类星体4C39.25的MERLIN图象：角秒尺度上的单边喷流

长时间以来被看作是典型致密双源之一的类星体４Ｃ ３９．２５,其主要成分显示坦谱,且具有特殊的视超光速结构变化,根据在１８厘米波长新的ＶＬＢＩ及ＭＥＲＬＩＮ观测,可以认为该源是一个核－喷流类星体。喷流在毫角秒尺度上旋转了大约９０度,并最终向７９度的方向角延伸,喷流中包含了几个“节”及在其终点的一个热斑。预期在更高频率的亚毫角秒观测可以证实这样的结构,并对其核本身在１８厘米,甚至６厘米波长都几乎是不可     

类星体4C39.25的MERLIN图象:角秒尺度上的单边喷流

长时间以来被看作是典型致密双源之一的类星体４Ｃ３９．２５,其主要成分显示坦谱,且具有特殊的视超光速结构变化。根据在１８厘米波长新的ＶＬＢＩ及ＭＥＲＬＩＮ观测,可以认为该源是一个核－喷流类星体．喷流在毫角秒尺度上旋转了大约９０度,并是终向７９度的方向角延伸,喷流中包含了几个“节”及在其终点的一个热斑。预期在更高频率的亚毫角秒观测可以证实这样的结构,并对其核本身在１８厘米,甚至６厘米波长都几乎是不可见的作出解释．     

在18及6厘米波长对4C 39.25的VLBI观测

在18及6厘米,以基线长分别达15及23兆波长的欧洲长基线干涉网(EVN),对类星体4C 39.25作了VLBI观测,试图搜寻该类星体的中等尺度——10到100毫角秒(mas)的结构。 观测未曾检测到这种尺度上超过核峰值亮度5％的明显结构。但核自身看来有2到4毫角秒的延伸,而且其流量可变。     

类星体3C286的一个超分解图象

本给出类星体3C286在毫角秒尺度上的一个超分解图象。它是历元1991.45用一个全球VLBI阵在波长18cm观测所得到的结果之一。整个结构延伸－500pc。在东北端有两个高亮度的子源，它们与喷流一起浸嵌于一个巨大的低亮度的发射区之中。没有检测到有反向喷流存在，我们提出了新的模型来解释这种结构形态。     

三颗类星体的亚毫角秒结构

使用全球ＶＬＢＩ网在１．３ ｃｍ波段对三颗类星体０４２０－０１４、０７４８＋１２６和２２５１＋１５８（３Ｃ ４５４．３）进行了观测,获得了这三个类星体的亚毫角秒分辨率的混杂图,给出了类星体核区内的亮度分布．通过用高斯模型对观测数据进行拟合,得到了组成它们的各个子源的参数．类星体２２５１＋１５８呈现出核－喷流结构,核区沿着ＰＡ～－１３０°方向拉长,喷流呈弯曲状．１９９２．９历元的观测展现了２２５１＋１５８处于一次大爆发,并伴随一系列相继出现的小爆发的情景．最强子源的积分流量密度为 ４．１１Ｊｙ（占探测到的总流量的 ６７％）,主要集中在０．１６ × ０．０１ ｍａｓ的区域内,可能由于多普勒增亮效应造成高达２．６×１０１２的亮温度．     

高频VLBI观测射电源的结构

高频VLBI观测揭示出河外射电源在pc或者亚pc尺度上大都有核-喷流的内部结构。尤其是对平谱致密射电源中毫角秒尺度的子源，能以相当高的概率观测到它的视超光速现象。多频观测可监测到一些新喷流子源的出现，特别在射电激变源中这些新喷流子源的出现与宽带内(从光学到γ射线)的爆发相关。且得到的一些源的核区谱指数分布，为确认源的VLBI核提供了支持。     

高频VLBI观测射电源的结构

高频VLBI观测揭示出河外射电源在pc或者亚pc尺度上大都有核-喷流的内部结构，尤其是对平谱致密射电源中毫角秒尺度的子源，能以相当高的概率观测到它的视超光速现象。多频观测可监测到一些新喷流子源的出现，特别在射电激变源中这些新喷流子源的出现与宽带内（从光学到γ射线）的爆发相关。且得到的一些源的核区谱指数分布，为确认源的VLBI核提供了支持。     

百秒差距尺度上的4C39.25

通过主要在短厘米波长的全球VLBI观测,已经发现强射电类星体4C39.25在十秒差距尺度结构中的视超光速运动,其运动学图景表明该源是一个很特殊的视超光速源.近几年已提出了若干模型,试图解释这特殊的运动图景.报道不多的百秒差距尺度的VLBI观测,很可能有助于检验提出的模型.本文介绍用欧洲网及上海25m天线,在18cm波长对4C39.25所作的VLBI 成象观测的初步结果,显示百秒差距尺度复杂结构及可能存在的视超光速运动.     

