COMMISSION 27 OF THE I. A. U.
            INFORMATION BULLETIN ON VARIABLE STARS
                        Number 2732

                                            Konkoly Observatory
                                            Budapest
                                            27 May 1985

                                            HU ISSN 0374 - 0676



    BEHAVIOUR OF THE X-RAY BINARY V1727 CYGNI = 4U 2129 +47 IN 1984


  On the basis of the sequence of comparison stars given by Wenzel (1983)
the star was inspected on 35 blue-sensitive plates (ORWO-ZU21+GG13+BG12)
from 31 nights taken with the 50/70/172 cm Schmidt camera of Sonneberg
Observatory covering the time interval between 1 May 1984 and 13 December
1984. The individual estimates are given in Table I. On most of the plates
the star is below the limiting magnitude. V1727 Cygni is only visible on
some individual plates. There, its brightness varies between mB= 17.9mag and

                      Table I
J.D.hel         mB       Rem.           J.D.hel       mB        Rem.
244....                                244....
5822.543      > 18.0mag                5945.502     > 17.9mag   iv
5843.438      > 17.9     iv            5946.454    >> 17.9      iv
5855.494        17.9::                 5946.513       18.2
5871.494      > 17.9     iv            5962.362    >> 17.5      iv
5905.437        18.0                   5973.372     > 17.9      iv
5905.473        18.05                  5991.341     > 17.9      iv
5907.435     >> 17.9     iv            6000.377       18.3
5911.444      > 17.5     iv            6001.336     > 17.9      iv
5912.415      > 17.9     iv            6002.337     > 17.9      iv
5913.401      > 17.9     iv            6003.350      >17.9      iv
5916.401      > 17.9     iv            6004.359    >> 17.9      iv
5916.426      > 17.9     iv            6005.393       18.0      iv
5930.367      > 18.05                  6018.283     > 17.9      iv
5934.463     >> 17.5     iv            6019.280       18.1
5935.484        18.1                   6019.303       18.2
5936.475        17.9                   6047.221     > 17.9      iv
5940.463      > 17.9     iv            6048.229     ? 17.9      iv
5942.470      > 17.9     iv
                      iv = invisible


                             [FIGURE 1]


mB = 18.3mag. The behaviour given here characterizes the inactive state of the
star which probably started near 7 September 1983 (Wenzel, 1983).
  Figure 1 shows the observations listed in Table I, reduced to one common
epoch by means of the elements:

     Min (hel.) = 244 4403.743 + 0.218 2579d 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:
Wenzel, W., 1983, I.B.V.S., No. 2452.
McClintock et al., 1982, Astrophys. J., 258, 245. [BIBCODE 1982ApJ...258..245M ]