COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 3013



                                        Konkoly Observatory
                                        Budapest
                                        17 April 1987

                                        HU ISSN 0374-0676



        OPTICAL BEHAVIOUR OF THE X-RAY BINARY V1727 CYGNI
                     = 4U 2129+47 IN 1986

The star was inspected on 79 blue-sensitive plates (ORWO-ZU21+GG13+BG12)
from 47 nights obtained with the 50/70/172 cm Schmidt camera of Sonneberg
Observatory covering the time interval between 18 March 1986 and 29 November
1986.
The individual estimates, which are 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...
6508.639    18.1          6616.507     >17.5      iv
6533.561   >17.9     iv   6626.505     >17.9      iv
6533.578   >17.9     iv   6626.524      18.2
6552.503   >17.9     iv   6641.410     >18.4      iv
6552.522   >17.5     iv   6641.428     >17.5      iv
6553.554    18.1          6642.447     >17.5      iv
6553.572   >17.9     iv   6644.485     >17.5      iv
6554.551   >17.5     iv   6645.478     >17.9      iv
6554.569   >17.9     iv   6645.497      18.2
6563.492    18.3          6646.515      18.1
6563.510    18.3          6646.537      18.1
6577.444   >18.4     iv   6648.521     >17.5      iv
6591.508   >17.9     iv   6649.487     >17.9      iv
6591.526   >17.9     iv   6649.512      18.2
6592.506   >17.9     iv   6650.480      18.2
6592.528   >17.9     iv   6651.480     >17.5      iv
6596.532   >17.9     iv   6651.500     >17.5      iv
6597.528   >17.5     iv   6678.443     >17.9      iv
6608.423   >17.9     iv   6678.463      18.2
6609.451   >17.9     iv   6679.429      18.3
6611.470    18.4          6679.448     >17.9      iv
6611.489    18.4          6683.440     >17.9      iv
6612.489    18.2          6683.461      18.4
6613.486    18.3          6685.424     >17.5      iv
6613.503    17.9     iv   6685.444     >17.5      iv
6614.500    18.0          6702.357      18.1
6616.491   >17.9     iv   6702.376      18.3
6702.395   >18.4     iv   6714.384     >17.9      iv
6704.354   >17.9     iv   6714.403      18.2
6704.372   >17.9     iv   6731.315     >17.9      iv
6705.384    18.4          6731.341     >17.9      iv
6705.404   >17.9     iv   6733.441     >17.9      iv
6706.396    18.2          6733.460     >17.9      iv
6706.415    18.3          6737.446      18.4
6707.364   >17.9     iv   6741.419     >17.9      iv
6707.382   >17.9     iv   6762.420     >17.9      iv
6708.389   >18.4     iv   6763.260     >17.9      iv
6708.408   >17.9     iv   6763.281     >18.4      iv
6713.366    18.3          6764.267     >17.9      iv
6713.406    18.4
iv = invisible

The object is only visible on 27 plates in the brightness range between
mB= 18.0m and mB = 18.4m. On most of the plates the star is below the limiting
magnitude and invisible. As in former series (Gotz 1985,1986) the behaviour
given here characterizes the low or inactive state of the star, which probably,
started near 7 September 1983 (Wenzel, 1983).
Observations listed in Table I are shown in Figure 1.


                            [FIGURE 1]


   They are reduced to one common epoch by means of the elements

          Min (hel.) = 244 4403.743 + 0.2182579d * E

given by McClintock et al. (1982). The arrows indicate "fainter than"
observations.




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





References:


Gotz, W., 1985, Inf. Bull. Var. Stars No. 2732
Gotz, W., 1986, Inf. Bull. Var. Stars No. 2895
McClintock, J.E., London, R.A., Bond, H.E, and Grauer, A.D., 1982,
  Astrophys. J. 258, 245 [BIBCODE 1982ApJ...258..245M ]
Wenzel, W., 1983, Inf. Bull. Var. Stars No. 2452