Origin of strong lithium enhancement in metal-poor halo stars of the sample

Identify the astrophysical mechanism responsible for the observed strong lithium enhancement in the three metal-poor ([Fe/H] ≈ −1.5) halo main-sequence stars within the Gaia DR3 neutron-star binary candidate sample, and determine whether scenarios such as accretion of Li-rich winds from super-AGB stars, supernova-ejecta pollution, or spallation can quantitatively account for the measured A(Li) values given the stars’ convective envelope masses and evolutionary histories.

Background

Three of the candidates on halo-like orbits are metal-poor and show exceptionally strong Li I λ6708 lines, corresponding to A(Li) ≈ 2.9–3.5, well above typical values for stars with similar parameters. The thin convective envelopes at low metallicity imply that modest accretion can produce large surface enhancements.

The authors discuss several plausible mechanisms (hot-bottom-burning winds from super-AGB stars, supernova ejecta, and spallation) but emphasize that the physical origin of the lithium overabundance in these specific systems is not yet established.