The puzzling origin of the 6Li plateau

TL;DR

This paper investigates the origin of the 6Li plateau in metal-poor halo stars, finding that standard cosmic ray spallation models tied to star formation cannot explain its level or flatness, suggesting alternative early mechanisms.

Contribution

It demonstrates that existing cosmic ray spallation models linked to star formation cannot reproduce the observed 6Li plateau, implying the need for alternative explanations.

Findings

Standard models fail to reproduce the 6Li abundance level.

The 6Li plateau's flatness is inconsistent with cosmic ray spallation tied to star formation.

An alternative early mechanism may be responsible for the 6Li plateau.

Abstract

We discuss the 6Li abundance evolution within a hierarchical model of Galaxy formation which correctly reproduces the [Fe/H] distribution of metal-poor halo stars. Contrary to previous findings, we find that neither the level (6Li/H=6x10^-12) nor the flatness of the 6Li distribution with [Fe/H] can be reproduced under the most favourable conditions by any model in which 6Li production is tied to a (data-constrained) Galactic star formation rate via cosmic ray spallation. Thus, the origin of the plateau might be due to some other early mechanism unrelated to star formation.