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1. Inflation of 430-parsec bipolar radio bubbles in the Galactic Centre by an energetic event

Author

Jasper Horrell, M. Serylak, T. D. Abbott, P. P. A. Kotzé, J. P. Burger, L. G. Magnus, A. A. Pate, P. S. Swart, A. Loots, S. Tshongweni, A. van der Byl, S. Buchner, Farhad Yusef-Zadeh, Jason Manley, T. W. Kusel, R. Renil, T. J. van Balla, D. H. Botha, A. R. Foley, N. Mnyandu, O. Mahgoub, A. G. Botha, B. M. Lunsky, L. C. Schwardt, Bruce Merry, A. J. Tiplad, C. J. Hoek, R. Siebrits, Dirk I. L. de Villiers, C. L. van Dyk, T. Cheetham, J. A. Malan, C.G. Van der Merwe, D. M. Horn, S. Salie, T. E. Monama, A. R. Isaacson, I. P. T. Moeng, Kshitij Thorat, E. F. Bauermeister, Roy Booth, F. Kapp, B. L. Fanaroff, Simon Perkins, M. C. Mphego, A. Rust, V. Van Tonder, W. S. New, Oleg Smirnov, S. Gounden, H. Kriel, J. D. B. L. Jordaan, M. A. Dikgale-Mahlakoana, R. T. Lord, L. J. du Toit, B. Ngcebetsha, S. W. P. Esterhuyse, P. Macfarlane, Sharmila Goedhart, D. T. Taylor, Justin L. Jonas, R. van Rooyen, C. Magozore, M. J. Hlakola, Dehann Fourie, Robert Lehmensiek, A. F. Joubert, Fernando Camilo, B. H. Wallace, D. Liebenberg, R. van Wyk, R. R. G. Gamatham, Gyula I. G. Józsa, Nadeem Oozeer, J. S. Kenyon, R. D. Malgas, Robert P. Millenaar, Matthys Maree, A. Hokwana, J. M. Chalmers, C. Tasse, L. P. Williams, R. M. Adam, Z. B. Brits, L. R. S. Brederode, W. D. Cotton, J. P. L. Main, M. G. Welz, B. Hugo, A. Peens-Hough, L. Sofeya, Ian Heywood, S. Ratcliffe, I. P. Theron, S. S. Passmoor, M. A. Aldera, A. J. Otto, S. K. Sirothia, R. P. M. Julie, Galaxies, Etoiles, Physique, Instrumentation (GEPI), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Active galactic nucleus, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Cosmic ray, Context (language use), Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, 01 natural sciences, Relativistic particle, 0103 physical sciences, Disc, 010306 general physics, 010303 astronomy & astrophysics, Astrophysics::Galaxy Astrophysics, ComputingMilieux_MISCELLANEOUS, Physics, [PHYS]Physics [physics], Supermassive black hole, Multidisciplinary, Star formation, Galactic plane, Astrophysics - Astrophysics of Galaxies, 13. Climate action, Astronomy and astrophysics, Astrophysics of Galaxies (astro-ph.GA), [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph]
Abstract

The Galactic Centre contains a supermassive black hole with a mass of 4 million suns within an environment that differs markedly from that of the Galactic disk. While the black hole is essentially quiescent in the broader context of active galactic nuclei, X-ray observations have provided evidence for energetic outbursts from its surroundings. Also, while the levels of star formation in the Galactic Centre have been approximately constant over the last few hundred Myr, there is evidence of elevated short-duration bursts, strongly influenced by interaction of the black hole with the enhanced gas density present within the ring-like Central Molecular Zone at Galactic longitude |l| < 0.7 degrees and latitude |b| < 0.2 degrees. The inner 200 pc region is characterized by large amounts of warm molecular gas, a high cosmic ray ionization rate, unusual gas chemistry, enhanced synchrotron emission, and a multitude of radio-emitting magnetised filaments, the origin of which has not been established. Here we report radio imaging that reveals bipolar bubbles spanning 1 degree x 3 degrees (140 parsecs x 430 parsecs), extending above and below the Galactic plane and apparently associated with the Galactic Centre. The structure is edge-brightened and bounded, with symmetry implying creation by an energetic event in the Galactic Centre. We estimate the age of the bubbles to be a few million years, with a total energy of 7 x 10^52 ergs. We postulate that the progenitor event was a major contributor to the increased cosmic-ray density in the Galactic Centre, and is in turn the principal source of the relativistic particles required to power the synchrotron emission of the radio filaments within and in the vicinity of the bubble cavities., 25 pages, 3 figures, 3 tables, authors' version of a Letter published in Nature on 11 September 2019

