Broad emission-line profile variability in NGC 5548. The optical emission lines in 1989.

Results of a study of broad optical emission line variations in NGC 5548 are presented. The line spectra have been obtained in 1989 as part of an international campaign. The emission lines of Hα, Hβ, Hγ, HeIλ5876, HeIIλ4686 have different mean and rms profiles. Variability studies show that the line profiles are structured. The location in velocity space of these structures remained constant in 1989. Individual features in the Balmer profiles have different decrements. The variations of the flux cover the whole line profile and are not restricted to the core. Different line segments in the broad emission lines vary with different amplitudes - with respect to each other and with respect to the ultraviolet continuum. The relative intensities depend on the investigated emission line as well as on the individual outburst. The profile structures and their variations indicate that the distribution of the emission line clouds is not homogeneous. The outer line wings tend to respond faster to continuum variations than the line cores for some periods.