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Relativistic Jet from Black Hole

An artist's impression of a relativistic jet propagating away from a black hole at close to the speed of light. Such jets are formed by the inner regions of the accretion flow: matter flowing inwards towards the black hole, via processes which are not yet fully understood. The accretion flow emits primarily in X-rays, the relativistic jet in the radio band: by combing observations in each band we can try and understand how such jets form and how much energy they carry away from the black hole.

Professor Rob Fender

Professor of Astrophysics

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Hintze Centre for Astrophysical Surveys
  • MeerKAT
  • Pulsars, transients and relativistic astrophysics
  • Rubin-LSST
  • The Square Kilometre Array (SKA)
  • Gamma-ray astronomy
Rob.Fender@physics.ox.ac.uk
Telephone: 01865 (2)73435
Denys Wilkinson Building, room 712
  • About
  • Publications

The connection between the fastest astrophysical jets and the spin axis of their black hole

Nature Astronomy Springer Science and Business Media LLC (2025)

Authors:

RP Fender, SE Motta

Abstract:

Abstract Astrophysical jets signpost the most extreme phenomena in the Universe. Despite a century of study, connections between the physics of black holes and the processes underpinning the formation and launch of these jets remain elusive. Here we present a statistically significant sample of transient jet speeds from stellar-mass black holes and neutron stars. The fastest jets are exclusively from black holes and propagate along a fixed axis across several ejection phases. This provides strong evidence that the most relativistic jets propagate along the spin axis of the black hole that launches them. However, we find no correlation between reported spin estimates and the jet speeds, indicating that some issues remain in connecting the theories of jet formation with spin measurements. By contrast, slower jets can be launched by both black holes and neutron stars and can change in direction or precess, indicating that they are launched from the accretion flow.
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Relativistic precessing jets powered by an accreting neutron star

Monthly Notices of the Royal Astronomical Society: Letters Oxford University Press (OUP) 544:1 (2025) L37-L44

Authors:

FJ Cowie, RP Fender, I Heywood, AK Hughes, K Savard, PA Woudt, F Carotenuto, AJ Cooper, J van den Eijnden, KVS Gasealahwe, SE Motta, P Saikia

Abstract:

ABSTRACT Precessing relativistic jets launched by compact objects are rarely directly measured, and present an invaluable opportunity to better understand many features of astrophysical jets. In this Letter we present MeerKAT radio observations of the neutron star X-ray binary system (NSXB) Circinus X-1 (Cir X-1). We observe a curved S-shaped morphology on $\sim 20\, \rm arcsec\, (\sim 1\:\text{pc})$ scales in the radio emission around Cir X-1. We identify flux density and position changes in the S-shaped emission on year time-scales, robustly showing its association with relativistic jets. The jets of Cir X-1 are still propagating with mildly relativistic velocities $\sim 1\:\text{pc}$ from the core, the first time such large scale jets have been seen from a NSXB. The position angle of the jet axis is observed to vary on year time-scales, over an extreme range of at least $110^\circ$. The morphology and position angle changes of the jet are best explained by a smoothly changing launch direction, verifying suggestions from previous literature, and indicating that precession of the jets is occurring. Steady precession of the jet is one interpretation of the data, and if occurring, we constrain the precession period and half-opening angle to $>10$ yr and $>33^\circ$, respectively, indicating precession in a different parameter space to similar known objects such as SS 433.
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The peculiar hard state behaviour of the black hole X-ray binary Swift J1727.8−1613

Monthly Notices of the Royal Astronomical Society Oxford University Press 542:3 (2025) 1803-1816

Authors:

AK Hughes, F Carotenuto, TD Russell, AJ Tetarenko, JCA Miller-Jones, RM Plotkin, A Bahramian, JS Bright, FJ Cowie, J Crook-Mansour, R Fender, JK Khaulsay, A Kirby, S Jones, M McCollough, R Rao, GR Sivakoff, SD Vrtilek, DRA Williams-Baldwin, CM Wood, D Altamirano, P Casella, N Castro Segura, S Corbel, S Motta

Abstract:

Tracking the correlation between radio and X-ray luminosities during black hole X-ray binary outbursts is a key diagnostic of the coupling between accretion inflows (traced by X-rays) and relativistic jet outflows (traced by radio). We present the radio–X-ray correlation of the black hole low-mass X-ray binary Swift J1727.8–1613 during its 2023–2024 outburst. Our observations span a broad dynamic range, covering 4 orders of magnitude in radio luminosity and 6.5 in X-ray luminosity. This source follows an unusually radio-quiet track, exhibiting significantly lower radio luminosities at a given X-ray luminosity than both the standard (radio-loud) track and most previously known radio-quiet systems. Across most of the considered distance range (–4.3 kpc), Swift J1727.8–1613 appears to be the most radio-quiet black hole binary identified to date. For distances kpc, while Swift J1727 becomes comparable to one other extremely radio-quiet system, its peak X-ray luminosity ( erg s) exceeds that of any previously reported hard-state black hole low-mass X-ray binary, emphasizing the extremity of this outburst. Additionally, for the first time in a radio-quiet system, we identify the onset of X-ray spectral softening to coincide with a change in trajectory through the radio–X-ray plane. We assess several proposed explanations for radio-quiet behaviour in black hole systems in light of this data set. As with other such sources, however, no single mechanism fully accounts for the observed properties, highlighting the importance of regular monitoring and the value of comprehensive (quasi-)simultaneous data-sets.
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New Metrics for Identifying Variables and Transients in Large Astronomical Surveys

(2025)

Authors:

Shih Ching Fu, Arash Bahramian, Aloke Phatak, James CA Miller-Jones, Suman Rakshit, Alexander Andersson, Robert Fender, Patrick A Woudt

A relativistic jet from a neutron star breaking out of its natal supernova remnant

(2025)

Authors:

KVS Gasealahwe, K Savard, IM Monageng, I Heywood, RP Fender, PA Woudt, J English, JH Matthews, H Whitehead, FJ Cowie, AK Hughes, P Saikia, SE Motta
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