Beryllium abundances along the evolutionary sequence of the open cluster IC 4651

TL;DR

This study measures beryllium abundances in stars of the open cluster IC 4651 to understand stellar mixing processes, revealing that Be and Li depletions occur earlier than classical models predict, with hydrodynamical models providing good explanations.

Contribution

It provides the first comprehensive Be abundance analysis along the entire evolutionary sequence of IC 4651, comparing observations with advanced hydrodynamical models.

Findings

Be and Li dips are correlated in the cluster stars.

Be dilution begins earlier in the Hertzsprung gap than classical models suggest.

Hydrodynamical models successfully reproduce observed abundance patterns.

Abstract

The simultaneous investigation of Li and Be in stars is a powerful tool in the study of the evolutionary mixing processes. Here, we present beryllium abundances in stars along the whole evolutionary sequence of the open cluster IC 4651. This cluster has a metallicity of [Fe/H] = +0.11 and an age of 1.2 or 1.7 Gyr. Abundances have been determined from high-resolution, high signal-to-noise UVES spectra using spectrum synthesis and model atmospheres. Lithium abundances for the same stars were determined in a previous work. Confirming previous results, we find that the Li dip is also a Be dip. For post-main-sequence stars, the Be dilution starts earlier within the Hertzsprung gap than expected from classical predictions, as does the Li dilution. Theoretical hydrodynamical models are able to reproduce well all the observed features.