A Statistical Study of XBLs, RBLs and FSRQs at 1.5 GHz

BL Lac objects are similar to the fiat spectrum radio quasars in many aspects except regarding the emission lines.In order to study their relationship,we selected 56 BL Lacertae objects(33 X-ray-selected,23 radio-selected)and 45 flat spectrum radio quasars,analyzed their radio luminosities and core-dominance parameters.We found that the radio luminosities of the radio selected BL Lac objects located in between the X-ray selected BL Lac objects and the fiat spectrum radio quasars.However,this intermediate position does not bold for the core-dominance parameter:the RBLs have the largest core-dominance parameters.This sug- gests that the core-dominance parameter can not be taken as a sequencing criterion.We also investigated the correlation between the luminosity and the core-dominance parameter for the three subclasses.We concluded that,here,the sequence XBL-RBL—FSRQ still exists.     

The Relationship between Radio Luminosity and Core-Dominance Parameter for XBLs

In this work, we investigate the correlation between the luminosity and the core-dominance parameter for a sample of X-ray selected BL Lacertae objects (XBLs), and found that the extended luminosity is strongly anti-correlated with the core-dominance parameter while the core (or the total) luminosity is not correlated with the core-dominance parameter. If this is the case, then we can expect that the lower extended luminosity XBLs and their core luminosity is relatively higher. This can be explained by a relativistic beaming model since in this case, the viewing angle is smaller and the emissions dominate the extended emissions. Therefore, the anti-correlation is in fact the result of the relativistic beaming model.     

An X-Ray Study of Lobe-Dominated Radio-Loud Quasars with XMM-Newton

We report on our results of X-ray spectral analysis for a sample of radio-loud quasars covering a wide range of the radio core-dominance parameter, R, from core-dominated to lobe-dominated objects, using data obtained mostly with the XMM-Newton Observatory. We find that the spectral shape of the underlying power-law continuum is flat even for the lobe-dominated objects (average photon index ～ 1.5), indistinguishable from that of core-dominated quasars. For lobe-dominated objects, contribution of X-rays from the jets is expected to be very small based on previous unification schemes, more than one order of magnitude lower than the observed X-ray luminosities. Assuming that radio-loud quasars follow the same X-ray-UV/optical luminosity relation for the disk-corona emission as found for radio-quiet quasars, we estimate the X-ray flux contributed by the disk-corona component from the optical/UV continuum. We find that neither the luminosity, nor the spectral shape, of the disk-corona X-ray emission can account for the bulk of the observed X-ray properties. Thus in lobe-dominated quasars, either the disk-corona X-ray emission is much enhanced in strength and flatter in spectral shape (photon index～1.5) compared to normal radio-quiet quasars, or their jet X-ray emission is much enhanced compared to their weak radio core-jet emission. If the latter is the case, our result may imply that the jet emission in X-rays is less Doppler beamed than that in the radio. As a demonstrating example, we test this hypothesis by using a specific model in which the X-ray jet has a larger opening angle than the radio jet.     

Core-dominance parameter and polarization for Fermi blazars

We study core-dominance parameter R and polarization for blazars detected by Fermi LAT. Our results are as follows. (i) The blazars detected by Fermi LAT have higher average R and polarizations than those not detected by Fermi LAT. (ii) Compared with BL Lacs, flat-spectrum radio quasars (FSRQs) have lower average R and the ratio of beamed luminosity to the unbeamed luminosity f. (iii) In the diagram of polarization-Doppler factor relations, FSRQs may have p=α+3 and BL Lacs for p=α+2. These results suggest that the high optical polarization is correlated to the beaming effect. High polarization and core-dominance parameters are significantly more common among the LAT sources. The difference in polarization and core-dominance parameters between FSRQs and BL Lacs are due to the difference in their beaming effects and jet model.     

Spectral properties of the accretion discs around rotating black holes

We study the radiation properties of an accretion disc around a rotating black hole. We solve the hydrodynamic equations and calculate the transonic solutions of accretion disc in the presence of shocks. Then we use these solutions to generate the radiation spectrum in the presence of radiative heating and cooling processes. We present the effect of spin parameter of the black hole on the emitted radiation spectrum. In addition, attention has also been paid to the variation in energy spectral index with Kerr parameter and accretion rate. We find that spectral index becomes harder as the spin parameter changes from negative (accretion disc is counter-rotating with respect to the black hole spin) to a positive value. Finally, we compute and compare the spectral characteristics due to a free-fall flow and a transonic flow. We notice significant differences in high energy contributions from these two solutions.     

