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Research in Astronomy and astrophysics 2024年第7期24卷 135-144页

作者： Ze-Yuan Tang Jun-Jie Feng Jun-Hui Fan School of Mathematics and Information Science Guangzhou UniversityGuangzhou 510006China Center for astrophysics Guangzhou UniversityGuangzhou 510006China 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

A warm corona has been widely proposed to explain the soft excess(SE)in X-ray above the 2-10 ke V power law extrapolation in Active Galactic Nuclei(AGNs).In actual spectral fittings,the warm coronal seed photon temperature(T_s)is usually assumed to be far away from the soft X-ray,but kT_scan reach close to 0.1 ke V in the standard accretion disk *** this study,we used Monte Carlo simulations to obtain radiation spectra from a slab-like warm corona and fitted the spectra using the spherical-geometry-based routine THCOMP or a thermal *** findings reveal tha high T_scan influence the fitting results.A moderately high kT_s(around 0.03 ke V)can result in an apparent low-temperature and flat SE,while an extremely high kT_s(around 0.07 ke V)can even produce an unobserved blackbody-like *** conclusions indicate that,for spectral fittings of the warm coronal radiation(SE in AGNs),kT_sshould be treated as a free parameter with an upper limit,and an accurate coronal geometry is necessary when kT_s>0.01 ke V.

关键词： galaxies active-accretion-accretion disks-black hole physics

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

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Research in Astronomy and astrophysics 2019年第5期19卷 75-90页

作者： Zhi-Yuan Pei Jun-Hui Fan Denis Bastieri Utane Sawangwit Jiang-He Yang Center for astrophysics Guangzhou University Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province Dipartimento di Fisica e Astronomia "G.Galilei" Universit`a di Padova Istituto Nazionale di Fisica Nucleare National Astronomical Research Institute of Thailand (NARIT) Department of Physics and Electronics Science Hunan University of Arts and Science

Active galactic nuclei(AGNs) can be divided into two major classes, namely radio-loud and radio-quiet AGNs. A small subset of the radio-loud AGNs is called blazars, which are believed to be unified with Fanaroff-Riley type Ⅰ/Ⅱ(FRI/Ⅱ) radio galaxies. Following our previous work(Fan et al.), we present a sample of 2400 sources with measured radio flux densities of the core and extended components. The sample contains 250 BL Lacs, 520 quasars, 175 Seyferts, 1178 galaxies, 153 FRI or FRⅡ galaxies and 104 unidentified sources. We then calculate the radio core-dominance parameters and spectral indices, and study their relationship. Our analysis shows that the core-dominance parameters and spectral indices are quite different for different types of sources. We also confirm that the correlation between core-dominance parameter and spectral index exists for a large sample presented in this work.

关键词： galaxies:active-galaxies galaxies:jets-quasars:general

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

Spectral energy distributions for TeV blazars

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Research in Astronomy and astrophysics 2018年第10期18卷 19-32页

作者： Chao Lin Jun-Hui Fan Center for astrophysics Guangzhou UniversityGuangzhou 510006China Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province Guangzhou 510006China

In this work, we collected a sample of 69 TeV blazars from TeVCat, obtained their multi-wavelength observations, and fitted their spectral energy distributions by using a second degree poly-nomial function. The structure parameters of synchrotron bumps for 68 blazars and those of inverse- Compton bumps for 56 blazars were derived. Then, we conducted statistical analysis on the parame-ters （curvature, peak frequency, peak luminosity, bolometric luminosity and X/γ-ray spectral indexes）. From our analysis and discussions, we can conclude the following：（1） There is a clear positive correla-tion between the synchrotron peak frequency, log （Vp）^s, and the inverse-Compton peak frequency, log （Vp）^IC, and between the synchrotron peak luminosity, log （Vp）^sL（Vp）^s, and the inverse-Compton peak luminosity,log（Vp）^IC L（Vp）^IC. （2） The correlation between the peak frequency and the curvature of synchrotron bump is clearly different from that of the inverse-Compton bump, which further indicates that there are differ-ent emission mechanisms between them. （3） There is a correlation between log （Vp）^IC and γ-ray spectral index, αγ, for the TeV blazars： log （Vp）^IC = -（4.59 ± 0.30）αγ ＋（32.67 ±0.59）, which is consistent with previous work. （4） An ＂L-shape＂ relation is found between log（Vp）^s Up and αx for both TeV blazars and Fermi blazars. A significant correlation between log（Vp）^s and X-ray photon index （αx） is found for the TeV blazars with high synchrotron peak frequency： log（Vp）^s = -（3.20 ± 0.34）αx ＋（24.33 ± 0.79）, while the correlation is positive for low synchrotron peaked TeV sources. （5） In the αx -αγ diagram, there is also an ＂L-shape.＂ The anti-correlation is consistent with results available in the literature, and we also find a positive correlation between them. （6） Inverse-Compton dominant sources have luminous bolometric luminosities.

