NRAO 530的高频甚长基线干涉测量研究
High-frequency very long baseline interferometry studies of NRAO 530
摘要：
NRAO 530是一个光变暴源，已被多历元多频高分辨率VLBI观测研究。2007年5月，在银河系中心（Sgr A*）的观测期间，用VLBA在三个频率（22、43和86 GHz）上连续10天监测NRAO 530。此外，档案数据的NRAO 530在15 GHz的过去十年的分析，使我们能够研究其详细的射流运动学。我们确定了紧凑的组件位于南端的喷气机作为VLBI核心，与以前的研究一致。在3个高频率的10维监测数据显示，产生高质量和自洽的组件位置的测量，从我们第一次检测到一个二维的频率相关的位置偏移。此外，重复的测量也使我们能够研究NRAO 530的日间通量密度和结构变化。我们发现，它是更可变的内部射流组件比那些更远。我们获得了八个喷流分量的表观速度，整个内部喷流（分量d和e）的$β_{\rm app} ranging from 2 to 26 c. 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 P.A. swing of $为$β_{\rm app} ranging from 2 to 26 c. 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 P.A. swing of $ 3^{ \circ }. 4 $/年。非弹道运动和射流方向的变化使该源成为螺旋形和可能的“摆动”射流的另一个突出例子。
英文摘要：
NRAO 530 is an optically violent variable source and has been studied with multi-epoch multi-frequency high-resolution VLBI observations. NRAO 530 was monitored with the VLBA at three frequencies (22, 43 and 86 GHz) on 10 consecutive days in 2007 May during observations of the Galactic Center (Sgr A*). Furthermore, analysis of archival data of NRAO 530 at 15 GHz over the last ten 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 3 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 $β_{\rm app} ranging from 2 to 26 c. 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 P.A. swing of $3^{\circ}.4$ per year for the entire inner jet (components d and e). The non-ballistic motion and change of jet orientation makes this source another prominent example of a helical and possibly `swinging' jet.
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