EDP Sciences
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Volume 380, Number 1, December II 2001
Page(s) 123 - 129
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20011439

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, 2

1  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 )

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 $0.105\pm0.02$ mas yr-1 of the jet component was estimated, which corresponds to an apparent velocity of $4.5\pm 0.86 h^{-1}$ 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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