The influence of intergalactic magnetic fields on the strong gravitational lensing of blazar secondary gamma radiation is discussed.Currently,two cases of strong gravitational lensing of blazar gamma-radiation are kno...The influence of intergalactic magnetic fields on the strong gravitational lensing of blazar secondary gamma radiation is discussed.Currently,two cases of strong gravitational lensing of blazar gamma-radiation are known,where radiation is deflected by galaxies on the line of sight between the blazars and Earth.The magnetic field can affect the movements of electron-positron pairs generated by primary radiation,thereby changing the directions of secondary gamma radiation.It modifies the equation of the gravitational lens and leads to the dependence of the observed signal in the secondary gamma radiation on the energy of photons and magnetic field.Accordingly,it is possible,in principle,to estimate the intergalactic magnetic fields from the time delay of signals,from the angular position of images(for future high-resolution gamma-ray telescopes)or from the shape of the observed energy spectrum.This method is demonstrated by the example of the blazar B0218+357.In this case,however,it is not possible to obtain useful constraints due to the large distances to the blazar and lens galaxy.The result is only a lower limit on the magnetic field B>2×10^(−17)G,which is weaker than other existing constraints.However,future discoveries of lensed blazars may provide more favorable opportunities for measuring the magnetic fields,especially with the help of a new generation of gamma-ray telescopes such as e-ASTROGAM,GECAM,and SVOM as well as future gamma-ray telescopes with a high angular resolution,∼0.1″.展开更多
运用REDFIT方法对4个费米耀变体的MOJAVE(Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments)15.3 GHz观测数据进行了周期分析,发现0851+202存在1.77年的周期成分,1308+326存在8.69年的周期成分,1641+399存在2.04年...运用REDFIT方法对4个费米耀变体的MOJAVE(Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments)15.3 GHz观测数据进行了周期分析,发现0851+202存在1.77年的周期成分,1308+326存在8.69年的周期成分,1641+399存在2.04年的周期成分,2251+158存在7.65年的周期成分,且这些周期成分的置信度均大于99%。运用超大质量双黑洞模型和螺旋喷流模型对这些周期成分进行了解释,并估算这4个耀变体的中心黑洞质量为10^(9) M_(⊙)~10^(10) M_(⊙)。展开更多
耀变体(Blazar)的光谱能量分布(Spectral Energy Distribution,SED)中显示有两个明显的峰,其中低能峰为同步辐射峰。耀变体同步辐射峰的峰值功率与峰值频率存在反相关关系,因此与光谱能量分布峰值有关的多波段复合光谱指数构建的谱指数...耀变体(Blazar)的光谱能量分布(Spectral Energy Distribution,SED)中显示有两个明显的峰,其中低能峰为同步辐射峰。耀变体同步辐射峰的峰值功率与峰值频率存在反相关关系,因此与光谱能量分布峰值有关的多波段复合光谱指数构建的谱指数平面可以作为耀变体的两个亚类(平谱射电类星体(Flat Spectrum Radio Quasar,FSRQ)和蝎虎座BL型天体(BL Lac))的分类器。通过斯特拉斯堡天文台的数据库为费米4期目录(4FGL-DR3)中的耀变体进行了多波段数据的交叉匹配,得到多波段数据样本。在此基础上发现,耀变体的8个宽波段谱指数(α_(rw1),α_(rw2),α_(rw3),αro,αrγ,α_(w1w2),α_(w1w3)和α_(w3x))分布具有双峰结构,且明显区分耀变体的两个亚类。通过机器学习中的支持向量机(Support Vector Machine,SVM)模型,进一步分析了谱指数平面对耀变体亚类的分类作用,发现大部分谱指数平面分类的准确率在80%以上。展开更多
In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three deca...In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three decades.Two prominent periodicities on time scales of ～6.3 and ～9.5 a are identified at all three frequencies,in agreement with previous results derived from different numerical techniques,confirming the multiplicity of the periodicities in NRAO 530.In addition to these two significant periods,there is also evidence of shorter-timescale periodicities of ～5.0,～4.2,～3.4 and ～2.8 a showing lower amplitude in the periodograms.The physical mechanisms responsible for the radio quasi-periodic oscillations and the multiplicity of the periods are discussed.展开更多
