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| 1 | Multifrequency polarization variations in 0917+624显示文摘 | S.J. Qian A. Kraus T.P. Krichbaum A. Witzel J.A. Zensus | 2001 | Astrophysics and Space Science (-)2001，，1： | 1 |
| 2 | A Possible Periodicity in the Radio Light Curves of 3C 454.3显示文摘During the period 1966.5–2006.2 the 15GHz and 8GHz light curves of 3C 454.3 (z = 0.859) show a quasi-periodicity of ~12.8 yr (~6.9 yr in the rest frame of the source) with a double-bump structure. This periodic behaviour is interpreted in terms of a rotating double-jet model in which the two jets are created from the black holes of a binary system and rotating with the period of the orbital motion. The periodic variations in the radio fluxes of 3C 454.3 are suggested to be mainly due to the lighthouse effects (or the variation in Doppler boosting) of the precessing jets caused by the orbital motion. In addition, variations in the rate of mass accreting onto the black holes may be also involved. | Shan-Jie Qian N. A. Kudryavtseva S. Britzen T. E Krichbaum Long Gao A. Witzel J. A. Zensus M. E Aller H. D. Aller Xi-Zhen Zhang | 2007 | Chinese Journal of Astronomy and Astrophysics2007，7，3： | 1 |
| 3 | Parsec-scale jets in extragalactic radio sources显示文摘 | ZENSUS J ANTON | 1997 | Annual Review of Astronomy and As- trophysics1997，35，： | 1 |
| 4 | Refractive Focusing by Interstellar Clouds and the Rapid Polarization Angle Swing in QSO 1150+812显示文摘A very rapid polarization position angle swing of~180°(with a time scale of~6 hours)observed at 2cm in QSO 1150+812(z=1.25)was reported by Kochenov & Gabuzda.This very rare event is difficult to explain.We found a pos- sible interpretation in the framework of a source model consisting of three polarized components,in which two compact polarized components are nearly simultaneously occulted by an interstellar cloud,with consequent focusing-defocusing effects.A spe- cific plasma-lens model is proposed which can reasonably fit the polarized flux density curve with results derived for the two lensed components.Some physical parameters of the plasma-lens and the source components are estimated.The two compact po- larized components are estimated to have brightness temperatures of~6×10^(12)K. Thus a bulk relativistic motion with a Lorentz factor less than 10 is required to meet the inverse-Compton limit. | Shan-Jie Qian T. P. Krichbaum Xi-Zhen Zhang L. Fuhrmann G. Cimò A. Kraus T. Beckert S. Britzen A. Witzel J.A. Zensus | 2006 | Chinese Journal of Astronomy and Astrophysics2006，6，1： | 0 |
| 5 | Periodicity of the ejection of superluminal components in 3C345显示文摘The search for periodic behavior in Blazars has been an important subject, which is helpful for providing significant clues to the structure and physical processes of their central energy engine. A binary black hole system has recently been suggested for causing precession of relativistic jets and rotation of the ejection position angle of VLBI knots in superluminal sources. It has been suggested that in QSO 3C345, the ejection direction of the superluminal knots rotates due to the precession of the central engine and thus the ejection position angle of the successive knots shows a periodic behavior. Some authors argue for a period of precession being ~5.6 yr (Abraham & Caproni), ~8–10 yr (Klare et al.) and ~9.5 yr (Lobanov & Roland). Applying the helical model proposed by Qian et al. and selecting appropriate parameters to fit the initial trajectories (within 0.3 mas) of all the components (C4 to C10), we derive the relation between the ejection position angle of the components and their precession phase, and thus find a 6.9-year precession period (4.3 yr in the source frame), which can fit the ejection position angle of all these superluminal knots well. Since the VLBI observations have covered more than two precession periods, confirmation in one or more future periods would be important. In addition, we emphasize that the initial parts of the trajectories of these knots can be fitted by a common helical pattern (channel) through a precessing of its initial phase. This scenario (or helical precessing model) is different from the usual ballistic precessing model in which the individual superluminal knots move along straight-lines after ejection (Tateyama & Kingham). | Shan-Jie Qian A. Witzel J. A. Zensus T. R Krichbaum S. Britzen Xi-Zhen Zhang | 2009 | Chinese Journal of Astronomy and Astrophysics2009，9，2： | 0 |
