Ben-Zhong Dai

Emitting electron spectra and acceleration processes in the jet of PKS 0447−439

We investigate the electron energy distributions (EEDs) and the corresponding acceleration processes in the jet of PKS 0447

Evolution of luminosity function and obscuration of AGN: connecting X-ray and Infrared

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Evolution of the luminosity function and obscuration of active galactic nuclei: comparison between X-ray and infrared

439 and estimate its redshift through modeling its observed spectral energy distribution (SED) in the frame of a one-zone synchrotron-self Compton (SSC) model. Three EEDs formed in different acceleration scenarios are assumed: the power-law with exponential cut-off (PLC) EED (shock-acceleration scenario or the case of the EED approaching equilibrium in the stochastic-acceleration scenario), the log-parabolic (LP) EED (stochastic-acceleration scenario and the acceleration dominating) and the broken power law (BPL) EED (no acceleration scenario), and then the corresponding fluxes of both synchrotron and SSC are calculated. The model is applied to PKS 0447-439 and modeling SEDs are compared to the observed SED of this object by using the Markov Chain Monte Carlo (MCMC) method. Calculating results show that PLC model fails to fit the observed SED well, while the LP and BPL models give comparably good fits for the observed SED. The results indicate that it is possible that stochastic acceleration process acts in the emitting region of PKS 0447-439 and the EED is far from equilibrium (acceleration dominating) or no acceleration process works (in the emitting region). The redshift of PKS 0447-439 is also estimated in our fitting, and

LONG-TERM MULTI-BAND PHOTOMETRIC MONITORING OF BLAZAR S5 0716+714

z=0.16\pm0.05

Optical quasi-periodic oscillation and color behavior of blazar PKS 2155–304

for LP case and

Evolution of optical spectral index and variability properties of S5 0716+714

z=0.17\pm0.04

Multi-wavelength emission from 3C 66A: clues to its redshift and gamma-ray emission location

for BPL case.

Long-term optical-infrared color variability of blazars

We present a detailed comparison between the 2 10 keV hard X-ray and infrared (IR) luminosity function (LF) of active galactic nuclei (AGN). The composite X-ray to IR spectral energy distributions (SEDs) of AGN used for connecting the hard X-ray LF (HXLF) and IR LF (IRLF) are modeled with a simple but well tested torus model based on the radiative transfer and photoionization code CLOUDY. Four observational determinations of the evolution of 2 10 keV HXLF and six evolution models of the obscured type-2 AGN fraction (f2) have been considered. The8.0 and 15 µm LFs for the total, unobscured type-1 and obscured type-2 AGN are predicted from the HXLFs, and then compared with the measurements currently available. We find that the IRLFs predicted from HXLFs tend to underestimate the number of the most IR-luminous AGN. This is independent of the choices of HXLF and f2, and even more obvious for the HXLFs recently measured. We show that the discrepancy between the HXLFs and IRLFs can be largely resolved when the anticorrelation between the UV to X-ray slope αox and UV luminosityLUV is appropriately considered. We also discuss other possible explanations for the discrepancy, such as the missing population of Compton-thick AGN and possible contribution of star-formation in the host to the m id-IR. Meanwhile, we find that the HXLFs and IRLFs of AGN can be more consistent with each other if the obscuration mechanisms of quasars and Seyferts are assumed to be different, corresponding to their different triggering and fueling mechanisms. More accurate measurements of the IRLFs of AGN, especially that determined at smaller redshift bins and more accurately separated to that for type-1 and type-2, are very helpful for clarifying these interesti ng issues.

The long-term color variability of the BL Lac object OQ 530

We present a detailed comparison between the 2 10 keV hard X-ray and infrared (IR) luminosity function (LF) of active galactic nuclei (AGN). The composite X-ray to IR spectral energy distributions (SEDs) of AGN used for connecting the hard X-ray LF (HXLF) and IR LF (IRLF) are modeled with a simple but well tested torus model based on the radiative transfer and photoionization code CLOUDY. Four observational determinations of the evolution of 2 10 keV HXLF and six evolution models of the obscured type-2 AGN fraction (f2) have been considered. The8.0 and 15 µm LFs for the total, unobscured type-1 and obscured type-2 AGN are predicted from the HXLFs, and then compared with the measurements currently available. We find that the IRLFs predicted from HXLFs tend to underestimate the number of the most IR-luminous AGN. This is independent of the choices of HXLF and f2, and even more obvious for the HXLFs recently measured. We show that the discrepancy between the HXLFs and IRLFs can be largely resolved when the anticorrelation between the UV to X-ray slope αox and UV luminosityLUV is appropriately considered. We also discuss other possible explanations for the discrepancy, such as the missing population of Compton-thick AGN and possible contribution of star-formation in the host to the m id-IR. Meanwhile, we find that the HXLFs and IRLFs of AGN can be more consistent with each other if the obscuration mechanisms of quasars and Seyferts are assumed to be different, corresponding to their different triggering and fueling mechanisms. More accurate measurements of the IRLFs of AGN, especially that determined at smaller redshift bins and more accurately separated to that for type-1 and type-2, are very helpful for clarifying these interesti ng issues.

Statistical Analysis on XMM-Newton X-Ray Flares of Mrk 421: Distributions of Peak Flux and Flaring Time Duration

We present long-term optical multi-band photometric monitoring of blazar S5 0716+714, from 2004 January 11 to 2012 November 4, with high temporal resolution of approximately 15 minutes in the BVRI bands. The source was in an active state during the whole monitoring campaign, showing intraday variability in 11 of 72 days. The average magnitudes in each band were B = 14.398, V = 13.821, R = 13.255, and I = 12.885. The overall variability amplitudes were , , , and . The structure function showed that typical timescales for intraday variability were between approximately 2 and 7.5 hr. The intraday variability amplitudes were from a few percent to approximately 30%. We found typical variation rates of approximately 0.05 mag hr−1 in both the rising and falling phases, with a minimal variability timescale of 130 minutes. A 10 day period short-term variability was observed simultaneously in the BVRI bands. The discrete correlation function suggests that there is significant correlated variability between the B- and I-band light curves. However, no significant time lags were detected. The spectral behaviors in the different variability episodes were studied, and our observations show bluer-when-brighter behavior on long, short, and intraday timescales for the blazar S5 0716+714. The variability and relevant spectral trends can be explained by the shock-in-jet scenario.