LBA observations for project V628 semester 2023OCTS

The Gaia space observatory has measured more precise trigonometric parallaxes than any other facility. Nevertheless, the latest released Gaia parallaxes are on average biased by ~0.02mas. This bias, aka. the Gaia parallax zero-point, varies with the position, the magnitude and the colour of the target. At low Galactic latitudes, owing to the rare identifications of Gaia quasars, the estimation of the Gaia parallax zero-points turns out to be extremely challenging. To refine the poorly constrained Gaia parallax zero-points at low Galactic latitudes, we look to first establishing a sample of ~96 southern-hemisphere radio stars that can potentially serve as ideal Gaia parallax calibrators, before carrying out precise astrometry on the sample using LBA. To pilot the astrometric program, this proposal aims at achieving LBA detections of more than 30 new radio star candidates that we identified, which will prepare us for the next-step expansion of the radio star sample. To cope with the generally sparse distribution of phase calibrators at low Galactic latitudes, the proposed observations will adopt the MultiView strategy.