COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                     NUMBER 656

                                       Konkoly Observatory
                                       Budapest
                                       1972 April 8


 REMARKS ON THE OBSERVATIONS OF FLARE STARS BY JAPANESE ASTRONOMERS


Recently the first results of three-canal synchronous electrophotometric
observations made by Japanese astronomers in UBV rays of flare stars were
published (Osawa et al. IBVS No. 608, 1971; No. 635, 1972). They have
obtained, in particular, amplitudes of brightness intensification Delta U,
Delta B and Delta V during six flares of UV Cet, three flares of EV Lac and 17
flares of YZ CMi. There is good reason to believe, however, that the Japanese
observers have witnessed a systematic reduction of the amplitude values in U
for the flares they have recorded. One can get convinced of this fact when one
compares the values of the ratios Delta U/Delta B obtained by the Japanese
observers with the results of other observers, the value of Delta B being the
same. For greater evidence such a comparison is made graphically in Fig.1 in
the form of empirical dependence of Delta U/Delta B on Delta B. To reduce
measurement errors data relating to Delta B >= 0,20 have been used in plotting
the curve.

In the Figure the upper curve depicts the empirical dependence (Delta U/Delta
B)~B, resulting from the observations of 13 flares of six various flare stars.
A similar dependence, based, on the results of the Japanese observers (the
broken curve), passes considerably lower than the first curve. On the other
hand, both curves are nearly parallel to each other. The upper curve in the
Figure is plotted according to the results of the observations of seven
independent groups of astronomers, (1. Japanese observations of YZ CMi, UV Cet
and EV Lac, Osawa et al. IBVS No. 608, 1971; No. 635, 1972. 2. EV Lac:
Chugainov, Izv. Krymsk. obs., 40, 33, 1969; Cristaldi, Rodono, IBVS No. 525,
600, 1971. 3. AD Leo: Abell, PASP, 71, 517, 1959. 4. EQ Peg: Andrews,
private commun. 5. HII 1306: Johnson, Mitchell, Ap.J., 127, 510, 1958. 6.
S 5114: Mumford, PASP, 81, 890, 1969. 7. BD +55deg1823: Cristaldi, Rodono,
Private commun.) and its weight coefficient is therefore equal to seven. The
weight coefficient for the homogeneous group of Japanese observations, on which
the lower curve is based, is equal to one. We come therefore to the conclusion
that the above discrepancy must be due to a regular reduction of the value of
Delta U by the Japanese observers. This reduction is rather appreciable -
50-60%. In other words, all the values of Delta U, found out by the Japanese
astronomers, should be multiplied by 1,5 - 1,6, in this case a complete inner
harmony will be achieved with the results of other observations. An
alternative assumption, that the above discrepancy might result from an
overestimation of Delta B, seems unlikely since in that case the inner harmony
between Delta B and Delta V would strongly be disturbed.

A certain disagreement is notable also in the measurements of Delta V, although
the high relative errors in the measurements of V-rays (due to small values of
Delta V) do not lead to unambiguous conclusions. Generally, one gets the
impression that the energy calibration of the three-canal electrophotometer of
the Japanese astronomers needs reconsideration.

                           [FIGURE 1]

22 March, 1972

G.A. GURZADYAN
Branch of the BAO on Space Research,
Armenian SSR, USSR