Pavlenko O. Cataclysmic variables and related binary stars with low mass ratio of the components.

The thesis is devoted to investigation of the different cataclysmic variables and related systems behavior that is seen in change of different photometric characteristics and that is caused by thermal and tidal instability of accretion disc, mass transfer rate and accretion rate variations, direction of accretion by magnetic field, effects of the black hole or neutron star gravitation. The conclusion of thesis are based on the observational data obtained by author since 1990 up to present time with different telescopes of CrAO, SAI with adding the data of foreign colleagues. It is shown that observational characteristics of the dwarf novae and active postnovae outbursts are similar and correspond to the theory of thermal disk instability. The non-linear of the spin-orbital asynchronism was found in the asynchronous polar V1500 Cyg, two stages of synchronization were determined. The observational evidences of the complex magnetic field structure are found, the geometry of accretion in the rotating magnetic field is defined. The dwarf nova SDSS J0804 is classified as the eclipsed WZ type binary with multiple rebrightenings; the white dwarf pulsations in SDSS J0804 were found at the 8-9 months after the outburst. The negative superhumps connected to the nodal precession of the tilted accretion disc in dwarf nova MN Dra are discovered. The secondary mass is estimated to be of 0.028-0.065 solar masses. The photometric periods of optical transients V404 Cyg and V406 Vul is discovered, for the optical transient XTE J2123-058 the evolution of reflection effect is studied.