Complex variability pattern in NGC 4151 II. Variable absorption features

We found and identified the blueshifted variable absorption features in the NGC 4151 optical spectra obtained in 1992-1996. Two of these features iden tified with He I lambda 4471 and lambda 7065 lines have been investigated i n detail. The most striking change in the He I lambda 4471 equivalent width was its strengthening between approximate to JD2450212-JD2450315. We prese nt some indications of the extremely low-ionization state of absorber in th is period of observations. We do not find clear evidence for a correlation (neither inverse nor direct) of equivalent widths with the state of the nuc leus activity. This probably means that strong changes in the covering fact or (or something else) affect this correlation. The decomposition method ba sed on the different behavior of broad emission lines and absorption lines allows us to separate these spectral features, and to obtain evidence that the H alpha, H beta and H gamma absorption lines are also present. The pres ence of the absorption lines cause the variations of the broad emission pro files to become more complicated. Possible explanations for the absorption variability are discussed.