COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 3166


                                              Konkoly Observatory
                                              Budapest
                                              25 March 1988

                                              HU ISSN 0374-0676


          OPTICAL BEHAVIOUR OF THE X-RAY BINARY V1727 CYGNI
                 = 4U 2129 + 47 IN THE SEASON 1987/88


  The star was inspected on 49 blue-sensitive plates (ORWO-ZU 21 + GG 13,+
BG 12) from 24 nights obtained with the 50/70/172 cm Schmidt camera of Sonneberg
Observatory covering the time interval between 26 March 1987 and 13
January 1988.
  The individual estimates, listed in Table I are linked to the sequence of
comparison stars given by Wenzel (1983).



                         Table I
J.D. hel.   mB       Rem.   J.D. hel.   mB      Rem.
244..                       244...
6881.601    >17.5     inv   7029.454    >17.5    inv
6884.588    >17.9     inv   7029.501    >17.9    inv
6884.605    >17.5     inv   7030.444    >17.9    inv
6885.587    >17.9     inv   7030.476    >17.9    inv
6885.606    >17.5     inv   7030.504    >17.5    inv
6909.566    >17.9     inv   7039.463    >17.5    inv
6910.554     18.3           7039.482    >17.5    inv
6910.573     18.4           7039.502    >17.5    inv
6914.553    >17.9     inv   7039.527    >17.9    inv
6914.570    >18.3     inv   7060.390    >17.9    inv
6917.554    >17.9     inv   7060.412     18.3
6917.570    >17.9     inv   7060.439     18.4
6939.532    >18.3     inv   7061.397    >17.9    inv
6941.512    >18.3     inv   7087.290     18.3
6941.532     17.9           7087.311    >17.9    inv
6976.449     17.9::         7094.344    >17.9    inv
6976.467     18.1           7094.364    >17.5    inv
6976.485    >18.3     inv   7141.276    >17.9    inv
6977.483    >17.9     inv   7141.335    >17.9    inv
6977.499    >17.9     inv   7143.209    >17.5    inv
6983.495    >18.1     inv   7152.290    >17.5    inv
7028.422     18.0:          7152.309    >17.9    inv
7028.456    >17.9     inv   7174.222    >18.3    inv
7028.475    >17.9     inv   7174.248    >17.5    inv
7029.454    >17.5     inv

On most of the plates the stars is below the plate limit. The object is
visible only on 8 plates. The brightness varies there between mB = 17.9 and
mB= 18.4 and characterizes, as in former series (Gotz, 1985, 1986, 1987),
the low or inactive state of the star, which probably started near 7 September
1983 (Wenzel 1983).



                         W. GOTZ
                         Akademie der Wissenachaften
                         der DDR,
                         Zentralinstitut fur Astrophysik
                         Sternwarte Sonneberg, DDR




References :

Gotz, W., 1985, I.B.V.S. No. 2732
Gotz, W., 1986, I.B.V.S. No. 2895
Gotz, W., 1987, I.B.V.S. No. 3013
Wenzel, W., 1983, I.B.V.S. No. 2452