High-precision effective temperatures of 161 FGK supergiants from line-depth ratios

Precise effective temperatures (T-eff) are determined for 161 FGK supergiants using method of line-depth ratios. We obtain a set of 131 relations for temperatures of supergiants as a function of line depths. These relations have been calibrated against previously published accurate temperature estimates. The application range of the method is 3600-7800 K (F0I-K5I). The internal error of a single calibration is less than 110 K, while combination of all calibrations reduces uncertainty to only 5-30 K (standard error). The error in the zero-point is estimated to be less than 100-200 K. A significant advantage of the line ratio method is its independence of the interstellar reddening, and only modest sensitivity to abundance, macroturbulence, rotation and other factors.