Related papers: Determination of the relativistic parameter gamma …
Optical Very Long Baseline Interferometry (VLBI) offers the potential for unprecedented angular resolution in both astronomical imaging and precision measurements. Classical approaches, however, face significant limitations due to photon…
Global Positioning System (GPS) satellites broadcast at frequencies of 1,575.42 MHz (L1) and of 1,227.60 MHz (L2). The dispersive property of the ionosphere can be used to combine independent measurements at the two frequencies to estimate…
General relativity's prediction that all black holes are described by the Kerr metric, irrespective of their size, can now be empirically tested using electromagnetic observations of supermassive black holes and gravitational waves from…
Astrometry, the measurement of positions and motions of the stars, is one of the oldest disciplines in Astronomy, extending back at least as far as Hipparchus' discovery of the precession of Earth's axes in 190 BCE by comparing his catalog…
Finding a suitable very long baseline (VLBI) interferometer geometry is a key task in planning observations, especially imaging sessions. The main characteristic of the quality of VLBI imaging data is the (u, v)-coverage. In the case when…
Many of the compact extragalactic radio sources that are used as fiducial points to define the celestial reference frame are known to have proper motions detectable with long-term geodetic/astrometric Very Long Baseline Interferometry…
Recent theoretical works on alternative metric theories of gravity give greater significance to solar-system tests of General Relativity. In particular, it is suggested that the post-Newtonian parameter $\gamma$ ought to be determined with…
Less than $200$ radio-loud active galactic nuclei (AGN) are known above redshift $4$. Around $40$ of them have been observed at milliarcsecond (mas) scale resolution with very long baseline interferometry (VLBI) technique. Some of them are…
The relativistic theories of light propagation are generalized by introducing two new parameters $\varsigma$ and $\eta$ in the second post-Newtonian (2PN) order, in addition to the parameterized post-Newtonian parameters $\gamma$ and…
With the increasing wealth of high-quality astronomical and cosmological data and the manifold departures from General Relativity in principle conceivable, the development of generalized parametrization frameworks that unify gravitational…
We discuss the technique of Wide-field imaging as it applies to Very Long Baseline Interferometry (VLBI). In the past VLBI data sets were usually averaged so severely that the field-of-view was typically restricted to regions extending a…
Astrometric positions of radio-emitting active galactic nuclei (AGNs) can be determined with sub-milliarcsec accuracy using very long baseline interferometry (VLBI). The usually small apparent proper motion of distant extragalactic targets…
The measurement of the parametrized post-Newtonian parameter $\gamma_{\rm{PPN}}$ is a robust test of general relativity (GR). In some modified theories of gravity, $\gamma_{\rm{PPN}}$ may evolve with the redshift and deviate from one at…
Extension of radio interferometric baselines into space is inevitable if a diffraction-limited angular resolution defined by the Earth diameter at a given observing wavelength limits a pursuit of specific scientific goals. This was…
Our present relativistic part of the geodetic VLBI model for Earthbound antennas is a consensus model which is considered as a standard for processing high-precision VLBI observations. It was created as a compromise between a variety of…
The global astrometric observations of a GAIA-like satellite were modeled within the PPN formulation of Post-Newtonian gravitation. An extensive experimental campaign based on realistic end-to-end simulations was conducted to establish the…
A relativistic sub-picosecond model of gravitational time delay in radio astronomical observations is worked out and a new experimental test of general relativity is discussed in which the effect of retardation of gravity associated with…
We connect two formalisms that describe deformations away from general relativity, one valid in the strong-field regime of neutrons stars and another valid in the radiative regime of gravitational waves: the post-Tolman-Oppenheimer-Volkoff…
Very long baseline interferometry (VLBI) astrometry is used to determine the three-dimensional position and proper motion of astronomical objects. A typical VLBI astrometric campaign generally includes around ten observations, making it…
To accurately link the radio and optical Celestial Reference Frames (CRFs) at optical bright end, i.e., with Gaia G band magnitude < 13, increasing number and improving sky distribution of radio stars with accurate astrometric parameters…