The Galactic Aberration and Its Impact on Astronomical Reference Frames

The Galactic aberration effect, also known as the secular aberration drift, is a consequence of the centripetal acceleration of the Solar System Barycenter in the circular orbit around the Galactic center. It causes distance-independent apparent proper motions (the amplitude is about 5 \uasyr) for extragalactic sources which were regarded as motionless before 21th century. As the very long baseline interferometry (VLBI) has been greatly developed and the ESA (European Space Agency) space mission Gaia has provided ultra high-precision astrometric data, the Galactic aberration effect has becoming important. It will cause slow spin of the reference frame due to the non-uniform distribution of extragalactic sources. Therefore systematic corrections have to be applied to the Earth rotation parameters. For the precession rate, the correction is about 1 \uasyr. For the very high accurate VLBI and Gaia reference frames, the Galactic aberration effect will introduce small distortion which is a crucial systematic effect for the link between the two reference frames.