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We have used multi-epoch long-baseline radio interferometry to determine theproper motion and orbital elements of Algol and UX Arietis, two radio-bright,close binary stellar systems with distant tertiary components. For Algol, werefine the proper motion and outer orbit solutions, confirming the recentresult of Zavala et al. (2010) that the inner orbit is retrograde. The radiocentroid closely tracks the motion of the KIV secondary. In addition, the radiomorphology varies from double-lobed at low flux level to crescent-shaped duringactive periods. These results are most easily interpreted as synchrotronemission from a large, co-rotating meridional loop centered on the K-star. Ifthis is correct, it provides a radio-optical frame tie candidate with anuncertainty {\pm}0.5 mas. For UX Arietis, we find a outer orbit solution thataccounts for previous VLBI observations of an acceleration term in the propermotion fit. The outer orbit solution is also consistent with previouslypublished radial velocity curves and speckle observations of a third body. Thederived tertiary mass, 0.75 solar masses, is consistent with the K1main-sequence star detected spectroscopically. The inner orbit solution favorsradio emission from the active K0IV primary only. The radio morphology,consisting of a single, partially resolved emission region, may be associatedwith the persistent polar spot observed using Doppler imaging.

Radio Astrometry Of The Triple Systems Algol And UX Arietis