Examination of the mass-dependent Li depletion hypothesis by the Li abundances of the very metal-poor double-lined spectroscopic binary G166-45

TL;DR

This study measures lithium abundances in a very metal-poor binary star system to test the mass-dependent Li depletion hypothesis, finding minimal depletion at certain temperatures and metallicities, thus refining our understanding of stellar Li evolution.

Contribution

It provides the first detailed Li abundance measurements for both components of G166-45, offering new insights into Li depletion at low metallicities and temperatures.

Findings

Li abundance of primary matches the Spite plateau.

Secondary's Li abundance is slightly lower, indicating minimal depletion.

Li depletion is not significant at Teff ~ 5800K for -2.5 metallicity.

Abstract

The Li abundances of the two components of the very metal-poor ([Fe/H]=-2.5) double-lined spectroscopic binary G166-45 (BD+26 2606) are determined separately based on high resolution spectra obtained with the Subaru Telescope High Dispersion Spectrograph and its image slicer. From the photometric colors and the mass ratio the effective temperatures of the primary and secondary components are estimated to be 6350+/-100K and 5830+/-170K, respectively. The Li abundance of the primary (A(Li)=2.23) agrees well with the Spite plateau value, while that of the secondary is slightly lower (A(Li)=2.11). Such a discrepancy of the Li abundances between the two components is previously found in the extremely metal-poor, double-lined spectroscopic binary CS22876-032, however, the discrepancy in G166-45 is much smaller. The results agree with the trends found for Li abundance as a function of effective temperature (and of stellar mass) of main-sequence stars with -3.0<[Fe/H]<-2.0, suggesting that the depletion of Li at Teff ~ 5800K is not particularly large in this metallicity range. The significant Li depletion found in CS22876-032B is a phenomenon only found in the lowest metallicity range ([Fe/H]<-3).