COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 627

                                   Konkoly Observatory
                                   Budapest
                                   1972 February 14


          PHOTOELECTRIC OBSERVATIONS OF AD Leo AND EV Lac 
          DURING THE 1971 INTERNATIONAL PATROL INTERVALS


As a part of regular flare star observations at Belgrade Astronomical
Observatory, AD Leo and EV Lac were monitored during the international
cooperative patrols including a NASA X-ray interval. The observations were
made with the 65 cm refractor and the Belgrade photoelectric polarimeter,

The time coverage and other data, partly in accordance with Andrews at al.
(1969), are given in Table I. The symbols used are as follows: In column
sigma_m the error of the observation is given according to formula
log m(I_0+sigma)/I_0. Here I_0 represents the mean intensity deflection of the
undisturbed star and sigma is the standard deviation of random noise
fluctuation. The quantity Delta m_lim has been calculated from Delta m_lim=
-2,5 log (3 sigma/I_0).

During 377 minutes of AD Leo patrols no flare activity has been noticed.
During 522 minutes of EV Lac monitoring one flare was observed. The
characteristics of the flare are given in Table II and the light curve is shown
in Figure 1.

In Table II Delta t_1 and Delta t_2 are durations of the flare before and after
maximum. Delta m_f has been found from Delta m_f=-2,5 log (I_0+f/I_0) where
I_0+f is the intensity deflection of the star at the moment of maximum. The
integrated intensity is given in the column P and the air mass in the column X.

Results of the polarimetric analysis of the observed flare will be published
later.


J. ARSENIJEVIC
A. KUBICELA
Astronomical Observatory, Belgrade

Reference:

Andrews A.D., Chugainov P.F., Gershberg R.E., Oskanian V.S., 1969, 
   IBVS, No. 326.

Table I.

Monitoring of AD Leo and EV Lac

 Date             Coverage
 1971               U.T.                   F  sigma_m   Delta m_lim

                     AD Leo
Apr.14  1940-2027, 2033-2136, 2140-2201    V   0.028     +2.8
    16  1900-1917, 1922-2041, 2045-2135    V   0.012     +3.7
    18  1905-1925, 1930-1950, 2000-2100    V   0.021     +3.1

                    EV Lac
Sep.18  2138-2158                          V     -         -
    21  2317-2323, 2422-2540,              V   0.021     +3.1
        2328-2422                          B   0.026     +2.8
    22  2113-2147, 2200-2252, 2319-2404,   V   0.014     +3.5
        2416-2452, 2503-2513
    23  2111-2220, 2244-2358, 2443-2517    V   0.011     +3.8

Table II.

Flare data for EV Lac (Date 1971 Sep. 23.)

 U.T.  of  max.   F  Delta t_1  Delta t_2  Delta m_f  sigma m     P        X
21^h13^m.0        V   2^m.0      52^m       1.22       0.011   11.^m28   1.000


                        [FIGURE 1]