No apparent superluminal motion in the first-known jetted tidal disruption event Swift J1644+5734
Journal article, 2016

The first-known tidal disruption event (TDE) with strong evidence for a relativistic jet - based on extensive multiwavelength campaigns - is Swift J1644+5734. In order to directly measure the apparent speed of the radio jet, we performed very long baseline interferometry (VLBI) observations with the European VLBI network (EVN) at 5 GHz. Our observing strategy was to identify a very nearby and compact radio source with the real-time e-EVN, and then utilize this source as a stationary astrometry reference point in the later five deep EVN observations. With respect to the in-beam source FIRST J1644+5736, we have achieved a statistical astrometric precision about 12 mu as (68 per cent confidence level) per epoch. This is one of the best phase-referencing measurements available to date. No proper motion has been detected in the Swift J1644+5734 radio ejecta. We conclude that the apparent average ejection speed between 2012.2 and 2015.2 was less than 0.3c with a confidence level of 99 per cent. This tight limit is direct observational evidence for either a very small viewing angle or a strong jet deceleration due to interactions with a dense circum-nuclear medium, in agreement with some recent theoretical studies.

radio continuum: galaxies

galaxies: individual: Swift J1644+5734

galaxies: jets


Jun Yang

Chalmers, Earth and Space Sciences, Onsala Space Observatory

Z. Paragi

Joint Institute for VLBI in Europe (JIVE)

A. J. van der Horst

George Washington University

L. I. Gurvits

Delft University of Technology

Joint Institute for VLBI in Europe (JIVE)

R. M. Campbell

Joint Institute for VLBI in Europe (JIVE)

D. Giannios

Purdue University

T. An

Chinese Academy of Sciences

Shanghai Astronomical Observatory

S. Komossa

Max Planck Society

Monthly Notices of the Royal Astronomical Society

0035-8711 (ISSN) 1365-2966 (eISSN)

Vol. 462 1 L66-L70

Advanced Radio Astronomy in Europe (RADIONET3)

European Commission (FP7), 2012-01-01 -- 2015-12-31.

Novel EXplorations Pushing Robust e-VLBI Services (NEXPReS)

European Commission (FP7), 2010-07-01 -- 2013-06-30.

Subject Categories

Astronomy, Astrophysics and Cosmology


Basic sciences


Onsala Space Observatory



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