COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 364

                                  Konkoly Observatory
                                  Budapest
                                  1969 July 17


            FLARE PHOTOMETRY OF AD LEO

As part of the international co-operative programme,
observations were made at Boyden Observatory of AD Leo over
the period 9th-24th February, 1969.
The instrument used in this monitoring was the
10 cm Nishimura reflector equipped with a Johnson B-filter
and a solid CO_2 cooled E. M. I. 6256 photomultiplier tube
feeding into a General Radio Company D.C. amplifier (Type
1230 - A).

      Table I. Monitoring Time and Observed Flares

                      Total        Flare      U.T.    Duration     Deltam
                    Hours per                  of       (min)
Date         U. T.    Night         No.      Flare       
Febr.1969
 9        19h24m-21h14m   1h50m
10        19 50-22 09     2 19       1       21h53m      12          0.17
19        18 44-21 35
          21 45-23 05
          23 13-23 25     4 23
20        18 54-22 22     3 28
21        18 40-21 37     2 57
             Total       14h57m

As will be seen from Table I. the   total monitoring
time was 14h57m. During this time one event was recorded,
a low magnitude flare with a relatively  long duration of
nearly 12 minutes (Fig.1).

                            [FIGURE 1]


       Although this flare was a minor one so far as Deltam
was concerned we consider it worthy of report as our equipment
ensures an accuracy of better than 5%. Especially 
interesting is the very gradual decline after the flash phase.
       Further observations of AD Leo have been made since
the February 1969 International co-operation period, the
total additional monitoring time being 30h20m as shown in
Table II. Five minor flares have been observed.

Table II. Monitoring Time and Observed Flares of AD Leo

Date   Universal Time of Coverage  Total  Flare  U.T. of  Duration  Deltam
                                   Hours   No.    Flares    (mns) 
                                    per
                                   Night
Mar.                                                          
16  17h50m-19h17m, 20h-46m-21h40m   2h21m   1     20h20.8m    6.2    0.17
                                            2     21 07.0     4      0.12
19  18 45-21 35, 21 45-23 05        4 22
                 23 13-23 25                               
20  18 53-22 22,                    3 29
21  18 40-21 38                     2 58
    Total                          13h10m
May
 7  17h33m-18h58m,19h05m-20h18m     2h38m   1     19h12.08m,  6.2   0.08  
                                            2     19 31.3     5.1   0.09
13     16 52-20 42                  3 50    3     17 32.0     6.1   0.12
12     18 59-20 40                  1 41
14     16 59-19 44,20 05-20 30      3 10
16     17 05-18 01                  0 56
18     16 41-18 11                  1 30
22     16 45-20 10                  3 25
       Total                       17h10m

       The most interesting was flare No.2 on the night of
16th-17th March 1969  in that a gradual rise preceded the
flash phase. The other flares showed the more usual initial
rapid increase in intensity, followed by a fairly gentle
decline.                                    

                           [FIGURE 2]



Boyden Observatory, Bloemfontein, RSA. 1st July, 1969

             A. H. JARRETT and J. P. EKSTEEN