Quasars

A statistical study of more than two million LQAC-6 quasars examines their sky distribution, astrometric uncertainties, redshift consistency, and optical luminosities, with implications for celestial reference frames.

VLBI source position time series indicate that the ICRF3 axes are stable at the 10–20 microarcsecond level and confirm the robustness of the commonly used four-step solution.

Quality analysis of Gaia-CRF2 quasar astrometry using visibility periods and correlation coefficients; quasars with 13–16 visibility periods yield the most reliable parameters.