视超光速源中3C454.3的特殊性

本文从简要总结迄今所发现的视超光速源开始。介绍近年来探测到的视超光速源之一——类星体3C 454.3的VLBI多频段,多历元观测及其主要结果。采用列表对比方式表明此源相对其他视超光速源的一般特征呈现的特殊性。最后对此特殊的视超光速源的可能解释作初步讨论。 本文可以看作是对3C453.3观测已有报导[12]和[13]的进一步补充。     

具有哈勃流的相对论抛射运动学.(Ⅲ)求出超光速源反喷流可观测波长和寻找类星体的蓝移谱线(英文)

在求解类星体的喷流和反喷流的问题时,必须考虑哈勃流所起的作用．超光速反喷流的观测波长应是λｃｊ＝（δ／δ′）λｏｂ,这里δ和δ′分别是正喷流和反喷流的多普勒因子,λｏｂ是正喷流的观测波长．由于多普勒因子的作用,（δ／δ′）值是较大的,对于大多数超光速源可大到两个数量级,远远超出一般ＶＬＢＩ的观测波长范围．不过,也有些超光速的（δ／δ′）值小于１０,足以观测它们的反喷流．因为反喷流的波长值主要由哈勃流常数Ｈ０所决定,一旦测定反喷流观测波长,即可反过来估计Ｈ０的值．本文提出寻找类星体蓝移谱线的方法,这些类星体以高速向视线方向抛射物质而形成吸收线．我们在文献中找到１８条可能的蓝移谱线．     

Bending of Jets in the QSO NRAO 530

We present radio images of NRAO 530 on scales ranging from pc to kpc. The observations include the EVN at 5 GHz, the VLBA at 1.6, 8.6 and 15 GHz, the MERLIN at 1.6 and 5 GHz, and the VLA at 5, 8.4, 15, 22, and 43 GHz. The VLBI images show a core-jet structure with an oscillating trajectory on a scale of about 30 mas north of the strongest compact component (core). Superluminal motions are detected in five of the jet compo-nents with apparent velocities in the range of 13.6 to 25.2c. A new component is detected at 15 GHz with the VLBA observations, which appears to be associated with the outburst in 2002. Significant polarized emission is detected around the core with the VLBA observationsat 15 GHz. Rapid variations of the polarization intensity and angle are found between the epochs in 2002 and 2004. On the kpc-scale, a distant component (labelled as WL) located 11 arcsec west (PA=-86°) of the core is detected beyond the core-jet structure which ex-tended to several hundreds of mas in the north-west direction (-50°). A significant emission between the core-jet structure and the WL is revealed. A clump of diffuse emission (labelled EL, 12 arcsec long) at PA 70° to the core, is also detected in the VLA observations, suggest-ing the presence of double lobes in the source. The core component shows a flat spectrum,while the distant components WL and EL have steep spectra. The steep spectra of the distantcomponents and the detection of the arched emission suggest that the distant components are lobes or hot-spots powered by the core of NRAO 530. The morphologies from pc-to kpc- scales and the bending of jets are investigated. The observed radio morphology from pc to kcp appears to favor the model in which precession or wobbling of the nuclear disk drives the helical motion of the radio plasma and produces the S-shaped structure on kpc scale.     

A VLBI study of 20 southern extragalactic radio sources

This paper describes a 5 GHz VLBI survey in the southern hemisphere. The first observation of 23 extragalactic radio sources was conducted in November 1992. Twenty VLBI images were obtained, of which 15 sources show core-jet structure, one has a two-sided jet, and three sources are unresolved. No compact double source was found. Eleven of the 16 sources with core-jet (including a two-aided jet) show evidence of jet bending. In addition, four sources appear to be superluminal, of which three sources are new.     

南天区20个河外射电源的VLBI研究

本文报道南天区5GHzVLBI普查式观测结果．首次观测是在1992年11月期间进行的，共观测了23个河外射电源，获得了20个河外射电源的VLBI高分辨率的射电图象．有15个射电源呈现核喷流结构，1个有双向喷流，3个未分解，末发现有致密观源．在16个核喷流（包括一个双向喷流源）源中有11个呈现弯曲喷流现象．此外还首次发现有3个源中可能有超光速运动现象．     

Studies of the quasar OH 471

Based on the 1964–1996 observations in the frequency range 0.325–90 GHz, we study peculiarities of the variability of the quasar OH 471 (z=3.4). The double-humped spectrum had peaks at frequencies near 1 and 20 GHz. The flux density of the low-frequency component first decreased and then began to increase. The high-frequency component rose to 2.5 Jy in the late 1970s. The peak frequencies were virtually constant. VLBI observations at 1.6 GHz revealed a core-jet structure with the jet extended eastward to 5 mas. The object is a powerful quasar.     

