Ludmila S. Nazarova

Steps toward determination of the size and structure of the broad-line region in active nuclei. 7: Variability of the optical spectrum of NGC 5548 over years

We report on the results of a continuation of a large monitoring program of optical spectroscopy of the Seyfert 1 galaxy NGC 5548. The new observations presented here were obtained between 1990 December and 1992 October, and extend the existing database to nearly 1400 days, dating back to 1988 December. The continuum variations are generally smooth and well-resolved, except during the third year of this 4 year project, when the variations were apparently more rapid and of lower amplitude than observed at other times. The broad H(beta) emission line is found to vary in response to the continuum variations with a lag of about 18 days, but with some changes from year to year. The H(beta) transfer functions for each of the 4 yr and for the entire 4 yr database are derived by using a maximum entropy method.

Variations of broad optical emission lines in AGN

Abstract AGN optical spectra (4000–5000A) are being observed with the TV scanner of the 6 m telescope at Special Astrophysical Observatory (N. Arkhyz-North Caucasus) since 1986 till now. The usual dispersion is 1A/channel, the signal-to-noise ratio in individual spectra is S/N = 10–25. NGC 4151, NGC 3516, NGC 5548, and NGC 7469 are the main objects of the programme. Strong variations of Hβ, Hγ, Hδ, and HeII 4686A line intensities and profile shapes have been observed on a time scale from 10–30 days to several years. The data are being used in international AGN watch programmes for diagnosis, estimation of the size and structure of the BLR.

Changes of the He II 4686 Å broad line asymmetry of NGC 4151 in 1986-1990

Abstract The NGC 4151 optical spectra obtained with the TV scanner of the 6-meter telescope in 1986-1990 are presented. The 4060-4860 A spectral range was observed. The dispersion was 0.5 ÷ 2 A/channel. The characteristic signal-to-noise ratio in individual spectra was S/N = 10 ÷ 25. Spectra averaged through periods ⩽2.5 months show changes of asymmetry of the He II Λ4686 A broad emission line with a characteristic timescale ≃2 years.

An additional broad line region in 3C 390.3 associated with the jet

We suggest the existence of two BLRs in 3C 390.3 which have different locations. The BLR1 is located at a distance in accordance to the hydrogen line time lags of ≈20 days. This disk-like region emits predominantly low ionization lines. The BLR2 forms around the radio-jet and is located at the distance corresponding to time lags of ≈ 40-80 days. The BLR2 is responsible for most of the emission in UV lines. The Lα line partly forms in BLR2 (40-60%) and partly in BLR1.

The Structure of the BLR in 3C 390.3

Velocity-dependent flux ratios of the broad Lyα, C iv, Hβ, and Hα lines are used to investigate conditions in the archetypical displaced BLR peak emitter 3C 390.3. Our results suggest that gas producing the the UV emission lines has a lower density than the higher-velocity gas producing broad disk-like profile and is less flattened.

Is there a precession-type movement in the nucleus of NGC 4151?

Optical spectra of the NGC 4151 with the TV scanner of the 6-meter telescope in 1986–1991 are presented. Spectra averaged over periods of ≈ 2.5 months show changes of asymmetry of the He II λ4686 A broad emission line with a characteristic time scale ≈ 2 years (the full cycle of the changes is approximately 4 years). Possible explanations involving a precession-type of movement of cones of ionizing radiation are discussed.