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，显示秒差距尺度复杂结构及可能存在     

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。     

类星体3C345中的VLBI核心在运动吗?

在视超光速源3C345(类星体)中,有5个VLBI节点被观测到有视超光速运动,特别是其中靠近核心的两个节点C_4和C_5沿着不同的弯曲轨道运动.本文考虑这种双轨道运动是由于射电核心运动造成的可能性.利用现有资料,把观测到的C_4和C_5的运动,分解成射电核心的运动和它们沿着一条共同的轨道运动.结果表明,这种分解可以很好地拟合现有关于节点C_4和C_5的观测结果.对进一步的观测检验和模型的物理涵义作了扼要的讨论。     

VLBI与视超光速源——(Ⅰ)观测手段与结果

类星体和活动星系核结构的变化及其中的视超光速运动,被认为是用VLBI方法所揭示的最重大的天体物理现象之一。十余年来积累了大量观测资料,迄今已经观测证实了不少于25个视超光速源,更广泛的监测和搜寻计划正在进行中。 本文从观测手段和结果两个方面,综述对视超光速源探测的方法及现状。在另一篇文章中将总结视超光速源的观测特征,以及为解释这些特征所作的有代表性而又较广为接受的理论探讨。     

3C390.3的弱秒差距尺度喷流及其变化

通过对射电星系３Ｃ３９０．３在历元１９８９．２９及６ｃｍ波长的ＶＬＢＩ观测数据的多软件包成象，辨认出其弱秒差距尺度喷流中几个分离的节，将它们和以前发表及未发表的同一波长的成象结果比较，显示了该源弱秒差距尺度喷流的弯曲和反喷流，并重新证认了喷流中节的视超光速运动。     

3C390．3的弱秒差距尺度喷流及其变化

通过对射电星系３Ｃ３９０．３在历元１９８９．２９及６ｃｍ波长的ＶＬＢＩ观测数据的多软件包成象，辨认出其弱秒差距尺度喷流中几个分离的节，将它们和以前发表及未发表的同一波长的成象结果比较，显示了该源弱秒差距尺度喷流的弯曲和反喷流，并重新证认了喷流中节的视超光速运动。     

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。     

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。     

河外低频射电变源研究的新进展

大多数低频变源的变化是由于星际媒质不均匀性引起的星际闪烁所造成的:少数是由于内部因素引起的。VLBI观测指出:未曾发现前者有结构变化;后者的结构变化及相关的其他变化似乎需要一个超光速现象或其他相对论性现象来解释。宽频带上变化相:关的低频变源绝大部分为视超光速源及其遴选者,这为我们寻找超光速源提供了一条重要的线索。     

Is the VLBI core of 3C 345 moving?

In the superluminal source quasar 3C 345, five VLBI knots have been observed to have superluminal motion and, in particular, the two knots C₄ and C₅ move along different curved orbits. This paper examines the possibility that this pair of orbits are due to the motion of the radio core. Using the available data, the motions of C₄ and C₅ are resolved as a superposition of a motion of the core and a motion along a common orbit. The results show that such a resolution can fit well the observations. A brief discussion is made on further test of the model and its physical implications.     

Superluminal motion in the parsec-scale jet in 3C 380

We present extensive multi-epoch VLBI observations of the quasar 3C 380 which reveal a bent parsec-scale radio jet with complex substructure which exhibits superluminal motion out to ∼100 pc from the active core. The general characteristics of the jet and its motion are similar to those in several other well-studied superluminal sources, most notably a rapid increase in the opening angle at a projected distance of a few tens of parsecs from the core and apparent acceleration along the jet. This acceleration could be a simple kinematic effect associated with bulk flow at a constant speed, but at a varying angle to the line of sight. The jet is well resolved in the transverse direction for the majority of its length and resembles numerical simulations of a jet disrupted by the rapid growth of sinusoidal 'Kelvin–Helmholtz' modes. Our maps also reveal extremely rapid localized variations in brightness which have not yet been seen in other nuclear jets. We suggest that phase effects, arising from the intersection of oblique shocks, may be the cause of these dramatic changes. 3C 380 is often classified as a compact steep spectrum (CSS) source; however, in contrast to the majority of CSS sources, it is likely that 3C 380 is simply a powerful FRII source seen approximately end-on.     

