Search

We present results of the 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 more than by a factor of two during 1992-2008. The lag between the continuum and Hbeta emission line flux variations is 21.1+-1.9 days. For the Halpha line the lag is about 27 days but its uncertainty is much larger. We use Monte-Carlo simulation of the 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 random subset selection (RSS) method of Peterson et al. (1998). The lag in the high-velocity wings are shorter than in the line core in accordance with the virial motions. However, the lag is slightly larger in the blue wing than in the red wing. This is a signature of the infall gas motion. Probably the BLR kinematic in the Mrk 6 nucleus is a combination of the Keplerian and infall motions. The velocity-delay dependence is similar for individual observational seasons. The measurements of the Hbeta line width in combination with the reverberation lag permits us to determine the black hole mass, M_BH=(1.8+-0.2)x10^8 M_sun. This result is consistent with the AGN scaling relationships between the BLR radius and the optical continuum luminosity (R_BLR is proportional to L^0.5) as well as with the black-hole mass-luminosity relationship (M_BH-L) under the Eddington luminosity ratio for Mrk 6 to be L_bol/L_Edd ~ 0.01.

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 longterm variability of the [O III] λ 5007 A 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 × 10 9 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 ratiosLbol/LEdd in AGNs.