COMMISSION 27 OF THE I. A. U.
             INFORMATION BULLETIN ON VARIABLE STARS
                          Number 3619  

                                          Konkoly Observatory
                                          Budapest
                                          7 June 1991

                                          HU ISSN 0374 - 0676


             V 592 HERCULIS - SECOND ERUPTION OBSERVED


   This object (V 592 Her = S 10376 = Nova Herculis 1968) was discovered
by Richter (1968) who described it as a fast or even very fast nova between
12.3m and [20m. The 1985 edition of the GCVS gives the type NA. Duerbeck
(1987) tentatively tried to identify the postnova on a CCD frame taken with
the Calar Alto 2.2 m telescope. Using the insufficient finding chart published 
in the discovery paper, he found 2 stars near the position of V 592
Her with magnitudes 21m and 22m, respectively. But an inspection of the
original Sonneberg plates showed that neither identification is correct:
V 592 Her is between Duerbeck's stars 1 and 2. Therefore, the amplitude is
>9.5 mag.

   210 plates of the 400 mm astrographs, taken since the 1968 outburst,
shows that another eruption occurred in 1986. The following observations
were obtained on ORWO ZU21 plates without filter:

                 JD        m

               2446500+
                54.12    16.9::
                63.54    13.6
                91.48    17.5::
                92.44    17.6::

   Because the outburst lightcurves of a long cyclic eruptive variable
are often remarkably similar, we tentatively combined the 1968 and 1986
lightcurves of V 592 Her, as can be seen in Figure 1.

   397 sky patrol plates between 1929 and 1966 give no indication of 
further outbursts (Richter, 1986). Only on two very poor (!) Tachar plates
faint traces of about 13m (plate limit) are indicated (1948 March 29 and
1950 May 16), but probably they are plate faults.


                               [FIGURE 1]


   The question arises whether V 592 Her is a recurrent nova (RN) or a
dwarf nova (DN). The DN with the largest known amplitude is WZ Sge with 8.5
mag (according to the GCVS). But there are 2 RNe with A>9.5 mag: U Sco
(10.6 mag) and V 394 CrA (10.5 mag). This fact speaks in favour of the RN
hypothesis of V 592 Her. On the contrary, the lightcurves of all known RNe
are rather smooth, those of the DN and V 592 Her are not. This, and the
blue colour during outburst (Richter, 1968), speak in favour of DN. If so,
V 592 Her is the dwarf nova with the largest known amplitude. According to
the amplitude cycle-length relationship by Richter (1986), from A>9.5 mag
follows C>10 000 days (27 years), which is not in contradiction to the
fact that only 2 outbursts could be found between 1929 and 1990.



                         G.A. RICHTER
                         Zentralinstitut fur Astrophysik
                         Sternwarte Sonneberg
                         O-6400 Sonneberg
                         Germany

References:

Duerbeck, H.W.: 1987, A Reference Catalogue and Atlas of Galactic Novae,
      D. Reidel Publishing Company, Dordrecht/Boston. [BIBCODE 1987QB841.D84...... ]
Richter, G.A.: 1968, I.B.V.S., No. 293.
Richter, G.A.: 1986, Astron. Nachrichten, 307, 221. [BIBCODE 1986AN....307..221R ]