Related papers: Connecting VLBI and Gaia celestial reference frame…
We have used the Very Large Array (VLA), linked with the Pie Town Very Long Baseline Array antenna, to determine astrometric positions of 46 radio stars in the International Celestial Reference Frame (ICRF). Positions were obtained in the…
Precision geodesy relies on the stability of the International Celestial Reference Frame (ICRF), yet its reference sources, Active Galactic Nuclei (AGN), exhibit changes in source structure that can manifest as apparent shifts in their…
Using photometric variability information from the new Gaia DR3 release, I show for the first time that photometric variability is inversely correlated with the prevalence of optical-radio position offsets in the active galactic nuclei…
The second release of Gaia data (Gaia DR2) contains the astrometric parameters for more than half a million quasars. This set defines a kinematically non-rotating reference frame in the optical domain referred to as the Gaia-CRF2. The…
Despite continuous increasing of the number of ICRF sources, their sky coverage is still not satisfactory. The goal of this study is to discuss some new considerations for extending the ICRF source list. Statistical analysis of the ICRF…
Despite their importance for astrometry and navigation, the active galactic nuclei (AGNs) that comprise the International Celestial Reference Frame (ICRF) are relatively poorly understood, with key information such as their spectroscopic…
Astrophysical space missions deliver invaluable information about our universe, stellar dynamics of our galaxy, and motion of celestial bodies in the solar system. Astrometric space missions SIM and Gaia will determine distances to stars…
Optical positions from the SuperCOSMOS Sky Survey have been compared in detail with accurate radio positions that define the second realisation of the International Celestial Reference Frame (ICRF2). The comparison was limited to the IIIaJ…
Context: To investigate the differences between positions, as determined by optical (direct imaging) and Very Long Baseline Interferometry (VLBI) techniques, of extragalactic sources listed in the second realization of the International…
Based on published data, we have assembled a sample of 88 radio stars for which there are both trigonometric parallax and proper motion measurements in the Gaia DR2 catalogue and VLBI measurements. A new estimate of the systematic offset…
In this paper, we propose to use the scatter of celestial pole offset (CPO) series obtained from VLBI observations as a measure of the accuracy of the celestial reference frame (CRF) realizations. Several scatter indices (SIs) including…
A new list of physical characteristics of 4261 astrometric radio sources, including all 717 ICRF-Ext.2 sources has been compiled. Comparison of our data of optical characteristics with the official International Earth Rotation and Reference…
While conventional imaging in VLBI provides information only about the relative position between different features of a given source, phase-referenced observations can provide precise positional information with respect to an external…
The celestial reference frame is realized by absolute positions of extragalactic sources that are assumed to be fixed in the space. The fixing of the axes is one of the crucial points for the International Celestial Reference System (ICRS)…
Using very long baseline interferometry data for the sources that comprise the third International Celestial Reference Frame (ICRF3), we examine the quality of the formal source position uncertainties of ICRF3 by determining the excess…
Astrometric space missions like Gaia have stimulated a rapid advance in the field of relativistic astrometry. Present investigations in that field aim at accuracies significantly less than a microarcsecond. We review the present status of…
Accurate alignment of the radio and optical celestial reference frames requires detailed understanding of physical factors that may cause offsets between the positions of the same object measured in different spectral bands. Opacity in…
Summarizes current status of radio interferometry at radio frequencies between Earth-based receivers, for astrometric and geodetic applications. Emphasizes theoretical models of VLBI observables that are required to extract results at the…
VLBI plays a unique and fundamental role in the maintenance of global reference frames which are required for precise positioning in many research areas related e.g to the understanding and monitoring of global changes, to geodesy, to space…
Galactic aberration (GA) is a small effect in proper motions of celestial objects with an amplitude of about 5 $\mu$as/yr already noticeable in highly accurate astrometric observations such as VLBI and Gaia. However accurate accounting for…