We determine interband lags between variations in the B band and variations in the V, R, and I bands for 14 active galactic nuclei observed at the Crimean Astrophysical Observatory. The computed lags ...range from tenths of a day to several days, and it is positive (that is, V, R, and I bands lag behind the B band) in most cases, except for a few cases for the V filter. In some cases, the lag is greater than zero, with more than 3 sigma confidence. The lag is systematically less for the V filter than for the red filters, and the lag determined from the cross-correlation function (CCF) centroid is systematically greater than the lag determined from the CCF peak. We find that the lag scales with luminosity as L super(b), where b approximately 0.4-0.5. We attribute this lag to the light time travel effect, so it reflects the geometrical size of the region that emits optical continuum. We consider a model in which optical emission is mainly reprocessed emission that arises in the accretion disk heated by an X-ray source above the disk.
We report a relation between radio emission in the inner jet of the Seyfert galaxy 3C 120 and optical continuum emission in this galaxy. Combining the optical variability data with multi-epoch ...high-resolution very long baseline interferometry observations reveals that an optical flare rises when a superluminal component emerges into the jet, and its maxima is related to the passage of such component through the location of a stationary feature at a distance of {approx}1.3 pc from the jet origin. This indicates that a significant fraction of the optical continuum produced in 3C 120 is non-thermal, and it can ionize material in a sub-relativistic wind or outflow. We discuss implications of this finding for the ionization and structure of the broad emission line region, as well as for the use of broad emission lines for determining black hole masses in radio-loud active galactic nucleus.
Abstract
We present the results of optical spectral and photometric observations of the nucleus of Markarian 6 made with the 2.6-m Shajn telescope at the Crimean Astrophysical Observatory. The ...continuum and emission Balmer-line intensities varied by more than a factor of two during 1992-2008. The lag between the continuum and Hβ emission-line flux variations is 21.1 ± 1.9 days. For the Hα line the lag is about 27 days, but its uncertainty is much larger. We use Monte Carlo simulations of random time series to check the effect of our data sampling on the lag uncertainties and we compare our simulation results with those obtained by the random subset selection (RSS) method of Peterson et al. The lags in the high-velocity wings are shorter than those in the line core in accordance with virial motion. However, the lag is slightly larger in the blue wing than in the red wing. This is a signature of infall gas motion. Probably the broad-line region kinematic in the Mrk 6 nucleus is a combination of Keplerian and infall motions. The velocity-delay dependence is similar for individual observational seasons. Measurements of the Hβ line width in combination with the reverberation lag permit us to determine the black hole mass, M
BH = (1.8 ± 0.2) × 108 M⊙. This result is consistent with active galactic nucleus scaling relationships between the broad-line region radius and the optical continuum luminosity (R
BLR ∝ L
0.5) as well as with the black hole mass-luminosity relationship (M
BH-L) under an Eddington luminosity ratio for Mrk 6 of L
bol/L
Edd ∼ 0.01.
We analyze a total of 827 optical spectra of NGC 5548 obtained over the 30 year period 1972-2001 for the purpose of studying the long-term behavior of the broad HB line profile. The variability ...characteristics, such as mean continuum and emission-line fluxes, rms variability amplitude, autocorrelation functions, and cross-correlation results, are found to be similar for CCD spectra obtained during the period 1989-2001 and for archival pre-CCD spectra from 1972 to 1988. The only significant difference between these two sets of data is that the mean HB flux is higher for 1972-1988. While the H beta profile can vary dramatically on timescales of months to years, the mean profiles for these two periods are similar, but not identical. We searched for correlations among H beta profile parameters (such as line width, line centroid, blue-to-red ratio of the line wing fluxes) and investigated their relationship to the continuum flux. Only trivial correlations were found, specifically the correlation between continuum and line fluxes and the anticorrelation between line width and line flux, the latter following from the former and from the inverse correlation between line time lag and line width expected for gravitationally dominated motion.
We investigate the photometric and polarimetric behavior of the blazar S5 0716+714 based on the observations carried out in 1991–2004 at the 125-cm Crimean Astrophysical Observatory telescope (AZT11) ...with a photopolarimeter that allows simultaneous polarization and brightness measurements to be made in the
U BV RI
bands. We also provide the
U BV
photometry for the blazar obtained in 2000–2009 with a 60-cm telescope at the Crimean Station of the Sternberg Astronomical Institute. The pattern of flux variability and the correlation between the brightness, color, and polarization variations have been investigated. In this time interval the blazar showed a significant brightness and polarization variability similar to noise processes.
