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

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Research in Astronomy and Astrophysics 2011年第12期11卷 1413-1428页

作者： Jun-Hui Fan jiang-he yang Jing Pan Tong-Xu Hua Center for Astrophysics Guangzhou University Guangzhou 510006 China Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province Guangzhou 510006 China Department of Physics and Electronics Science Hunan University of Arts and Science Changde 415000 China

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 parameter, R. The R, to some extent, is associated with the beaming effect. Blazars are believed to be unified with Fanaroff ＆ Riley type I/II （FRI/II） radio galaxies. In this work, we collected relevant observations from the literature for a sample of 1223 AGNs including 77 BL Lacertae objects, 495 quasars, 460 galaxies, 119 FRs and 72 unidentified sources, and calculated the core-dominance parameters and spectral indexes, discussed the relationship between the two parameters, and gave some discussions. Our analysis suggests that the core-dominance parameters in BL Lacertae objects are larger than those in quasars and galaxies, and the radio spectral indexes in BL Lacertae objects are lower than those in quasars and galaxies. We also found that the core-dominance parameter-spectral index correlation exists for a large sample presented in this work, which may come from a relativistic beaming effect.

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

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The gamma-ray Doppler factor determinations for a Fermi blazar sample

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Research in Astronomy and Astrophysics 2013年第3期13卷 259-269页

作者： Jun-Hui Fan jiang-he yang Yi Liu Jing-Yi Zhang Center for Astrophysics Guangzhou University Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province Department of Physics and Electronics Science Hunan University of Arts and Science

Observations suggest that γ-ray loud blazars are strongly beamed. The Fermi mission has detected many of blazars, which provide us with a good opportunity to investigate the emission mechanism and the beaming effect in the γ-ray region. We compiled the X-ray observations for 138 Fermi blazars （54 flat spectrum radio quasars, 36 low-peaked BL Lacertae objects, and 48 high-peaked BL Lacertae objects） and calculated their Doppler factors, δγ. It is interesting that the calculated Doppler factors, δγ, are strongly correlated with the γ-ray luminosity.

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

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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

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The Optical Variability Properties of TeV Blazars

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Research in Astronomy and Astrophysics 2024年第9期24卷 66-75页

作者： Zi-An Su Wen-Xin yang Xiang-Tao Zeng Le-Jian Ou Ze-Lin Li jiang-he yang Jun-Hui Fan Department of Physics School of Physics and ElectronicsHunan Normal UniversityChangsha 410081China Center for Astrophysics Guangzhou UniversityGuangzhou 510006China Greater Bay Brand Center of the National Astronomical Data Center Guangzhou 510006China Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province Guangzhou 510006China College of Microelectronics Feicuihu Campus of Hefei University of TechnologyHefei 230601China College of Mathematics and Physics Science Hunan University of Arts and ScienceChangde 415000China

Variability is one of the typical observational properties of blazars and the spectral changes are usually associated with variability,although this kind of association is unclear *** this work,we used data from the Steward Observatory blazar monitoring program to investigate the optical variability properties including the short-term timescale,the brightness-dependent spectral property,the correlation between the the brightness variation and the polarization,and then estimate the Doppler factors based on the obtained short timescale to study the polarization property for a sample of 20 TeV *** analyses arrive at the following results:(1)The largest variation amplitude in R-band,ΔR_(M),covers a range from ΔR_(M)=0.29 mag(1ES 2344+514)to ΔR_(M)=4.66 mag(3C 279).(2)Intra-day variability was found from five sources with timescales from 0.14 day for S50716+714 to 0.98 day for PKS *** sources show spectra that are bluer when they become brighter,suggesting a common bluer-when-brighter property.(3)The plot of the polarization versus estimated Doppler factor is consistent with the Doppler factor dependent formula of polarization.(4)The largest polarization is correlated with the largest optical variation,suggesting that the high polarization and high amplitude variation are both the indicator of beaming effect.

