COMMISSION 27 OF THE I. A. U.
        INFORMATION BULLETIN ON VARIABLE STARS
                    Number 1846
 
                                   Konkoly Observatory
                                   Budapest
                                   1980 September 19

                                   HU ISSN 0374-0676




        RAPID VARIABILITY OF SYMBIOTIC STARS:
            CH CYGNI AND EG ANDROMEDAE




    Previous investigations of 12 symbiotic stars have shown
that they do not exhibit flickering activity (Walker, 1977).
Only for one star CH Cyg the presence of flickering similar in
nature to that seen in the cataclysmic variables has been confirmed 
during the course of its outburst in 1977 (Slovak,
Africano, 1978).
    Two of the symbiotic stars were observed by us in September
1980 by using the 1 m telescope of the Konkoly Observatory of
the Hungarian Academy of Sciences, equipped with an automatic
one-channel photometer with an unrefrigerated photomultiplier
EMI 9058. All the observations were made in standard U filter.
Because all the observations were made near to the zenith so
the differential atmospherical extinction could be neglected.
    CH Cyg: BD +49d2994 was used as comparison star. The integration 
time of one measure was 3s. After every 75 measurements 
the comparison star and the background were observed with
the same integration time. The mean standard error determined
from measures for the comparison star was 0.005mag. The results
are shown in Fig.1. It seems that CH Cyg shows rapid variability
with an amplitude above 0.1mag on time scales about 15-20mag. similar
to that described by Slovak and Africano (7978). Additional
rapid flickering activity (about some hundredths of magnitude
and on the time scales of some minutes) may also be present but
it is not clearly discernable because of the method of observation.

                         [FIGURE 1]

 Fig.1. Rapid light variation of CH Cyg in the standard U filter.
 The observation was made on 4 September 1980. Time marks are
 500s apart.

                         [FIGURE 2]

 Fig.2. U observations of EG And. Crosses correspond to the 
 comparison star; dark points to differences in magnitudes of EG And
 and comparison star; open circles to control series of measures of
 comparison star. The observation was made on 5 September 1980.
 Time marks are 500s apart.


    EG And: BD +40d758 was used as comparison star. The method
of observations was the same ns in the case of CH Cyg. The integration 
time was 5s. The mean standard error was about 0.005mag.
It seems that the quiescent symbiotic star EG And does not
show any rapid variability with the amplitude above the noise
(Fig.2). Small differences in brightness are caused rather by
interpolation errors.



              JOANNA MIKOLAJEWSKA and MACIEJ MIKOLAJEWSKI
                  Institute of Astronomy
                  Nicolaus Copernicus University
                  Torun, Poland

References:
Slovak, M.H.,Africano,J.,1978, Mon.Not.R.astr.Soc. 185, 591 [BIBCODE 1978MNRAS.185..591S ]
Walker, A.R., 1977, Mon.Not.R.ast.Soc. 179, 587 [BIBCODE 1977MNRAS.179..587W ]