# Determination of the relativistic parameter gamma using very long baseline interferometry - General Relativity and Quantum Cosmology

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Abstract: Relativistic bending in the vicinity of a massive body is characterized onlyby the post-Newtonian parameter $\gamma$ within the standard parameterizedpost-Newtonian formalism, which is unity in General Relativity. Aiming atestimating this parameter, we use very long baseline interferometry VLBI tomeasure the gravitational deflection of radio waves emitted by distant compactradio sources, by Solar System bodies. We analyze geodetic VLBI observationsrecorded since 1979. We compare estimates of $\gamma$ and errors obtained usingvarious analysis schemes including global estimations over several time spansand with various Sun elongation cut-off angles, and analysis of radio sourcecoordinate time series. We arrive at the conclusion that the relativisticparameter $\gamma$ cannot be estimated at better than $2\times10^{-4}$. Themain factor of limitation is the uncertainty in the determination of global orsession-wise radio source coordinates. A sum of various instrumental andmodeling errors and analysis strategy defects, that cannot be decorrelated andcorrected yet, is at the origin of the limitating noise.

Autor: S. B. Lambert, C. Le Poncin-Lafitte

Fuente: https://arxiv.org/