1997A&A...318..721P

23 spectrograms of the nucleus of the Seyfert galaxy NGC 7469 in the optical region have been obtained at the prime focus of the 6-m telescope during 1977 January 13-15, while the nucleus was at minimum brightness. Spectral dispersion was ∼95Å/mm, spectral resolution ∼8Å. Equivalent widths, relative intensities and profiles of the emission lines H_γ, H_β, [OIII]λλ 4959, 5007ÅÅ, (H_α+[NII]) and [SII]λλ 6717, 6731ÅÅ were studied to reveal their night-to-night variability. The variations were found of profiles of Balmer lines, of relative intensities (H_α+[NII])/H_β, and of [OIII](4959+5007)/H_β. We suppose that this variability is produced by gas flares, with durations of several days. We have compared the obtained spectral properties of the nucleus with published colours and spectral properties observed by other authors during 1943-1986. The relation and character of variability of the line ratios (H_α + [NII])/H_β and [OIII]/H_β on neighbouring nights are the same as for monthly and annual observations. Profiles of the Balmer lines contain variable components keeping their positions during 20 years. These can be understood as reflecting the ingredients in the gaseous structure of the NGC 7469 nucleus, which change their brightness with time without changing their velocities.