文摘The influence of intergalactic magnetic fields on the strong gravitational lensing of blazar secondary gamma radiation is discussed.Currently,two cases of strong gravitational lensing of blazar gamma-radiation are known,where radiation is deflected by galaxies on the line of sight between the blazars and Earth.The magnetic field can affect the movements of electron-positron pairs generated by primary radiation,thereby changing the directions of secondary gamma radiation.It modifies the equation of the gravitational lens and leads to the dependence of the observed signal in the secondary gamma radiation on the energy of photons and magnetic field.Accordingly,it is possible,in principle,to estimate the intergalactic magnetic fields from the time delay of signals,from the angular position of images(for future high-resolution gamma-ray telescopes)or from the shape of the observed energy spectrum.This method is demonstrated by the example of the blazar B0218+357.In this case,however,it is not possible to obtain useful constraints due to the large distances to the blazar and lens galaxy.The result is only a lower limit on the magnetic field B>2×10^(−17)G,which is weaker than other existing constraints.However,future discoveries of lensed blazars may provide more favorable opportunities for measuring the magnetic fields,especially with the help of a new generation of gamma-ray telescopes such as e-ASTROGAM,GECAM,and SVOM as well as future gamma-ray telescopes with a high angular resolution,∼0.1″.
文摘运用REDFIT方法对4个费米耀变体的MOJAVE(Monitoring Of Jets in Active Galactic Nuclei with VLBA Experiments)15.3 GHz观测数据进行了周期分析,发现0851+202存在1.77年的周期成分,1308+326存在8.69年的周期成分,1641+399存在2.04年的周期成分,2251+158存在7.65年的周期成分,且这些周期成分的置信度均大于99%。运用超大质量双黑洞模型和螺旋喷流模型对这些周期成分进行了解释,并估算这4个耀变体的中心黑洞质量为10^(9) M_(⊙)~10^(10) M_(⊙)。
文摘耀变体(Blazar)的光谱能量分布(Spectral Energy Distribution,SED)中显示有两个明显的峰,其中低能峰为同步辐射峰。耀变体同步辐射峰的峰值功率与峰值频率存在反相关关系,因此与光谱能量分布峰值有关的多波段复合光谱指数构建的谱指数平面可以作为耀变体的两个亚类(平谱射电类星体(Flat Spectrum Radio Quasar,FSRQ)和蝎虎座BL型天体(BL Lac))的分类器。通过斯特拉斯堡天文台的数据库为费米4期目录(4FGL-DR3)中的耀变体进行了多波段数据的交叉匹配,得到多波段数据样本。在此基础上发现,耀变体的8个宽波段谱指数(α_(rw1),α_(rw2),α_(rw3),αro,αrγ,α_(w1w2),α_(w1w3)和α_(w3x))分布具有双峰结构,且明显区分耀变体的两个亚类。通过机器学习中的支持向量机(Support Vector Machine,SVM)模型,进一步分析了谱指数平面对耀变体亚类的分类作用,发现大部分谱指数平面分类的准确率在80%以上。
基金supported by the National Basic Research Program of China (Grant Nos.2009CB24900 and 2012CB821800)the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No.XDA04060700)+1 种基金the National Natural Science Foundation of China (Grant No.61261017)The University of Michigan Radio Astronomy Observatory is supported by the funds from NSF,NASA,and the University of Michigan
文摘In this paper,the time series analysis method CLEANest is employed to search for characteristic periodicities in the radio light curves of the blazar NRAO 530 at 4.8,8.0 and 14.5 GHz over a time baseline of three decades.Two prominent periodicities on time scales of ～6.3 and ～9.5 a are identified at all three frequencies,in agreement with previous results derived from different numerical techniques,confirming the multiplicity of the periodicities in NRAO 530.In addition to these two significant periods,there is also evidence of shorter-timescale periodicities of ～5.0,～4.2,～3.4 and ～2.8 a showing lower amplitude in the periodograms.The physical mechanisms responsible for the radio quasi-periodic oscillations and the multiplicity of the periods are discussed.
