COMMISSION 27 OF THE I. A. U.
         INFORMATION BULLETIN ON VARIABLE STARS
                     Number 933

                                     Konkoly Observatory
                                     Budapest
                                     1974 October 18


              OPTICAL PHOTOMETRY OF CYGNUS X-2

     It was reported by Lyutyj (1974) that the optical counterpart
of the x-ray source Cygnus X-2 is a double line spectroscopic binary 
with a period 0d.251451.
     We have made photometric observations in order to check Lyutyj's
suggestion, looking for brightness variability with a period of 
orbital revolution. No deep eclipses could be expected because there
are no x-ray eclipses observed. However because of relatively large
range of radial velocity variations (Burbidge et al. 1967, Kristian
et al. 1967, Kraft and Demoulin 1967) we may expect periodic 
variability due to tidal deformation of the components or even shallow
grazing eclipses.
     The unfiltered 1P21 photomultiplier was used on a 60 cm reflector 
in the Ostrowik station of the Warsaw University Observatory. As
a comparison we used star no. 1 from the Fig. 3 in a paper by Giacconi 
et al. (1967).
     Figure 1 gives results of our observations. The arrows point
on times of spectroscopic conjuction with the HeII component behind
according to Lyutyj's elements. It can be seen that the observed 
variability is not related to the Lyutyj's period of the orbital motion.
     The object's average brightness decreased by 0.4 mag during the week
covered by our observations. Beside that there are variations on a
time scale of 1 hour and an amplitude about 0.2 mag, and these variations 
seem to be more pronounced when the object is brighter. Similar
short time scale flickering was already observed by Kristian et al.
(1967).
     With the present observational material it could not be excluded 
that the shallow dips in the light curve that occur at the beginning 
of nights Sept. 15, 17, and 19 are due to eclipses even though
that possibility is not very likely. The possible periods that fit
these three dips are 1d.990, 0d.663, and 0d.398. Few other values of
the period could be considered if one is willing to believe that the
intrinsic flickering has prevented us from detecting an additional
minimum on the night of Sept. 12 and in case of period 0d.249 still
another minimum on Sept. 19.

                           [FIGURE 1]


Warsaw University Observatory                     A. KRUSZEWSKI
                                                  I. SEMENIUK
                                                  A. SCHWARZENBERG-CZERNY

References:
Burbidge, E.M., Lynds, C.R., and Stockton, A.N. 1967, Ap.J.Letters
          150, L95 [BIBCODE 1967ApJ...150L..95B ]
Giacconi, R., Gorenstein, P., Gursky, H., Usher, P.D., Waters, J.R.,
          Sandage, A., Osmer, P., and Peach, J.V. 1967, Ap.J.Letters,
          148, L129 [BIBCODE 1967ApJ...148L.129G ]
Kraft, R.P., and Demoulin, M.-H. 1967, Ap.J.Letters, 150, L183 [BIBCODE 1967ApJ...150L.183K ]
Kristian, J., Sandage, P., and Westphal, J.A. 1967, Ap.J.Letters,
          150, L99 [BIBCODE 1967ApJ...150L..99K ]
Lyutyj, W.M. 1974, IAU Circular, 2691 [BIBCODE 1974IAUC.2691....1L ]