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Paper: Multi-Frequency VLBI Observations of the GPS Source 1934-638
Volume: 144, Radio Emission from Galactic and Extragalactic Compact Sources, IAU Colloquium 164
Page: 179
Authors: Tzioumis, A. K.; King, E. A.; Reynolds, J. E.; Jauncey, D. L.; Gough, R. G.; Preston, R. A.; Murphy, D. W.; Tingay, S. J.; Meier, D. L.; Jones, D. L.; Lovell, J. E. J.; Edwards, P. G.; McCulloch, P. M.; Costa, M. E.; Kedziora-Chudczer, L.; Campbell-Wilson, D.; Nicolson, G. D.; Quick, J. F. H.
Abstract: PKS 1934-638 is an archetypal GPS source, peaking at 1.4 GHz and exhibits almost no flux density variability. VLBI images at frequencies of .843, 2.3, 4.8, & 8.4 were made with the southern hemisphere VLBI array and they reveal that the source is a 42 mas compact double. There is no detectable change in separation over the last 20 years, yielding an upper limit of ~0.03c +/- 0.2c on any expansion velocity. The spectral shapes of the two components are remarkably similar, despite indications of finer structure on longer baselines. Magnetic field calculations indicate fields of a few mGauss and the results are consistent with equipartition.
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