| 1. |
- Bartel, N., et al.
(author)
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The Compact Radio Source 2021+614 : Simultaneous 2.3 and 8.3 GHz Mark III VLBI Observations
- 1984
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In: Astrophysical Journal. - Philadelphia, PA : Institute of Physics Publishing (IOPP). - 0004-637X .- 1538-4357. ; 279:1, s. 116-121
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Journal article (peer-reviewed)abstract
- Second-epoch VLBI observations of the flat-spectrum radio source 2021+614 made simultaneously at 2.3 and 8.3 GHz with the Mark III system are reported. The maps derived from these observations reveal a complex, frequency-dependent radio structure on the milliarcsecond scale. The object has four nearly collinear components oriented at a position angle of about 35 degrees and embedded in an extended region. Two of these are optically thin, one has a flat spectrum, and the other appears to be synchrotron self-absorbed in the frequency range 2.3-8.3 GHz. No significant structural variation is found at either frequency between epochs separated by about three years. The formal estimate of the transverse velocity between two components, one with a flat and the other with an inverted spectrum, is v/c = 0.7 + or - 2.3. Remarkable similarities between 2021+614 and the unusual source 0316+413 are discussed.
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| 2. |
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| 3. |
- Marcaide, J. M., et al.
(author)
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The quasars 1038+528 A and B
- 1985
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In: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 142:1, s. 71-84
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Journal article (peer-reviewed)abstract
- The results of VLBI observations of the quasars 1038 + 528 A and B at 2.8, 3.6, 13, and 18 cm at various times between November 1979 and March 1981 are reported. The observations and data calibration are described, as are the mapping and astrometric techniques applied in the study. Both quasars are found to have 'core-jet' morphologies. The core of the A quasar dominates its morphology at centrimetric wavelengths with the brightness temperature of its 400 pc long jet being about 1/100 that of the core. By contrast, the 'jet' in the B quasar is very short (about 70 pc); the tail of this jet has the steepest spectral index found to date in extragalactic compact sources, indicating that high electron losses are responsible for the shortness of the jet. No evidence for appreciable morphological change in the B quasar was found over the time span of the study, whereas a new feature may be emerging from the A quasar core at superluminal speed.
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| 4. |
- Romney, J., et al.
(author)
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The milliarcsecond scale structure of low frequency variable sources
- 1984
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In: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 135:2, s. 289-299
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Journal article (peer-reviewed)abstract
- VLBI observations were performed of 21 radio sources which exhibit low frequency variability. The integrated flux densities, variability indices at 0.4 GHz, optical magnitudes, redshifts, spectral indices at 0.4 GHz, and flux intensities with respect to a reference energy flux are provided. The VLBI data were synthesized from observatories located on different continents around the world. All structures were emitted from compact sources with sizes confined to milliarcsc scales. Nearly half displayed core-jet morphologies, while 28 percent had complex structures and 14 percent had either simple structures or were not resolvable. Further observations are proceeding at 400 mHz to confirm the presence of synchrotron electrons and magnetic fields ejected at relativistic speeds along the line of sight, which has the appearance of superluminal velocities.
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| 5. |
- Tang, G., et al.
(author)
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Recent Evolution of Jet Components in 3C345 at 3.6 cm
- 1990
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In: Parsec-Scale radio jets. - Cambridge : Cambridge University Press. - 0521392268 ; , s. 32-37
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Book chapter (peer-reviewed)abstract
- A series of 3.6 cm VLBI maps of 3C345 (1980.79 to 1988.38) is presented. The evolution of the jet components in this quasar is briefly discussed. Recent behavior of component C5 is described and the presence of a new component, tentatively labeled C6, is suggested.
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