High precision effective temperatures for 181 F-K dwarfs from line-depth ratios☆,☆☆

Line depth ratios measured on high resolution (R = 42 000), high S/N echelle spectra are used for the determination of precise effective temperatures of 181 F, G, K Main Sequence stars with about solar metallicity (- 0.5 < [Fe/H] < + 0.5). A set of 105 relations is obtained which rely T-eff on ratios of the strengths of lines with high and low excitation potentials, calibrated against previously published precise ( one per cent) temperature estimates. The application range of the calibrations is 4000 6150 K (F8V - K7V). The internal error of a single calibration is less than 100 K, while the combination of all calibrations for a spectrum of S/N = 100 reduces uncertainty to only 5 - 10 K, and for S/N = 200 or higher - to better than 5 K. The zero point of the temperature scale is directly defined from reflection spectra of the Sun with an uncertainty about 1 K. The application of this method to investigation of the planet host stars properties is discussed.