三颗河外射电源第一历元的VLBI图像

本给出了利用上海,乌鲁木齐,意大利ＮＯＴＯ和南非ＨａｒｔＲＡＯ射电望远镜,对三颗河外射电源（１５３２＋０１６,２３２０－０２０,２３５１－１５４）,在５ＧＨｚ频率上的第一历元ＶＬＢＩ观测成图结果。     

几个河外射电源第二历元的327MHz VLBI观测

１９９１年３月，我们利用上海２５ｍ射电望远镜和欧洲ＶＬＢＩ网联合对几个河外射电源进行了第二历元的３２７ＭＨｚＶＬＢＩ观测．数据的相关处理先后在上海天文台三台站ＭＫ２相关处理机和美国的Ｃａｌｔｅｃｈ／ＪＰＬ相关处理机进行，以便于比较相关结果。本文给出３Ｃ８４、３Ｃ３４５和３Ｃ３８０的混合图。与第一历元的观测比较，３Ｃ３４５和３Ｃ３８０的流量密度没有明显的变化，但３Ｃ３４５的结构变化明显。３Ｃ８４和３Ｃ３４５有喷流的迹象．３Ｃ４５４．３的总流量在不到两年的时间内增加了２５％，如果这个变化是内禀的话，那么可能意味着一次新的流量爆发。     

几个河外射电源的第二历元的327MHz VLBI观测

１９９１年３月，我们利用上海２５米射电望远镜和欧洲ＶＬＢＩ网联合对几个河外射电源进行了第二历元的３２７ＭＨｚ ＶＬＢＩ观测，数据的相关处理先后在上海天文台三台站ＭＫ２相关处理机和美国的Ｃａｌｔｅｃｈ／ＪＰＬ相关处理机进行，以便于比较相关结果，本文给出３Ｃ８４、３Ｃ３４５和３Ｃ３８０的混合图，与第一历元的观测比较，３Ｃ３４５和３Ｃ３８０的流量密度没有明显的变化，但３Ｃ３４５的结构变化明显，３Ｃ８４和     

南天区20个河外射电源的VLBI研究

本报道南天区５ＧＨｚ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，未发现有致密双源，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。此外还首次发现了３个源中可能有超光速运动现象。     

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．     

IERS综合河外射电源表的检验

本文对ＩＥＲＳ综合河外射电源表进行了检验，指出１９８８至１９９１各年度的ＩＥＲＳ综合河外射电源表中均存在坐标系统不一致问题，部分射电源的位置坐标中带有几个毫角秒的偏差，与公认精度不符，坐标系统不一致问题影响了ＩＥＲＳ综合表的指向维持，使此维持仅限于数学意义上的平均水平，失去了明确的物理意义。     

IERS综合河外射电源表的检验

本文对ＩＥＲＳ综合河外射电源表进行了检验，指出１９８８至１９９１各年度的ＩＥＲＳ综合河外射电源表中均存在坐标系统不一致问题，部分射电源的位置坐标中带有几个毫角秒的偏差，与公认精度不符。坐标系统不一致问题影响了ＩＥＲＳ综合表的指向维持，使此维持仅限于数学意义上的平均水平，失去了明确的物理意义。     

河外射电源变化的观测研究

在本文中评述河外射电源变化的观测进展。首先对几个射电变源的一些专门术语和定义作介绍。然后叙述在整个频谱上各种变化测量的结果，包括流量、频谱和偏振的变化。讨论了ＶＬＢＩ对变化研究的重要影响。简要地触及短时标变化引发的逆康普顿灾变的理论问题，最后，强调指出了多波段同时观测河外射电源在深入了解活动星系核方面的重要作用。     

河外射电源PKS2345—267视超光速运动的新证据

给出了利用上海、乌鲁木齐、意大利NOTO、南非HartRAO射电望远镜对河外射电源PKS2345－167的VLBI观测结果,并讨论其喷流中的子源的视超光速运动。     

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。     

ISS of Polarized Compact Extragalactic Radio Sources

It is shown that the detailed inter-relations of the 8.6 GHz IDV in Stokes' parameters I, Q and U of the quasar 0405–385, as quantified by their auto and cross correlations, can be successfully modelled by interstellar scintillation (ISS) of a double source with two components separated by about 10 micro-arcseconds. Though this is not a unique source model it confirms that ISS can explain quantitatively the rapid variations in both flux and linear polarization. Thus there is no evidence in support of an intrinsic component in the IDV. This revised version was published online in July 2006 with corrections to the Cover Date.     

On the Asymmetries in Powerful Extragalactic Radio Sources

We have investigated the correlations between the asymmetries in depolarization and spectral index in a bright source sample. We find a significant correlation between these asymmetries which can be understood in terms of the relativistic beaming hypothesis in which the counter jet side is steeper and more polarized than the jet side due to the presence of a halo of hot gas surrounding the source and contribution from the beamed jet and hot spot emission to the observed lobe emission. This simple interpretation is however complicated by the presence of a stronger correlation between these parameters and extended luminosity which is expected to be aspect-invariant; suggesting that the observed spectral index – depolarization correlation is an artefact of their being separately correlated with radio luminosity. This revised version was published online in July 2006 with corrections to the Cover Date.     

Annual Modulation in Intraday Variability Timescales of Extragalactic Radio Sources

Annual modulations in timescales of intraday variability (IDY here-after) are discussed for six extragalactic sources:0716 714,0917 624,0954 65,1749 70,1803 78 and 2007 77.The timescales calculated from scintillation the-ory are compared with the observational data.It is emphasized that systematic observations are required to identify the phenomenon and to determine the motion of the interstellar medium with respect to the Local Standard of Rest.In addi-tion,significant deviations from the annual modulation could be due to intrinsic variations.     

Synergy Between Radio and Optical Telescopes: Optical Followup of Extragalactic Radio Sources

Distance measurement is a must to characterize any source in the sky. In the radio band, it is rarely possible to get distance or redshift measurements. The optical band is the most used band to get distance estimate of sources, even for those originally discovered in other bands of the electromagnetic spectrum. However, the spectroscopic redshift measurements even for fairly bright radio sample is grossly incomplete, implying un-explored discovery space. Here we discuss the scope of optical follow up of radio sources, in particular the radio loud AGNs, from the present generation radio telescopes.     

Ellipticity of Nearby Elliptical Galaxies Identified with Extended Extragalactic Radio Sources

The dependence of the ellipticity of nearby optical galaxies associated with extragalactic radio sources on the type of radio galaxy is considered. It is shown that elliptical galaxies identified with radio galaxies of the FRI type and with radio sources having a radio image with a small elongation have a smaller ellipticity, on the average, than those associated with radio galaxies of the FRII type and with radio sources with greater elongation. As one possible explanation for this phenomenon, one can assume that the optical galaxies associated with radio galaxies of type FRI and with radio sources of small elongation are oriented in space so that they are observed edge-on relatively rarely.