L. E. Chen

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.

EXCITATION OF KINETIC ALFVEN WAVES BY DENSITY STRIATION IN MAGNETO-PLASMAS

Field-aligned density striation is one of the most common inhomogeneity phenomena in magneto-plasmas, such as in the solar coronal plasma and terrestrial auroral plasma. Kinetic Alfven waves (KAWs) can play an important role in the inhomogeneous heating of coronal magneto-plasmas as well as in the local acceleration of auroral energetic electrons. In this paper, we study the dispersion and instability of KAWs in a magneto-plasma with density striation structures. Results show that KAWs become unstable in the presence of the density striation and the corresponding instability has a maximal growth rate at the perpendicular wavelength close to the spatial scale of the density gradient. Related experimental phenomena in both laboratory and space plasmas are discussed. It is suggested that the excitation of KAWs by the density striation of magneto-plasmas can be of potential importance in understanding the physics of the formation of magneto-plasma filaments and their heating mechanisms, which are often present in the terrestrial auroral plasma, the solar coronal plasma, and other astrophysical plasmas.

Spectrophotometry and Photometry for Five Blazars and Their Central Black Hole Masses

We have spectrophotometrically observed a sample of five optically violently variable quasars, for which short-timescale optical variabilities have been observed during our optical monitoring campaign since 1994. Using the relationship between black hole masses and optical continuum luminosity at the rest wavelength of 5100 angstrom, we derived the central black hole masses, M-BH. We also estimated the relevant black hole masses, M-H, using rapid-variability timescales and our new formula for black hole mass estimates. The differences log M-BH/M-H are limited by vertical bar log M-BH/M(H)vertical bar <= 0.62, which implies that the two methods of estimating black hole masses by the rapid-variability timescales and the reverberation mapping method should be reliable. We also discuss the origin of the double-peaked H beta emission line in PKS 1510-089 and show it to be probable that the double-peaked H beta emission line is mainly produced by a nonaxisymmetric accretion disk surrounding the central Kerr black hole.

Correlation between eddington ratios and broad-line luminosities in flat-spectrum radio quasars, BL lacertae objects, and radio galaxies

We compiled a sample of 16 flat-spectrum radio quasars (FSRQs), 8 BL Lac objects, and 15 Fanaroff-Riley (FR) I and FR II radio galaxies, for which the intrinsic Eddington ratios and broad-line luminosities are available. In the diagram of the intrinsic Eddington ratio-broad-line luminosity relation, FSRQs are found in the high broad-line luminosity, high intrinsic Eddington ratio region, while BL Lac objects, as well as FR I and FR II radio galaxies, are found in the low broad-line luminosity, low intrinsic Eddington ratio region. In addition, the intrinsic Eddington ratios are strongly correlated with the broad- line luminosities and also with the intrinsic bolometric luminosities, but the correlation with the broad- line luminosities is better. Thus, the broad- line luminosity, rather than the intrinsic bolometric luminosity, should be used as a fundamental parameter of the unified scheme and evolution of active galactic nuclei. On the other hand, we analyze the theory proposed by Czerny and coworkers that the formation of the broad-line region (BLR) is intrinsically connected to the existence of a cold accretion disk. Our studies support that BLR formation is intimately connected with the cold disk. Thus, our results provide solid experimental evidence for the theory that has been proposed by Czerny and coworkers.

The two-color diagram: The "double-hump'' behavior at the radio band and the evolution of blazars

We compiled a sample of 29 flat-spectrum radio quasars (FSRQs) and 48 BL Lac objects for which both B - V and U - B are available. The two-color (U - B, B - V) stellar evolution diagram of FSRQs and BL Lac objects in this sample shows that FSRQs and BL Lac objects can be considered to be in the same family, but they occupy different extreme regions in the diagram. The result of the two- color diagram of FSRQs and BL Lac objects in this paper is consistent with the intrinsic accretion rate - luminosity relation for FSRQs and BL Lac objects that was obtained in a previous paper. In addition, based on the quasi-simultaneous spectral properties of core-dominated radio sources observed by Punsly, we compiled another sample of FSRQs and BL Lac objects for which the quantities Delta log [(F-nu)(cm)/(F-nu)(mm)] have been well obtained. We found that there is a significant correlation between the intrinsic bolometric luminosity log L-bol(in) and the quantity Delta. We also found that FSRQs have a relatively higher bolometric luminosity and larger Delta than BL Lac objects. This result is also consistent with the intrinsic accretion rate - luminosity relation because the physical parameters Delta are strongly correlated with the accretion rates (M) and nuclear gas densities.

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.

