Fast Radio Bursts (FRBs) are short, intense radio signals from distant astrophysical sources, and their accurate localisation is crucial for probing their origins and utilising them as cosmological tools. This study focuses on improving the astrometric precision of FRBs discovered by the Australian Square Kilometre Array Pathfinder (ASKAP) by correcting systematic positional errors in the Rapid ASKAP Continuum Survey (RACS), which is used as a primary reference for ASKAP FRB localisation. Akhil et al. present a detailed methodology for refining astrometry in two RACS epochs (RACS-Low1 and RACS-Low3) through crossmatching with the Wide-field Infrared Survey Explorer (WISE) catalogue. The uncorrected RACS-Low1 and RACS-Low3 catalogues had significant astrometric offsets, with all-sky median values of 0.58′′ in RA and −0.26′′ in Dec. (RACS-Low1) and 0.29′′ in RA and 1.24′′ in Dec. (RACS-Low3), with a substantial and direction-dependent scatter around these values. After correction, the median offset was completely eliminated, and the 68% confidence interval in the all-sky residuals was reduced to 0.2′′ or better for both surveys. By validating the corrected catalogues against other, independent radio surveys, we conclude that the individual corrected RACS source positions are accurate to a 1-σ confidence level of 0.3′′ over the bulk of the survey area, degrading slightly to 0.4′′ near the Galactic plane. This work lays the groundwork to extend our corrections to the full RACS catalogue that will enhance future radio observations, particularly for FRB studies.

The top row of the figure above shows the RA (left) and Dec. (right) offsets of RACS-Low1 vs VLASS and the bottom row shows the RA (left) and Dec. (right) offsets of RACS-Low3 vs VLASS. The underperforming regions in both RACS-Low1 and RACS-Low3 can be clearly visualised from these plots.