Observation of Radio Stars Del Lib and HR 1099 Using Piggy-back Phase Referencing Mode in Geodetic Observation postprint

Abstract: The GCRF (Gaia Celestial Reference Frame) based on Gaia astrometric data has systematic differences from the ICRF (International Celestial Reference Frame) based on VLBI (Very Long Baseline Interferometry). An external independent evaluation of the data from Gaia is required to link optical and radio reference frame. Celestial bodies with both optical and radio radiation are generally used to link the two frames, quasars are used at the dark end (magnitude G≥15), and radio stars are used at the bright end (G≤13). It is very difficult to apply for the ordinary VLBI observations, so we try to focus on some geodesic observations that can use phase reference mode to observe radio stars in geodesic observations. In order to test the feasibility of this kind of observation, we use piggy-back phase referencing mode in geodetic observation of IVS (The International VLBI Service for Geodesy and Astrometry) and LBA (Large Baseline Array), and select Del Lib and HR 1099 as the targets. Our observations have obtained the VLBI images, flux densities and single￣epoch coordinates of these two radio stars, and the coordinate accuracy is higher than that of the previous work; at the same time, we also combine the data of the previous work to fit parallax and proper motion of the two radio stars. Our results are consistent with the results of the previous VLBI work and Gaia′s, and some of the accuracy is higher. Our work verify the feasibility of observing radio stars with piggy-back phase referencing mode in geodetic observation, and lay a certain foundation for the subsequent enrichment of VLBI astrometric samples of radio stars and linking of optical and radio reference frames.