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Some statistical correlation analyses for Fermi/LAT Blazars

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science china(physics,Mechanics & Astronomy) 2014年第10期57卷 2007-2014页

作者： NIE JianJun fan junhui yang rushu yang jianghe department of physics and electronics science Hunan University of Arts and Science Center for Astrophysics Guangzhou University

A sample including 664 blazars （301 Flat Spectrum Radio Quasars and 363 BL Lacs） with ）γ-ray data in both 1FGL and 2FGL catalogues were selected. The average values of both y-photon average energy and the photon spectral index for FSRQs, LBLs, IBLs and HBLs, follow the blazars sequence, FSRQs → LBLs →IBLs → HBLs. The slopes of correlation between photon spectral index and ）,-ray luminosity for 4 the sub-classes of blazars also follow the blazars sequence. Also, there was close an- ti-correlations between the difference of two ）,-ray photon spectral indices and the logarithm of the ratio of two y-ray luminosities from 2FGL and 1FGL catalogs. It implies that the spectrum becomes flat when the source becomes brighter in high energetic γ-ray band. Lastly, the Kolmogolov-Smirnov test （KS test） of the average γ-photon energy showed that HBLs differs from LBLs and FSRQs, while there was no clear difference between LBLs and FSRQs, which implied that the γ-ray emissions in LBLs and FSRQs may be a result of the same emission mechanism.

关键词： Fermi blazars gamma-ray emission spectral index

The gamma-ray spectral index changes for blazars

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science china(physics,Mechanics & Astronomy) 2012年第11期55卷 2179-2185页

作者： yang jianghe fan junhui NIE JianJun yang rushu department of physics and electronics science Hunan University of Arts and ScienceChangde 415000China Center for Astrophysics Guangzhou UniversityGuangzhou 510405China

Based upon Fermi 1FGL and EGRET 3EG samples, a sample including 79 blazars （53 FSRQs, 26 BL Lacs） is presented. It is investigated that the correlations between the ratio of EGRET to Fermi blazars g-ray flux densities and the spectral index differ for EGRET to Fermi blazars for three subclasses of high-frequency peaked BL Lacertae objects-HBL, low-frequency peaked BL Lacertae objects-LBL, and flat spectrum radio quasars-FSRQs. There is a consistent relationship between the ratio of the two γ-ray flux densities and the spectral index difference for the three subclasses. It suggests that the spectrum changed with the source brightness in the gamma-ray band. Both the spectral index difference and the correlation slopes follow a continuous sequence from FSRQs to LBLs to HBLs, which is consistent with the noted blazar sequence.

关键词： active galactic nuclei (AGN) blazars gamma-ray emission spectral index

The central black hole masses for the γ-ray loud blazars

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science china(physics,Mechanics & Astronomy) 2010年第10期53卷 1921-1927页

作者： yang jianghe fan junhui department of physics and electronics science Hunan University of Arts and ScienceChangde 415000China Center for Astrophysics Guangzhou UniversityGuangzhou 510405China Key Laboratory of Astronomy Observation and Technology Guangzhou UniversityGuangzhou 510405China

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (formerly GLAST) provides an increase in sensitivity and has detected rapid variability of gamma-ray *** variability time scales detected from the gamma-ray loud blazars by LAT and EGRET,and gamma-ray luminosity are used to estimate the central black hole *** this work,we find that the lower limits of central black hole masses are in a range of (0.3-24)×107M⊙,which are compared with those obtained by other *** results are consistent with other authors' ***,the Lorentz factor,Γ,and the propagation angle,θ,are obtained for 18 blazars for which superluminal motions are known.

