Lithium on the surface of cool magnetic CP stars I. Summary of spectroscopic observations with three telescopes

We present new results of observations of the 6708 Angstrom line in twelve CP stars made with three telescopes: the ESO CAT telescope, the Crimean Obs ervatory (CrAO) 2.6-m telescope, and the Nordic Optical Telescope (NOT). Un ique profile and wavelength variations of the line at 6708 Angstrom were di scovered in two stars, HD 60435 and HD 83368. We present arguments in favou r of the identification of this feature with the resonant Li I line. Accord ing to the incidence and variability of this line, spectra of twelve stars were divided in four groups: Group 1 - the line is remarkably variable in i ntensity and wavelength; this group includes the stars HD 83386 and HD 6043 5; Group 2 - the line is variable to a lesser extent; includes beta CrB, an d HD 188041; Group 3 - the line is not variable; includes 33 Lib, HD 134214 , HD 166473 and gamma Equ; Group 4 - the line is not present; includes HD 4 2659, HD 80316, HD 118022 and HD 128898. The behaviour in Groups 1-3 can be explained by the existence of Li rich spots on the star's surface using th e oblique rotator model with different inclination and magnetic obliquity f or each star. For HD 83368 we have found a tight correlation between the vi sibility of the spots and the orientation of the dipole pulsation mode.