Our investigations of the quiescent period 1987-1989 of CH Cyg lead to the following conclusions:
- The existing models of CH Cyg cannot be generally applied. They do not even fit consistently the observed features in a particular phase and can only partially explain some phenomena of this symbiotic star.
- The presence of an accretion disc in the system, indicated by flickering variability and jet activity during the outburst has not been confirmed in quiescence. It means that it can be regarded as a transient phenomenon associated with outbursts of the system.
- It is important to understand that the physical properties of the cool giant ultimately determine the observable characteristics of a symbiotic star. Investigations of the manner in which the physical parameters of its atmosphere depend on time should be of great interest.
- Further systematic photometric and spectroscopic observations of CH Cyg in the optical and other spectral regions are necessary to understand the symbiotic phenomenon.
Acknowledgements
This research has made use of the SIMBAD database, operated at CDS, Strasbourg, France. Thanks are due to the referee, Dr. M. Friedjung, for helpful comments and valuable remarks.
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