COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                      NUMBER 498

                                 Konkoly Observatory
                                 Budapest
                                 1970 December 18


     PHOTOELECTRIC OBSERVATIONS OF AD Leo DURING THE
         1970 MARCH 1-15 INTERNATIONAL PATROL

       The observations of AD Leo carried out during the
above mentioned period, according to the observing schedule
prepared by the I.A.U. Working Group on Flare Stars (Andrews
and Chugainov, 1970), are presented. Within the 15.5 hours
of patrol in b light (Table 2) four flares were observed. A
Cassegrain reflector of 91 cm aperture and a quasi-Cassegrain
reflector of 61 cm aperture referred to in Table 2
as 91 and 61 fed similar photometers equipped with EMI 6256
photomultipliers and the Schott filter combinations:
BG 12/1 + GG 13/2 (b), GG 14/2 (v).

                   Table 1. Observed flares

No Date    t_max       d_b    d_a   m_lim-m_0 (m_f-m_0)_max P  Remarks
   1970
1  Mar 7   02h40.2min 0.5min 1.5min  +4.95m       +2.61m   0.06  1
2  Mar 8   02 27.3    0.1    0.7     +5.34        +2.30    0.04  3*
3  Mar 9   00 22.1    0.3    0.2     +5.36        +1.80    0.04  2*
4  Mar 9   02 29.6    0.1    8.4     +5.07        +1.34    0.79  2

	t_max = U. T. of maximum intensity
        d_b   = rise-time, d_a = decay-time,
     m_lim-m_0= -2.5 log (3sigma/I_0)

where sigma and I_0 indicate the standard deviation of the random
noise fluctuations and the mean intensity of the quiet star
near the observed flare, respectively.
(m_f-m_0)_max = -2.5 log [(I_0+f-I_0)/I_0]_max, where I_0+f is the 
intensity deflection due to the variable star (I_0) plus that
of flare (I_f) at maximum; P = summa^te_tb[(I_0+f-I_0)/I_0] dt
integrated intensity (in minutes).

Remarks: sky condition, 0 very clear, 2 clear with some thin
layers, 3 extended thin stratus, * uncertain.
 

                    Table 2.

Date     Tel.   F   Coverage U.T.                    TC       m_lim-m_0
1970
March               
07       91     b   01h21min-0340                    139min   +4.95m
07       61     b   2233-2248,2250-2306,2311-2315,
                    2328-2354,2357-2400.
08                  0000-0007,0019-0048,0100-0127,
                    0138-0220,0224-0238,0244-0251,
                    0254-0338.                       230      +5.44
08       91     b   1857-1909,1920-2128,2219-2310,
                    2345-2400.
09                  0000-0042,0044-0107,0110-0120,
                    0124-0133,0213-0218,0222-0232,
                    0234-0257,0305-0328.             347      +4,89 
08       91     v   2147-2148,2152-2154.
09                  0208-0209.                       004
09       91     b   1918-2007,2014-2018,2020-2022.   055      +4.91
10       91     b   1843-1910,2027-2031,2048-2050,
                    2052-2055,2058-2059,2101-2111.   049      +4.84
10       91     v   1943-1944,1948-1949.             004
12       91     b   1844-1848,1854-1904.             012      +4.97
14       91     b   1908-2000.                       054      +4.92
15       91     b   1908-1981,2000-2001.             044      +4.95

   Tel.= cm aperture telescope; F = Schott filters; u = UG1
   (1 mm), b = BG12 (1 mm) + GG13 (2 mm), v = GG14 (2 mm);
   TC = total coverage per night; m_lim-m_0 = -2.5 log (3sigma/I_0),
   where sigma represents the standard deviation of the random noise
   fluctuation for a night, and I_0 represents the mean intensity
   of the quiet star during the same night.


                          S. CRISTALDI
                          M. RODONO
                    Catania Astrophysical Observatory



  Reference
  Andrews, A. D., Chugainov P. F. 1970, Comm. 27. IAU, 
           Inf. Bull. Var. Stars No. 418


                           [FIGURE 1]