A bright feature 80 pc away from the core in the powerful jet of M87 shows highly unusual properties. Earlier radio, optical and X-ray observations have shown that this feature, labeled HST-1, is superluminal, and is possibly connected with the TeV flare detected by HESS in 2005. It has been claimed that this feature might have a blazar nature, due to these properties. To examine the possible blazar-like nature of HST-1, we analyzed lambda 2 cm VLBA archival data from dedicated full-track observations and the 2 cm survey/MOJAVE VLBI monitoring programs obtained between 2000 and 2009. Applying VLBI wide-field imaging techniques, the HST-1 region was imaged at milliarcsecond resolution. Here we present the first 2 cm VLBI detection of this feature in observations from early 2003 to early 2007, and analyze its evolution over this time. Using the detections of HST-1, we find that the projected apparent speed is 0.61 +/- 0.31 c. A comparison of the VLA and VLBA flux densities of this feature indicate that is mostly resolved on molliarcsecond scales. This feature is optically thin between lambda 2 cm and lambda 20 cm. We do not find evidence of a blazar nature for HST-1.
Parsec structure and properties of the jet of 3C273. Results of Space VLBI data processing
本文介绍了W068地空VLBI实验的数据处理结果。特别地，成功地处理了该观测会话的一部分数据。这些数据是在2000年3月17日9：00 UT和10：30 UT之间获得的。本次实验采用了美国甚长基线干涉仪VLBA（Very Long Baseline Array）和日本VLBI空间观测计划VSOP（Space Observatory Programme）的10个天线。此外，27个VLA（甚大阵）天线用作附加的地面天线。数据从NRAO（美国国家射电天文台）的档案中转移，并使用名为“Astro Space Space”（ASL for Windows）的软件进行处理。这一处理的主要结果是标题为3C273的类星体的高分辨率和高精度图像。利用这幅图像，我们对该天体喷流的射电结构作出了一些结论。我们的结果与许多作者早先发表的3C273空间VLBI数据处理的结果并不矛盾。我们可以在结果中添加一些新的方面。给出了3C273在6厘米波段的再现像和该光源的一些参数值。
Multifrequency VLBA study of the blazar S5 0716+714 during the active state in 2004 II. Large-scale jet kinematics and the comparison of the different methods of VLBI data imaging as applied to kinematic studies of AGN
