2019MNRAS.484.4619G

We present here new medium resolution spectra (λ/Δλ ∼ 1200) of K-M giants covering wavelength ranges 1.50-1.80 and 1.95-2.45 µm. The sample includes 72 K0-M8 giants from our TIRSPEC observations and all available 35 giants in that spectral range from archival IRTF spectral library. We have calibrated here the empirical relations between fundamental parameters (e.g. effective temperature and surface gravity) and equivalent widths of some important spectral features like Si I, Na I, Ca I, and ¹²CO. We find that the ¹²CO first-overtone band at 2.29 µm and second-overtone band at 1.62 µm are a reasonably good indicator of temperature above 3400 K and surface gravity. We show that the dispersion of empirical relations between ¹²CO and T_eff significantly improves considering the effect of surface gravity.