High precision difference astrometry applied to the triplet of S 5 radio sources B 1803 + 784 / Q 1928 + 738 / B 2007 + 777

High precision difference astrometry applied to the triplet of S 5 radio sources BL 1803 + 784 / QSO 1928 + 738 / BL 2007 + 777

We determined the separations of the radio sources in the triangle formed by the BL Lac objects 1803+784 and 2007+777, and the QSO 1928+738 from in-tercontinental interferometric observations carried out in November 1991 at the frequencies of 2.3 and 8.4 GHz. Difference phase-delay astrometry yielded the following separations: ∆α (1803+784)−(1928+738) =–1 h 27 m 2.

High Precision Astrometry with Vlbi: from the Triangle 1803+784/1928+738/2007+777 to the Complete S5 Polar Cap Sample

On the way to global phase-delay astrometry

The use of the phase-delay improves substantially the accuracy obtained in VLBI astrometry with respect to the group-delay observable. Recently, Ros et al. (1999) have extended the related phase-connection technique to a triangle of radio sources with relative separations up to 6.8◦ (the S5 sources BL 1803+784/QSO 1928+738/BL 2007+777). This technique has also been extended for separations up t...

Letter to the Editor VLBI difference astrometry at 43 GHz

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 differential astrometric techniques at millimeter wavelengths. For a pair of sources with 5◦ separation and high antenna elevations, we have shown that present astrometric models and millimeter arrays are advanced enough to model the differential ...

Submilliarcsecond shift of the brightness peak of the radio sources 1928 + 738 and 2007 + 777

From two sets of very-long-baseline interferometry (VLBI) observations, one each at 5 GHz (1985.77) and at 2.3 and 8.4 GHz simultaneously (1988.83), of the quasar 1928+738 phase-referenced to the BL Lac object 2007+777, we infer a change in their relative position of 0.74±0.22 milliarcseconds (mas) along a position angle of –9◦±25◦, where the quoted standard errors account for errors in our mod...