COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 343

                                  Konkoly Observatory
                                  Budapest
                                  1969 April 7

      PHOTOELECTRIC OBSERVATIONS OF UV Ceti

      The flare star UV Ceti was observed photoelectrically
with the 36-inch reflector of Steward Observatory in the
period of co-operative observations 14-28 October, 1968.
      The U magnitude of the star was measured continuously
with an integration time of 15 seconds. V and B magnitudes
were measured at the beginning and end of each series of
observations. Several UBV standards were observed before
and after the observations of UV Ceti.
      The dates and times of coverage are given in
Table I. Table II contains the characteristics of the 
observed flares which are obtained according to the proposals
given in (I). The columns give: 1) the date; 2) the time,
UT, of flare maximum; 3) the flare intensity at maximum 
expressed in U magnitude scale; 4) the integrated intensity
of the flare found by the formula: integrated intensity =


            Integral ((I_0+f - I_0) / I_0 dt),                  
                  

were I_0 is the mean intensity of the star radiation just
before and after the flare, and I_0+f is the intensity of
the star radiation during the flare; 5) U_0 = the U magnitude
corresponding to the intensity I_0; 6) U_lim = the limiting
magnitude, i.e. magnitude of the imaginary flare which could
be detected on the background of noise fluctuations. This
value was found by the formula U_lim = -2.5 lg 3sigma/I_0 + U_0,
where the standard deviation of noise fluctuations expressed
in the same units as I_0. Finally, Col 7) gives the air mass,
M(z), corresponding to the flare maximum. The time intervals
between the maximum of the flare and its beginning and
end are not obtained from our observations because these
might be distorted by the integration process. The light
curves of the flares are given below in relative intensities
(I_0+f-I_0)/I_0 (Figs. 1-8).
       Note that U_0 and U_lim differ from one flare to 
another. This is due (except possibly for the flare 19.10.68)
to the secondary variations of the star. The amplitude of
these variations, as obtained from our observations, is
about 0.1m in the V and B-bands and 1.5m in the U-band (see
also [2]).
       It is interesting to note that the largest of the
observed flares (18.10.68) took place during the deep 
minima of the slowly varying component of the star radiation.
The flare of 19.10.68 may be erroneous because of possible
interference of clouds before and after the flare.


                          Table I

Date        UT of coverage                      Remarks
Oct 15   6h46m-6h54m, 7h00m-8h29m,         Clouds at horizon
         8h33m-8h40m
    16   7h32m-7h49m, 7h51m-8h06m,
         8h12m-8h48m, 8h56m-9h24m
    17   7h44m-8h56m, 9h06m-10h01m                     
    18   6h32m-6h57m, 7h03m-7h27m,
         7h30m-9h49m
    19   7h58m-9h50m, 9h52m-10h27m            Clouds at end
    21   6h15m-7h05m, 7h11m-7h24m,
         7h27m-7h30m, 7h33m-7h55m,
         7h58m-8h00m, 8h03m-8h32m,
         9h32m-10h13m
    23   6h13m-8h41m

			[FIGURE 1]
			[FIGURE 2]
			[FIGURE 3]
			[FIGURE 4]
			[FIGURE 5]

 
                       Table II

                           Flare
Date         UT          Intensity  Integr.  U_0   U_lim   M(z)
                           at      Intensity,
                         Maximum    minutes
October 16   7h36m7        14.26     1.4   14.69   15.39   1.56
             9 02.0        15.48     0.6   14.75   15.35   1.76
        17   7 50.4        13.53     3.1   14.73   15.77   1.58
             7 54.9*       14.45           14.73   15.77   1.58
        18   7 31.7        14.81     2.1   15.22   15.92   1.56
             8 32.1        11.66   254.0   15.68   15.51   1.67
             8 58.3*       11.13           15.68   15.51   1.78
        19  10 12.7        13.86     5.2   14.30   14.65   2.47
        21   8 04.1        13.24     5.0   14.92   15.47   1.63
        23   7 47.4        12.99    22.8   14.90   15.77   1.61
             8 23.0        14.67     1.4   14.90   15.77   1.71



 * secondary maximum of previous flare

			[FIGURE 6]
			[FIGURE 7]
			[FIGURE 8]



REFERENCES:

(1) A.D. Andrews, P.F. Chugainov, R.E. Gershberg, V.S. Oskanjan,
    I.B.V.S. No. 326, 1969.
(2) W.E. Kunkel, I.B.V.S. No. 315, 1968.



                             R.J. HAVLEN, B.E. WESTERLUND,
     P.F. CHUGAINOV                   R.E. WHITE
   Crimean Astrophysical         Steward Observatory
      Observatory               University of Arizona