Published
2019

2. Revival of the Magnetar PSR J1622-4950:Observations with MeerKAT, Parkes, XMM-Newton, Swift, Chandra, and NuSTAR

Author

G C Du Toit, T. D. Abbott, A. J. T. Ramaila, P. S. Swart, P. Ntuli, G. de Bruin, Stephanie Smith, T. E. Monama, C. Stuart, Andrew Jameson, R. Spann, H. Kriel, N. Matthysen, J. Horrell, K. M. B. Asad, D. H. Botha, L. P. Williams, L. D. Mc Nally, R. T. Lord, A. Struthers, W. de Villiers, H. Niehaus, E. F. Bauermeister, John Sarkissian, B. Jordaan, R. Andreas, T. G. H. Bennett, J. P. Conradie, Riana Geschke, I. Wait, B. Ngcebetsha, A. van der Byl, Ben Stappers, A. Robyntjies, J. P. Jansen van Rensburg, N. Mabombo, D. H. Hoorn, A. Nzama, Bruce Merry, L. Sofeya, Sharmila Goedhart, L. R. S. Brederode, M. J. Hlakola, I. Rammala, O. Toruvanda, S. Rakoma, B. L. Fanaroff, A. Rust, A. Martens, M. G. Welz, Y. Padayachee, C. T. G. Schollar, S. J. Marais, B. Xaia, J. P. van Staden, F. Karels, T. Baloyi, B. de Swardt, I. Liebenberg, Vanessa A. Moss, A. L. Walker, C.G. Van der Merwe, W. S. New, E. C. Knox-Davies, R. Millenaar, P. Prozesky, L. J. du Toit, O. J. Mokone, K. Madisa, G. Sethosa, Griffin Foster, T. L. Grobler, Tom Alberts, S. S. Passmoor, F. Joubert, A. A. Patel, D. Koch, Ramesh Karuppusamy, L. Richter, Kshitij Thorat, O. Mahgoub, Jason Manley, C. Sharpe, M. J. Slabber, P. L. van der Merwe, S. Fataar, G. B. Taylor, M. Rasivhaga, P. Sunnylall, MacCalvin Kariseb, Gyula I. G. Józsa, A. R. Foley, N. Marais, M. A. Dikgale, J. P. Burger, C. Olyn, S. Paula, A. J. Otto, S. Ratcliffe, B. Pholoholo, R. Renil, T. Macdonald, Justin L. Jonas, R. van Rooyen, P. Scholz, Oleg Smirnov, B. H. Wallace, Fernando Camilo, A. Peens-Hough, S. Lamoor, F. Obies, L. Marais, T. J. Steyn, M. T. O. Ockards, O. Jacobs, C. Mjikelo, A. J. Tiplady, Roy Booth, D. Liebenberg, R. Strong, T. J. van Balla, P. C. van Niekerk, S. D. Matshawule, V. Van Tonder, C. de Waal, S. K. Sirothia, D. Rosekrans, R. M. Adam, L. Mafhungo, Matthew Bailes, G. Adams, P. P. A. Kotzé, D. M. Horn, S. Salie, M. S. de Villiers, Howard C. Reader, A. R. Isaacson, Dehann Fourie, B. Taljaard, C. de Villiers, A. F. Joubert, M. Serylak, T. Mauch, N. Sambu, Victoria M. Kaspi, C. C. Julius, N. Mnyandu, S. Seranyane, A. Krebs, Simon Johnston, N. Young, L. van den Heever, M. Manzini, R. van Wyk, M. Obrocka, N. Songqumase, T. W. Kusel, M. C. Mphego, J. A. Malan, I. P. T. Moeng, P. Malgas, K. J. Ngoasheng, B. M. Lunsky, L. C. Schwardt, M. Merryfield, W. van Straten, V. Thondikulam, B. Hugo, Nadeem Oozeer, Robert F. Archibald, P. Macfarlane, T. Cheetham, Aris Karastergiou, J. Conradie, D. Steyn, S. C. Gumede, S. Makhathini, S. W. P. Esterhuyse, N. Mkhabela, D. Booisen, R. P. M. Julie, Gianni Bernardi, L. Boyana, N. Kriek, Dirk I. L. de Villiers, T. Baxana, Cyril Tasse, M. Maree, Robert Lehmensiek, R. R. G. Gamatham, S. Zitha, D. E. Baker, K. Montshiwa, C. Magozore, Z. R. Ramudzuli, T. Gatsi, George Hobbs, S. J. Buchner, I. P. Theron, R. Siebrits, John Reynolds, A. Hokwana, F. Kapp, L. G. Magnus, V. A. Kasper, J. P. L. Main, J. van Aardt, David B. Davidson, ZAF, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Galaxies, Etoiles, Physique, Instrumentation (GEPI), Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris Diderot - Paris 7 (UPD7)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Université d'Orléans (UO)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO)-Observatoire de Paris, PSL Research University (PSL)-PSL Research University (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS), and PSL Research University (PSL)-PSL Research University (PSL)-Centre National de la Recherche Scientifique (CNRS)

