| 1. |
- Bååth, L.B. 1948-, et al.
(författare)
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The Radio Fine Structure of the BL Lacertae Objects AO0235+164, 0735+178, BL Lac, 1749+701, Mk 421 and 3C 66 A at 5 GHz
- 1981
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 96:1-2, s. 316-324
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Tidskriftsartikel (refereegranskat)abstract
- Very long baseline interferometer observations at 4997 MHz (lambda = 6 cm) on European and intercontinental baselines with lengths up to 1.35 108lambda have been used to probe the milliarc s structure of the BL Lacertae objects AO 0235+164, 0735+178, BL Lac, 1749+701, Mk 421, and 3C 66A. Two sets of observations are reported, made in November 1978 and March 1979. AO 0235+164 and 0735+178 both showed structures consisting of a very bright, unresolved core and a jet-like component extending ˜5".4 10-3 along position angle ˜20° and ˜4".2 10-3 along position angle ˜45°, respectively. AO 0235+164 contained more than 98% of the total flux density within a diameter of ≲ 36" 10-3. BL Lac, 1749+701 and Mk 421 all showed evidence for a complex structure of several components, including an unresolved core. 3 C 66A was elongated along position angle ˜ -45°.
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| 2. |
- Bååth, L.B. 1948-, et al.
(författare)
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Time-Dependent Radio Fine Structure of the Compact Sources NRAO 150 and 4C 39.25
- 1980
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 86:3, s. 364-372
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Tidskriftsartikel (refereegranskat)abstract
- Very long baseline interferometer observations at 7.85 GHz have been used to probe the milliarcsecond structure of the unidentified, very compact radio source NRAO 150 and QSO 4 C 39.25. NRAO 150 exhibited no structural variations from 1972 to the end of 1974. A model with two circular Gaussian components fits the data well. NRAO 150 had a flux density of 7.6 plus or minus 0.5 Jy in the compact component; 4 C 39.25 showed a two-component structure, the components having a separation of (2.02 plus or minus 0.05 arc sec) x 10 to the -3rd power. The upper bound on the speed of transverse separation is 0.0001 arc sec per year or less than 2.7 c. From the spectrum there are also indications of a third, larger component.
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| 3. |
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| 4. |
- Romney, J., et al.
(författare)
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The milliarcsecond scale structure of low frequency variable sources
- 1984
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 135:2, s. 289-299
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Tidskriftsartikel (refereegranskat)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. |
- van Genderen, A. M., et al.
(författare)
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A discussion on new VBLUW observations of the X-ray binary Sk. 160=SMC X-1
- 1981
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 101:1, s. 101-104104
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Tidskriftsartikel (refereegranskat)abstract
- VBLUW photometry (Walraven system) of Sk. 160=SMC X-1 made in 1973, 1975, and 1977 are discussed. They are compared with those of van Paradijs (1977) made in 1976. Using all available photometric and X-ray mid-eclipse data, a period is determined by a weighted least-squares solution: P=3.89235 dplusmn0.00002 d m.e
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| 6. |
- van Groningen, E.
(författare)
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Accretion disks in Seyfert nuclei : broad line profiles and asymmetries
- 1983
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 126:2, s. 363-371371
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Tidskriftsartikel (refereegranskat)abstract
- Keplerian rotation around a massive object in the centre of a Seyfert galaxy is considered as the main broadening mechanism for the broad emission lines. The resultant line profiles are shown to be of power-law form in the wings and are compared with recently published high quality observations. Several possible solutions are given for the [O III]-problem raised by Shields (1978). Asymmetries in the line profiles are explained by anisotropically radiating filaments in two oppositely directed jets emanating from the centre of the disk and by radial motions in or above the disk
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| 7. |
- Van Groningen, E., et al.
(författare)
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One-sided jets in extragalactic radiosources
- 1980
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 90:1-2, s. L7-L9L9
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Tidskriftsartikel (refereegranskat)abstract
- Some explanations for the existence of one-sided jets in symmetrical extended radio sources are discussed. It is shown that in the case of the quasar 4C32.69, a relativistic Doppler interpretation is improbable. Observational constraints on a model involving anisotropic radiation are also examined. This model cannot be ruled out, although non-relativistic interpretations of one-sided jets are most likely
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