  The ratio of the depths of spectral lines is a powerful indicator of the
effective temperature. The method based on this analysis is capable of
discerning small temperature variations of individual stars.
  We apply this spectroscopic data analysis to three type of stars, namely an
RS CVn type binary system, a young solar-type star and a Cepheid variable. We
show that individual LDRs converted into temperature through calibration
relations lead to rotational and pulsational modulation of the average surface
temperature with amplitudes of 127 K, 48 K and 1466 K in the three types of
stars, with average estimated errors of some tens Kelvin degrees.
