COMMISSION 27 OF THE I.A.U.
                 INFORMATION BULLETIN ON VARIABLE STARS
                             Number 3280

                                                         Konkoly Observatory
                                                         Budapest
                                                         2 January 1989

                                                         HU ISSN 0374 - 0676


             ON THE SUPPOSED PERIODICITY OF RZ PISCIUM

Unpublished results of 113 photoelectric UBV observations, secured at
Sonneberg Observatory during the years 1964 to 1974, and of approximately 850
brightness determinations (partly by E. Splittgerber) on Sonneberg sky patrol
plates of the years 1929 to 1975 are not consistent with the elements given
by Kardopolov and Filip'ev (1988) for photoelectric data of 20 nights of
1978. These authors' doubts on the reality of their period are thus supported.
I suppose that their "mean light-curve" is the result of their data being too
meagre.
  Of course it can never be completely excluded that during a more or less
short time interval some periodicity of brightness minima is effective in
otherwise irregular variables. See for instance our very dense photoelectric
series of SV Cephei (Wenzel 1969) or the behaviour of the central star of the
bipolar planetary nebula NGC 2346. In both cases "eclipses" by temporary
dust clouds, albeit different in origin, have been taken into consideration.
At the later-type Is variables we should rather think of the well known
spotted outer layers as an explanation of occasional quasiperiodic brightness 
changes. RZ Piscium (K0 IV) with its large range (>2 mag), however, needs
much more dense observations for clearing up its nature, which is strange
enough because of the star's rather large angular distance from the galactic
equator alone.
   Because of possible misunderstandings it might be dangerous to show the
"mean light-curves" of RZ Piscium and IP Persei (see in this context Wenzel
1984) in connection with that of the genuine eclipsing star SY Cephei.


                       W. WENZEL

                  Sternwarte Sonneberg
             Zentralinstitut fur Astrophysik
               Akademie der Wiesenschaften
                       der DDR



References:

Kardopolov, V.J., Filip'ev, G.K., 1988. Astron. Zh. 65, 816 [BIBCODE 1988AZh....65..816K ]
Wenzel, W., 1969, Mitt. Veradnderl. Sterne 5, 75 [BIBCODE 1969MitVS...5...75W ]
Wenzel, W., 1984, Inf. Bull. Variable Stars No. 2598.