COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    NUMBER 783

                                    Konkoly Observatory
                                    Budapest
                                    1973 April 18

         A FLARE OF "ANTIFLARE" STAR RZ Psc




  RZ Psc is one of the most striking representative of the so-called 
"antiflare" stars, in which the intervals of relative quiescence 
(m_v ~ 11.5m) are interrupted by sharp Algol-like minima
(m ~1.5m). Hoffmeister and Parenago (1,2) considered the star as
being an Algol system. However, the later investigations especially 
by Zessewitsch (3,4) have shown the assumption to be incorrect.
RZ Psc turned out to be a rapid irregular variable of spectral
class K0 (GCVS, III ed.).
  The star was observed photoelectrically at minimum light on
August 20, 1972. Modern pulse-counting technique with the 20" 
reflector was used. Three-colour observations reduced in the standard 
UBV system are listed in the Table. These data are somewhat
uncertain due to a correction that must be made for differential
extinction.


-----------------------------------------------------------------
U.T.    m_v     m_b    m_u    U.T.   m_v    m_b    m_u
-----------------------------------------------------------------
23h20m 13.03m 13.82m 13.31m  00h02 13.00m 13.90m 14.52m
   30    .03    .87    .74      05 12.98  14.01    .68
   37    .09    .73    .29      10 13.12    .09    -
   42    .04    .84  14.08      14 12.90  13.91    -
   48    .00    .99    .39      19   .86    .93  13.79
   55  12.78    .72  12.90      50 13.00  14.04  14.61
------------------------------------------------------------------



  When the ordinary three-colour run of observations was over we
launched two series of continual measuring through B filter using
15-second integration time. The results are given in the Figure. As
the star was badly faint, the mean error was near 0.04m in each 
instance.
  The present flare strongly resembles that of UV Cet. Moreover,
one can see from the Table that before the flare U-magnitudes change
six times as much as B-ones do, i.e.
         
              DeltaU/DeltaB ~= 6.0   


If the ratio DeltaU/DeltaB within the flare in supposed to be same we can
assume that the U-amplitude was about 5m.
  On the basis of the form of the flare and the possibly large
U-amplitude we can expect RZ Psc at minimum light to reveal usual
features of a flare star.
  We would like to express our gratitude to Prof. V.P. Zessewitsch
and Dr. V.S. Oskanjan for useful and variable discussion.


Kiev, March 19, 1973


    V.G. KARETNIKOV                     A.F. PUGACH
Odessa Astronomical Observatory      Main Astronomical Observatory
                                     Ukrainian Academy of Sciences


References:

1. C. Hoffmeister, AN 242, 129, 1931. [BIBCODE 1931AN....242..129H ]
2. P.P. Parenago, VS (Russ) 4, 159, 1933.
3. W. Wenzel, MVS n 217, 1956.
4. V.P. Zessewitsch, VS (Russ) 10, n 6, 405, 1956.



                          [FIGURE 1]