DOI

https://doi.org/10.48717/wah6-ht68

Project

EL065

Title

Gaia/VLBI alignment with radio stars

Abstract

We propose to observe 27 known radio stars at continuum X band using phase-referencing with the EVN in one epoch (47 hours total) in term #3, 2022 to obtain their absolute positions. Additionally, the observations of 13 of these stars should be repeated in three epochs (three 24-hour experiments) in spring/summer 2023. This provides relative positions of these 13 radio stars with respect to the ICRF3 calibrators. Combining this new set data with the VLBA observations (done in 2020) shall obtain such parameters as position, proper motion, parallax, non-linear motion (if it is detected) from VLBI data for these 13 stars for the first time. The absolute positions and the new model estimates are needed to enhance the alignment of the Gaia optically bright (G < 13 mag) frame to the ICRF3. The proper motions contribute to the determination of the spin between the radio and optical reference frames, whereas the absolute positons contribute to both orientation offset and spin. Our simulations have shown that inclusion of the new positions and the proper motions will improve the determination of the Gaia bright frame orientation offset by 26% and the spin by 22%.