Lithium abundances in CEMP stars

TL;DR

This study investigates lithium abundances in a sample of metal-poor CEMP stars, revealing that some can retain the Li-Spite plateau while others show unexplained depletion, possibly linked to stellar rotation.

Contribution

It demonstrates that dilution can explain Li retention in some CEMP stars and introduces a new spectral analysis technique for binary star parameters.

Findings

Li abundance varies among CEMP stars, with some maintaining the Spite plateau.

Evidence suggests rotation may influence Li depletion in certain stars.

A new spectral method estimates stellar parameters without evolutionary models.

Abstract

Carbon-enhanced metal-poor (CEMP) stars are believed to show the chemical imprints of more massive stars (M > 0.8 Msun) that are now extinct. In particular, it is expected that the observed abundance of Li should deviate in these stars from the standard Spite lithium plateau. We study here a sample of 11 metal-poor stars and a double-lined spectroscopic binary with -1.8 <[Fe/H]< -3.3 observed with VLT/UVES spectrograph. Among these 12 metal-poor stars, there are 8 CEMP stars for which we measure or constrain the Li abundance. In contrast to previous arguments, we demonstrate that an appropriate regime of dilution permits the existence of "Li-Spite plateau and C-rich" stars, whereas some of the "Li-depleted and C-rich" stars call for an unidentified additional depletion mechanism that cannot be explained by dilution alone. We find evidence that rotation is related to the Li depletion in some CEMP stars. Additionally, we report on a newly recognized double-lined spectroscopic binary star in our sample. For this star, we develop a new technique from which estimates of stellar parameters and luminosity ratios can be derived based on a high-resolution spectrum alone, without the need for input from evolutionary models.