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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

Blast waves and reverse shocks: from ultra-relativistic GRBs to moderately relativistic X-ray binaries

Monthly Notices of the Royal Astronomical Society Oxford University Press 539:3 (2025) 2665-2684

Authors:

James H Matthews, Alex J Cooper, Lauren Rhodes, Katherine Savard, Rob Fender, Francesco Carotenuto, Fraser J Cowie, Emma L Elley, Joe Bright, Andrew K Hughes, Sara E Motta

Abstract:

Blast wave models are commonly used to model relativistic outflows from ultra-relativistic gamma-ray bursts (GRBs), but are also applied to lower Lorentz factor ejections from X-ray binaries (XRBs). Here, we revisit the physics of blast waves and reverse shocks in these systems and explore the similarities and differences between the ultra-relativistic () and moderately relativistic () regimes. We first demonstrate that the evolution of the blast wave radius as a function of the observer frame time is recovered in the on-axis ultra-relativistic limit from a general energy and radius blast wave evolution, emphasizing that XRB ejections are off-axis, moderately relativistic cousins of GRB afterglows. We show that, for fixed blast wave or ejecta energy, reverse shocks cross the ejecta much later (earlier) on in the evolution for less (more) relativistic systems, and find that reverse shocks are much longer lived in XRBs and off-axis GRBs compared to on-axis GRBs. Reverse shock crossing should thus typically finish after 10–100 of days (in the observer frame) in XRB ejections. This characteristic, together with their moderate Lorentz factors and resolvable core separations, makes XRB ejections unique laboratories for shock and particle acceleration physics. We discuss the impact of geometry and lateral spreading on our results, explore how to distinguish between different shock components, and comment on the implications for GRB and XRB environments. Additionally, we argue that identification of reverse shock signatures in XRBs could provide an independent constraint on the ejecta Lorentz factor.
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Sub-second optical/near-infrared quasi-periodic oscillations from the black hole X-ray transient Swift J1727.8–1613

Monthly Notices of the Royal Astronomical Society Oxford University Press 539:3 (2025) 2347-2361

Authors:

FM Vincentelli, T Shahbaz, P Casella, VS Dhillon, J Paice, D Altamirano, N Castro Segura, R Fender, P Gandhi, S Littlefair, T Maccarone, J Malzac, K O’Brien, DM Russell, AJ Tetarenko, P Uttley, A Veledina

Abstract:

We report on the detection of optical/near-infrared (O-IR) quasi-periodic oscillations (QPOs) from the black hole (BH) X-ray transient Swift J1727.8–1613. We obtained three X-ray and O-IR high-time-resolution observations of the source during its intermediate state (2023 September 9, 15, and 17) using NICER, HAWK-I@VLT, HIPERCAM@GTC, and ULTRACAM@NTT. We clearly detected a QPO in the X-ray and O-IR bands during all three epochs. The QPO evolved, drifting from 1.4 Hz in the first epoch, up to 2.2 Hz in the second, and finally reaching 4.2 Hz in the third epoch. These are among the highest O-IR QPO frequencies detected for a BH X-ray transient. During the first two epochs, the X-ray and O-IR emission are correlated, with an optical lag (compared to the X-rays) varying from +70 to 0 ms. Finally, during the third epoch, we measured, for the first time, a lag of the band with respect to the band at the QPO frequency ( +10 ms). By estimating the variable O-IR SED we find that the emission is most likely non-thermal. Current state-of-the-art models can explain some of these properties, but neither the jet nor the hot flow model can easily explain the observed evolution of the QPOs. While this allowed us to put tight constraints on these components, more frequent coverage of the state transition with fast multiwavelength observations is still needed to fully understand the evolution of the disc/jet properties in BH low-mass X-ray binaries.
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A persistent disk wind and variable jet outflow in the neutron-star low-mass X-ray binary GX 13+1

(2025)

Authors:

Daniele Rogantini, Jeroen Homan, Richard M Plotkin, Maureen van den Berg, James Miller-Jones, Joey Neilsen, Deepto Chakrabarty, Rob P Fender, Norbert Schulz
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A MeerKAT survey of nearby dwarf novae: I. New detections

Monthly Notices of the Royal Astronomical Society Oxford University Press 539:3 (2025) 1894-1907

Authors:

J Kersten, E Körding, PA Woudt, PJ Groot, DRA Williams, I Heywood, DL Coppejans, C Knigge, JCA Miller-Jones, GR Sivakoff, R Fender

Abstract:

A programme to search for radio emission from dwarf-novae-type cataclysmic variables was conducted with the South African MeerKAT radio telescope. The dwarf novae RU Pegasi, V426 Ophiuchi, and IP Pegasi were detected during outburst at L band (1284 MHz central frequency). Previously, only one cataclysmic variable was radio-detected at a frequency this low. We now bring the number to four. With these three newly found radio-emitters, the population of dwarf novae confirmed to be radio-emitting at any frequency reaches 10 systems. We found that the radio luminosity is correlated with the optical luminosity. For V426 Ophiuchi and RU Pegasi we found a radio decline contemporary with the outburst’s optical decline. The peak radio luminosity of dwarf novae in outburst is very similar to that of novalike Cataclysmic Variables and no correlation with orbital period is seen.
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MeerKAT discovers a jet-driven bow shock near GRS 1915+105

Astronomy & Astrophysics EDP Sciences 696 (2025) a222

Authors:

SE Motta, P Atri, James H Matthews, Jakob van den Eijnden, Rob P Fender, James CA Miller-Jones, Ian Heywood, Patrick Woudt
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