| 6 | 3C345 VLBI核心的可能的视超光速运动显示文摘对类星体3C345的最新VLBI观测表明,节点C_6和C_7在向西北方向作视运动,这与节点C_4在1981—1984期间的视运动大致上平行.观测到的节点C_6和节点C_7的这种视运动是与钱善瑎所提出的'核心运动模型'所作出的预测的结果相符合的.本文利用现有关于3C345的所有VLBI观测数据,用比较严格的方法,定出了3C345的VLBI核心的南北方向视运动曲线和各个节点的视运动所沿的共同轨道的形式.结果表明,3C345的VLBI核心的南北方向视运动是振荡式的(见图4),导出的最大视运动速度为(0.10—0.15)mas/yr(即2c或3c,H_0=100公里·秒^(-1)·百万秒差距^(-1)).在1993年之前,对节点C_6和节点C_7的视轨道的VLBI监测,对于检验这个模型具有决定性的意义.非常希望对VLBI核心用VLBI相位参考技术来进行视运动的直接测定. | 钱善瑎 Krichbaum T.P.Witzel A. Quirrenbach A4. Zensus J.A. | 1992 | 天文学报1992，33，4： | 0 |
| 7 | High Brightness Temperatures in IDV Sources显示文摘高亮度温度是银河系外的收音机来源的 IntraDayVariability (IDV ) 的一个典型特征。一些 IDV 来源的极化性质的最近的研究(例如, 1150+812, PKS 0405-385 和 0716+714 ) 证明了这些来源与~ 1 0-30 μ a s 和很高的极化的尖尺寸怀有几个紧缩的 IDV 部件(直到~ 5 0%-70%) 。这些结果在 IDV 部件显示一致磁场的存在的可能性。我们调查支离破碎的同步加速器和自我 -- 在磁场附近旋转的相对论的电子的各向异性的分布的康普顿放射在小沥青角度排队。秒顺序康普顿损失引起的亮度温度限制被讨论,与亮度相比,温度源于精力 equipartition 争论。搬进来的电子的各向异性的分布命令磁场能由一个因素提起 equipartition 和康普顿亮度温度,这被发现直到~ 3 -5。这将在极其高内在的亮度温度的解释移开一些困难 > 10 ^(12 ) K (或~ 1 的明显的亮度温度有~ 3 的一个 Doppler 因素的 0 ^(14 ) K 0 ) 。 | Shan-Jie Qian T.P. Krichbaum A. Witzel J. A. Zensus Xi-Zhen Zhang | 2006 | Chinese Journal of Astronomy and Astrophysics2006，6，5： | 0 |
| 8 | Inner jet kinematics and the viewing angle towards the γ-ray narrow-line Seyfert 1 galaxy 1H 0323+342显示文摘Near-Eddington accretion rates onto low-mass black holes are thought to be a prime driver of the multi-wavelength properties of the narrow-line Seyfert 1(NLS1) population of active galactic nuclei(AGNs). Orientation effects have repeatedly been considered as another important factor involved, but detailed studies have been hampered by the lack of measured viewing angles towards this type of AGN. Here we present multi-epoch, 15 GHz VLBA images(MOJAVE program) of the radio-loud and Fermi/LATdetected NLS1 galaxy 1H 0323+342. These are combined with single-dish, multi-frequency radio monitoring of the source's variability, obtained with the Effelsberg 100-m and IRAM 30-m telescopes, in the course of the F-GAMMA program. The VLBA images reveal six components with apparent speeds of^1- 7 c, and one quasi-stationary feature. Combining the obtained apparent jet speed(β_(app)) and variability Doppler factor(D_(var)) estimates together with other methods, we constrain the viewing angle θ towards1 H 0323+342 to θ≤ 4°–13°. Using literature values of βapp and D_(var), we also deduce a viewing angle of≤8°–9°towards another radio- and γ-ray-loud NLS1, namely SBS 0846+513. | Lars Fuhrmann Vassilis Karamanavis Stefanie Komossa Emmanouil Angelakis Thomas E Krichbaum Robert Schulz Annika Kreikenbohm Matthias Kadler Ioannis Myserlis Eduardo Ros Ioannis Nestoras J. Anton Zensus | 2016 | Research in Astronomy and Astrophysics2016，16，11： | 0 |
| 9 | Refractive Focusing of Interstellar Clouds and Intraday Polarization Angle Swings显示文摘Intraday variations of compact extragalactic radio sources in flux density and po- larization are generally interpreted in terms of refractive scintillation from the continuous interstellar medium of our Galaxy. However, continuous polarization angle swings of~180° (for example, the one observed in the QSO 0917+624) could not be interpreted in this way. Qian et al. have shown that the polarization angle swing observed in the QSO 1150+812 can be explained in terms of focusing-defocusing effect by an interstellar cloud, which occults two closely-placed polarized components. Here we further show that the polarization angle swing event observed in the QSO 0917+624 can also be explained in this way. We also found evidence for the cloud eclipsing a non-polarized (core) component during a short period out- side the swing. A particular (and specific) plasma-lens model is proposed to model-fit the polarization swing event of 0917+624. Some physical parameters related to the plasma-lens and the source components are estimated. The brightness temperatures of the two lensed components are estimated to be ~1.6×1013 K. Thus bulk relativistic motion with a Lorentz factor less than ~20 may be sufficient to avoid the inverse - Compton catastrophe. | Shan-Jie Qian T. E Krichbaum Long Gao Xi-Zhen Zhang A. Witzel J. A. Zensus | 2007 | Chinese Journal of Astronomy and Astrophysics2007，7，2： | 0 |
