Comparison of dynamical and kinematic reference frames via pulsar positions from timing, Gaia, and interferometric astrometry

Context. Pulsars are special objects whose positions can be determined independently from timing, radio interferometric, and Gaia astrometry at sub-milliarcsecond (mas) precision; thus, they provide a unique way to monitor the link between dynamical and kinematic reference frames. Aims. We aim to assess the orientation consistency between the dynamical reference frames represented by the planetary ephemerides and the kinematic reference frames constructed by Gaia and very long baseline interferometry (VLBI) through pulsar positions. Methods. We identified 49 pulsars in Gaia Data Release 3 and 62 pulsars with VLBI positions from the PSR pi and MSPSR pi projects and searched for the published timing solutions of these pulsars. We then compared pulsar positions measured by timing, VLBI, and Gaia to estimate the orientation offsets of the ephemeris frames with respect to the Gaia and VLBI reference frames by iterative fitting. Results. We found orientation offsets of similar to 10 mas in the DE200 frame with respect to the Gaia and VLBI frame. Our results strongly depend on the subset used in the comparison and they could be biased by underestimated errors in the archival timing data, reflecting the limitation of using the literature timing solutions to determine the frame rotation.