Derivation of Stellar Abundances with Near-Infrared Spectra: The Case of Metallic Standard Stars

Previous studies show that the abundances of stars increase on average towards the inner part of the Galactic disk. Among obscured stars in the inner Galaxy, Cepheid variable stars are of particular interest, because we can measure their distances using the period-luminosity relation. With their locations identified, Cepheids are useful to investigate chemical properties of stellar populations across the disk. The severe foreground reddening for stars in the inner Galaxy requires observations in the infrared rather than in the optical, but almost no one has done high-resolution spectroscopy of Cepheids in the near infrared. We obtained H-band spectra of Cepheids in the Galactic Center using SUBARLARCS (R=20,000, lambda = 14600 similar to 17900 angstrom). We also observed calibrating stars, including Cepheids and normal stars, whose metallicities are well determined. Here we report our analysis on the spectra of K-type standard stars to establish our method of measuring abundances with H-band spectra. We use SPTOOL based on ATLAS9 to calculate atmospheric models and synthesize spectra. We found that synthesized model spectra reasonably fit with observational data and the metallicifies of the K-1ype stars we obtained agree well with the values in literatures.