在M87的射流中继续监测HST-1的EVN
Continuing EVN monitoring of HST-1 in the jet of M87
摘要：
M87中的相对论性喷流提供了一个独特的机会，了解详细的喷流结构和排放过程，由于其接近。特别是，奇特的喷流区HST-1在~1弧秒（或80 pc，投影）从核吸引了大量的兴趣，在过去的十年中，因为它的超光速运动和宽带无线电到X射线爆发，这可能进一步连接到伽马射线的生产高达TeV的能量。在过去的五年里，我们一直在用EVN在5GHz对HST-1进行密集监测，以研究详细的结构演变及其与高能活动的可能联系。虽然该计划已经在详细的质量尺度结构，自行测量和结构变化方面产生了有趣的结果，但最近的HST-1亮度在这个频率上持续下降。为解决此问题，我们已于2013年10月起将监察频率调整至1.7 GHz。该策略成功地恢复了在上一个5GHz会话中丢失的较微弱的发射。此外，我们再次发现在HST-1的上游边缘突然出现了一个新的组件，这表明使用EVN 1.7GHz确实能够有力地探测HST-1当前的弱性质。在这里，我们报告的早期结果，从1.7GHz的监测以及进一步的进展，长期的运动学研究。
英文摘要：
The relativistic jet in M87 offers a unique opportunity for understanding the detailed jet structure and emission processes due to its proximity. In particular, the peculiar jet region HST-1 at ~1 arcsecond (or 80 pc, projected) from the nucleus has attracted a great deal of interest in the last decade because of its superluminal motion and broadband radio-to-X-ray outbursts, which may be further connected to the gamma-ray productions up to TeV energies. Over the last five years, we have been doing an intensive monitoring of HST-1 with EVN at 5GHz in order to examine the detailed structural evolution and its possible connection to high-energy activities. While this program already yielded interesting results in terms of the detailed mas-scale structure, proper motion measurements and structural variations, the recent HST-1 brightness is continuously decreasing at this frequency. To counter this, we have shifted our monitoring frequency to 1.7GHz from October 2013. This strategy successfully recovered the fainter emission that was missed in the last 5GHz session. Moreover, we again discovered the sudden emergence of a new component at the upstream edge of HST-1, demonstrating that the use of EVN 1.7GHz is indeed powerful to probe the current weak nature of HST-1. Here we report early results from the 1.7GHz monitoring as well as further progress on the long-term kinematic study.
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