COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        NUMBER 816

	                                 Konkoly Observatory
        	                         Budapest
                	                 1973 August 2


      PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR AD Leo



Continuous photoelectric monitoring of the flare star AD Leo
has been carried out at the Stephanion Astronomical Station
(lambda = -22d49'44", phi = +37d45'15") during the period of cooperative 
optical observations of this star proposed by the IAU Working Group
on Flare Stars i.e. January 27-February 9, 1973 (Chugainov, 1972) using
the 30-inch Cassegrain reflector of the Department of Geodetic 
Astronomy University of Thessaloniki. Observations have been made with
a Johnson dual channel photoelectric photometer in the B colour of
the international UBV system. The telescope and photometer will be
described elsewhere. Here we mention only that the transformation
of our instrumental UBV system to the international UBV system is
given by the following equations:

		V = v_0 + 0.039(b-v)_0 + 1.560,
		(B-V) = 0.737 + 1.033(b-v)_0,
		(U-B) = -1.365 + 1.007(u-b)_0.

The monitoring intervals in UT as well as the total monitoring
time for each night are given in Table 1. Any interruption of more
than one minute has been noted.

				TABLE 1
Date 			Monitoring intervals(UT) 	 		Total
1973 				       				Monitoring time
Feb.
6-7       20h56m-21h13m,2114-2121,2127-2200,2203-2225,
          2228-2258,2304-2333,2335-0005,0007-0101,
          0104-0133. 							4h11m
7-8       2102-2130,2133-2159,2204-2234,2237-2314,
          2317-2337,2343-0033,0035-0110. 				3h46m
								Total   7h57m

During the 7.95 hours of monitoring time no flare was observed.
It should be noted that the standard deviation of random noise fluctuation 
sigma(mag) = 2.5{log(I_0 + sigma)/I_0} (Andrews et al., 1969) was equal
to sigma = 0.01m during all the monitoring time.

Department of Geodetic Astronomy
University of Thessaloniki, Greece.      G. ASTERIADIS and L.N. MAVRIDIS

References:
Andrews, A.D., Chugainov, P.F., Gershberg, R.E. and Oskanian, V.S. 1969,
          Comm. 27 IAU, IBVS No. 326.
Chugainov, P.F. 1972, Comm.27 IAU, IBVS No. 744.