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VLBI Difference Astrometry at 43 GHz
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J.C. Guirado, J.M. Marcaide, M.A. Pérez-Torres, & E. Ros,
Astronomy & Astrophysics, 353:L37-L40 (2000)
- Abstract
From 43 GHz VLBA observations of the pair of radio sources
QSO 1928+738 and
BL 2007+777 we have demonstrated the feasibility of precision phase-delay difference
astrometric techniques at millimeter wavelengths.
For a pair of sources with 50, separation and high
antenna elevations, we have shown that present astrometric models and millimeter
arrays are advanced enough
to model the difference phase delay to within 2 picoseconds, less than one tenth
of a phase-cycle at 43 GHz. The root-mean-square of the
difference phase residuals is dominated by the
fluctuations of the atmospheric water vapor.
We have determined the relative position of the observed sources with a precision
twofold better than previous determinations at lower frequencies and, more
importantly, free from ambiguous definitions of the reference point on the structure of
the radio sources. Our result makes 43 GHz VLBI phase-delay difference astrometry an ideal tool
for study the absolute kinematics of the highly variable structures of
regions near the core of extragalactic radio sources.
Eduardo Ros
ros@mpifr-bonn.mpg.de