关键词： galaxies:active galaxies:jets radiation mechanisms:non-thermal

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Rapid variability in S5 0716+714

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Research in Astronomy and Astrophysics 2011年第11期11卷 1311-1316页

作者： Jun-Hui Fan Jun Tao Bo-Chen Qian Yi Liu jiang-he yang Fei-Peng Pi Wei Xu Center for Astrophysics Guangzhou University Guangzhou 510006 China Astronomy Science and Technology Research Laboratory of Department of Education ofGuangdong Province Guangzhou 510006 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China Joint Institute for Galaxies and Cosmology Shanghai Astronomical Observatory and Universityof Science and Technology of China Chinese Academy of Sciences Shanghai 200030 China Department of Physics and Electronics Science Hunan University of Arts and Science Changde415000 China

S5 0716＋714 is one of the targets in our long term blazar monitoring program carried out with the 1.56-m telescope at Sheshan Station of Shanghai Astronomical Observatory, China. We report a very rapid variability of △I=0.611±0.102 mag over 3.6 min detected in our monitoring program during the period from December 2000 to March 2007. The rapid variability suggests that the mass for the central black hole is log（M/M⊙） = 7.68 - 8.38.

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

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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

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The lower limit of the Doppler factor for a Fermi blazar sample

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Research in Astronomy and Astrophysics 2014年第9期14卷 1135-1145页

作者： Jun-Hui Fan Denis Bastieri jiang-he yang Yi Liu Tong-Xu Hua Yu-Hai Yuan De-Xiang Wu Center for Astrophysics Guangzhou University Astronomy Science and Technology Research Laboratory of Department of Education of Guangdong Province Department of Physics & Astronomy University of Padua and I.N.F.N. 35131 Padova 35131Italy Department of Physics and Electronics Science Hunan University of Arts and Science

We selected 457 blazars （193 fiat spectrum radio quasars, 61 low- synchrotron peaked blazars, 69 intermediate-synchrotron peaked blazars and 134 high-synchrotron peaked blazars） from the second Fermi-LAT catalog （2FGL） of γ- ray sources, which have X-ray observations. We calculated the lower limits for their Doppler factors, δγ, and compared the lower limits with the available Doppler factors and the apparent superluminal velocities in the literature.

关键词： galaxies: BL Lacertae objects -- galaxies: quasars -- galaxies: jets -- gamma-rays: galaxies

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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

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The estimations of four basic parameters for gamma-ray loud blazars

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Chinese Journal of Astronomy and Astrophysics 2009年第5期9卷 538-546页

作者： Jun-Hui Fan Yu-Hai Yuan Yi Liu Jing-Yi Zhang Yi-Ping Qin Hua Liu Yong Huang jiang-he yang Hong-Guang Wang jiang-Shui Zhang Center for Astrophysics Guangzhou University Guangzhou 510400 China Department of Physics and Electronics Science Hunan University of Arts and Science Changde 415000 China

The method used in our previous papers is adopted to estimate four basic parameters （the central black hole mass （M）, the boosting factor （or Doppler factor）（6）, the propagation angle （Φ） and the distance along the axis to the site of the γ-ray production （d）） for 59 γ-ray loud blazars （20 BL Lacertae objects and 39 flat spectrum radio quasars）. The central black hole masses estimated for this sample are in a range of from 107 Me to 109 MG. In the case of black hole mass, there is no clear difference between BL Lacertae objects and flat spectrum radio quasars, which is consistent with the previous results suggesting that the central black hole masses do not play an important role in the evolutionary sequence of blazars.

关键词： galaxies quasars -- galaxies BL Lacertae objects -- galaxies jet -- galaxies nuclei

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Brightness temperature for 166 radio sources

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Research in Astronomy and Astrophysics 2009年第7期9卷 751-760页

作者： Jun-Hui Fan Yong Huang Yu-Hai Yuan jiang-he yang Yi Liu Jun Tao Ying Gao Tong-Xu Hua Rui-Guang Lin jiang-Shui Zhang Jing-Yi Zhang Yi-Ping Qin Center for Astrophysics Guangzhou University Guangzhou 510006 China Physics Institute Hunan Normal University Changsha 410081 China Center for Astrophysics University of Science and Technology of China Hefei 230026 China Department of Physics and Electronics Science Hunan University of Arts and Science Changde 415000 China Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai 200030 China

Using the database of the University of Michigan Radio Astronomy Observatory （UMRAO） at three radio frequencies （4.8, 8 and 14.5 GHz）, we determined the short-term variability timescales for 166 radio sources. The timescales are 0.15d （2007＋777） to 176.17 d （0528-250） with an average timescale of Atobs = 17.1 4- 16.5 d for the whole sample. The timescales are used to calculate the brightness temperatures, TB. The value of log TB is in the range of log TB = 10.47 to 19.06 K. In addition, we also estimated the boosting factor for the sources. The correlation between the polarization and the Doppler factor is also discussed.

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

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