Quantum statistical cluster abundances in hot nuclear matter and elemental composition of cosmic-ray sources

A simple model for superluminal double radio sources is presented. A relativistic electron-positron beam drives the expansion of an elongated magnetic loop configuration. This is treated using basic conservation laws. Relativistically expanding radio components on a scale of parsecs result for plausible physical parameters.     

4C 39.25: Multi-epoch polarisation observations at 15, 22 and 43 GHz

We present multi-epoch simultaneous 15, 22 and 43 GHz VLBA polarimetric radio observations of the quasar 4C 39.25 which provide further evidence for the ongoing interaction between components `a' and `b' through the monitoring of the total and polarised flux densities of both components, the proper motion of `b' and, more importantly, of the polarisation angle associated with components `a' and `b'. There are strong pieces of evidence indicating that the superluminal component `b' is “colliding” or “crossing” the region associated with the stationary component `a': (i) at millimeter wavelengths, the total flux density of 4C 39.25 has reached a maximum and is already beginning to decline; (ii) at centimeter wavelengths, the total flux density light curve has reached a “plateau” at its maximum value while the polarised flux density is already decreasing; and (iii) the proper motion of 4C 39.25 with respect to the quasi-inertial reference frame defined by the sources observed in the USNO-programme shows a sharp change in the slope during 1997–1998.     

Variations in the integral fluxes and structure of the radio source 3C120

The variability of the radio source 3C120 is studied using data from the international geodesic VLBI observation programs at 8.6 GHz and regular monitoring over frequencies of 4.8–36.8 GHz carried out at the Crimean Astrophysical Observatory (Ukraine) and the Radio Astronomy Observatory of the University of Michigan (USA). A combined analysis of the integral fluxes and structures on millisecond scales reveals the existence of flares at high frequencies accompanied by the appearance of new VLBI components at centimeter wavelengths. It is found that the variations in the fluxes for 3C120 at various radio frequencies have delayed maxima at low frequencies, and the flare of 1998 was accompanied by the birth of a new superluminal component. __________ Translated from Astrofizika, Vol. 50, No. 3, pp. 325–334 (August 2007).     

Radio Properties of BL Lac Object S5 2007+777

S5 2007+777 is a typical BL Lac object with a low peak frequency, and a kpc-scale extended X-ray jet. In the literature, the Doppler factor derived at the X-ray waveband by means of model estimation is about 13.0, then the intrinsic jet scale can reach the order of magnitude of 1 Mpc. In this work, we have studied the radio structure of the jet, the brightness temperature, proper motion and other properties of this source with the collected EVN (European VLBI Network) high-resolution archive data, and the American VLBA (Very Long Baseline Array) 15 GHz observed data, etc. It is found that the jet directions measured at the different wavebands of the VLBI (Very Long Baseline Interferometry) are consistent, but slightly different from the direction of the kpc-scale X-ray jet given by the literature and the direction of the VLA (Very Large Array) radio jet, which means that the Doppler brightening effect exists in the jet emission of the source. Both the mean value and median value of the radio Doppler factor of this source estimated from the brightness temperature that measured by the VLBI are 5.0, which is smaller than the Doppler factor at the X-ray waveband given by the literature, but consistent with the Doppler factor at the radio waveband obtained by using the other methods in the literature. Furthermore, by fitting the data observed in multiple epochs, it is found that the various components of the source at the same waveband do not have an evident proper motion in a long epoch, but the proper motion in short epochs exhibits even a super-luminal motion. This may be caused by the transfer of the central position of the component with a low surface brightness. Meanwhile, this also verifies the conclusion that the radio Doppler factor estimated previously is not very large, and smaller than the Doppler factor in the X-ray waveband. By using the obtained radio Doppler factor, it is found that the source has an intrinsic radio jet of rather large scale, which may reach 0.5 Mpc, because the mean value is adopted in this case, thus it indicates that the source also possibly possesses a jet close to the scale of a giant radio galaxy.     

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。     

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.