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A&A 380, 123-129 (2001)
DOI: 10.1051/0004-6361:20011439
An accelerated jet in DA193 ?
W. H. Wang1, 2, X. Y. Hong1, 2, D. R. Jiang1, 2, T. Venturi3, Y. J. Chen1, 2 and T. An1, 21 Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, PR China
2 National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012, PR China
3 Institutor di Radioastronomia del CNR, Via P. Gobetti 101, 40129 Bologna, Italy
(Received 14 August 2001 / Accepted 10 October 2001 )
Abstract
We present four epoch images with milliarcsecond resolution,
from VLBI (Very Long Baseline
Interferometry) observations of the quasar
DA193
(J0555+3948) at 5GHz. The model-fitting results show that the
source is resolved with a core-jet structure. A proper motion of
mas yr-1 of the jet component was
estimated, which corresponds to an apparent velocity of
c at its redshift of z=2.365. Estimates of the
Doppler factor and of the brightness temperature confirm that this
source is considerably boosted towards the line of sight. The
velocity is about 4 times larger than previous estimates, which
may indicate (1) that the jet component is being accelerated, possibly
due to a bending jet aligned close to the line of sight;
or (2) that there are two different components ejected in two flares.
The possibility that multiple ejection of short-lived components is
taking place in the core region of DA193 is also presented.
Throughout this paper, the
values q0=0.5, H0=100 km s-1Mpc-1 will be used.
Key words: galaxies: jets -- galaxies: quasars: general -- galaxies: quasars: individual: DA193
Offprint request: W. H. Wang, whwang@center.shao.ac.cn
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