The source structure of 0642+449 detected from the CONT14 observations

Abstract

The CONT14 campaign with state-of-the-art VLBI data has observed the source 0642+449 with about one thousand observables each day during a continuous observing period of fifteen days, providing tens of thousands of closure delays---the sum of the delays around a closed loop of baselines. The closure delay is independent of the instrumental and propagation delays and provides valuable additional information about the source structure. We demonstrate the use of this new "observable" for the determination of the structure in the radio source 0642+449. This source, as one of the defining sources in the second realization of the International Celestial Reference Frame (ICRF2), is found to have two point-like components with a relative position offset of -426 microarcseconds in right ascension and -66 microarcseconds in declination. The two components are almost equally bright with a flux-density ratio of 0.92. The standard deviation of closure delays for source 0642+449 was reduced from 139 ps to 90 ps by using this two-component model. Closure delays larger than one nanosecond are found to be related to the source structure, demonstrating that structure effects for a source with this simple structure could be up to tens of nanoseconds. The method described in this paper does not rely on a priori source structure information, such as knowledge of source structure determined from direct (Fourier) imaging of the same observations or observations at other epochs. We anticipate our study to be a starting point for more effective determination of the structure effect in VLBI observations.

arXiv comment14 pages, 13 figures, Accepted by Astronomical Journal on 12 Jul, 2016

References in corpus (9)

• MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets
• MOJAVE. X. Parsec-Scale Jet Orientation Variations and Superluminal Motion in AGN
• MOJAVE: Monitoring of Jets in AGN with VLBA Experiments - II. First-Epoch 15 GHz Circular Polarization Results
• Relativistic Jets in The Radio Reference Frame Image Database I: Apparent Speeds from the First Five Years of Data
• The Celestial Reference Frame at 24 and 43 GHz. II. Imaging
• On the connection of the apparent proper motion and the VLBI structure of compact radio sources
• RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz
• On accuracy assessment of celestial reference frame VLBI realizations
• The Position/Structure Stability of Four ICRF2 Sources

Cited by in corpus (5)

• Observational consequences of optical band milliarcsecond-scale structure in active galactic nuclei discovered by Gaia
• Evidence of the $Gaia$--VLBI position differences being related to radio source structure
• Observable quality assessment of broadband very long baseline interferometry system
• The impacts of source structure on geodetic parameters demonstrated by the radio source 3C371
• Robust 1-norm periodograms for analysis of noisy non-Gaussian time series with irregular cadences: Application to VLBI astrometry of quasars