A new estimate of the zero-point shift of the Gaia DR3 parallaxes obtained from a comparison with VLBI measurements of masers and radio stars

TL;DR

This paper compares Gaia DR3 parallaxes with VLBI measurements of radio stars and masers to estimate and refine the zero-point systematic shift, confirming minimal rotation relative to extragalactic reference frames.

Contribution

It provides a new estimate of the Gaia DR3 parallax zero-point shift using a comprehensive VLBI comparison, improving calibration accuracy.

Findings

Zero-point shift estimate: -0.038 mas

No significant rotation of Gaia DR3 system

Sample of 151 radio stars and masers

Abstract

The most complete sample of radio stars and masers with trigonometric parallaxes measured by the VLBI method, common with the Gaia EDR3 and Gaia DR3 catalogs, has been compiled using literature data. The sample contains 151 stars. An analysis of the differences in parallaxes and proper motions of Gaia-VLBI stars has been performed. A new estimate of the systematic shift of the Gaia parallax zero point relative to the inertial coordinate system has been obtained: $\Delta\pi=-0.038\pm0.011$ mas. The obtained estimates of the relative rotation rates confirm the absence of a significant rotation of the Gaia\,DR3 system relative to the extragalactic coordinate system, which in this case is represented by VLBI measurements.