Abstract
Symbiotic binaries are a suitable laboratory for study of complex physical phenomena related to outflows in the form of jets or accretion-related winds. In these strongly interacting systems, physical mechanisms related to transfer and accretion of matter cause observable activity by manifesting increases of brightness (about 2 - 5 mag) and significant changes in their spectra.
Symbiotic binaries are consisting of a cool giant of spectral type K-M and hot compact star, mostly a white dwarf. The mass transfer most likely takes place by the stellar wind of the cool giant, which is also the source of a dense circumbinary envelope of these systems.
Furthermore, as we have shown in our recent research, an increase of mass-loss rate from the hot component would be responsible for the observed spectroscopic behaviour of some symbiotic binaries that have recently manifested the Z And-type outbursts. In present work, the results of our investigation of selected symbiotic binaries based on analysis of the emission lines formed in their circumbinary envelopes are presented in detail.