Shallow extra mixing in solar twins inferred from Be abundances

TL;DR

This study investigates the depletion of lithium and beryllium in solar twins across different ages, revealing that shallow extra mixing explains the observed abundance patterns.

Contribution

It provides new Be abundance measurements for solar twins and demonstrates that shallow mixing accounts for Li and Be depletion trends.

Findings

Be abundances show no significant variation with age

Li abundances decrease monotonically with age

Shallow extra mixing explains the observed abundance patterns

Abstract

Lithium and beryllium are destroyed at different temperatures in stellar interiors. As such, their relative abundances offer excellent probes of the nature and extent of mixing processes within and below the convection zone. We determine Be abundances for a sample of eight solar twins for which Li abundances have previously been determined. The analyzed solar twins span a very wide range of age, 0.5-8.2 Gyr, which enables us to study secular evolution of Li and Be depletion. We gathered high-quality UVES/VLT spectra and obtained Be abundances by spectral synthesis of the Be II 313 nm doublet. The derived beryllium abundances exhibit no significant variation with age. The more fragile Li, however, exhibits a monotonically decreasing abundance with increasing age. Therefore, relatively shallow extra mixing below the convection zone is necessary to simultaneously account for the observed Li and Be behavior in the Sun and solar twins.