关键词： active galactic nuclei(AGNs) time scale central black hole mass Doppler factor

Investigating jet physical properties of Fermi blazars with broad-line emissions

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中国科学:物理学、力学、天文学英文版 2023年第10期66卷 138-154页

作者： Lixia Zhang jianghe yang Yi Liu junhui fan Center for Astrophysics Guangzhou UniversityGuangzhou 51006China Astronomy science and Technology Research Laboratory of department of Education of Guangdong Province Guangzhou 510006China Key Laboratory for Astronomical Observation and Technology of Guangzhou Guangzhou 510006China Great Bay Center National Astronomical Data CenterGuangzhou 510006China department of physics and electronics science Hunan University of Arts and ScienceChangde 415000China

Relativistic outflows often exhibit extreme observational characteristics due to beaming effects, which makes measuring their jet power a challenging task. Although the spectral energy distribution(SED) obtained from multi-wavelength data can constrain the physical parameters of these jets, accurately estimating the Doppler factor remains difficult. To address this challenge, we assemble a comprehensive sample containing available SEDs of synchrotron and inverse Compton(IC) components, monochromatic luminosity, and broad-line region(BLR) emissions. We employ a parabolic equation to fit the synchrotron radiation SEDs,constraining jet physical parameters within the framework of a one-zone leptonic model. Our study delves into the jet properties and Doppler factor estimations, yielding the following key findings:(1) The fitting results of SED data for the entire sample reveal normal distributions of jet physical parameters for two subclasses of blazars.(2) Correlation analysis demonstrates that synchrotron peak luminosity exhibits a proportional relationship with both the radio and the γ-ray luminosities.(3) We introduce a novel method for estimating Doppler factors, which uncovers discrepancies between Doppler factors from this work and others from different techniques.

关键词： active galactic nuclei blazars jets spectral energy distribution

Lorentz factor estimation for radio sources

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science china(physics,Mechanics & Astronomy) 2012年第8期55卷 1510-1514页

作者： yang jianghe fan junhui YUAN YuHai department of physics and electronics science Hunan University of Arts and Science Changde 415000 China Center for Astrophysics Guangzhou University Guangzhou 510006 China Astronomy science and Technology Research Laboratory of department of Education of Guangdong Province Guangzhou 510006 China Laboratory Center Guangzhou University Guangzhou 510006 China

In this paper, a sample including 68 blazars (18 BL Lacs and 50 FSRQs) with known Doppler factors and superluminal velocity from our previous papers is presented. Both the Lorentz factors (/') and viewing angles (0) are estimated for the 68 sources The relationship between BL Lacs and FSRQs is also revisited using the two variables off'and 0. The Lorenz factors are in the range of 2.33 to 64.07. The viewing angles are in the range of 0.04 to 24.56. The averaged value of the viewing angle for BL Lacs is slightly larger than that for FSRQs, while the averaged value of the Lorentz factor for BL Lacs is smaller than that for FSRQs.

关键词： radio sources Lorentz factor viewing angle

Radio core dominance of Fermi/LAT-detected AGNs

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science china(physics,Mechanics & Astronomy) 2020年第5期63卷 105-123页

作者： ZhiYuan Pei junhui fan Denis Bastieri jianghe yang HuBing Xiao Diparimento di Fisica e Astronomia“G.Galilei”.Universita di Padova Padova 1-35131Italy Istituto Nazionale di Fisica Nucleare Sezione di PadovaPadova 1-35131Italy Center for Astrophysics Guangzhou UniversityGuangzhou 510006China Astronomy science and Technology Research Laboratory of department of Education of Guangdong Province Guangzhou 510006China department of physics and electronics science Hunan University of Arts and ScienceChangde 415000China

