COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                         Number 3532

                                                 Konkoly Observatory
                                                 Budapest
                                                 29 October 1990

                                                 HU ISSN 0374 - 0676


        ON THE NATURE OF THE CATACLYSMIC VARIABLE
                    V 426 OPHIUCHI

   Previous photometric observational series of V 426 Oph led
the authors to characterize it as "ex-nova" or as "nova-like"
(Meinunger 1967; Beyer 1977; Shugarov 1980, 1983), after the
earlier classification as RW Aurigae type (Hoffmeister 1949)
had been discarded by Herbig (1960) because of the presence
of the Balmer series end of He I in emission over a structureless 
continuum. Since the He I emission and parts of the
previous light-curves are typical for dwarf novae, we decided
to investigate the object on all suitable Sonneberg plates.
   1676 observations on exposures of the Sky Patrol (SSP) and
255 observations on plates of the two 40 cm astrographs (time
interval 1931...1988) could be gained. Our pg. magnitude
system is based on the B system of Shugarov (1983). Pronounced
standstills in intermediate magnitude could not be observed.
Remarkable, however, is the presence of two different minimum
levels (12.90m and 13.45m), which follow each other in an 
obviously irregular manner. Eruptions are frequent; their average
height and their breadth (at a level of 12.0m) are 11.5m and 4
days, respectively. From the latter quantity a mean cycle length
of C = 33 days (SSP) can be derived by statistical methods,
for instance according to Wenzel and Richter (1986).
   What is important: On the average the cycle length depends
on the magnitude of the minimum from which the eruptions ascend.
This effect can be easily found already in the visual lightcurve 
of Beyer (1977): Compare for instance the series of 1951
- minimum 12m via., C = 21 days, and 1952 - minimum 13m,
C = 42 days. Fig. 1, which is drawn on the basis of a concerted
series of four-minute exposures with the GB astrograph, also
shows a good example for a short cycle length connected with
a high level of the minimum (C = 22 days, minimum = 12.9m).
In spring 1957 5 eruptions follow each other with a mean cycle
length of 13 days and a minimum brightness of 12.8m; on the
other hand there are numerous intervals of 25 to 40 days between 
eruptions, and the accompanying minimum state is around
13.5m. Also the photoelectrically determined curse of Shugarov
(1983) seems to show the short value of C ~= 16 days at a 
minimum level of B = 12.9m.


                         [FIGURE 1]


   Orbital period (0.285 days, Hessman 1988), amplitude
(~= 2 mag) and mean cycle length (33 days) fit into the 
relationships governing these quantities of dwarf novae and found
by Richter and Brauer (1989).
   We suppose that V 426 Oph is an SS Cygni star which can
switch between stronger and lower mass-transfer rates. Hessman
(l.c.) and Szkody/Mateo (1988) observed the object in the
upper minimum level, as we can see from the brightness data
given by them. They found an unusually high transfer rate
and that (at least in the UV) a large part of the brightness
comes from the accretion disc. The shortening of the cycle
length (see above) in this "upper state" is also typical for
a higher mass transfer,
   Here possibly a single star demonstrates us (at least 
qualitatively) what Vogt (1981) considered as a statistical 
property of the group of the dwarf novae as a whole, namely that
the relationship amplitude/cycle length should be replaced
by the relationship minimum luminosity/cycle length.
    We thank Mr. G. Hacke and Mr. K. Heiland for nonschedule
exposures and Dr. G.A. Richter for stimulating discussions.


                            W. WENZEL and E. SPLITTGERBER
                                 Sternwarte Sonneberg
                          Zentralinstitut fur Astrophysik der
                              Akademie der Wissenschaften
                                      Deutschland



References:

Beyer, M., 1977, Weroff. Remeis-Sternwarte Bamberg 12, no.123, p.2 [BIBCODE 1977VeBam.123.....B ]
Herbig, G.H., 1960, Atrophys. J. 131, p.632 [BIBCODE 1960ApJ...131..632H ]
Hessman, F.V., 1988, Astron. Astrophys. Supp. 72, p.515 [BIBCODE 1988A&AS...72..515H ]
Hoffmeister, C., 1949, Astron. Nachr. 278, p.24 [BIBCODE 1949AN....278...24H ]
Meinunger, L., 1967, Mitt. Veranderl. Sterne 4, p.69
Richter, G.A., Brauer, H.-J., 1989, Astron. Nachr. 309, p.416 (Fig. 3) [BIBCODE 1989AN....310..413R ]
Shugarov, S. Yu., 1980, Astron. Tsirk. no. 1113 [BIBCODE 1980ATsir1113....7S ]
Shugarov, S. Yu., 1983, Pis'ma Astron. Zhurn. 9, p.31 [BIBCODE 1983PAZh....9...31S ]
Szkody, P., Mateo, M., 1988, Publ. Astron. Soc. Pacific 100, p.1111 [BIBCODE 1988PASP..100.1111S ]
Vogt, N., 1981, Mitt. Astron. Gesellschaft 57, p.79 [BIBCODE 1982MitAG..57...79V ]
Wenzel, W., Richter, G., 1986, Astron. Nachr. 307, p.209 [BIBCODE 1986AN....307..209W ]