Observational signatures of lithium depletion in the metal-poor globular cluster NGC6397

TL;DR

This study investigates lithium depletion in metal-poor stars within the globular cluster NGC6397, providing observational evidence that supports the stellar surface depletion hypothesis as a solution to the cosmological lithium problem.

Contribution

It offers a detailed analysis of lithium abundances in over 450 stars, highlighting the effects of cluster self-enrichment and temperature uncertainties on lithium depletion interpretations.

Findings

Evidence for lithium depletion in cluster stars

Impact of self-enrichment on lithium measurements

Systematic uncertainties affect abundance interpretations

Abstract

The "stellar" solution to the cosmological lithium problem proposes that surface depletion of lithium in low-mass, metal-poor stars can reconcile the lower abundances found for Galactic halo stars with the primordial prediction. Globular clusters are ideal environments for studies of the surface evolution of lithium, with large number statistics possible to obtain for main sequence stars as well as giants. We discuss the Li abundances measured for >450 stars in the globular cluster NGC6397, focusing on the evidence for lithium depletion and especially highlighting how the inferred abundances and interpretations are affected by early cluster self-enrichment and systematic uncertainties in the effective temperature determination.