The spherical infall model in a cosmological background density field

We discuss the influence of the cosmological background density field on the spherical infall model. The spherical infall model has been used in the PressSchechter formalism to evaluate the number abundance of clusters of galaxies, as well as to determine the density parameter of the Universe from the infalling flow. Therefore, the understanding of collapse dynamics plays a key role for extracting cosmological information. Here, we consider a modified version of the spherical infall model. We derive the mean field equations from the Newtonian fluid equations, in which the influence of cosmological background inhomogeneity is incorporated into the averaged quantities as the backreaction . By calculating the averaged quantities explicitly, we obtain simple expressions and find that, in the case of a scale-free power spectrum, density fluctuations with a negative spectral index make the infalling velocities slow. This suggests that we underestimate the density parameter when using the simple spherical infall model. In cases with the index n >0, the effect of background inhomogeneity could be negligible and the spherical infall model becomes a good approximation for infalling flows. We also present a realistic example with a cold dark matter power spectrum. In this case, the mean infall tends to be slow owing to the anisotropic random velocity.     

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

We analyze the spectral variability and spectral evolution in the optical energy region by using multiband (BVRI) optical observations of S5 0716+714 spanning 1994 to 2005. The spectrum hardens when the source becomes brighter, which is consistent with general BL Lac objects. The spectral evolution parameter implies that the spectral variability is small in optical bands over 10 years. A simple model representing the variability of a synchrotron component can explain the spectral changes. In addition, we em...     

Ratio of the Core to the Extended Emissions in the Comoving Frame for Blazars

In a two-component jet model, the emissions are the sum of the core and extended emissions: \(S^{\mathrm{ob}}=S_{\mathrm{core}}^{\mathrm{ob}}+S_{\mathrm{ext}}^{\mathrm{ob}}\), with the core emissions, \(S_{\mathrm{core}}^{\mathrm{ob}}= f S_{\mathrm{ext}}^{\mathrm{ob}}\delta ^{q}\) being a function of the Doppler factor \(\delta \), the extended emission \(S_{\mathrm{ext}}^{\mathrm{ob}}\), the jet type dependent factor q, and the ratio of the core to the extended emissions in the comoving frame, f. The f is an unobservable but important parameter. Following our previous work, we collect 65 blazars with available Doppler factor \(\delta \), superluminal velocity \(\beta _{\mathrm{app}}\), and core-dominance parameter, R, and calculated the ratio, f, and performed statistical analyses. We found that the ratio, f, in BL Lacs is on average larger than that in FSRQs. We suggest that the difference of the ratio f between FSRQs and BL Lacs is one of the possible reasons that cause the difference of other observed properties between them. We also find some significant correlations between \(\log f\) and other parameters, including intrinsic (de-beamed) peak frequency, \(\log \nu _{\mathrm{p}}^{\mathrm{in}}\), intrinsic polarization, \(\log P^{\mathrm{in}}\), and core-dominance parameter, \(\log R\), for the whole sample. In addition, we show that the ratio, f, can be estimated by R.     

Fermi耀变体的能谱分布研究

从SSDC (Italian Space Agency Science Data Center)搜集了68个Fermi耀变体的射电至X射线波段的观测数据,用对数抛物线拟合计算了其同步辐射峰的参数.研究了有效谱指数、同步辐射峰值频率和曲率的关系并用有效谱指数估算同步峰频.主要结果有:(1)研究同步峰频和曲率的线性关系发现,对于全部的蝎虎天体(BL Lac),结果与能量依赖加速概率模型的预测一致.但是,如果仅仅考虑高峰频BL Lac,即同步峰频lg (ν_p/Hz)> 15.3的BL Lac,其结果却与分数变换加速增益模型的预测结果一致.(2)对于同步峰频相同的源,射电-光学的有效谱指数αro与曲率间有显著的负相关,而光学-X射线的有效谱指数α_ox与曲率无关.通过α_ro可以确定一个同步峰频与曲率的关系.     