Estimates of AGN Black Hole Mass and Minimum Variability Timescale

Black hole mass is one of the fundamental physical parameters of active galactic nuclei (AGNs), for which many methods of estimation have been proposed. One set of methods assumes that the broad-line region (BLR) is gravitationally bound by the central black hole potential, so the black hole mass can be estimated from the orbital radius and the Doppler velocity. Another set of methods assumes the observed variability timescale is determined by the orbital timescale near the innermost stable orbit around the Schwarzschild black hole or the Kerr black hole, or by the characteristic timescale of the accretion disk. We collect a sample of 21 AGNs, for which the minimum variability timescales have been obtained and their black hole masses (M,) have been well estimated from the stellar velocity dispersion or the BLR size-luminosity relation. Using the minimum variability timescales we estimated the black hole masses for 21 objects by the three different methods, the results are denoted by M-s, M-k and M-d, respectively. We compared each of them with M-sigma individually and found that: (1) using the minimum variability timescale with the Kerr black hole theory leads to small differences between M-sigma and M-k, none exceeding one order of magnitude, and the mean difference between them is about 0.53 dex; (2) using the minimum variability timescale with the Schwarzschild black hole theory leads to somewhat larger difference between M-sigma and M-s, larger than one order of magnitude for 6 of the 21 sources, and the mean difference is 0.74 dex; (3) using the minimum variability timescale with the accretion disk theory leads to much larger differences between M-sigma and M-d, for 13 of the 21 sources the differences are larger than two orders of magnitude; and the mean difference is as high as about 2.01 dex.

A possible mechanism for the formation of filamentous structures in magnetoplasmas by kinetic Alfvén waves

Due to having strong anisotropy in their polarization state and spatial structure, it is believed that kinetic Alfven waves (KAWs) can play an important role in various energization phenomena of plasma particles and the fine-structure formation in magnetoplasma environments. The filamentous fine structures are a kind of the common density inhomogeneity phenomena in magnetoplasmas, and hence, the density gradient is one of the sources of free energy that can lead to KAWs instabilities. In this paper, based on the two-fluid model in which ions and electrons are treated as separate fluids, we investigate the effect of density gradient inhomogeneous on the dispersion and instability of KAWs in a magnetoplasma. The results show that KAW instability can be excited effectively by the density gradient. Especially, both the real frequency (R) and the growth rate (I) of KAWs are dramatically dependent on the spatial position x in the presence of an inhomogeneous density gradient. The results also show that the real frequency increases with the characteristic spatial scale of inhomogeneity k(0)(-1), while the growth rate of KAWs has a maximum in the growing ranges of k(0)(-1). On the other hand, the excited KAWs are weakly dispersive with (e)k(x)<1. The results have potential importance for a better understanding of the microphysics of the filamentous fine-structure formation since the phenomena of density gradient inhomogeneous are ubiquitous in various magnetoplasmas, such as in the laboratory plasma as well as in both the solar coronal and terrestrial auroral plasmas.

EXCITATION OF KINETIC ALFVÉN WAVES BY FAST ELECTRON BEAMS

Energetic electron beams, which are ubiquitous in a large variety of active phenomena in space and astrophysical plasmas, are one of the most important sources that drive plasma instabilities. In this paper, taking account of the return-current effect of fast electron beams, kinetic Alfven wave (KAW) instability driven by a fast electron beam is investigated in a finite-beta plasma of Q < beta < 1 (where beta is the kinetic-to-magnetic pressure ratio and Q = m(e)/m(i) is the mass ratio of electrons to ions). The results show that the kinetic resonant interaction of beam electrons is the driving source for KAW instability, unlike the case driven by a fast ion beam, where both the kinetic resonant interaction of beam ions and the return-current are the driving source for the KAW instability. KAW instability has a nonzero growth rate in the range of the perpendicular wave number, 0 < k(perpendicular to) < k(perpendicular to)(u), and the maximum growth rate, gamma(m), occurs between 0.5k(perpendicular to)(u) < k(perpendicular to)(m) < 0.8k(perpendicular to)(u). Both the maximal growing perpendicular wave number k(perpendicular to)(m) and the maximal growth rate gamma(m) depend sensitively on the velocity of electron beam upsilon(b), and the most favorable beam velocity occurs between 8 upsilon(A) < upsilon(b) < 10 upsilon(A). On the other hand, the excited KAWs are weakly dispersive with k(perpendicular to) rho(i) < 1 and have the maximum growth rate at relatively low perpendicular wave numbers in the range 0.3 < k(perpendicular to)(m) rho(i) < 0.6 for a beam velocity upsilon(b) < 10 upsilon(A). A possible application to the upward electron beams in the terrestrial magnetosphere is briefly discussed.

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.