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

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