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 temper...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 model.In 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 component.Our 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 SE.Our 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.展开更多
Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r ban...Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r band and 5010 at i band)in 155 nights from 2014 December 13 to 2019 March15.Based on the upper observations,we obtain the following results.(1)The total variation amplitude is~2.3 mag.(2)There are intra-day variabilities(IDVs).The IDV timescales(△T)are in the range from 7.69 min(Δm=0.06±0.02 mag)to 371.09 min(Δm=0.26±0.04 mag).(3)There are strong correlations betweenΔT andΔm,△m=(2.91±0.66)×10^(-4)ΔT+(0.08±0.009),with r=0.52,p=5.33×10^(-5).(4)There are intra-day periods in this source,with the period P≈94 min on 2017 December 10.When we supplement the observations from the literature,we can obtain that the long-term period is about 12.02±0.41 yr.(5)The spectral properties of OJ 287 show the bluer-when-brighter behavior,whatever state the source is at.展开更多
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 ...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 al.to investigate variability properties for Fermi blazars.Our 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 FSRQs.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 V.I.plots 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 candidate.Our classification results are quite consistent with those by Kang et al(2019).展开更多
The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and...The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and MeV bands,employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C+21.35,Ton 599,B21420+32,and PKS 1510-089,we identified a time lag spanning several days,while for PKS 1441+25,the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources,whereas for PKS1441+25,they seem to be sourced mainly from the broad-line region.Further analysis of the opacity(τγγ)and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption.Notably,for PKS 1441+25,the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs,during Te V flaring events,the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources,with the exceptions of 4C+21.35 and PKS1441+25.In terms of the overall jet power,particle energy is the dominant contributor,and the observed blazar radiation cannot be solely attributed to the magnetic field,except in the case of 4C+21.35.Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.展开更多
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 ...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.展开更多
基金partially supported by the National Natural Science Foundation of China(NSFC,grant Nos.U2031201 and11733001)the Natural Science Foundation of Guangdong Province(2019B030302001)+3 种基金the science research grants from the China Manned Space Project,with No.CMS-CSST-2021-A06support from Astrophysics Key Subjects of Guangdong Province and Guangzhou Citysupport from Scientific and Technological Cooperation Projects(2020-2023)between the People’s Republic of China and the Republic of Bulgariasupport that was received from Guangzhou University(No.YM2020001)。
文摘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 model.In 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 component.Our 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 SE.Our 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.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.U1831119,U1531245,U1431112,11733006,11503004 and 11403006)Science and Technology Program of Guangzhou(201707010401)。
文摘Using the 1.26 m National Astronomical Observatory-Guangzhou University Infrared/Optical Telescope(NGT),we monitor one BL Lac object,OJ 287.For this source,we obtain 15094 gri observations(4900 at g band,5184 at r band and 5010 at i band)in 155 nights from 2014 December 13 to 2019 March15.Based on the upper observations,we obtain the following results.(1)The total variation amplitude is~2.3 mag.(2)There are intra-day variabilities(IDVs).The IDV timescales(△T)are in the range from 7.69 min(Δm=0.06±0.02 mag)to 371.09 min(Δm=0.26±0.04 mag).(3)There are strong correlations betweenΔT andΔm,△m=(2.91±0.66)×10^(-4)ΔT+(0.08±0.009),with r=0.52,p=5.33×10^(-5).(4)There are intra-day periods in this source,with the period P≈94 min on 2017 December 10.When we supplement the observations from the literature,we can obtain that the long-term period is about 12.02±0.41 yr.(5)The spectral properties of OJ 287 show the bluer-when-brighter behavior,whatever state the source is at.
基金the National Natural Science Foundation of China(NSFC U2031201,11733001,U2031112,12133004 and 12103012)Guangdong Major Project of Basic and Applied Basic Research(Grant No.2019B030302001)+2 种基金the science research grants from the China Manned Space Project with NO.CMSCSST-2021-A06the supports for Astrophysics Key Subjects of Guangdong Province and Guangzhou Citysupported by Guangzhou University(YM2020001)。
文摘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 al.to investigate variability properties for Fermi blazars.Our 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 FSRQs.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 V.I.plots 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 candidate.Our classification results are quite consistent with those by Kang et al(2019).
基金support from the National Natural Science Foundation of China(NSFC,Grant No.12203034)from the Shanghai Science and Technology Fund under grant No.22YF1431500+11 种基金from the science research grants from the China Manned Space Projectsupport from the National Natural Science Foundation of China(NSFC,grant No.12203043)support from the National Natural Science Foundation of China(NSFC,grant No.11933002)support from the National Natural Science Foundation of China(NSFC,grant No.12173026)the National Key Research and Development Program of China(grant No.2022YFC2807303)the Shanghai Science and Technology Fund(grant No.23010503900)the Program for Professor of Special Appointment(Eastern Scholar)at Shanghai Institutions of Higher Learningthe Shuguang Program(23SG39)of the Shanghai Education Development Foundation and Shanghai Municipal Education Commissionsupport from the National Natural Science Foundation of China(NSFC,grant No.U2031201,and 11733001)the Scientific and Technological Cooperation Projects(20202023)between the People’s Republic of China and the Republic of Bulgariathe science research grants from the China Manned Space Project with No.CMS-CSST-2021A06partially supported by the Bulgarian National Science Fund of the Ministry of Education and Science under grants KP-06-H38/4(2019),KP-06-KITAJ/2(2020),and KP-06-H68/4(2022)。
文摘The location ofγ-ray emission of blazars remains a contested topic,inspiring the development of numerous investigative techniques to address this issue.In this work,we analyzed Fermiγ-ray light curves in the GeV and MeV bands,employing the discrete cross-correlation function method to discern time lags between the two bands.For 4C+21.35,Ton 599,B21420+32,and PKS 1510-089,we identified a time lag spanning several days,while for PKS 1441+25,the time lag was not statistically found.The results imply that the soft photons necessary for inverse Compton scattering predominantly originate from the dusty torus in the first four sources,whereas for PKS1441+25,they seem to be sourced mainly from the broad-line region.Further analysis of the opacity(τγγ)and the GeV spectra study supports the conclusion that the location of the dissipation region must be beyond the BLR to avoid significant absorption.Notably,for PKS 1441+25,the emission region is also posited to lie outside yet proximate to the BLR.The parameters of describing the emission region were obtained by fitting broadband spectral energy distribution with contemporaneous observation data.Our findings suggest that for the five TeV FSRQs,during Te V flaring events,the jet appears to maintain an equilibrium between the energy density of the magnetic field and that of the particles for all investigated sources,with the exceptions of 4C+21.35 and PKS1441+25.In terms of the overall jet power,particle energy is the dominant contributor,and the observed blazar radiation cannot be solely attributed to the magnetic field,except in the case of 4C+21.35.Consequently,magnetic reconnection is unlikely to be the primary mechanism behind particle acceleration in these systems.
基金financial support from the National Natural Science Foundation of China(Grant No.12303018)supported by the National Natural Science Foundation of China(Grant Nos.U2031201,11733001,and U2031112).+1 种基金the science research grants from the China Manned Space Project with(Grant No.CMSCSST-2021-A06)Scientific and Technological Cooperation Projects(20202023)between China and the Republic of Bulgaria。
文摘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.
