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Optical Variability of Extragalactic Objects Used to Tie the HIPPARCOS Reference Frame to an Extragalactic System Using Hubble Space Telescope Observations

Bozyan, Elizabeth P.; Hemenway, Paul D.; Argue, A. Noel

Observations of a set of 89 extragalactic objects (EGOs) will be made with the Hubble Space Telescope Fine Guidance Sensors and Planetary Camera in order to link the HIPPARCOS Instrumental System to an extragalactic coordinate system. Most of the sources chosen for observation contain compact radio sources and stellarlike nuclei; 65% are optical v…

VLBI and Optical Astrometry of Southern Extragalactic Radio Sources and Radio Stars

White, Graeme L.; Jauncey, David L.; Lestrade, Jean-Francois +3 more

Mark III very long baseline interferometry (VLBI) has been used to determine the positions of ten compact extragalactic radio sources in the southern hemisphere. These positions are relative to the Jet Propulsion Laboratory VLBI celestial reference frame and are accurate at the 0.01" level, more than an order of magnitude improvement compared to t…