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Silicon and Strontium are key elements to explore the nucleosynthesis andchemical evolution of the Galaxy by measurements of very metal-poor stars.There are, however, only a few useful spectral lines of these elements in theoptical range that are measurable for such low-metallicity stars. Here wereport on abundances of these two elements determined from near-infraredhigh-resolution spectra obtained with the Subaru Telescope Infrared Dopplerinstrument (IRD). Si abundances are determined for as many as 26 Si lines forsix very and extremely metal-poor stars (-4.0<[Fe/H]<-1.5), which significantlyimproves the reliability of the abundance measurements. All six stars,including three carbon-enhanced objects, show over-abundances of Si([Si/Fe]~+0.5). Two stars with [Fe/H]~-1.5 have relatively smallover-abundances. The [Mg/Si] ratios agree with the solar value, except for onemetal-poor star with carbon excess. Strontium abundances are determined fromthe triplet lines for four stars, including two for the first time. Theconsistency of the Sr abundances determined from near-infrared and opticalspectra require further examination from additional observations.

Silicon and Strontium abundances of very metal-poor stars determined from near-infrared spectra