G. Z. Xie

Optical Monitoring Sample of the GeV Gamma-Ray-loud Blazars

We present optical monitoring between 1994 February and 1997 December of 10 gamma-ray-loud blazars included in our blazar monitoring program. Most of the monitored objects show significant rapid variations. The typical minimum variability timescale in the optical range is about 1 hour. We have analyzed the relationships between optical variability and gamma-ray variability, and discussed theoretical models for the gamma-ray-loud blazar emission.

The correlated optical and radio variability of BL Lacertae. WEBT data analysis 1994-2005

Context: Since 1997, BL Lacertae has undergone a phase of high optical activity, with the occurrence of several prominent outbursts. Starting from 1999, the Whole Earth Blazar Telescope (WEBT) consortium has organized various multifrequency campaigns on this blazar, collecting tens of thousands of data points. One of the main issues in the study of this huge dataset has been the search for correlations between the optical and radio flux variations, and for possible periodicities in the light curves. The analysis of the data assembled during the first four campaigns (comprising also archival data to cover the period 1968-2003) revealed a fair optical-radio correlation in 1994-2003, with a delay of the hard radio events of ~100 days. Moreover, various statistical methods suggested the existence of a radio periodicity of ~8 years. Aims: In 2004 the WEBT started a new campaign to extend the dataset to the most recent observing seasons, in order to possibly confirm and better understand the previous results. Methods: In this campaign we have collected and assembled about 11 000 new optical observations from twenty telescopes, plus near-IR and radio data at various frequencies. Here, we perform a correlation analysis on the long-term R-band and radio light curves. Results: In general, we confirm the ~100-day delay of the hard radio events with respect to the optical ones, even if longer (~200-300 days) time lags are also found in particular periods. The radio quasi-periodicity is confirmed too, but the “period” seems to progressively lengthen from 7.4 to 9.3 years in the last three cycles. The optical and radio behaviour in the last forty years suggests a scenario where geometric effects play a major role. In particular, the alternation of enhanced and suppressed optical activity (accompanied by hard and soft radio events, respectively) can be explained in terms of an emitting plasma flowing along a rotating helical path in a curved jet. The radio-to-optical data presented in this paper are stored in the WEBT archive; for questions regarding their availability, please contact the WEBT President Massimo Villata.

Optical periodicity analysis for radio selected BL Lacertae objects (RBLs)

The recently compiled historical lightcurves of 10 RBLs are probed with the Jurkevich method in a search for periodic behaviour. Monte Carlo simulations of artificial lightcurves are used to detect spurious periods and evaluate sources of error in this kind of analysis. Additional analysis based on the discrete correlation function (DCF) provides confirmation for those periods that could have physical significance. We find that periods in the range 1.4-17.85 yr are present in nine objects of the sample.

PERIODICITY ANALYSIS OF THE RADIO CURVE OF PKS 1510-089 AND IMPLICATIONS FOR ITS CENTRAL STRUCTURE

We have analyzed the radio light curves of PKS 1510-089 at 37 and 22 GHz from 1990 to 2005 taken from the database of the Metsahovi Radio Observatory, and find evidence of quasi-periodic outbursts. The light curves show great activity with very complicated non-sinusoidal variations. Using Jurkervichs method, the power spectrum method, and the discrete autocorrelation function to analyze these data, we have found two periods of p(1) = 0.92 +/- 0.04 yr and p(2) = 1.82 +/- 0.12 yr for the outbursts in PKS 1510-089. It is interesting to note that the results for two frequencies and three methods are almost the same and p(2) approximate to 2p(1). In addition, these results are in good agreement with the periodic deep flux minima of 1.84 +/- 0.1 yr ( half period similar to 0.92 +/- 0.03 yr) observed by us and other authors in the optical band in 2002, 2004, and 2005.

Observational distinction between two types of active galactic nuclei

Using three criteria, we discuss the observational distinction between relativistic beaming and pure accretion for 69 active galaxies, including Seyferts, Quasars, and BL Lac objects. The first criterion is whether the inferred efficiency of the conversion of accreted matter into energy is greater than 0.1 or not. The second one is whether the observed flux is larger than the classical Eddington luminosity or not. The third is concerned in the strong coupling of geometrical and physical effects in jets. The result suggests distinguishing active galactic nuclei into two types.

