An accelerated jet in DA193?

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

Corresponding author: W. H. Wang, whwang@center.shao.ac.cn

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 . 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 , km s^-1Mpc^-1 will be used.