COMMISSION 27 OF THE I. A. U.
           INFORMATION BULLETIN ON VARIABLE STARS
                       Number 2839

                                         Konkoly Observatory
                                         Budapest
                                         20 December 1985

                                         HU ISSN 0374 - 0676



        HIGH SPEED PHOTOMETRY OF SS CYGNI AFTER AN OUTBURST



  The cataclysmic variable SS Cygni has been investigated in great detail
by a number of authors over the past ninety years. During July and August
1984, a co-ordinated ultraviolet and optical monitoring of the source had
been planned, using instruments operating onboard IUE and Voyager spacecrafts
and with ground-based optical telescopes (Polidan et al., 1984). Outbursts
of the source were predicted to occur approximately around July 1 and August
25, 1984, with an uncertainty of +-5 days in each case. The star did not,
however, flare up exactly as predicted. It reached a maximum on 26 June as
per prediction. It flared again in late July 1984, considerably earlier than
the 25 August prediction (Mattei, 1984). In order to follow-up the object
as per the earlier prediction, and as a target of opportunity in our program
of high speed photometry of optical counterparts of X-ray sources, we carried 
out a relatively short observation of SS Cygni on 27 August 1984.

  The observations reported here were conducted with a high speed single
photon counting photometer attached to the one meter telescope of the Kavalur
Observatory. The star was monitored with an integration time of either 0.5
sec or 1 sec from 19h14m UT to 20h24m UT. A 12 arcsec diaphragm was used.
The star SAO 051 224 was used as the comparison star.
  Figures 1 and 2 show the light curves in blue filter and unfiltered light
respectively of SS Cygni, after subtracting the sky background. Extreme level
of flickering activity is evident throughout our observations. The decline
from the outburst appears to have been not very calm. Large flares seen in
unfiltered light curves have amplitudes as large as 0.7 magnitude and durations 
of 3 to 4 minutes. The V magnitude estimated at 19h50m UT is 12.0m.
Figure 3 shows the average light curve of the outburst based on our observation 
in association with published results in IAU Circulars as indicated. It
is seen from the figure that although the star had almost reached its low
luminosity state at the time of our observations, the flare activity had
continued unabated.


                            [FIGURE 1]

             Figure 1.  Blue filtered light curve of SS Cygni

                            [FIGURE 2]

             Figure 2.  Unfiltered light curve of SS Cygni


                            [FIGURE 3]

          Figure 3. V magnitude profile of July-Aug 1984 outburst

                            [FIGURE 4]

        Figure 4.  FFT output of the blue run started at 19h13m


  Coherent optical pulsations in SS Cyg with periods between 8.2 and 10.6
sec during outbursts have been reported by a number of authors (Patterson
et al., 1978; Horne and Gomes, 1980 ; Hildebrand et al., 1981). Quasi-periodic
oscillations with a mean period in the range of 32 - 36 sec and mean amplitudes
of about 0.1% have also been reported (Patterson, 1981). In order to search
for these periodicities in our data, we have carried out an FFT and a period


folding analysis. The results of this analysis (shown partly in Figure 4)
with the long blue filter starting at 19h21m UT and the unfiltered run
starting at 20h15m UT are consistent with the presence of oscillations with
a period of 34 +- 1 sec.




                    S. SEETHA, V.N. PADMINI, T.M.K. MARAR,
                     K. KASTURIRANGAN and U.R. RAO

                        ISRO Satellite Centre
                        Airport Road
                        Bangalore - 560017, India



                          J.C. BHATTACHARYYA

                     Indian Institute of Astrophysics
                         Sarjapura Road
                         Bangalore - 560034
                         India





References:

Hildebrand, R.H., Spillar, E.J., and Stiening, R.F., 1981, Ap.J., 243, 223. [BIBCODE 1981ApJ...243..223H ]
Horne, K., and Gomes, R., 1980, Ap.J., 237, 845. [BIBCODE 1980ApJ...237..845H ]
Mattei, J.A., 1984, IAU Circ., No. 3971 [BIBCODE 1984IAUC.3971....3M ]
Patterson, J., Robinson, E.L., and Kiplinger, A.L., 1978, Ap.J., Letters,
    226, L137. [BIBCODE 1978ApJ...226L.137P ]
Patterson, J., 1981, Astrophys. J., Suppl., 45, 517. [BIBCODE 1981ApJS...45..517P ]
Polidan, R.S., Holberg, J.B., Holm, A.V., and Mattei, J.A., 1984, IAU Circ.,
    No. 3945. [BIBCODE 1984IAUC.3945....1P ]