| 1. |
- Bååth, L.B. 1948-, et al.
(författare)
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0735+178 : The cosmic conspiracy
- 1991
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 250:1, s. 50-56
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Tidskriftsartikel (refereegranskat)abstract
- This paper discusses a radio outburst in the BL Lac-object 0735+178 which started in early 1988, ended during 1990 and was succeeded by a new outburst which is still in progress. Our image obtained with a global VLBI network shows the source to mainly consist of a core-jet like structure ending in diffuse emission region of low surface brightness located to the east of the core. We identify two new components as having been produced during the late 1980's. They are moving out with apparent superluminal motion in a viewing angle of greater-than-or-similar-to 10-degrees at a distance of less-than-or-similar-to 2 mas from the core. The core includes another new component, but our resolution is just sufficient to resolve out this component from the core at our epoch of observation. We suggest that the weak emission region is caused by an older component reaching the point at which the Doppler boosting is at its maximum and that the long time scale flux variation are due to successive events when evolved components reach that point.
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| 2. |
- Bååth, L.B. 1948-, et al.
(författare)
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EVN as a phase stable interferometer
- 1991
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Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific Conference. - 0937707384 - 9780937707388 ; , s. 298-301
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Konferensbidrag (refereegranskat)
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| 3. |
- Bååth, L.B. 1948-
(författare)
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Global Fringe Fitting Applied to 100 GHZ VLBI Data
- 1991
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Ingår i: Frontiers of VLBI. - Tokyo : Universal Academy Press. - 494644307X ; , s. 353-359
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Bokkapitel (refereegranskat)abstract
- Earlier epoches of mm VLBI observations relied on single baseline fit of delays and rates to find the fringes. This approach does not, however, make use of all available information and therefore is less sensitive than is necessary. Global fringe fitting makes use of all simultaneous data to find station related clock offsets and rates over a certain period of time. © Universal Academy Press, Inc.
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| 4. |
- Bååth, L.B. 1948-
(författare)
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Global fringe fitting applied to Mk3 VLBI data
- 1991
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Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific. - 0937707384 - 9781583813553 ; , s. 321-325
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Konferensbidrag (refereegranskat)abstract
- A system has been developed where data from a Mk3 VLBI processor can be read into the AIPS-package. Multiband and single-band delays can then be fitted globally by station. The technique has been used to phasereference a background to two radiogalaxies in the Abell cluster A2634.
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| 5. |
- Bååth, L.B. 1948-
(författare)
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mm VLBI vs. VSOP
- 1991
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Ingår i: Frontiers of VLBI. - Tokyo : Universal Academy Press. - 494644307X ; , s. 197-201
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Bokkapitel (refereegranskat)abstract
- VSOP-to-ground VLBI and mm VLBI are both needed if we want to further increase our knowledge of quasars, radio galaxies and their radio jets, mm VLBI will be a better instrument to study the "central engine" while satellite VLBI will better show the structure of the jets. The two instruments complement each other, and it is important to have a close collaboration. © Universal Academy Press, Inc.
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| 6. |
- Bååth, L.B. 1948-, et al.
(författare)
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MmVLBI - High resolution imaging
- 1991
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Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific. - 0937707384 - 9781583813553 ; , s. 326-329
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Konferensbidrag (refereegranskat)abstract
- Hybrid maps at 100 GHz have been produced using VLBI data obtained at 100 GHz. The observations and global fringe fitting technique used to produce the maps are briefly described.
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| 7. |
- Bååth, L.B. 1948-
(författare)
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Results from 100 GHz VLBI
- 1991
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Ingår i: Frontiers of VLBI. - Tokyo : Universal Academy Press. - 494644307X ; , s. 285-295
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Bokkapitel (refereegranskat)abstract
- Development of receiver and data reduction techniques have now made it possible to produce hybrid maps from global VLBI experiments observing at 100 GHz. Maps are shown here of the compact radio sources 3C 273, 3C 345, 3C 84, BL Lac and OJ 287 with angular resolution of 50 μas. The component born during the 1988 outburst of 3C 273 is seen only 2 month after its birth. The jet of 3C 345 is seen to have a larger curvature than has previously been observed.A component is seen moving outwards from the core of 3C84 with a speed of ≈21000 km sec-1. © Universal Academy Press, Inc.
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| 8. |
- Bååth, L.B. 1948-, et al.
(författare)
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The microarcsecond structure of 3C 273 at 3 MM
- 1991
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 241:1, s. L1-L4
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Tidskriftsartikel (refereegranskat)abstract
- Recent improvements in data analysis and receiver techniques have allowed us to produce a map of the 100GHz emission from the compact radio source 3C273 with the unsurpassed resolution of 50-mu-as (microarcseconds). Our map shows that the structure within 300-mu-as (approximately 1.5.10(18).h-1 cm) has a position angle significantly different from the position angle of the jet observed at lower frequencies. There are also indications in our map that the inner structure has a more pronounced wiggling structure than has been observed on larger scales. The observations were made about 60 days from the start of the outburst of 1988. Most of the flux from the outburst is concentrated in a component which is elongated approximately (56 x 5).10(16).h-1 cm perpendicular to the overall jet-axis. The distance between this component and the core is approximately 128-mu-as, which corresponds to the distance expected from an apparent velocity of approximately 800-mu-as year-1.
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| 9. |
- Bååth, L.B. 1948-, et al.
(författare)
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The radio fine structure of the BL Lacertae object 0735 + 178
- 1991
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Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 243:2, s. 328-332
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Tidskriftsartikel (refereegranskat)abstract
- The BL Lacertae object 0735 + 178 has been mapped with global VLBI arrays at four epochs from 1979 to 1983. The hybrid maps presented in this paper show a complex structure with a component separating from the core with an apparent transverse velocity of almost-equal-to 7.9 c. We suggest a model in which new components are born in the core during an outburst, initially move away towards northeast and then at a distance of almost-equal-to 4.2 mas turn towards the southeast. At this point, the component does not show any discernible motion away from the core. We suggest that the jet curls towards the south and towards the observer and at this point has its minimum viewing angle, with maximum boosting and minimum apparent velocity. We associate the outburst of 1989 with the event when a superluminally moving component reaches this point.
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| 10. |
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