Subjects
Swift, individual (PSR J16224950) [pulsars], 010504 meteorology & atmospheric sciences, Astrophysics::High Energy Astrophysical Phenomena, FOS: Physical sciences, Magnetosphere, Flux, Astrophysics, Astrophysics::Cosmology and Extragalactic Astrophysics, Ephemeris, Magnetar, 01 natural sciences, general [pulsars], stars: neutron, stars: magnetars, neutron [stars], Pulsar, pulsars: general, 0103 physical sciences, magnetars [stars], 010303 astronomy & astrophysics, 0105 earth and related environmental sciences, computer.programming_language, High Energy Astrophysical Phenomena (astro-ph.HE), Physics, Quiescent state, Astronomy and Astrophysics, Neutron star, pulsars: individual, Space and Planetary Science, Astrophysics - High Energy Astrophysical Phenomena, [PHYS.ASTR]Physics [physics]/Astrophysics [astro-ph], computer
Abstract

New radio (MeerKAT and Parkes) and X-ray (XMM-Newton, Swift, Chandra, and NuSTAR) observations of PSR J1622-4950 indicate that the magnetar, in a quiescent state since at least early 2015, reactivated between 2017 March 19 and April 5. The radio flux density, while variable, is approximately 100x larger than during its dormant state. The X-ray flux one month after reactivation was at least 800x larger than during quiescence, and has been decaying exponentially on a 111+/-19 day timescale. This high-flux state, together with a radio-derived rotational ephemeris, enabled for the first time the detection of X-ray pulsations for this magnetar. At 5%, the 0.3-6 keV pulsed fraction is comparable to the smallest observed for magnetars. The overall pulsar geometry inferred from polarized radio emission appears to be broadly consistent with that determined 6-8 years earlier. However, rotating vector model fits suggest that we are now seeing radio emission from a different location in the magnetosphere than previously. This indicates a novel way in which radio emission from magnetars can differ from that of ordinary pulsars. The torque on the neutron star is varying rapidly and unsteadily, as is common for magnetars following outburst, having changed by a factor of 7 within six months of reactivation., Comment: Published in ApJ (2018 April 5); 13 pages, 4 figures

