Parameters of the Link between the Optical and Radio Frames from Gaia DR2 Data and VLBI Measurements

Abstract

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 between the optical and radio frames has been obtained by analyzing the GaiaDR2-VLBI trigonometric parallax differences: $\Delta \pi =-0.038\pm 0.046$ mas (with a dispersion of 0.156 mas). This means that the Gaia DR2 parallaxes should be increased by this correction. The parallax scale factor is shown to be always very close to unity within $\sim$3 kpc of the Sun: $b=1.002\pm \mathrm{0.007.}$ Our analysis of the proper motion differences for the radio stars based on the model of solid-body mutual rotation has revealed no rotation components differing significantly from zero: $({\omega }_x,{\omega }_y,{\omega }_z)=(-0.14,0.03,-0.33)\pm (0.15,0.22,0.16)$ mas yr${}^{-1}.$

14 pages, 3 figures, 1 table

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• Galactic Rotation Based on OB Stars from the Gaia DR2 Catalogue
• Link between the Optical and Radio Frames from Gaia DR3 Data and VLBI Measurements
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• Validation of the Gaia Early Data Release 3 parallax zero-point model with asteroseismology