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We report the results of the first long-term (1990-2014) optical spectro-photometric monitoring of a binary black hole candidate QSO E1821+643, a low-redshift high-luminosity radio-quiet quasar. In the monitored period the continua and H$\gamma$ fluxes changed for around two times, while the H$\beta$ flux changed around 1.4 times. We found the periodical variations in the photometric flux with the periods of 1200, 1850 and 4000 days, and 4500 days periodicity in the spectroscopic variations. However, the periodicity of 4000-4500 days covers only one cycle of variation and should be confirmed with a longer monitoring campaign. There is an indication of the period around 1300 days in the spectroscopic light curves, but with small significance level, while the 1850 days period could not be clearly identified in the spectroscopic light curves. The line profiles have not significantly changed, showing an important red asymmetry and broad line peak redshifted around +1000 km s$^{-1}$. However, H$\beta$ shows broader mean profile and has a larger time-lag ($\tau\sim120$ days) than H$\gamma$ ($\tau\sim60$ days). We estimate that the mass of the black hole is $\sim2.6\times10^9\rm M_\odot$. The obtained results are discussed in the frame of the binary black hole hypothesis. To explain the periodicity in the flux variability and high redshift of broad lines we discuss a scenario where dense gas-rich cloudy-like structures are orbiting around a recoiling black hole., Comment: Accepted in ApJS

Quasar 3C 279 is known to exhibit episodes of optical polarization angle rotation. We present new, well-sampled optical polarization data for 3C 279 and introduce a method to distinguish between random and deterministic electric vector position angle (EVPA) variations. We observe EVPA rotations in both directions with different amplitudes and find that the EVPA variation shows characteristics of both random and deterministic cases. Our analysis indicates that the EVPA variation is likely dominated by a random process in the low brightness state of the jet and by a deterministic process in the flaring state., Comment: 6 pages, 2 figures, 4 tables, proceeding to appear on EPJ Web of Conferences "The Innermost Regions of Relativistic Jets and their Magnetic Fields (Granada, Spain,10-14 June 2013)"

Here we present results of the long-term (1987-2010) optical spectral monitoring of the broad line radio galaxy Arp 102B, a prototype of active galactic nuclei with the double-peaked broad emission lines, usually assumed to be emitted from an accretion disk. To explore the structure of the broad line region (BLR), we analyze the light curves of the broad H\alpha and H\beta lines and the continuum flux. We aim to estimate the dimensions of the broad-line emitting regions and the mass of the central black hole. We use the CCF to find lags between the lines and continuum variations. We investigate in more details the correlation between line and continuum fluxes, moreover we explore periodical variations of the red-to-blue line flux ratio using Lomb-Scargle periodograms. The line and continuum light curves show several flare-like events. The fluxes in lines and in the continuum are not showing a big change (around 20%) during the monitoring period. We found a small correlation between the line and continuum flux variation, that may indicate that variation in lines has weak connection with the variation of the central photoionization source. In spite of a low line-continuum correlation, using several methods, we estimated a time lag for H\beta around 20 days. The correlation between the H\beta and H\alpha flux variation is significantly higher than between lines and continuum. During the monitoring period, the H\beta and H\alpha lines show double-peaked profiles and we found an indication for a periodical oscillation in the red-to-blue flux ratio of the H\alpha line. The estimated mass of the central black hole is \sim 1.1 \times 10^8 M\odot that is in an agreement with the mass estimated from the M-\sigma* relation., Comment: Accepted for publication in A&A