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 .