No apparent superluminal motion in the first-known jetted tidal disruption event Swift J1644+5734
Artikel i vetenskaplig tidskrift, 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.

galaxies: jets

radio continuum: galaxies

galaxies: individual: Swift J1644+5734


Jun Yang

Chalmers, Rymd- och geovetenskap, Onsala rymdobservatorium

Z. Paragi

Joint Institute for VLBI in Europe (JIVE)

A. J. van der Horst

George Washington University

L. I. Gurvits

Joint Institute for VLBI in Europe (JIVE)

TU Delft

R. M. Campbell

Joint Institute for VLBI in Europe (JIVE)

D. Giannios

Purdue University

T. An

Shanghai Astronomical Observatory

Chinese Academy of Sciences

S. Komossa


Monthly Notices of the Royal Astronomical Society

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

Vol. 462 1 L66-L70

Advanced Radio Astronomy in Europe (RADIONET3)

Europeiska kommissionen (EU) (EC/FP7/283393), 2012-01-01 -- 2015-12-31.

Novel EXplorations Pushing Robust e-VLBI Services (NEXPReS)

Europeiska kommissionen (EU) (EC/FP7/261525), 2010-07-01 -- 2013-06-30.


Astronomi, astrofysik och kosmologi


Grundläggande vetenskaper


Onsala rymdobservatorium



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