HP and continuum variability in the Seyfert galaxy Akn 120 from Crimean observations during 1974-1990

Crimean spectroscopic observations of the nucleus of the Seyfert galaxy Akn 120 during 1974-1990 are presented. Observations of the H beta region are used to show that the flux variations in H beta follow the flux variations in the continuum near lambda 5100 Angstrom with a lag of 34-54 days. The cr oss-correlation between the H beta wings and the continuum provides evidenc e for accretion of the matter that is responsible for the line emission. Th e reproducibility of the H beta profiles on time scales of about a year or longer at significant continuum variations suggests that the ionization con ditions in the broad-line region are reproducible. The emission of the Fe I I lines, which form the so-called "red shelf," has been separated from the blend of H beta with Fe II. The flux variations in the lines of ionized iro n in this shelf and in the Fe II (lambda 4570 Angstrom) blend correlate wit h the H beta-flux variations, suggesting that the H beta- and Fe II-line re gions are close in space. An attempt is made to represent the broad-H beta- line profile by Gaussians. If the line profile is fitted by three Gaussian components, then the fur in the short-wavelength component, which is shifte d from the systematic velocity by -750 km s(-1), correlates best with the c ontinuum.