We present further results of the optical observations of the 3C 390.3 nucleus undertaken at the Crimean Astrophysical Observatory since 1992. From the new data obtained in 2000-2007, we find ...differences in the responses of the Balmer emission lines to the optical continuum variations. Moreover, these responses (i.e. the relationship between line and continuum fluxes) show long-term changes that can be presumably attributed to the evolution of the relationship between the fluxes of the optical and driving continua. We suspect that some small discrepancy between our spectral and photometric measurements of 3C 390.3 can be attributed to the long-term variability of the O iii λ 5007 Å forbidden line. The cross-correlation analysis of the light curves let us to improve the values of the time delays between continuum and emission-line variations: τcent= 94 ± 6 and 174 ± 16 d for the Hβ and Hα lines, respectively. The black hole mass, derived from the Hβ line, was found to be 2.0 × 109 M⊙. This result suggests an even larger black hole mass for the 3C 390.3 nucleus and, therefore, a lower accretion rate under a given luminosity than was previously thought and thus it provides more evidence for anticorrelation between broad-line widths and Eddington luminosity ratios L
bol/L
Edd in AGNs.
We present the first results from a detailed analysis of photometric and spectrophotometric data on the narrow-line Seyfert 1 (NLS1) galaxy Mrk 335, collected over a 120 day span in the fall of 2010. ...From these data we measure the lag in the He II lambda4686 broad emission line relative to the optical continuum to be 2.7 + or - 0.6 days and the lag in the Hbetalambda4861 broad emission line to be 13.9 + or - 0.9 days. Combined with the line width, the He II lag yields a black hole mass M sub(BH) = (2.6 + or - 0.8) x 10 super(7) M sub(sm circle in circle). This measurement is consistent with measurements made using the Hbetalambda4861 line, suggesting that the He II emission originates in the same structure as Hbeta, but at a much smaller radius. This constitutes the first robust lag measurement for a high-ionization line in an NLS1 galaxy and supports a scenario in which the He II emission originates from gas in virial motion rather than outflow.
Between 1996 and 2002, we have carried out a spectral monitoring program for the Seyfert galaxy NGC 5548 with the 6 m and 1 m telescopes of SAO (Russia) and with the 2.1 m telescope of Guillermo Haro ...Observatory (GHO) at Cananea, Mexico. High quality spectra with S/N > 50 in the continuum near H alpha and H beta were obtained, covering the spectral range similar to (4000-7500) AA with a (4.5 to 15) AA-resolution. We found that both the flux in the lines and the continuum gradually decreased, reaching minimum values during May-June 2002. In the minimum state, the wings of H beta and H alpha became extremely weak, corresponding to a Sy1.8 type, not to a Sy1, as observed previously when the nucleus was brighter. The line profiles were decomposed into variable and constant components. The variable broad component is well correlated with the continuum variation. It consists of a double peaked structure with radial velocities similar to plus or minus 1000 km s super(-1) relative to the narrow component. A constant component, whose presence is independent of the continuum flux variations, shows only narrow emission lines. The mean, rms, and the averaged over years, observed and difference line profiles of H beta and H alpha reveal the same double peaked structure. The relative intensity of these peaks changes with time. During 1996, the red peak was the brightest, while in 1998-2002, the blue peak became the brighter one. Their radial velocities vary in the similar to (500-1200) km s super(-1) range. In 2000-2002 a distinct third peak appeared in the red wing of H alpha and H beta line profiles. The radial velocity of this feature decreased between 2000 and 2002: from the observed profiles, from similar to +(2500-2600) km s super(-1) to similar to +2000 km s super(-1) and is clearly seen on the difference profiles. The fluxes of the various parts of the line profiles are well correlated with each other and also with the continuum flux. The blue and red parts of the line profiles at the same radial velocities vary in an almost identical manner. Shape changes of the different parts of the broad line are not correlated with continuum variations and, apparently, are not related to reverberation effects. Changes of the integral Balmer decrement are, on average, anticorrelated with the continuum flux variations. This is probably due to an increasing role of collisional excitation as the ionizing flux decreases. The behavior of the Balmer decrement of the various parts of the line profiles was different in 1996-2000 as compared with the 2001 behavior. Our results favor the formation of the broad Balmer lines in a turbulent accretion disc with large and moving "optically thick" inhomogeneities, capable of reprocessing the central source continuum.
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