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

                    Number 1004

                                  Konkoly Observatory
                                  Budapest
                                  1975 June 4



           OPTICAL VARIATIONS OF Cen X-3


    A recent report (Mauder, 1975) suggests that optical 
activity of Cen X-3 exists on a time scale of minutes or shorter.
The existence of flickering would provide valuable insight into 
the rate of mass transfer in the system.
    An observation of Cen X-3 was made on June 17, 1974 with
the 100 cm telescope of the South African Astronomical Observatory 
at Sutherland, using the University of Cape Town high speed
photometric system (Nather and Warner, 1971). Both seeing and
photometric conditions were excellent, enabling a small focal
plane aperture to be used thus excluding with certainty any of
the close companion stars. One second integrations were made
for 4100 seconds, at a time corresponding to orbital phases
165deg to 173deg. No filter was used.
    No variations apart from those of a stochastic nature due
to photon statistics were found, to a limit of 0.01 magnitude in
10 seconds. The data were also subjected to a power spectrum analysis 
which gave negative results, in agreement with Lasker (1974)
and Peterson et al. (1975).


                              A. R. WALKER
                              P. R. HURLY
                          Department of Astronomy,
                          University of Cape Town




References:

Lasker, B.M., 1974, Nature, 250, 398. [BIBCODE 1974Natur.250..308L ]
Mauder, H., 1975, Ap.J. (Letters), 195, L27. [BIBCODE 1975ApJ...195L..27M ]
Nather, R.E. and Warner, B., 1971, M.N.R.A.S., 152, 209. [BIBCODE 1971MNRAS.152..209N ]
Peterson, B.A., Middledich, J. and Nelson, J., 1975, Ap.J.
          (Letters), 195, L31. [BIBCODE 1975ApJ...195L..31P ]