High‐frequency very long baseline interferometry studies of NRAO 530
High‐frequency very long baseline interferometry studies of NRAO 530
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DOI：
10.1111/j.1365-2966.2011.19537.x
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发表时间：
2011-07
影响因子：
4.8
通讯作者：
R. Lu;R. Lu;T. Krichbaum;J. Zensus
中科院分区：
文献类型：
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作者：
R. Lu;R. Lu;T. Krichbaum;J. Zensus
NRAO 530 是一种光猛变源，已通过多历元多频率高分辨率甚长基线干涉测量 (VLBI) 观测进行了研究。 2007 年 5 月在银河系中心 (Sgr A*) 观测期间，连续 10 天用甚长基线阵列 (VLBA) 在三个频率（22、43 和 86 GHz）下对 NRAO 530 进行了监测。此外，通过分析过去 10 年 NRAO 530 在 15 GHz 下的档案数据，我们能够研究其详细的喷气运动学。我们将位于喷气机南端的紧凑部件确定为 VLBI 核心，这与之前的研究一致。三个高频的 10 d 监测数据显示出可以对组件位置产生高质量且自洽的测量结果，从中我们首次检测到二维频率相关位置偏移。此外，重复测量还使我们能够研究 NRAO 530 的日间通量密度和结构变异性。我们发现内部射流组件的变化性比外部射流组件的变化更大。我们获得了 8 个射流组件的表观速度，其 beta(app) 范围为 2 到 26c。因此，我们估计了物理射流参数，最小洛伦兹因子为 14，多普勒因子在 14-28 范围内（分量 f）。 NRAO 530 形态的变化与单独射流组件的运动有关，最明显的变化发生在靠近核心的区域。对于 NRAO 530，我们估计整个内部射流（d 和 e 部分）的位置角摆动为每年 3.4 度。非弹道运动和射流方向的变化使该源成为螺旋且可能摆动射流的另一个突出例子。
NRAO 530 is an optically violent variable source and has been studied with multi-epoch multifrequency high-resolution very long baseline interferometry (VLBI) observations. NRAO 530 was monitored with the Very Long Baseline Array (VLBA) at three frequencies (22, 43 and 86 GHz) on 10 consecutive days in 2007 May during observations of the Galactic Centre (Sgr A*). Furthermore, analysis of archival data of NRAO 530 at 15 GHz over the last 10 years allows us to study its detailed jet kinematics. We identified the compact component located at the southern-end of the jet as the VLBI core, consistent with previous studies. The 10-d monitoring data at the three high frequencies were shown to produce high-quality and self-consistent measurements of the component positions, from which we detected for the first time a two-dimensional frequency-dependent position shift. In addition, the repeated measurements also permit us to investigate the interday flux density and structure variability of NRAO 530. We find that it is more variable for the inner jet components than those further out. We obtained apparent velocities for eight jet components with beta(app) ranging from 2 to 26c. Accordingly, we estimated physical jet parameters with the minimum Lorentz factor of 14 and Doppler factors in the range of 14-28 (component f). The changes in the morphology of NRAO 530 were related to the motion of separate jet components with the most pronounced changes occurring in the regions close to the core. For NRAO 530, we estimated a position angle swing of 3.4 per year for the entire inner jet (components d and e). The non-ballistic motion and change of jet orientation make this source another prominent example of a helical and possibly swinging jet.