Published
2018

3. Engineering and science highlights of the KAT-7 radio telescope

Author

W. New, D. Rosekrans, Nadeem Oozeer, F. Curtolo, M. Fijalkowski, S. Seranyane, A. Rust, J. R. Manley, I. P. Theron, N. Marais, A. C. Schröder, P. A. Woudt, R. T. Lord, Sharmila Goedhart, M. S. de Villiers, R. P. M. Julie, B. L. Fanaroff, Rob Fender, G. Coreejes, L. Sofeya, Claude Carignan, D. S. Shepherd, R. Lehmensiek, L. P. Williams, S. J. Marais, O. J. Mokone, Jonathan T. L. Zwart, R. Springbok, P. Gibbs, I. Liebenberg, P. Prozesky, Vanessa A. Moss, J. Horrell, Justin L. Jonas, R. van Rooyen, D. H. Botha, Roy Booth, A. Martens, L. G. Magnus, M. G. Welz, L. Richter, J. A. Malan, Tom Alberts, A. J. Tiplady, S. Mthembu, M. Madlavana, P. P. A. Kotzé, J. Grobbelaar, L. van den Heever, A. Langman, Venkatasubramani L. Thondikulam, S. Rajan, K. Cloete, S. Tshongweni, A. Peens-Hough, P. C. van Niekerk, N. J. Young, P. Herselman, S. J. Buchner, A. L. Walker, P. Macfarlane, F. Kapp, R. P. Armstrong, R. Spann, A. Dikgale, Kelley M. Hess, L. J. du Toit, M. Wolleben, M. Maree, J. Ludick, S. S. Passmoor, R. Siebrits, S. Blose, T. Cheetham, D. George, R. Renil, G. D. Nicholson, L. C. Schwardt, B. S. Frank, P. S. Swart, A. Loots, S. W. P. Esterhuyse, S. Wakhaba, C. J. T. van der Merwe, C. Magozore, T. W. Kusel, S. Ratcliffe, R. C. Crida, S. C. Gumede, M. Serylak, A. R. Foley, H. Bester, J. D. B. L. Jordaan, L. Marais, D. M. Lucero, S. D. Cross, D. Liebenberg, A. Barta, A. B. Pińska, E. F. Bauermeister, Dehann Fourie, O. Toruvanda, N. Hoek, Research School of Earth Sciences, Australian National University ( ANU ), Estrato Research and Development Ltd, Interdisciplinary Centre for Security, Reliability and Trust [Luxembourg] ( SnT ), Université du Luxembourg ( Uni.lu ), Faculty of Science, Technology and Communication [Luxembourg] ( FSTC ), University of Luxembourg [Luxembourg], Département de Physique [Montréal], Université de Montréal, Department of Paediatric Endocrinology, Royal Victoria Infirmary, Institute of Human Genetics, Centre for Life, Newcastle University [Newcastle], Développement et Communication Chimique chez les Insectes ( DCCI ), Centre National de la Recherche Scientifique ( CNRS ) -Université de Bourgogne ( UB ) -AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement, Animal Demography Unit, University of Cape Town, University of Southampton (Southampton, UK), Institute of Physics, University of Silesia, Rapita Systems Ltd [York], Department of Medical Oncology, Royal Melbourne Hospital, Brain and Mind Institute, Ecole Polytechnique Fédérale de Lausanne ( EPFL ), Service d'Explorations fonctionnelles multidisciplinaires [CHU Tenon], CHU Tenon [APHP]-Assistance publique - Hôpitaux de Paris - AP-HP (FRANCE), Service d'urologie [Mondor], Assistance publique - Hôpitaux de Paris (AP-HP)-Hôpital Henri Mondor-Université Paris-Est Créteil Val-de-Marne - Paris 12 ( UPEC UP12 ), OMedical Oncology, Guy's and St Thomas' Hospital [London], Institute of Cardiovascular and Medical Sciences, Electrocardiology Section, University of Glasgow, Glasgow, United Kingdom, Department of Computer and Information Science [Trondheim], Norwegian University of Science and Technology [Trondheim] ( NTNU ), Bordeaux Imaging Center ( BIC ), Université de Bordeaux ( UB ) -Institut François Magendie-Institut National de la Santé et de la Recherche Médicale ( INSERM ) -Centre National de la Recherche Scientifique ( CNRS ), Laboratoire de l'Accélérateur Linéaire ( LAL ), Université Paris-Sud - Paris 11 ( UP11 ) -Institut National de Physique Nucléaire et de Physique des Particules du CNRS ( IN2P3 ) -Centre National de la Recherche Scientifique ( CNRS ), School of Mathematics [Birmingham], University of Birmingham [Birmingham], Institut für Spezielle Botanik und Funktionelle Biodiversität, University of Leipzig, German Aerospace Center ( DLR ), University of the Western Cape, Unité Scientifique de la Station de Nançay ( USN ), Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire de Paris-Université d'Orléans ( UO ) -Centre National de la Recherche Scientifique ( CNRS ), Materials Laboratory Rand Afrikaans University, Rand Afrikaans University, Jodrell Bank Centre for Astrophysics, University of Manchester [Manchester], School of Physics & DST-NRF, University of the Witwatersrand, University of the Witwatersrand [Johannesburg] ( WITS ), University of Southampton, Unité Scientifique de la Station de Nançay (USN), Centre National de la Recherche Scientifique (CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire des Sciences de l'Univers en région Centre (OSUC), Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire de Paris, Université Paris sciences et lettres (PSL)-Université d'Orléans (UO)-Centre National de la Recherche Scientifique (CNRS)-Université d'Orléans (UO), Jodrell Bank Centre for Astrophysics (JBCA), University of the Witwatersrand [Johannesburg] (WITS), and Astronomy

