VLBI detection of the HST-1 feature in the M 87 jet at 2 cm
VLBI detection of the HST-1 feature in the M 87 jet at 2 cm
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DOI：
10.1051/0004-6361/200913915
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发表时间：
2010-02
影响因子：
6.5
通讯作者：
C. Chang;E. Ros;E. Ros;Y. Kovalev;Y. Kovalev;M. Lister
中科院分区：
文献类型：
--
作者：
C. Chang;E. Ros;E. Ros;Y. Kovalev;Y. Kovalev;M. Lister
语境。 M 87 强大射流中距核心 80 pc 的明亮特征显示出极不寻常的特性。早期的无线电、光学和 X 射线观测表明，这个标记为 HST-1 的特征是超光速的，并且可能与 HESS 在 2005 年检测到的 TeV 耀斑有关。有人声称，由于这些特性，该特征可能具有耀变体性质。目标。为了检验 HST-1 是否具有类耀变体性质，我们分析了 2000 年至 2009 年间进行的专门全轨迹观测和 2 厘米调查/MOJAVE VLBI 监测计划中的 λ2 厘米 VLBA 档案数据。在检查了干涉能见度随距离变化的不同权重后，我们使用宽视场成像技术研究了 M 87 喷气机的亚秒差距结构。 HST-1 区域以毫弧秒分辨率成像。结果。我们首次在 2003 年初至 2007 年初进行的观测中对 HST-1 进行 2 cm VLBI 检测，并分析其随时间的演变。使用 HST-1 的检测，我们发现预计的视速度为 0.61 ±0.31c。对该特征的 VLA 和 VLBA 通量密度的比较表明，它主要在毫弧秒尺度上解析。该特征在 λ2 cm 和 λ20 cm 之间是光学薄的（对于 S ∝ ν +α ，α ∼ ―0.8）。结论。我们没有发现 HST-1 具有耀变体性质的证据。
Context. A bright feature 80 pc away from the core in the powerful jet of M 87 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 because of these properties. Aims. To examine whether HST-1 has a blazar-like nature, we analyzed λ2 cm VLBA archival data from dedicated full-track observations and the 2 cm survey/MOJAVE VLBI monitoring programs performed between 2000 and 2009. Methods. We studied the subparsec scale structure of M 87 jet by using wide-field imaging techniques, after checking different weighting of the interferometric visibilities as a function of distance. The HST-1 region was imaged at milliarcsecond resolution. Results. We present the first 2 cm VLBI detection of HST-1 in observations performed between early 2003 and early 2007, and analyze its evolution with time. Using the detections of HST-1, we find that the projected apparent speed is 0.61 ±0.31c. A comparison of the VLA and VLBA flux densities of this feature indicates that it is mostly resolved on milliarcsecond scales. This feature is optically thin (α ∼ ―0.8 for S ∝ ν +α ) between λ2 cm and λ20 cm. Conclusions. We do not find evidence that HST-1 has a blazar nature.