University of Leicester
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Do jets precess...or even move at all?

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journal contribution
posted on 2016-05-16, 09:15 authored by Chris J. Nixon, Andrew King
Observations of accreting black holes often provoke suggestions that their jets precess. The precession is usually supposed to result from a combination of the Lense-Thirring effect and accretion disk viscosity. We show that this is unlikely for any type of black hole system, as the disk generally has too little angular momentum compared with a spinning hole to cause any significant movement of the jet direction across the sky on short timescales. Uncorrelated accretion events, as in the chaotic accretion picture of active galactic nuclei (AGNs), change AGN jet directions only on timescales gsim 107 yr. In this picture AGN jet directions are stable on shorter timescales, but uncorrelated with any structure of the host galaxy, as observed. We argue that observations of black hole jets precessing on timescales short compared to the accretion time would be a strong indication that the accretion disk, and not the standard Blandford-Znajek mechanism, is responsible for driving the jet. This would be particularly convincing in a tidal disruption event. We suggest that additional disk physics is needed to explain any jet precession on timescales short compared with the accretion time. Possibilities include the radiation warping instability, or disk tearing.


Support for this work was provided by NASA through the Einstein Fellowship Program, grant PF2-130098. Research in theoretical astrophysics at Leicester is supported by an STFC Rolling Grant.



The Astrophysical Journal Letters, 2013, 765 (1), L7

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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