Origin of the discrepancy in the age–[Si/Fe] slope between near-infrared and optical analyses

Determine the cause of the discrepancy between the nearly flat age–[Si/Fe] slope measured from near-infrared YJ-band spectra of 46 solar analogs observed with the WINERED spectrograph at R≈28,000 and the moderately positive age–[Si/Fe] slope reported by Bedell et al. (2018) from high-precision optical spectra; ascertain whether differences in the adopted silicon line lists or systematic effects specific to optical versus near-infrared abundance analyses are responsible for this discrepancy.

Background

This study derives age–[X/Fe] relations for elements measured in near-infrared YJ-band spectra of solar analogs and compares the slopes to those obtained from optical analyses, notably Bedell et al. (2018). For most elements, the slopes agree within uncertainties.

Silicon is a notable exception: the near-infrared analysis yields a nearly flat age–[Si/Fe] trend, whereas the optical study reported a moderately positive slope. The authors highlight that the origin of this difference is not yet resolved and suggest it may stem from differences in the line lists or systematics intrinsic to optical versus near-infrared methods, motivating a targeted investigation to reconcile the two abundance scales.