| 10 | Radio observations of the first three-months of Fermi AGN at 4.8 GHz显示文摘Using the Urumqi 25 m radio telescope,sources from the first three months of the Fermi-large area telescope detected active galactic nuclei (AGN) catalog with a declination of > 0° were observed in 2009 at 4.8 GHz.The radio flux density appeared to correlate with the γ-ray intensity.Intra-day variability (IDV) observations were performed in March,April and May 2009 for 42 selected γ-ray bright blazars,and ~ 60% of them showed evidence of flux variability at 4.8 GHz during the IDV observations.The IDV detection rate was higher than that in previous flat-spectrum AGN samples.IDV appeared more often in the very long baseline interferometry-core dominant blazars,and the non-IDV blazars showed relatively 'steeper' spectral indices than the IDV blazars.Pronounced inter-month variability was also found in two BL Lac objects:J0112+2244 and J0238+1636. | Nicola Marchili Thomas P.Krichbaum Lars Fuhrmann Anton Zensus | 2012 | Research in Astronomy and Astrophysics2012，12，2： | 0 |
| 11 | A new three-stage evolution model for millimeter to centimeter wavelength outbursts in BL Lacertae显示文摘The multi-frequency light curves of BL Lacertae during 1997.5 – 1999.5 have been modeled by four outbursts,each having a 3-stage evolution in the (S m,νm) plane with distinct rising–plateau–decaying phases.It is shown that the observed light curves can be well fitted for the eight frequencies from 350GHz to 4.8GHz.The main characteristics of the model-fitting are: (1) the outbursts are found to have very flat spectra with an optically thin spectral index α (defined as Sν∝ν-α) of about 0.15.This is consistent with the results previously obtained by Valtaoja et al.(1992); (2) it is found that there is no spectral flattening between the rising–plateau phase and the decay phase.In other words,the optically thin spectral index does not change from the rising–plateau phase to the decay phase.These features are in contrast to the 3-stage shocked-in-jet model proposed by Marscher & Gear (1985) for submm– IR–optical flares,in which a spectral flattening of Δα = 0.5 is predicted when a transition occurs from the Compton/synchrotron phase (or rising–plateau phase) to the adiabatic phase (or decay phase) with α~> 0.5 for the shock being non-radiative.We propose a new model to interpret the fitting results,suggesting that the 3-stage evolution of the mm--cm outbursts in BL Lacertae may be related to the process of shock formation and propagation in a highly collimated jet (for example,a ‘parabolic’ jet).In particular,during the rising phase,the thickness of the synchrotron–radiating region created by the shock may rapidly increase with time (relative to the jet width) due to the rapid injection of relativistic electrons and a magnetic field,and this leads to the observed behavior that the turnover flux density Sm rapidly increases while the turnover frequency νm decreases.In the decay phase,the emitting plasma enters into a free expansion regime without further injection of relativistic electrons and a magnetic field (for example,when a transition from a collimated regime into a conical regime occurs).The plateau phase is a short period between the two regimes with no distinct features determined. | Shan-Jie Qian T. P. Krichbaum A. Witzel J. A. Zensus Xi-Zhen Zhang H. Ungerechts H. D. Aller M. E Aller | 2010 | Research in Astronomy and Astrophysics2010，10，1： | 0 |
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