COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3429

                                               Konkoly Observatory
                                               Budapest
                                               5 February 1990

                                               HU ISSN 0374 - 0676



     PHOTOELECTRIC OBSERVATIONS OF THE FLARE STAR UV Cet IN 1983

   Photoelectric monitoring of the flare star UV Cet has been carried out
at the Stephanion Observatory (lambda =+22d49'44", phi = +37d45'15", H=800 m)
during the year 1983 using the 30-inch Cassegrain reflector of the Department 
of Geodetic Astronomy, University of Thessaloniki. Observations were
made with a Johnson dual channel photoelectric photometer in the B colour of
the international UBV system. The telescope and photometer used were 
described elsewhere (Mavridis et al., 1982). The transformation of our 
instrumental ubv system to the international UBV system is given by the 
following equations:

           V = v0 + 2.722 - 0.104 (b-v)0

           B-V = 0.448 + 1.084(b-v)0     .

The monitoring intervals in UT as well as the total monitoring time for
each night are given in Table I. Any interruption of more than one minute
has been noted.
   During the 6.25 hours of monitoring time one flare was observed, the
characteristics of which are given in Table II. In this table following
characteristics (Andrews et al., 1969) are given: a) the date and universal
time of flare maximum, b) the duration before and after the maximum (t_b
and t_a, respectively), as well as the total duration of the flare, c) the
value of the ratio (If-I0)/I0 corresponding to flare maximum, where I0 is
the intensity deflection less sky background of the quiet star and If is the
total intensity deflection less sky background of the star plus flare, d)
the integrated intensity of the flare over its total duration, including
preflares, if present, P = Integral(If-I0)/I0 dt, e) the increase of the apparent
magnitude of the star at flare maximum Delta m(b) = 2.5 log (If/I0), where b is
the blue magnitude of the star in the instrumental system, f) the standard
deviation of random noise fluctuations sigma (mag) = 2.5 log (I0+sigma)/I0 during
the quiet-state phase immediately preceding the beginning of the flare, and
(g) the air mass at flare maximum.

    The light curve of the observed flare in the b colour is shown in 
Figure 1.

                                Table      I
Date          Monitoring Intervals (UT)              Total Monitoring
1983                                                       Time
October         h  m     h  m     h  m     h  m
3-4           22 00  - 22 29 ,  22 35  - 22 44 ,
              22 49  - 23 06 ,  23 10  - 23 39 ,
              23 43  - 00 07 ,  00 21  - 00 36 ,
              00 43  - 01 13 ,  01 16  - 01 46             3h03m
4             21 49  - 22 19 ,  22 24  - 22 54 ,
              22 58  - 23 37.                              1 39
5             21 54  - 22 23 ,  22 27  - 23 00  ,
              23 05  - 23 36.                              1 33


                                                           Total 6h15m

                    Table II

             Characteristics of the flare observed


Date       U.T.      t_b    t_a    Duration  (If-I0)/I0    P Delta m sigma     Air
1983       max       min   min       min        max        min  mag   mag      mass
Oct.
 4    00h 21m 37 >/= 1.16  7.64  >/= 8.80       3.46   >/= 5.21 1.62  0.09      1.91


                                   [FIGURE 1]


   The first of the authors (L.N.M.) would like the acknowledge the 
financial assistance of the Empirikos Foundation for the final phase of the
present research programme.


      L.N. MAVRIDIS           P. VARVOGLIS
  University of Thessaloniki  Department of Mathematics
                              University of Thrace


References:

Andrews, A.D., Chugainov, P.F., Gershberg, R.E., and Oskanian, V.S.: 1969,
        Inf. Bull. Var. Stars No. 326
Mavridis, L.N., Asteriadis, G.A., and Mahmoud, F.M.: 1982, in Compendium
        in Astronomy (ed. by E.G. Mariolopoulos, P.S. Theocaris,
        and L.N. Mavridis) D. Reidel Publishing Company, Dordrecht,
        Holland, p. 253. [BIBCODE 1982coas.conf..253M ]