We present a sample of 4388 AGNs with available radio core-dominance parameters—defined as the ratio of the core flux densities to the extended ones, R = S_(core)/S_(ext).—which includes 630 Fermi-detected AGNs from the fourth source catalog(4FGL) of the Fermi Large Area Telescope(Fermi/LAT);the rest are non-Fermi-detected AGNs. In our sample, 584 blazars are Fermi-detected and 1310 are not. The sample also contains other subclasses, such as Seyferts, fanaroff-Riley I/II galaxies, and normal *** investigate various properties of the Fermi-detected and non-Fermi-detected AGNs by using core-dominance parameters,capitalizing on a previous study which showed that R is a good indicator of beaming. We then calculate radio spectral indices for the whole sample, and adopt γ-ray-photon indices for the Fermi AGNs from the 4FGL catalog to discuss the properties of different subclasses. We obtain a relation between the core-dominance parameters and the radio spectral indices for both Fermi and non-Fermi sources, assuming a two-component model in the radio band. Our previous study ruled out the assumption that the core-dominance parameters and radio spectral indices are quite different for different AGN subclasses. This holds not only for Fermi sources but also for non-Fermi sources. In particular, R is, on average, greater for the former AGNs than for the *** this study, we enlarge our sample with available values of R to 4388 AGNs, and the obtained conclusions are consistent with our previous study. We assume that the same two-component model holds for the γ-ray band as for the radio band, and therefore,adopt the same relation between the core-dominance parameters and the γ-ray-photon indices for Fermi AGNs. Our fitting results indicate that the γ-ray emissions of Fermi blazars originate mainly from the jet, and therefore, we conclude that the Fermi blazars are beamed.

关键词： active galactic nuclei(AGNs) quasars γ-rays

Effective spectral index properties for Fermi blazars

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science china(physics,Mechanics & Astronomy) 2018年第5期61卷 46-52页

作者： jianghe yang junhui fan Yi Liu YueLian Zhang ManXian Tuo JianJun Nie YuHai Yuan department of physics and electronics science Hunan University of Arts and Science Changde 415000 China Center for Astrophysics Guangzhou University Guangzhou 510006 China Astronomy science and Technology Research Laboratory of department of Education of Guangdong Province Guangzhou 510006 China Mathematics and Computational science Hunan University of Arts and Science Changde 415000 China

Blazars are a special subclass of active galactic nuclei with extreme observation properties. This subclass can be divided into two further subclasses of flat spectrum radio quasars(FSRQs) and BL Lacertae objects(BL Lacs) according to their emission line features. To compare the spectral properties of FSRQs and BL Lacs, the 1.4 GHz radio, optical R-band, 1 keV X-ray, and 1 GeVy-ray flux densities for 1108 Fermi blazars are calculated to discuss the properties of the six effective spectral indices of radio to optical(α_(RO)), radio to X-ray(α_(RX)), radio to y ray(α_(Ry)), optical to X-ray(α_(OX)), optical to y ray(α_(Oy)), and X-ray to y ray(α_(Xy)).The main results are as follows: For the averaged effective spectral indices, α_(OX_> α_(Oy)> α_(Xy)> α_(Ry)> α_(RX)> α_(RO) for samples of whole blazars and BL Lacs; α_(Xy)≈α_(Ry)≈α_(RX) for FSRQs and low-frequency-peaked BL Lacs(LBLs); and α_(OX)≈α_(Oy)≈α_(Xy) for high-synchrotron-frequency-peaked BL Lacs(HBLs). The distributions of the effective spectral indices involving optical emission(α_(RO), α_(OX), and α_(Oy)) for LBLs are different from those for FSRQs, but if the effective spectral index does not involve optical emission(α_(RX), α_(Ry), and α_(Xy)), the distributions for LBLs and FSRQs almost come from the same parent population. X-ray emissions from blazars include both synchrotron and inverse Compton (IC) components; the IC component for FSRQs and LBLs accounts for a larger proportion than that for HBLs; and the radiation mechanism for LBLs is similar to that for FSRQs, but the radiation mechanism for HBLs is different from that for both FSRQs and LBLs in X-ray bands. The tendency of α_(Ry) decreasing from LBLs to HBLs suggests that the synchrotron self-Compton model explains the main process for highly energetic y rays in BL Lacs.