关键词： galaxies active - BL Lacertae objects general - quasars general - galaxies jets

Simultaneous optical g, r, i monitoring and IDV periodic analysis for quasar 3C 454.3

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Research in Astronomy and astrophysics 2019年第10期19卷 43-50页

作者： Jun-Hui Fan Yu-Hai Yuan Hong Wu Feng Wang Jun Tao Min-Feng Gu Center for astrophysics Guangzhou University Guangzhou 510006 China Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province Guangzhou 510006 China key Laboratory of Optical Astronomy National Astronomical Observatories Chinese Academy of Sciences Beijing 100101 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China key Laboratory for Research in Galaxies and Cosmology Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

With the 1.26 m National Astronomical Observatory-guangzhou University Infrared/Optical Telescope(NAGIOT) at Xinglong Station of National Astronomical Observatories, Chinese Academy of Sciences, we obtained 419 groups of simultaneous observations at g, r and i bands, for the first time,targeting quasar 3 C 454.3 during 15 nights from 2016 October 23 to 2016 December 15. Based on our observations, we investigate the optical variabilities, the relation between brightness and color index, and the periodicity variability. The presented analyses demonstrate that: 1. The maximum variations at the g, r and i bands are △mg|max= 1.015 ± 0.042 mag,△mr|max= 1.188 ± 0.050 mag and △mi|max= 1.305 ± 0.057 mag respectively. 2. During our 15 night monitoring program, intra-day variability was detected on one night(Nov. 2). Also, the brightness increased by A = 15.86% over 50.8 min,then decreased by A = 22.42% over 40.1 min. After a small bright state, its brightness increased again by18.1% over 55 min at the g band. Similar phenomena happened at r and i bands. The intra-day variabilities at the three bands on 2016 November 2 indicate a period of 105 min, which implies a black hole mass of MBH =(0.3 ~ 1.85)× 10^9 M⊙. 3. There is an anti-correlation between color index and magnitude,suggesting the source becomes redder when it brightens.

关键词： galaxies quasars individual (3C 454.3)

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

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Research in Astronomy and astrophysics 2020年第2期20卷 101-111页

作者： Zhi-Yuan Pei Jun-Hui Fan Denis Bastieri Jiang-He Yang Hu-Bing Xiao Wen-Xin Yang Center for astrophysics Guangzhou UniversityGuangzhou 510006China Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province Guangzhou 510006China Dipartimento di Fisica e Astronomia“G.Galilei” Universita di Padova1-35131 PadovaItaly Istituto Nazionale di Fisica Nucleare Sezione di Padova1-35131 PadovaItaly Department of Physics and Electronics Science Hunan University of Arts and ScienceChangde 415000China

Active galactic nuclei(AGNs) can be divided into two major classes,namely radio-loud and radio-quiet AGNs.A small subset of the radio-loud AGNs is called blazars,which are believed to be unified with Fanaroff-Riley type Ⅰ and type Ⅱ(FRI&Ⅱ) radio *** our previous work,we present a latest sample of 966 sources with measured radio flux densities of the core and extended *** sample includes 83 BL Lacs,473 flat spectrum radio quasars,101 Seyferts,245 galaxies,52 FRIs&Ⅱs and12 unidentified *** then calculate the radio core-dominance parameters and spectral indices and study their *** analysis shows that the core-dominance parameters and spectral indices are quite different for different types of *** also confirm that the correlation between core-dominance parameter and radio spectral index extends over all the sources in a large sample presented.

