COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3405
                        		        Konkoly Observatory
                                        	Budapest
                                        	14 December 1989

                                                HU ISSN 0374 - 0676


      REMARK ON THE TWO DWARF NOVAE V 632 CYGNI AND V 630 CYGNI

    The two dwarf novae V 630 and V 632 Cygni were discovered by
Hoffmeister (1949) on Sonneberg plates taken with the 40 cm astrograph. He
already recognized the type of variability, which was confirmed later by
Rohlfs (1951).

V 632 Cygni
    Only the following three eruptions described by Hoffmeister and Rohlfs
are mentioned in the literature:

             J.D. 242 9244 (13.9m),
                  242 9571 (12.8), and
                  242 9794 (pg. brightness indefinite).
    Scattered observations by members of the AAVSO, AFOEV and SVSO obviously 
did not result in detecting further maxima, and Romano (1966) found
only fluctuations in minimum light. Unfortunately the star is situated 
beyond the edge of our post-war astrographic plates. A sample of 110 far
reaching sky patrol exposures of the years 1962 to 1965 (limiting magnitude
14.5m) did not show any maximum. According to the POSS charts 806 the star
is blue in minimum.
   All findings and the statistical considerations pursuant to the paper
of Wenzel and Richter (1986) point to a cycle length of 100 days or longer.
   It should be noted that the remark of Darsenius (1966) concerning the
existing charts for this star is not correct: In reality the map of
Hoffmeister (1957) is quite good, whereas that of Brun and Petit (1957)
shows the variable at a (wrong) position 6 mm to the right (west) of the
exact one and without any star of the near surroundings. Furthermore, in
the listings of observations of the AFOEV in Bull. 38; 42; 43 the star has
been given the wrong position 2031+39 instead of 2131+39.

V 630 Cygni
   When checking 117 astrograph plates of the years 1961 to 1989 (centred
at rho Cygni) for the small possibility of containing, contrary to expectation, 
V 632 Cygni at the edge of the field, I noticed the following 6 eruptions 
of the nearby V 630 Cygni, in addition to those given by Rohlfs
(1951) from former Sonneberg plates:
      J.D.      brightness number of plates
    243 8204.5   14m0          4
        8290.6   14.7          3
        9776.5   15.2          1
    244 0839.4   15.1          1
        3044.5   15.6          1
        4117.5   14.4          2
  The first eruption seems to have been a supermaximum: it lasted 4 days
at least. The minimum brightness is below 16.3.
                         
  Romano (1966) derived from his dense series of photographic observations 
a cycle length of 40 days. Our observations do not grossly contradict
this result.



                             W. WENZEL

                           Sternwarte Sonneberg
                        Zentralinstitut fur Astrophysik
                        der Akademie der Wissenschaften
                               der DDR



References:
Brun, A., Petit, M.: 1957, Perem. Zvezdy 12, No. 1, 18. [BIBCODE 1957PZ.....12...18B ]
Darsenius, G.: 1966, Astron. Notes Univ. Gothenburg 9, 30.
Hoffmeister, C.: 1949, Astron. Nachr. - Astron. Abh. 12, No. 1.
Hoffmeister, C.: 1957, Mitt. Veranderl. Sterne 1, 309
Rohlfs, E.: 1951, Veroff. Sternw. Sonneberg 1, No. 5.
Romano, G.: 1966, Publ. Oss. Astron. Padova 132 = Mem. Soc. Astron.
       Italiana 37, fasc. 3. [BIBCODE 1966MmSAI..37..535R ]
Wenzel, W., Richter, G.A.: 1986, Astron. Nachr. 307, 209. [BIBCODE 1986AN....307..209W ]