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Black Hole

Lensing of space time around a black hole. At Oxford we study black holes observationally and theoretically on all size and time scales - it is some of our core work.

Credit: ALAIN RIAZUELO, IAP/UPMC/CNRS. CLICK HERE TO VIEW MORE IMAGES.

Dr James Allison

CDF (Christ Church)

Research theme

  • Astronomy and astrophysics

Sub department

  • Astrophysics

Research groups

  • Galaxy formation and evolution
  • Hintze Centre for Astrophysical Surveys
  • MeerKAT
james.allison@physics.ox.ac.uk
Christ Church webpage
  • About
  • Teaching
  • Research
  • Publications

WALLABY Pilot Survey: Public release of HI data for almost 600 galaxies from phase 1 of ASKAP pilot observations

ArXiv 2211.07094 (2022)

Authors:

T Westmeier, N Deg, K Spekkens, TN Reynolds, AX Shen, S Gaudet, S Goliath, MT Huynh, P Venkataraman, X Lin, T O'Beirne, B Catinella, L Cortese, H Dénes, A Elagali, B-Q For, GIG Józsa, C Howlett, JM van der Hulst, RJ Jurek, P Kamphuis, VA Kilborn, D Kleiner, BS Koribalski, K Lee-Waddell, C Murugeshan, J Rhee, P Serra, L Shao, L Staveley-Smith, J Wang, OI Wong, MA Zwaan, JR Allison, CS Anderson, Lewis Ball, DC-J Bock, D Brodrick, JD Bunton, FR Cooray, N Gupta, DB Hayman, EK Mahony, VA Moss, A Ng, SE Pearce, W Raja, DN Roxby, MA Voronkov, KA Warhurst, HM Courtois, K Said
Details from ArXiV

Radio observations of the Black Hole X-ray Binary EXO 1846-031 re-awakening from a 34-year slumber

Monthly Notices of the Royal Astronomical Society Oxford University Press 517:2 (2022) 2801-2817

Authors:

Dra Williams, Se Motta, R Fender, Jca Miller-Jones, J Neilsen, Jr Allison, J Bright, I Heywood, Pfl Jacob, L Rhodes, E Tremou, Pa Woudt, J van den Eijnden, F Carotenuto, Da Green, D Titterington, Aj van der Horst, P Saikia

Abstract:

We present radio [1.3 GHz MeerKAT, 4–8 GHz Karl G. Jansky Very Large Array (VLA), and 15.5 GHz Arcminute Microkelvin Imager Large Array (AMI-LA)] and X-ray (Swift and MAXI) data from the 2019 outburst of the candidate Black Hole X-ray Binary (BHXB) EXO 1846−031. We compute a Hardness–Intensity diagram, which shows the characteristic q-shaped hysteresis of BHXBs in outburst. EXO 1846−031 was monitored weekly with MeerKAT and approximately daily with AMI-LA. The VLA observations provide sub-arcsecond-resolution images at key points in the outburst, showing moving radio components. The radio and X-ray light curves broadly follow each other, showing a peak on ∼MJD 58702, followed by a short decline before a second peak between ∼MJD 58731–58739. We estimate the minimum energy of these radio flares from equipartition, calculating values of Emin ∼ 4 × 1041 and 5 × 1042 erg, respectively. The exact date of the return to ‘quiescence’ is missed in the X-ray and radio observations, but we suggest that it likely occurred between MJD 58887 and 58905. From the Swift X-ray flux on MJD 58905 and assuming the soft-to-hard transition happened at 0.3–3 per cent Eddington, we calculate a distance range of 2.4–7.5 kpc. We computed the radio:X-ray plane for EXO 1846−031 in the ‘hard’ state, showing that it is most likely a ‘radio-quiet’ BH, preferentially at 4.5 kpc. Using this distance and a jet inclination angle of θ = 73◦, the VLA data place limits on the intrinsic jet speed of βint = 0.29c, indicating subluminal jet motion.
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FLASH pilot survey: detections of associated 21 cm H i absorption in GAMA galaxies at 0.42 < z < 1.00

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 516:2 (2022) 2947-2970

Authors:

Renzhi Su, Elaine M Sadler, James R Allison, Elizabeth K Mahony, Vanessa A Moss, Matthew T Whiting, Hyein Yoon, JNHS Aditya, Sabine Bellstedt, Aaron SG Robotham, Lilian Garratt-Smithson, Minfeng Gu, Bärbel S Koribalski, Roberto Soria, Simon Weng
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Observations of cold extragalactic gas clouds at z = 0.45 towards PKS 1610-771

Monthly Notices of the Royal Astronomical Society Oxford University Press (OUP) 512:3 (2022) 3638-3650

Authors:

Simon Weng, Elaine M Sadler, Caroline Foster, Céline Péroux, Elizabeth K Mahony, James R Allison, Vanessa A Moss, Renzhi Su, Matthew T Whiting, Hyein Yoon
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WALLABY pilot survey: Public release of H i data for almost 600 galaxies from phase 1 of ASKAP pilot observations

Publications of the Astronomical Society of Australia Cambridge University Press (CUP) 39 (2022) e058

Authors:

T Westmeier, N Deg, K Spekkens, TN Reynolds, AX Shen, S Gaudet, S Goliath, MT Huynh, P Venkataraman, X Lin, T O’Beirne, B Catinella, L Cortese, H Dénes, A Elagali, B-Q For, GIG Józsa, C Howlett, JM van der Hulst, RJ Jurek, P Kamphuis, VA Kilborn, D Kleiner, BS Koribalski, K Lee-Waddell, C Murugeshan, J Rhee, P Serra, L Shao, L Staveley-Smith, J Wang, OI Wong, MA Zwaan, JR Allison, CS Anderson, Lewis Ball, DC-J Bock, D Brodrick, JD Bunton, FR Cooray, N Gupta, DB Hayman, EK Mahony, VA Moss, A Ng, SE Pearce, W Raja, DN Roxby, MA Voronkov, KA Warhurst, HM Courtois, K Said
More details from the publisher
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