Analysis identifies the parallax effect's significance in VLBI astrometric data, suggesting improvements for celestial reference systems.
We present an analysis of the parallax effect observed in VLBI astrometric data for extragalactic radio sources based on observations from 1993 to 2025. While the classical parallax is negligible for such distant objects, a systematic effect consistent with the parallax has been detected with a mean value for 2014–2017 of about -16.3± 0.8μ as. This estimated value is close to the parallax zero-point offset found in Gaia EDR3. Parallax effect depends on equatorial coordinates, highlighting the region of positive ‘‘parallaxes’’ possibly associated with the Virgocentric flow or CMB cold spot. A study of this systematic effect is important for future improvements of the International Celestial Reference Frame.
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A. A. Osetrova (2025) studied this question.
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