COMMISSION 27 OF THE I. A. U.
                INFORMATION BULLETIN ON VARIABLE STARS
                            Number 3550

                                                   Konkoly Observatory
                                                   Budapest
                                                   2 January 1991

                                                   HU ISSN 0374 - 0676


   SIMULTANEOUS TWO-COLOUR OBSERVATION OF THE FLARE STAR EV Lac IN
                           AUGUST 1990

   Photoelectric monitoring of flare star EV Lac was carried out on
27-28 August with the help of the two-channel photoelectric photometer
attached on the Cassegrain focus of the 2.6 m telescope of Byurakan
Astrophysical Observatory.
   Registration was simultaneous in both U and B colours with time
resolution 0.1 sec. Algorithm of the observations is described (Zalinian
V. and Tovmassian H., 1987; Tovmassian H. and Zalinian V., 1988; Zalinian
V., 1988).
   On 29 August 1990 a flare of nearly 4 sec duration was recorded in
U colour. The light curve and colours of flare are given in Figures 1 and
2. In Fig. 2 the light curve of the flare is averaged over 5 points. The
light curve shows that the flare in U colour consists of two maxima,
which are better visible in Fig. 2. Amplitudes of flare DeltaU = 0.77m, time
of increase 1.5 sec. The flare practically could not be observed in the
B colour.

                              [FIGURE 1]
                              [FIGURE 2]




                                    KARAPETIAN A., ZALINIAN V.
                                    Byurakan Astrophysical Observatory
                                    Byurakan, Armenia



References:

Tovmassian, H., Zalinian, V.: 1988, Astrofisica, v.28, 131. [BIBCODE 1988Afz....28..131T ]
Zalinian, V.: 1988, IBVS No. 3142.
Zalinian, V., Tovmassian, H.: 1987, IBVS No. 2992.