Subjects
Cryogenic system, radio continuum: general, FOS: Physical sciences, 01 natural sciences, law.invention, Radio telescope, Telescope, Pulsar, law, 0103 physical sciences, Very-long-baseline interferometry, Aerospace engineering, Open architecture, instrumentation: interferometers, 010303 astronomy & astrophysics, Instrumentation and Methods for Astrophysics (astro-ph.IM), [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph], Physics, Protocol data unit, 010308 nuclear & particles physics, business.industry, Astronomy, Astronomy and Astrophysics, [SDU.ASTR.IM]Sciences of the Universe [physics]/Astrophysics [astro-ph]/Instrumentation and Methods for Astrophysic [astro-ph.IM], Space and Planetary Science, business, Astrophysics - Instrumentation and Methods for Astrophysics, radio lines: general, [ SDU ] Sciences of the Universe [physics]
Abstract

The construction of the seven-dish Karoo Array Telescope (KAT-7) array in the Karoo region of the Northern Cape in South Africa was intended primarily as an engineering prototype for technologies and techniques applicable to the MeerKAT telescope. This paper looks at the main engineering and scientific highlights from this effort, and discusses their applicability to both MeerKAT and other next-generation radio telescopes. In particular, we found that the composite dish surface works well, but it becomes complicated to fabricate for a dish lacking circular symmetry; the Stirling cycle cryogenic system with ion pump to achieve vacuum works but demands much higher maintenance than an equivalent Gifford-McMahon cycle system; the ROACH (Reconfigurable Open Architecture Computing Hardware)-based correlator with SPEAD (Streaming Protocol for Exchanging Astronomical Data) protocol data transfer works very well and KATCP (Karoo Array Telescope Control Protocol) control protocol has proven very flexible and convenient. KAT-7 has also been used for scientific observations where it has a niche in mapping low surface-brightness continuum sources, some extended H I haloes and OH masers in star-forming regions. It can also be used to monitor continuum source variability, observe pulsars, and make Very Long Baseline Interferometry observations.

Published
2016

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