COMMISSION 27 OF THE I. A. U.
       INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 497

                               Konkoly Observatory
                               Budapest
                               1970 December 14


        COOPERATIVE OBSERVATIONS OF EV Lac

     The programme of cooperative observations of flare
stars for the year 1970 was published in IBVS 416.
According to this programme a series of observations was
carried out with the 16" telescope of the Byurakan 
Observatory in the time interval 23 August - 9 September 1970.
The observations were effectuated with a photoelectric
polarimeter having a fast rotating polaroid (1).
     The photomultiplier used was a multicaly FEU-79
having a spectral sensitivity range from 3000 to 8300 A.
with a maximum at 4000-4400 A.
      The observational data are given in the Table below.

               Observations of EV Lac

   Date                           Moment  Duration  Colour
    of                              of      of      range
observation  Coverage UT     m    maximum  flare

23.VIII-70   17h50m-18h30m   -      -       -        blue
             18 35 -21 00    - -    -       -        yellow
24.VIII      17 30 -21 00    -      -       -          "
25.VIII      17 10 -23 10    -      -       -          "
             23 33 -00 00    -      -       -          "
26.VIII      18 10 -23 35    -      -       -          "
28.VIII      18 00 -23 10    -      -       -         blue
31.VIII      19 43 -22 10    -      -       -          "
 2.IX        17 00 -19 35    -      -       -          "
             20 30 -00 10    -      -       -          "
             00 15 -00 45    -      -       -          "
 3.IX        18 35 -22 27    -      -       -          "
 5.IX        17 00 -23 12    -      -       -          "
 6.IX        16 53 -20 30    -      -       -          "
             21 20 -23 00    -      -       -          "
             23 29 -01 10    -      -       -          "
 7.IX        17 35 -23 00    -      -       -          " 
 8.IX        16 40 -01 00   0.6  16h54m24s  2m30s      "
 9.IX        17 05 -23 30   0.75 18 26 50   3 95       "


			[FIGURE 1]
			[FIGURE 2]

     The star EV Lac has been observed on the whole
during 85h11m during this time interval two flares with
amplitudes Delta m = 0.8m and Delta m = 0.75m have been registered,
both in the blue colour. These magnitudes have been corrected
for the influence of the optical companion (2).
      The light curves are presented in the Figure. The
excess flux of the flare expressed in the units of the
normal flux of the star, i = (n_fl/n_nor-1), was taken versus
UT.


                         K. A. GRIGORIAN
                         M. A. ERITSIAN



1. M. A. Eritsian, A Photoelectric Polarimeter with a Fast
   Rotating Polarization Modulator (in press).

2. P. F. Chugainov, Izv. Crimean Astrophysical Observatory
     (in Russian) 26, 171-179, 1961.