| 11. |
|
|
| 12. |
|
|
| 13. |
- Bååth, L.B. 1948-, et al.
(författare)
-
0735+178 : The cosmic conspiracy
- 1991
-
Ingår i: Astronomy and Astrophysics. - Les Ulis : EDP Sciences. - 0004-6361 .- 1432-0746. ; 250:1, s. 50-56
-
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.
|
|
| 14. |
- Bååth, L.B. 1948-
(författare)
-
A closer look at active galactic nuclei — the great engines of the universe
- 1992
-
Ingår i: Physica scripta. T. - Stockholm, Sweden : Kungliga Vetenskapsakademien. - 0281-1847. ; T43, s. 57-66
-
Tidskriftsartikel (refereegranskat)abstract
- The intensive radio emission from powerful radio galaxies and quasars Make these attractive candidates to become "standard candles" to probe the Universe. This paper discusses this possibility and the physics of the radio sources.
|
|
| 15. |
- Bååth, L.B. 1948-
(författare)
-
AGN Variability and VLBI
- 1994
-
Ingår i: Multi-Wavelength Continuum Emission of Agn. - Dordrecht : Kluwer Academic Publishers. - 0792327446 - 0792327454 ; , s. 181-186
-
Bokkapitel (refereegranskat)abstract
- This contribution discusses the connection between variability in radio and optical with structural variations observed with VLBI. Structural changes do not have to start in the core, and intensity variations may be caused by components in the jet outside the core. The scenario is probably more complicated than present day theories assume.
|
|
| 16. |
- Bååth, L.B. 1948-, et al.
(författare)
-
EVN as a phase stable interferometer
- 1991
-
Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific Conference. - 0937707384 - 9780937707388 ; , s. 298-301
-
Konferensbidrag (refereegranskat)
|
|
| 17. |
- Bååth, L.B. 1948-
(författare)
-
Global Fringe Fitting Applied to 100 GHZ VLBI Data
- 1991
-
Ingår i: Frontiers of VLBI. - Tokyo : Universal Academy Press. - 494644307X ; , s. 353-359
-
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.
|
|
| 18. |
- Bååth, L.B. 1948-
(författare)
-
Global fringe fitting applied to Mk3 VLBI data
- 1991
-
Ingår i: Radio Interferometry. - San Francisco, USA : Astronomical Society of the Pacific. - 0937707384 - 9781583813553 ; , s. 321-325
-
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.
|
|
| 19. |
- Bååth, L.B. 1948-
(författare)
-
High resolution images of Blazar cores
- 1992
-
Ingår i: Variability of Blazars. - Cambridge, UK : Cambridge University Press. - 0521413516 ; , s. 196-204
-
Konferensbidrag (refereegranskat)
|
|
| 20. |
- Bååth, L.B. 1948-, et al.
(författare)
-
IMAGES OF THE BL LACERTAE OBJECT 1749+701 AT 5 GHZ
- 1992
-
Ingår i: Astronomy and Astrophysics. - Les Ulis, France : EDP Sciences. - 0004-6361 .- 1432-0746. ; 262:1, s. 1-7
-
Tidskriftsartikel (refereegranskat)abstract
- This paper presents images of 1749+701 from data obtained between 1980 and 1983 as a part of our VLBI programme to monitor a subsample of BL Lac objects at 5GHz. Our images show that this source has a complex structure with a jet pointing towards the north-west at a position angle of about -65-degrees. The brightest component is growing in extension along this position angle. We suggest this to be the core and that the growing extension was caused by a shock generated during an outburst and moving out along the jet. From the extension rate, we obtain an angular separation speed of 0.18 mas yr-1, which corresponds to an apparent transverse speed of 5c. The distances and position angles of two outer components seem remarkably constant. The phenomenon can be understood through a model in which a relativistic jet bends such that its axis is very close to the line of sight in two points. We also deduce that the Lorentz factor must be 4.5 less-than-or-equal-to gamma less-than-or-equal-to 6.5 and that the viewing angle must be 5-degrees less-than-or-equal-to theta less-than-or-equal-to 10-degrees. In this paper, we also present two images obtained from 5GHz MERLIN and combined MERLIN-VLBI data respectively. These maps show that there is a weak component located at a distance of 0.42 arcsec from the core at p.a -155-degrees.
|
|
