A non-LTE study of silicon abundances in giant stars from the Si I infrared lines in the zJ-band

TL;DR

This study evaluates the use of Si I infrared lines for determining silicon abundances in giant stars, emphasizing the importance of non-LTE corrections for accurate results.

Contribution

It demonstrates that non-LTE analysis significantly improves the reliability of silicon abundance measurements from IR lines in giant stars.

Findings

Non-LTE corrections reduce line-to-line scatter.

Si I IR lines are reliable abundance indicators with proper non-LTE treatment.

Average non-LTE correction for [Si/Fe] is about -0.35 dex.

Abstract

We investigate the feasibility of the Si I infrared (IR) lines as Si abundance indicators for giant stars. We find that Si abundances obtained from the Si I IR lines based on the local thermodynamic equilibrium (LTE) analysis show large line-to-line scatter (mean value of 0.13dex), and are higher than those from the optical lines. However, when the non-LTE effects are taken into account, the line-to-line scatter reduces significantly (mean value of 0.06dex), and the Si abundances are consistent with those from the optical lines. The typical average non-LTE correction of [Si/Fe] for our sample stars is about $-$0.35dex. Our results demonstrate that the Si I IR lines could be reliable abundance indicators provided that the non-LTE effects are properly taken into account.