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A. de Witt, D. Gordon, C. Jacobs, H. Krasna, J. McCallum, J. Quick, B. Soja:
"The K-band (24 GHz) 2019a Celestial Reference Frame";
Poster: 24th Meeting of the European VLBI Group for Geodesy and Astrometry, Gran Canaria, Spain; 2019-03-17 - 2019-03-19.

AK-band(24GHz) celestial reference frame of 918 sources covering the full sky has been constructed using 0.68 million observations from 69 observing sessions from the VLBA and HartRAO-Hobart. Observations at K-band are motivated by their access to more compact source morphology and reduced core shift relative to observations at the historically standard S/X-band(2.3/8.4GHz). The factor of three increase in interferometer resolution at K-band should resolve out source structure which is a concern for AGN centroid stability. K median precision is comparable to S/X precision (for common sources) thereby raising the question of which frame is more accurate. The accuracy of the K CRF is quantified by comparison of 783 sources in common with the current (2019Jan) S/X-band producing wRMS agreement of 78 μas in αcos(δ)and 133 μas in δ. There is evidence for systematic errors below the ~60 μas level. The success of Gaia optical astrometry motivates work to tie the radio and optical frames. K-band data and Gaia Data Release-2 data give a frame tie precision of ~15 μas (1-σ, per 3-D rotation component).If K-band precision can be pushed below ~20-30 μas, the K frame has potential to produce a tie to Gaia that is superior to S/X due to reduced astrophysical systematics at K relative to S/X. The K-band 2019a frame is an incremental update to the ICRF-3´s K-band component thereby answering the IAU´s call for maintenance of the ICRF-3.

http://www.oan.es/evga2019/EVGA2019_PDF/P306_EVGA2019_deWitt.pdf