关键词： active galactic nuclei (AGNs) blazars effective spectral index

Comparison between Fermi detected and non-Fermi detected superluminal sources

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science china(physics,Mechanics & Astronomy) 2019年第12期62卷 110-125页

作者： HuBing Xiao junhui fan jianghe yang Yi Liu YuHai Yuan Jun Tao Denise Costantin YuTao Zhang ZhiYuan Pei LiXia Zhang WenXin yang Center for Astrophysics Guangzhou UniversityGuangzhou 510006China department of physics and Astronomy University of PadovaPadova PD 35131Italy Astronomy science and Technology Research Laboratory of department of Education of Guangdong Province Guangzhou 510006China department of physics and electronics science Hunan University of Arts and ScienceChangde 415000China Shanghai Astronomical Observatory Chinese Academy of SciencesShanghai 210006China

Active galactic nuclei（AGNs） have been attracting research attention due to their special observable properties. Specifically,a majority of AGNs are detected by Fermi-LAT missions, but not by Fermi-LAT, which raises the question of weather any differences exist between the two. To answer this issue, we compile a sample of 291 superluminal AGNs（189 FDSs and 102 nonFDSs） from available multi-wavelength radio, optical, and X-ray（or even γ-ray） data and Doppler factors and proper motion（μ）(or apparent velocity(βapp)); calculated the apparent velocity from their proper motion, Lorentz factor（Γ）, viewing angle（?） and co-moving viewing angle(?co) for the sources with available Doppler factor（δ）; and performed some statistical analyses for both types. Our study indicated that（1） in terms of average values, FDSs have higher proper motions（μ）, apparent velocities(βapp),Doppler factor（δ）, Lorentz factor（Γ）, and smaller viewing angle（?）. Nevertheless, there is no clear difference in co-moving viewing angles（?∞）. The results reveal that FDSs show stronger beaming effect than non-FDSs.（2） In terms of correlations:1) both sources show positive, mutually correlated fluxes, which become closer in de-beamed fluxes; 2) with respect to apparent velocities and γ-ray luminosity, there is a tendency for the brighter sources to have higher velocities; 3) with regard to viewing angle and observed γ-ray luminosity, log? =-（0.23 ± 0.04）log Lγ+（11.14 ± 1.93）, while for the co-moving viewing angle and the intrinsic γ-ray luminosity, log?∞=（0.09 ± 0.01）log Lγn-（1.73 ± 0.48）. These correlations show that the luminous γ-ray sources have smaller viewing angles and a larger co-moving viewing angle, which indicate a stronger beaming effect in γ-ray emissions.

关键词： active galactic nuclei jets γ-rays correlations

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耀变体的峰频估计（英文）

湖南文理学院学报（自然科学版） 2017年第1期29卷 13-18,34页

作者：张丽霞林潮樊军辉杨江河广州大学物理与电子工程学院广东广州510006 广州大学天体物理中心广东广州510006 广东省教育厅天文科学与技术实验室广东广州510006 湖南文理学院物理与电子科学学院湖南常德415000

收集了60个耀变体样本,考察了有效谱指数(α_(RO),α_(OX)和α_(RX))与同步峰频(logv_p^s)之间的关系。斯皮尔曼秩检验的结果显示有效谱指数与同步峰频之间有很好的反相关。根据两者的相关给出了同步峰频与有效谱指数关联的经验公式。... 详细信息

收集了60个耀变体样本,考察了有效谱指数(α_(RO),α_(OX)和α_(RX))与同步峰频(logv_p^s)之间的关系。斯皮尔曼秩检验的结果显示有效谱指数与同步峰频之间有很好的反相关。根据两者的相关给出了同步峰频与有效谱指数关联的经验公式。通过该公式用α_(RO)和α_(OX)估算了耀变体的同步峰频,所得结果与文献的经验公式结果进行了比较,发现本文公式的结果更精确。

关键词：活动星系核耀变体同步峰频