In this paper, we investigate the influences of two continuum radiation pressures of the central engines on the black hole mass estimates for 40 active galactic nuclei (AGNs) with high accretion rates. The two continuum radiation pressure forces, usu
ally believed negligible or not considered, are from the free electron Thomson scattering, and the recombination and re-ionization of hydrogen ions that continue to absorb ionizing photons to compensate for the recombination. The masses counteracted by the two radiation pressures $M_{rm{RP}}$ depend sensitively on the percent of ionized hydrogen in the clouds $beta$, and are not ignorable compared to the black hole virial masses $M_{rm{RM}}$, estimated from the reverberation mapping method, for these AGNs. As $beta$ increases, $M_{rm{RP}}$ also does. The black hole masses $M_{rm{bullet}}$ could be underestimated at least by a factor of 30--40 percent for some AGNs accreting around the Eddington limit, regardless of redshifts of sources $z$. Some AGNs at $z < 0.3$ and quasars at $z ga 6.0$ have the same behaviors in the plots of $M_{rm{RP}}$ versus $M_{rm{RM}}$. The complete radiation pressures will be added as AGNs match $M_{rm{RP}}ga 0.3 M_{rm{RM}}$ due to the two continuum radiation pressures. Compared to $M_{rm{RM}}$, $M_{rm{bullet}}$ might be extremely underestimated if considering the complete radiation pressures for the AGNs accreting around the Eddington limit.
In this paper, we investigated the issue of black hole masses and minimum timescales of jet emission for blazars. We proposed a sophisticated model that sets an upper limit to the central black hole masses $M_{bullet}$ with the minimum timescales $De
lta t^{rm{ob}}_{rm{min}}$ of variations observed in blazars. The value of $Delta t^{rm{ob}}_{rm{min}}$ presents an upper limit to the size of blob in jet. The blob is assumed to be generated in the jet-production region in the vicinity of black hole, and then the expanding blob travels outward along the jet. We applied the model to 32 blazars, 29 of which were detected in gamma rays by satellites, and these $Delta t^{rm{ob}}_{rm{min}}$ are on the order of hours with large variability amplitudes. In general, these $M_{bullet}$ estimated with this method are not inconsistent with those masses reported in the literatures. This model is natural to connect $M_{bullet}$ with $Delta t^{rm{ob}}_{rm{min}}$ for blazars, and seems to be applicable to constrain $M_{bullet}$ in the central engines of blazars.
In the paper, we investigate correlation between broad-line and radio variations for broad-line radio galaxy 3C 120. By the z-transformed discrete correlation function method and the model-independent flux randomization/random subset selection (FR/RS
S) Monte Carlo method, we find that the broad Hbeta line variations lead the 15 GHz variations. The FR/RSS method shows that the Hbeta line variations lead the radio variations by a factor of tau_{ob}=0.34 +/- 0.01 yr. This time lag can be used to locate the position of emitting region of radio outbursts in jet, on the order of ~ 5 light-years, from the central engine. This distance is much larger than the size of broad-line region. The large separation of the radio outburst emitting region from the broad-line region will observably influence the gamma-ray emission in 3C 120.
We selected a sample of a dozen blazars which are the prime candidates for simultaneous multi-wavelength observing campaigns in their outburst phase. We searched for optical outbursts, intra-day variability and short term variability in these blazars
. We carried out optical photometric monitoring of nine of these blazars in 13 observing nights during our observing run October 27, 2006 - March 20, 2007 by using the 1.02 meter optical telescope. From our observations, our data favor the hypothesis that three blazars were in the outburst state; one blazar was in the post outburst state; three blazars were in the pre/post outburst state; one blazar was in the low-state; and the state of one blazar was not known because there is not much optical data available for the blazar to compare with our observations. Out of three nights of observations of AO 0235+164, intra-day variability was detected in two nights. Out of five nights of observations of S5 0716+714, intra-day variability was detected in two nights. In one night of observations of PKS 0735+178, intra-day variability was detected. Out of six nights of observations of 3C 454.3, intra-day variability was detected in three nights. No intra-day variability was detected in S2 0109+224, OJ 287, ON 231, 3C 279 and 1ES 2344+514 in their 1, 4, 1, 2 and 1 nights of observations respectively. AO 0235+164, S5 0716+714, OJ 287, 3C 279 and 3C 454.3 were observed in more than one night and short term variations in all these blazars were also noticed. From our observations and the available data, we found that the predicted optical outburst with the time interval of ~ 8 years in AO 0235+164 and ~ 3 years in S5 0716+714 have possibly occurred.
