The light elements in the light of 3D and non-LTE effects

TL;DR

This review examines how 3D hydrodynamical models and non-LTE line formation codes improve the accuracy of light element abundance analyses in late-type stars, highlighting their impact on astrophysical interpretations especially at low metallicities.

Contribution

It provides a comprehensive overview of the effects of 3D and non-LTE modeling on light element abundance determinations, emphasizing recent advances and remaining challenges.

Findings

3D and non-LTE effects can significantly alter abundance estimates

The near-cancellation of effects stabilizes 7Li abundance results

Beryllium shows minor non-LTE corrections, while Boron is more sensitive

Abstract

In this review we discuss possible systematic errors inherent in classical 1D LTE abundance analyses of late-type stars for the light elements (here: H, He, Li, Be and B). The advent of realistic 3D hydrodynamical model atmospheres and the availability of non-LTE line formation codes place the stellar analyses on a much firmer footing and indeed drastically modify the astrophysical interpretations in many cases, especially at low metallicities. For the Teff-sensitive hydrogen lines both stellar granulation and non-LTE are likely important but the combination of the two has not yet been fully explored. A fortuitous near-cancellation of significant but opposite 3D and non-LTE effects leaves the derived 7Li abundances largely unaffected but new atomic collisional data should be taken into account. We also discuss the impact on 3D non-LTE line formation on the estimated lithium isotopic abundances in halo stars in light of recent claims that convective line asymmetries can mimic the presence of 6Li. While Be only have relatively minor non-LTE abundance corrections, B is sensitive even if the latest calculations imply smaller non-LTE effects than previously thought.