Sources with Significant Astrometric Offsets Between the S/X and K-band Celestial Frames

The latest astrometric celestial reference frame (CRF) solutions at S/X-band and K-band have 1014 sources in common, of which 36 are outliers with significant differences between the X and K-band coordinates. We investigate possible astrophysical reasons for the large differences seen for the 36 outlier sources. These large differences may indicate significant structural differences between S/X and K-band. In order to study the astrophysical differences, we conducted multi-epoch, quasi-simultaneous S/X and K-band astrometric and imaging observations using the Very Long Baseline Array (VLBA). These images allow us to directly compare the source structure at X and K-band and allow us to compare the direction of the extended emission from our imaging to the astrometric offset direction obtained from our CRF solutions.