Superluminal Motion and Polarization in Blazars

A relativistic beaming model has been successfully used to explain the observed properties of active galactic nuclei (AGNs). In this model there are two emission components, a boosted one and an unbeamed one, shown up in the radio band as the core and lobe components. The luminosity ratio of the core to the lobe is denned as the core-dominance parameter (R = LCore/LLobe). The de-beamed radio luminosity (Ldbjet) in the jet is assumed to be proportional to the unbeamedluminosity (Lub) in the co-moving frame, i.e., f = Ldbjet/Lub, and f is determined in ourprevious paper. We further discuss the relationship between BL Lacertae objects (BLs) and flat spectrum radio quasars (FSRQs), which are subclasses of blazars with different degrees of polarization, using the calculated values of the ratio f for a sample of superluminal blazars. We found 1) that the BLs show smaller averaged Doppler factors and Lorentz factors, larger viewing angles and higher core-dominance parameters than do the FSRQs, and 2) that in th     

The relationship between the radio core dominance parameter and the spectral index in different classes of extragalactic radio sources

Active galactic nuclei(AGNs)have two major classes,namely radio loud AGNs and radio quiet AGNs.A small subset of the radio-loud AGNs is called blazars,which display extreme observational properties,such as rapid variability,high luminosity,high and variable polarization,and superluminal motion.All of those observational properties are probably due to a relativistic beaming effect with the jet pointing close to the line of sight.Observations suggest that the orientation can be expressed by a core-dominance p...     

Global fits for the spectral index of the cosmological curvature perturbation

Best-fitting values of the spectral index of the curvature perturbation are presented, assuming the ΛCDM cosmology. Apart from the spectral index, the parameters are the Hubble parameter, the total matter density and the baryon density. The data points are intended to represent all measurements that are likely to affect the result significantly. The cosmic microwave anisotropy is represented by the COBE normalization, and heights of the first and second peaks are given by the latest Boomerang and Maxima data. The slope of the galaxy correlation function and the matter density contrast on the 8  h ⁻¹ Mpc scale are each represented by a data point, as are the expected values of the Hubble parameter and matter density. The 'low-deuterium' nucleosynthesis value of the baryon density provides a final data point, the fit giving a value higher by about one standard deviation. The reionization epoch is calculated from the model by assuming that it corresponds to the collapse of a fraction f ≳10⁻⁴ of matter. We consider the case of a scale-independent spectral index, and also the scale-dependent spectral index predicted by running mass models of inflation. In the former case, the result is compared with the prediction of models of inflation based on effective field theory, in which the field value is small on the Planck scale. A detailed comparison is made with other fits, and other approaches to the comparison with theory.     

Analytic forms of the perpendicular cosmic ray diffusion coefficient for an arbitrary turbulence spectrum and applications on transport of Galactic protons and acceleration at interplanetary shocks

We investigate cosmic ray scattering in the direction perpendicular to a mean magnetic field. Unlike in previous articles we employ a general form of the turbulence wave spectrum with arbitrary behavior in the energy range. By employing an improved version of the nonlinear guiding center theory we compute analytically the perpendicular mean free path. As shown, the energy range spectral index, has a strong influence on the perpendicular diffusion coefficient. If this parameter is larger than one we find for some cases a perpendicular diffusion coefficient that is independent of the parallel mean free path and particle energy. Two applications are considered, namely transport of Galactic protons in the solar system and diffusive particle acceleration at highly perpendicular interplanetary shock waves.     

Cosmological parameter estimation and the spectral index from inflation

Accurate estimation of cosmological parameters from microwave background anisotropies requires high-accuracy understanding of the cosmological model. Normally, a power-law spectrum of density perturbations is assumed, in which case the spectral index n can be measured to around ± 0.004 using microwave anisotropy satellites such as MAP Planck . However, inflationary models generically predict that the spectral index n of the density perturbation spectrum will be scale-dependent. We carry out a detailed investigation of the measurability of this scale dependence by Planck , including the influence of polarization on the parameter estimation. We also estimate the increase in the uncertainty in all other parameters if the scale dependence has to be included. This increase applies even if the scale dependence is too small to be measured, unless it is assumed absent. We study the implications for inflation models, beginning with a brief examination of the generic slow-roll inflation situation, and then move to a detailed examination of a recently devised hybrid inflation model for which the scale dependence of n may be observable.     