Variability of GPS Radio Sources at 5 GHz

We carry out flux monitoring on a sample of 169 Gigahertz Peaked Spectrum (GPS) radio sources at 5 GHz and find that about one-third of them show considerable Inter-Month Variability (IMV), and these IMV phenomena are likely to be caused by interstellar scintillation (ISS). Furthermore, we find that those showing IMV tend to be point-like or core-jet structures at VLBI scale.     

S5 2007+777的射电性质研究

S5 2007+777是一个典型的低峰值频率的蝎虎天体,该天体具有kpc尺度的X射线喷流,文献中利用模型估算的方法,得出X射线波段的多普勒因子达到13.0,从而喷流尺度可以达到Mpc量级.在此,搜集了有关S5 2007+777的欧洲甚长基线射电干涉网(European VLBI Network, EVN)高分辨率档案数据、美国甚长基线射电干涉网(Very Long Baseline Array, VLBA) 15 GHz观测数据等,研究了喷流的射电结构、亮温度、自行等方面的性质,发现该源的甚长基线干涉测量(Very Long Baseline Interferometry,VLBI)不同波段的喷流方向一致,但与文献中给出的kpc尺度的X射线喷流和甚大阵(Very Large Array, VLA)射电喷流方向存在一定的差异,说明该源的喷流辐射存在多普勒增亮效应.由VLBI观测得到的亮温度,估算了该源的射电多普勒因子的平均值及中值均为5.0,此值小于文献中X射线波段的多普勒因子,但与文献中利用其他方法得到的射电波段多普勒因子是一致的;另外,对多历元观测数据的拟合发现此源相同波段的各个成分在长历元上没有明显的自行,短历元上的自行甚至是视超光速运动.这可能是由低表面亮度成分中心位置的转移造成的.这同时也验证了之前估算的射电多普勒因子不是很大,小于X射线波段多普勒因子的结论.利用所得到的射电多普勒因子,发现该源具有较大尺度的本征射电喷流,可达到0.5 Mpc,由于这里使用的是均值,因此说明该源也有可能具有接近巨射电星系尺度的喷流.     

Search for Binary Black Hole Candidates from the VLBI Images of AGNs

We have searched the core-jet pairs in the VLBI scales (<1 kpc), from several VLBI catalogues, and found out 5 possible Binary Black Hole (BBH) candidates. We present here the search results and analyse the candidates preliminarily. We plan to study with multi-band VLBI observation. We also plan to carry out optical line investigation in future.     

VLBA multi-frequency monitoring of SS433

We present results of VLBA observations of SS433 at two epochs at 5, 8.4, and 15 GHz. The AU-scale region of the source is resolved and shows the familiar quasi-symmetric core-jet structures. But at another epoch, the maps show bright knots ejected a few days before the observation, while the core-complex disappeared. The bright jet components are completely depolarised with fractional polarization less than 0.5%. We also present the first VLBI image of SS433 at 22 GHz.     

Elaboration of the new magnetohydrostatic sunspot theory (double return flux model)

An extension of the recently formulated Return Flux Sunspot Model is presented. The basic equation for a Double Return Flux Sunspot Model is derived, and a pressure distribution and magnetic field are calculated. The possible topology of the magnetic structure and its thermodynamic consequences are discussed. The paper includes a magnetogram of a single round sunspot (9 August, 1981). The authors attempt to interpret the observational data for the vertical component of magnetic field of this sunspot on the basis of the Double Return Flux Model.     

A MERLIN pilot study of faint variable VLA FIRST radio sources

We present the results of a pilot study in which we obtained Multi-Element Radio Linked Interferometer Network (MERLIN) L-band snapshot images of the 20 strongest radio sources from a sample of 123 radio objects that exhibit significant flux density variations at 1.4 GHz on a seven year base-line. The sample was created using FIRST VLA B-array data from 1995 and 2002 on a strip around zero declination near the south Galactic cap. The primary purpose is to assess the presence of radio jets and provide direct evidence between long-term variability and jet structures, as several models suggest. The radio structure of all the sources in this subsample appears very compact and our high resolution MERLIN observations reveal for the first time the presence of small milli-arcsecond (mas) jets and/or jet-like extensions in 17 of the 20 variable sources (literature data show core-jet structures or hints of extended structure in the other three objects which are point sources in our MERLIN observations). In the future we will use the radio results from the complete study, in combination with their optical Sloan Digital Sky Survey (SDSS) data, in order to investigate trends and possible differences or similarities between the quasars and galaxies that host these radio sources, and so examine existing unification schemes or open up new aspects in AGN unification.