关键词： galaxies:active galaxies:general galaxies:jets quasars:general

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 TeV and non-TeV BL Lac Objects

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Research in Astronomy and astrophysics 2016年第7期16卷 15-28页

作者： Chao Lin Jun-Hui Fan Center for astrophysics Guangzhou University Guangzhou 510006 China Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province Guangzhou 510006 China

BL Lacertae objects（BL Lacs） are the dominant population of Te V emitting blazars. In this work, we investigate whether there are any special observational properties associated with Te V *** do so, we will compare the observational properties of Te V detected BL Lacs（Te V BLs） with non-Te V detected BL Lac objects（non-Te V BLs）. From the 3rd Fermi/LAT source catalog（3FGL）, we can obtain662 BL Lacs, out of which 47 are Te V BLs and 615 are non-Te V BLs. Their multi-wavelength flux densities（FpR, FO, FX and Fγ）, photon spectral indexes（α^phXand α^phγ）, and effective spectral indexes（αRO and αOX）are compiled from the available literature. Then the luminosities（log ν LR, log ν LO, log ν LX, log ν Lγ）are calculated. From comparisons, we find that Te V BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but Te V BLs show similar properties to high synchrotron peaked（HSP） BLs. Therefore, we concentrated on a comparison between Te V HSP BLs and non-Te V HSP *** results suggest that Te V HSP BLs and non-Te V HSP BLs exhibit some differences in their αRO and αphγ, but their other properties are quite similar.

关键词： galaxies active BL Lacertae objects general gamma rays galaxies

The intrinsic γ-ray emissions of Fermi blazars

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Research in Astronomy and astrophysics 2017年第7期17卷 25-38页

作者： Chao Lin Jun-Hui Fan Hu-Bing Xiao Center for astrophysics Guangzhou University Astronomy Science and Technology Research Laboratory of Department of Education of guangdong province

The beaming effect is important for understanding the observational properties of *** this work, we collect 91 Fermi blazars with available radio Doppler factors. γ-ray Doppler factors are estimated and compared with radio Doppler factors for some sources. The intrinsic（de-beamed）γ-ray flux density（fγin）, intrinsic γ-ray luminosity（Lγin） and intrinsic synchrotron peak frequency（VPin）are calculated. Then we study the correlations between finγand redshift and find that they follow the theoretical relation： log f =-2.0 log z ＋ const. When the subclasses are considered, we find that stationary jets are perhaps dominant in low synchrotron peaked blazars. Sixty-three Fermi blazars with both available short variability time scales（？T） and Doppler factors are also collected. We find that the intrinsic relationship between Lγin and ？Tinobeys the Elliot ＆ Shapiro and Abramowicz ＆ Nobili relations. Strong positive correlation between fγinand VPinis found, suggesting that synchrotron emissions are highly correlated with γ-ray emissions.

关键词： galaxies active - BL Lacertae objects general - gamma-rays galaxies

Correlation between Brightness Variability and Spectral Index Variability for Fermi Blazars

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Research in Astronomy and astrophysics 2022年第8期22卷 23-33页

作者： Wen-Xin Yang Hu-Bing Xiao Hong-Guang Wang Jiang-He Yang Zhi-Yuan Pei De-Xiang Wu Yu-Hai Yuan Jun-Hui Fan Center for astrophysics Guangzhou UniversityGuangzhou 510006China 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 Shanghai key Lab for astrophysics Shanghai Normal UniversityShanghai 200234China Department of Physics and Electronics Science Hunan University of Arts and ScienceChangde 415000China

In this work,theγ-ray photon flux,photon spectral index(α_(ph)),variability index(log V.I.),and the synchrotron peak frequency(log v_(p))are compiled for 851 common blazars from the 3 FGL and 4 FGL catalogs and Fan et *** investigate variability properties for Fermi *** calculations and analyses reach following results:(1)the averaged luminosity,spectral index,and variability index of FSRQs are higher than those of BL Lacs for the whole sample.(2)It is found that the spectral index variation is closely anti-correlated with the luminosity variation implying that the spectrum becomes harder when the source becomes brighter in theγ-ray band.(3)Positive correlations are found between the photon spectral index and bothγ-ray luminosity and variability index(log V.I.)for the whole sample,but anti-correlations are found in the two correlations for *** BL Lac subclass,there is a marginal anti-correlation between the photon spectral index and bothγ-ray luminosity,and a positive correlation between the photon spectral index and the variability index(log V.I.).We think those two positive correlations found for the whole sample are apparent.(4)We adopted the SVM machine learning method to separate BL Lacs and FSRQs in theα_(ph)versus log L_(γ)andα_(ph)versus log *** and proposed that a BCU is an FSRQ candidate if it satisfies log V.I.>-10.119 a+24.855,orα_(ph)>-0.048 log L_(γ)+4.498,otherwise,it is a BL Lac *** classification results are quite consistent with those by Kang et al(2019).

关键词： (galaxies:)BL Lacertae objects:general (galaxies:)quasars:general galaxies:active