NRAO 530 is an optically violent variable source and has been studied with multi-epoch multi-frequency 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 center ( 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 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 position angle swing of 3 \aas@@fstack { \circ } 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 .