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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

Radio observations of the 2022 outburst of the transitional Z-Atoll source XTE J1701−462

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 533:2 (2024) 1800-1807

Authors:

KVS Gasealahwe, IM Monageng, RP Fender, PA Woudt, AK Hughes, SE Motta, J van den Eijnden, P Saikia, E Tremou
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Swift J1727.8–1613 Has the Largest Resolved Continuous Jet Ever Seen in an X-Ray Binary

The Astrophysical Journal Letters American Astronomical Society 971:1 (2024) L9

Authors:

Callan M Wood, James CA Miller-Jones, Arash Bahramian, Steven J Tingay, Steve Prabu, Thomas D Russell, Pikky Atri, Francesco Carotenuto, Diego Altamirano, Sara E Motta, Lucas Hyland, Cormac Reynolds, Stuart Weston, Rob Fender, Elmar Körding, Dipankar Maitra, Sera Markoff, Simone Migliari, David M Russell, Craig L Sarazin, Gregory R Sivakoff, Roberto Soria, Alexandra J Tetarenko, Valeriu Tudose

Abstract:

Multiwavelength polarimetry and radio observations of Swift J1727.8–1613 at the beginning of its recent 2023 outburst suggested the presence of a bright compact jet aligned in the north–south direction, which could not be confirmed without high-angular-resolution images. Using the Very Long Baseline Array and the Long Baseline Array, we imaged Swift J1727.8–1613 during the hard/hard-intermediate state, revealing a bright core and a large, two-sided, asymmetrical, resolved jet. The jet extends in the north–south direction, at a position angle of −0.60° ± 0.07° east of north. At 8.4 GHz, the entire resolved jet structure is ∼110(d/2.7kpc)/sini au long, with the southern approaching jet extending ∼80(d/2.7kpc)/sini au from the core, where d is the distance to the source and i is the inclination of the jet axis to the line of sight. These images reveal the most resolved continuous X-ray binary jet, and possibly the most physically extended continuous X-ray binary jet ever observed. Based on the brightness ratio of the approaching and receding jets, we put a lower limit on the intrinsic jet speed of β ≥ 0.27 and an upper limit on the jet inclination of i ≤ 74°. In our first observation we also detected a rapidly fading discrete jet knot 66.89 ± 0.04 mas south of the core, with a proper motion of 0.66 ± 0.05 mas hr−1, which we interpret as the result of a downstream internal shock or a jet–interstellar medium interaction, as opposed to a transient relativistic jet launched at the beginning of the outburst.
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Radio observations of the 2022 outburst of the transitional Z-Atoll source XTE J1701-462

(2024)

Authors:

KVS Gasealahwe, IM Monageng, RP Fender, PA Woudt, AK Hughes, SE Motta, J van den Eijnden, P Saikia, E Tremou
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A Radio Flare in the Long-lived Afterglow of the Distant Short GRB 210726A: Energy Injection or a Reverse Shock from Shell Collisions?

The Astrophysical Journal American Astronomical Society 970:2 (2024) 139

Authors:

Genevieve Schroeder, Lauren Rhodes, Tanmoy Laskar, Anya Nugent, Alicia Rouco Escorial, Jillian C Rastinejad, Wen-fai Fong, Alexander J van der Horst, Péter Veres, Kate D Alexander, Alex Andersson, Edo Berger, Peter K Blanchard, Sarah Chastain, Lise Christensen, Rob Fender, David A Green, Paul Groot, Ian Heywood, Assaf Horesh, Luca Izzo, Charles D Kilpatrick, Elmar Körding, Amy Lien

Abstract:

We present the discovery of the radio afterglow of the short gamma-ray burst (GRB) 210726A, localized to a galaxy at a photometric redshift of z ∼ 2.4. While radio observations commenced ≲1 day after the burst, no radio emission was detected until ∼11 days. The radio afterglow subsequently brightened by a factor of ∼3 in the span of a week, followed by a rapid decay (a “radio flare”). We find that a forward shock afterglow model cannot self-consistently describe the multiwavelength X-ray and radio data, and underpredicts the flux of the radio flare by a factor of ≈5. We find that the addition of substantial energy injection, which increases the isotropic kinetic energy of the burst by a factor of ≈4, or a reverse shock from a shell collision are viable solutions to match the broadband behavior. At z ∼ 2.4, GRB 210726A is among the highest-redshift short GRBs discovered to date, as well as the most luminous in radio and X-rays. Combining and comparing all previous radio afterglow observations of short GRBs, we find that the majority of published radio searches conclude by ≲10 days after the burst, potentially missing these late-rising, luminous radio afterglows.
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Constraints on Short Gamma-Ray Burst Physics and Their Host Galaxies from Systematic Radio Follow-up Campaigns

(2024)

Authors:

SI Chastain, AJ van der Horst, GE Anderson, L Rhodes, D d'Antonio, ME Bell, RP Fender, PJ Hancock, A Horesh, C Kouveliotou, KP Mooley, A Rowlinson, SD Vergani, RAMJ Wijers, PA Woudt
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