Study of some chaotic inflationary models in $$ gravity

In this paper, we discuss an inflationary scenario via scalar field and fluid cosmology for an anisotropic homogeneous universe model in \(f(R)\) gravity. We consider an equation of state which corresponds to a quasi-de Sitter expansion and investigate the effect of the anisotropy parameter for different values of the deviation parameter. We evaluate potential models like linear, quadratic and quartic models which correspond to chaotic inflation. We construct the observational parameters for a power-law model of \(f(R)\) gravity and construct the graphical analysis of tensor–scalar ratio and spectral index which indicates the consistency of these parameters with Planck 2015 data.     

On the Absence of Core Luminosity–Core-Dominance Parameter (P C − R) Correlation in Radio Galaxies and BL Lacs

We have presented an alternative interpretation for the absence of correlation in the relationship between the core radio power (P _C) and core-dominance parameter (R) for a sample of BL Lacs and radio galaxies found in Fan & Zhang (Astron. Astrophys. 407, 899 (2003)). This is contrary to the predictions of the relativistic beaming and radio source orientation models in which the core luminosity is expected to be Doppler-boosted relative to the extended luminosity which is generally assumed to be isotropic. Our analysis of the P _C???R data indicates a strong luminosity selection effect (reminiscent of bright source samples due to Malmquist bias) in the sample. In particular, we showed that a strong P _C???R correlation exists above some redshift cut-off which may correspond to the flux limit of the sample used.     

Long-Term Optical Spectra Variability of BL Lacertae Object S5 0716+714

Based on the long-term data from observations, we present an evidence for its spectral index variability behaviour in optical bands for BL Lacertae object S5 0716+714. We find that the spectral index variability period is in agreement with the flux variability period of about 1180 days in optical bands. We also find that the spectral index variability has periods of about 71 and 60 days which cannot be compared with the amplitude of long-term variability.     

The INTEGRAL complete sample of type 1 AGN

In this paper we discuss the broad-band X-ray characteristics of a complete sample of 36 type 1 active galactic nuclei (AGN), detected by INTEGRAL in the 20–40 keV band above the 5.5σ level. We present, for all the objects in the sample, the broad-band (1–110 keV) spectral analysis obtained by using INTEGRAL / Swift /Burst Alert Telescope observations together with XMM–Newton , Chandra , ASCA and Swift /X-Ray Telescope data. We also present the general average properties of the sample, i.e. the distribution of photon indices, high-energy cut-offs, reflection fractions and absorption properties, together with an in-depth analysis of their parameter space. We find that the average Seyfert 1 power law has an index of 1.7 with a dispersion of 0.2. The mean cut-off energy is at around 100 keV, with most objects displaying E _c in the range 50–150 keV; the average amount of Compton reflection is 1.5 with a typical dispersion of 0.7. We do not find any convincing correlation between the various parameters, an indication that our analysis is not strongly dependent by the interplay between them. Finally, we investigate how the results presented in this work fit into current frameworks for AGN spectral modelling and cosmic diffuse X-ray background synthesis models.     

Diagnostics of the Low-Cutoff Energy of Nonthermal Electrons in Solar Microwave and Hard X-Ray Bursts

The low-cutoff energy has a strong effect on the relationship between the radiation and electron spectral indices in both nonthermal gyrosynchrotron and bremsstrahlung theories. Hence, we have to calculate or fit the low-cutoff energy together with the electron spectral index as two independent parameters. Theoretical calculations of nonthermal gyrosynchrotron and bremsstrahlung radiations suggest a new method to obtain the exact solutions of the low-cutoff energy and the electron spectral index from the observable photon spectral indices at two adjacent energy or frequency bands (double power law). One flare on 10 June 2000 was studied as an example of the hard X-ray and microwave diagnostics for the low-cutoff energy and the electron spectral index. The results showed some differences between hard X-ray and microwave diagnostics.