THE SPECTRAL ENERGY DISTRIBUTIONS OF THE FERMI BLAZARS AND CONNECTION AMONG LOW-ENERGY PEAKED BL LACERTAE, HIGH-ENERGY PEAKED BL LACERTAE, AND FLAT SPECTRUM RADIO QUASARS

We complied the optical, X-ray, and gamma-ray data for 54 Fermi blazars and studied the relationship between the broadband spectral index alpha(ox) and alpha(x gamma), as well as the relationship between the intrinsic composite spectral indices alpha(xox) and alpha(gamma x gamma) for this sample. The relationship between alpha(xox) and alpha(gamma x gamma) reveals that flat spectrum radio quasars and low-energy peaked BL Lacertae follow a continuous trend, which is consistent with previous results, whereas high-energy peaked BL Lacertae follow a separate distinct trend. Even so, a unified scheme is also revealed from alpha(xox)-alpha(gamma x gamma) diagram when all three subclasses of blazars are considered.

The Periodicity Analysis of the Light Curve of 3C 279 and Implications for the Precession Jet

We have analyzed the light curves of 3C 279 at 22 GHz, 37 GHz, optical R band, and X-ray (2-10 KeV), and found evidence of quasi-periodic outbusts. The light curves show that 3C 279 is an extremely active object. A period of P = 130:6 +/- 1:3 days was consistently confirmed by three methods: the power-spectrum method, the discrete correlation function (DCF) method, and the Jurkevich method. Based on the relationship between observed period Pobs and the precession period Pp given by Rieger and our result, the precession period of jet in 3C 279 is P(p) similar or equal to 29.6 yr, which is completely consistent with the precession period of jet of about 30 yr obtained by Carrara et al.. This suggests that there is a precession jet in 3C 279 and the variability period of about 130.6 days that we obtained is most likely caused by the helical motion of the jet.

The accretion rates-luminosity relations and evolutionary sequence of FSRQs, BL Lac objects and radio galaxies

A: sample of 39 blazars with well-established rapid variability timescale and bolometric luminosity has been compiled from literature. Based on the assumption that central supermassive black holes (SMBHs) are Kerr black holes, the upper limits of SMBHs were estimated. The masses ranged from 10(7.2)M(circle dot) to 10(9.4)M((C)), showing a distribution of three subclasses: massive flat spectra radio quasars (FSRQs) and smaller mass BL Lacs, occupy separate regions, while medium mass FSRQ and BL Lac object bridge the gap. In addition, we complied a sample of radio galaxies including 9 sources for which their black holes masses have been derived from the M-BH - sigma correlation and their optical and infrared data have been well observed. We find that the intrinsic accretion rates axe quite different between FSRQs, BL Lacs and the radio galaxies. The diagram of the intrinsic accretion rate-luminosity relations shows that FSRQs occur in the earlier, high luminosity, violent phase of galactic evolution sequence, while BL Lacs occur in the low luminosity, transition phase between quasars and radio galaxies, and the radio galaxies occur in the late stage of the elliptical galaxy evolution sequence. Our theoretical results prove that the evolutionary track of the elliptical galaxy evolutionary sequence is from FSRQs to BL Lacs and then to the radio galaxies. The evolution diagram of blazars derived in this paper seems to be similar to Hertzsprung-Russell diagram of star evolution.

TESTING A NEW LUMINOSITY/REDSHIFT ESTIMATOR OF GRBs

Using a generalized method, we have tested an estimator of luminosity/redshift proposed by Zhang et al. (2006a), in which relative spectral lag (RSL) is tightly related with luminosity and redshift, respectively. The derived luminosities from the new estimator are found to be comparable with the observed ones. For two different GRB samples, we have examined that there are no outliers violated the luminosity relation within 3 sigma confidence level. Several potential outliers for other luminosity relations are otherwise found to match the estimator well. These results suggest that the luminosity/redshift relation could be a potential tool for cosmological studies.

Several observed features and their implications for gamma-ray-loud blazar PKS 1510-089

The new results of spectrophotometry, and X-ray imaging spectroscopy observations for the high-polarization, radio-loud and Gev gamma-ray-loud blazar PKS 1510-089 have been observed. The main results show that: (1) A double-horned broad H-beta line in the spectrum of PKS 1510-089 has been discovered. The H-beta double-peaked emission profiles are impressive with the line asymmetry that the red peak seems to be higher than the blue peak; (2) The observation of X-rays, performed with the ACIS-S detector aboard the Chandra X-ray observatory, led to the discovery of a bending X-ray jet, coincident with the radio arcsecond jet of PKS 1510-089; (3) According to the reverberation mapping method and the empirical relation between the broad line region (BLR) size and the optical continuum luminosity at 5100 angstrom (the rest frame), we obtained the Virial mass of the central primary black hole, which coincides with our previous result by extremely rapid optical variability method. In addition, based on these new observational results mentioned above and the other previous observations, we have discussed the theoretical models for PKS 1510-089.