V. P. Mikhailov

Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. XVI. A 13 Year Study of Spectral Variability in NGC 5548

We present the final installment of an intensive 13 year study of variations of the optical continuum and broad Hemission line in the Seyfert 1 galaxy NGC 5548. The database consists of 1530 optical continuum measurements and 1248 Hmeasurements. The Hvariations follow the continuum variations closely, with a typical time delay of about 20 days. However, a year-by-year analysis shows that the magnitude of emission-line time delay is correlated with the mean continuum flux. We argue that the data are consistent with the simple model prediction between the size of the broad-line region and the ionizing luminosity, r / L 1=2 ion . Moreover, the apparently linear nature of the correlation between the Hresponse time and the nonstellar optical continuum Fopt arises as a consequence of the changing shape of the continuum as it varies, specifically Fopt / F 0:56 UV . Subject headings: galaxies: active — galaxies: individual (NGC 5548) — galaxies: nuclei — galaxies: Seyfert

Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. XII. Ground-based monitoring of 3C 390.3

Results of a ground-based optical monitoring campaign on 3C 390.3 in 1994-1995 are presented. The broadband fluxes (B, V, R, and I), the spectrophotometric optical continuum flux Fλ(5177 A), and the integrated emission-line fluxes of Hα, Hβ, Hγ, He I λ5876, and He II λ4686 all show a nearly monotonic increase with episodes of milder short-term variations superposed. The amplitude of the continuum variations increases with decreasing wavelength (4400-9000 A). The optical continuum variations follow the variations in the ultraviolet and X-ray with time delays, measured from the centroids of the cross-correlation functions, typically around 5 days, but with uncertainties also typically around 5 days; zero time delay between the high-energy and low-energy continuum variations cannot be ruled out. The strong optical emission lines Hα, Hβ, Hγ, and He I λ5876 respond to the high-energy continuum variations with time delays typically about 20 days, with uncertainties of about 8 days. There is some evidence that He II λ4686 responds somewhat more rapidly, with a time delay of around 10 days, but again, the uncertainties are quite large (~8 days). The mean and rms spectra of the Hα and Hβ line profiles provide indications for the existence of at least three distinct components located at ±4000 and 0 km s-1 relative to the line peak. The emission-line profile variations are largest near line center.

Nuclear activity of NGC 4151 as inferred from UBVRI observations in 1989–2000

We present our broadband UBVRI observations of the nucleus of the Seyfert galaxy NGC 4151 from 1989 until 2000 at three astronomical observatories: the Crimean Station of the Sternberg Astronomical Institute, the Special Astrophysical Observatory in the Caucasus, and the Maidanak Observatory of the Ulugbek Astronomical Institute in Uzbekistan. All data have been reduced to a single system and are given for an A=27.″5 aperture. Regular R and I observations show that the pattern of optical variability is the same in all bands; the relative variability amplitude decreases from U to V, but it is even slightly larger in R than in V. The variability amplitude of the component fluctuating on time scales of several months is proportional to the UBV flux from the component varying on times scales of several years. The correlation between the slow and rapid components significantly weakens in the red, and no correlation has been found between the flux from the slow component and the amplitude of the rapid component in R. The color characteristics correspond to the recombination radiation from an optically thick plasma beyond the Balmer limit.

Two-colour CCD imaging of 15 Seyfert galaxies. Observations

Abstract We present the results of V (Johnson) and I/R (Cousins) CCD imaging of 15 Seyfert galaxies. Grey–scale and contour maps are provided as well as the results of elliptical fits to isophotes. The position angles and the axial ratios of the bars and the outer isophotes are obtained for each galaxy. We have found one clear and one possible unidentified bar, four inner and two outer rings in the galaxies not previously classified as barred or having these rings. The presence of four bars, and one outer ring has been confirmed for the galaxies with uncertain classification. Three galaxies previously classified as having inner rings did not reveal these. Four multiple-barred galaxies have been found. Two of them clearly show a secondary bar within a primary bar and another two have been classified as possible double-barred galaxies. The bar orientations have been compared with the [OIII] and radio major axes for five galaxies with known [OIII] and radio maps. It has been determined that the bar is aligne...

Nuclear activity of NGC 5548 from UBVRI observations during 1990–2000

AbstractWe present our UBV RI observations of the nucleus of the Seyfert Galaxy NGC 5548 from 1990 until 2000 at four astronomical observatories: the Crimean Station of the Sternberg Astronomical Institute, the Special Astrophysical Observatory of the Russian Academy of Sciences, the Crimean Astrophysical Observatory (Ukraine), and the Mount Maidanak Observatory of the Ulugbek Astronomical Institute (Uzbekistan). All data have been reduced to a single system and are given for an A=14.3″ aperture. Large light variations have been observed in the galactic nucleus over the last ten years: the total variability amplitude through the A=14.3″ aperture was

Spectral and photometric monitoring of Seyfert galaxies and quasars in 1998. 1. observations

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Optical Monitoring of Seyfert Galaxies and Quasar Nuclei in 1998. I. Observations

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