COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3050


                                              Konkoly Observatory
                                              Budapest
                                              20 July 1987

                                              HU ISSN 0374-0676


                       FLARES OF HD 97766

  TT Hydrae was observed in UBV colours using a photoelectric photometer
attached to the 35-cm Cassegrain telescope at Yunnan Observatory during April
15 to May 24 (UT) in 1987. HD 97766 and HD 97637 were used as the comparison
star and the check star, respectively. The UBV bands are close to the Johnson
standard system, 20 sec integration time for each colour and 38" diaphragm
were employed.
  Flares of HD 97766 (=CD -26 8440; mV = 8.5; G5) had been found on May 7
and May 9 (UT).
  HD 97766 was observed in BV colours on May 7 from 12h59m to 15b58m UT
and in UBV colours on May 9 from 14h26m to 15h53m UT. The obtained differential
magnitudes in the sense of HD 97637 - HD 97766 are listed in Table I
and Table II, and plotted in Figure 1 and Figure 2, respectively.

                   Table I

BV photoelectric observations of HD 97766, 1987 May 7 (UT)

G.M.T.   DeltaVmag   G.M.T.   DeltaBmag
12h59m7    0.601    13h00m1    -0.058
13 07.9    0.620    13 08.5    -0.062
13 16.2    0.638    13 16.7    -0.035
13 31.1    0.634    13 31.6    -0.055
13 38.6    0.628    13 39.1    -0.021
13 45.9    0.643    13 46.4    -0.017
13 53.2    0.622    13 53.7    -0.039
14 01.5    0.633    14 02.2    -0.040
14 09.5    0.609    14 10.0    -0.063
14 16.7    0.602    14 17.2    -0.061
14 35.8    0.615    14 36.4    -0.062
14 46.8    0.630    14 47.5    -0.050
14 55.5    0.611    14 56.1    -0.066
15 06.2    0.601    15 06.6    -0.047
15 13.7    0.874    15 14.2     0.238
15 21.7    0.640    15 22.2    -0.052
15 29.9    0.624    15 30.5    -0.045
15 39.2    0.633    15 39.8    -0.041
15 48.2    0.617    15 48.7    -0.056
15 56.8    0.620    15 57.2    -0.061


                            [FIGURE 1]
                            [FIGURE 2]




                   Table II
UBV photoelectric observations of HD 97766, 1987 May 9(UT)

 G.M.T.  DeltaVmag   G.M.T.   DeltaBmag   G.M.T.   DeltaUmag
 14h26m7   0.617    14h27m2    -0.041    14h27m8    -0.108
 14 35.0   0.618    14 35.6    -0.042    14 36.1    -0.133
 14 42.9   0.629    14 43.4    -0.062    14 43.9    -0.131
 15 02.6   0.618    15 03.1    -0.046    15 03.9    -0.124
 15 10.5   0.622    15 11.0    -0.018    15 11.6    -0.131
 15 18.2   0.782    15 18.7     0.136    15 19.2     0.118
 15 34.7   0.621    15 35.2    -0.071    15 35.8    -0.130
 15 42.5   0.632    15 43.1    -0.055    15 43.8    -0.156
 15 51.0   0.637    15 51.5    -0.037    15 52.8    -0.134


   The recorded amplitudes of the flares in UBV bands,
and the errors of observation in a single intergration in UBV bands, DeltaV,
DeltaB, DeltaU are given in Table III.


                  Table III

      The recorded amplitudes of the flares and the standard
       deviations of observation in a single integration

         G.M.T. DeltamV   sigmaV  DeltamB sigmaB  DeltamU   sigmaU
  May 7, 15h14m 0.252   +/-0.013   0.287 +/-0.014   --         --
  May 9, 15h19m 0.157   +/-0.007   0.183 +/-0.016  0.249    +/-0.013


   Our observations indicate that the amplitude of the flare in U band
is larger than in V band.

   More observations would be desirable.





                ZHANG ZHOUSHENG, LI YULAN, WANG XUNHAO
                 Yunnan Observatory, Academia Sinica