E. A. Sergeeva

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.

Optical continuum properties of the NLS1 galaxy Mrk 335 in 1995-2004

We present results of UBVRI photometry of Mrk 335 in 1995-2004. This object has a large amplitude of variability, reaching about 1.1, 0.9, 0.7 mag in the U, B, V and 0.3 mag in the Rc, Ic bands, respectively. This photomerical behaviour as well as the spectral energy distribution in the optical part of the spectrum is typical of Seyfert 1 galaxies. The structure function (SF) analysis of Mrk 335 has shown that the variability of Mrk 335 can be caused by stochastic superposition of independent flares in a wide interval of durations, the longest of which has a duration of about several hundred days. The slope of the power-law portion of the SF b ∼ 0.6-0.7 for the time scale from several days to several hundreds of days. It is close to the estimates for disk instability models. The estimate of the extension of the instability zone in an accretion disk (about 300Rs) is also evidence that the instability in an accretion disk is able to explain the long-term optical variability. A cross-correlation function (CCF) shows some evidence that the delay of fluxes in the V,R, I bands relative to the U band can be of some days, and there is a tendency for lags lo be systematically higher for the R, I bands than for B, V.

Optical variability of the NLS1 galaxy Ark 564 in 1987–2004

We present the results of our U BV RcIc photoelectric and CCD photometry of the NLS1 galaxy Ark 564 in 1987–2004. Between late 1997 and 2002, a slight increase in brightness was observed followed by a small but systematic decline until 2004. Ark 564 has a low variability amplitude, within 0.2m in the U BV RcIc bands. The galaxy’s spectral energy distribution at 3600–9000 Å is unlike those for Seyfert 1 (Syl) galaxies. A delay of the Ic flux relative to the B flux of about three days was found, which is in agreement with the standard disk model. This delay probably reflects the geometric size of the region that emits the observed continuum.

Photometry of the Supernova SN 2002ap in M 74 during 2002

UBVRcIc observations of SN 2002ap during February, October, and November 2002 at the Crimean Astrophysical Observatory are reported. An examination of our photometric data, along with published data, shows that over a period of about a year from the day the SN 2002ap supernova burst, the light curve passed through three developmental stages: a sharp rise, followed by a stage of rapid exponential decrease, and then a slower fading. Based on the shape of the light curve, this supernova is of type SN I, but according to the variation in its color indices, it more likely belongs to the SN Ic supernovae. In the premaximum stage, the energy distribution from λ 3000 Å to λ 6000 Å resembles the emission from a star of spectral class F5V. In the second stage of the light curve evolution, when the brightness falls off rapidly, the changes in the color indices are associated with a change in the radiation temperature indicative of rapid cooling of the ejected material. Taking the effective radiation temperature in the premaximum stage to be Teff ≈ 6500 K, we estimate the expansion velocity of the quasiphotosphere to be about 9700 km/s.