COOPERATIVE OBSERVATIONS OF THE FLARE RED DWARF STAR EV-LAC IN 1990

Results of photometrical monitoring of EV Lac in August 1990 are given , its mean level of flare activity is estimated. Colourimetrical analy sis of registered powerful flares leads to the conclusion thal near fl are maxima the emission of flares can be represented by a short-lived blackbody radiation and radiation of a hydrogen plasma of some optical thickness al the Balmer continuum frequencies. Parameters of stellar spottedness are found: the differential spottedness of the dark and br ight hemispheres is about 7% and a temperature difference between star spots and the normal photosphere is about 300 K. During 3 powerful fla res, noticeable variations of the H(alpha) profile are found, and smal l differences in decay rates of the H(beta), H(gamma) and H(delta) emi ssions are suggested at the end of the flare of 29.VIII.90 UT 2339. Ra dio monitoring in the decimeter wavelength range did not detect radio flares.