactic zones. Its results are in fair agreement with the observational data for most open clusters, but small discrepancies appear in the outer disc.