1507.08236.pdf - ApJL, in press Preprint typeset using...

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ApJL, in pressPreprint typeset using LATEX style emulateapj v. 5/2/11MURCHISON WIDEFIELD ARRAY OBSERVATIONS OF ANOMALOUS VARIABILITY: A SERENDIPITOUSNIGHT-TIME DETECTION OF INTERPLANETARY SCINTILLATIOND. L. Kaplan1, S. J. Tingay2,3, P. K. Manoharan4, J.-P. Macquart2,3, P. Hancock2,3, J. Morgan2,D. A. Mitchell5,3, R. D. Ekers5, R. B. Wayth2,3, C. Trott2,3, T. Murphy6,3, D. Oberoi4, I. H. Cairns6, L. Feng7,N. Kudryavtseva2, G. Bernardi8,9,10, J. D. Bowman11, F. Briggs12, R. J. Cappallo13, A. A. Deshpande14,B. M. Gaensler6,3,15, L. J. Greenhill10, N. Hurley-Walker2, B. J. Hazelton16, M. Johnston-Hollitt17,C. J. Lonsdale13, S. R. McWhirter13, M. F. Morales16, E. Morgan7, S. M. Ord2,3, T. Prabu14,N. Udaya Shankar14, K. S. Srivani14, R. Subrahmanyan14,3, R. L. Webster18,3, A. Williams2, and C. L. Williams7ApJL, in pressABSTRACTWe present observations of high-amplitude rapid (2 s) variability toward two bright, compact ex-tragalactic radio sources out of several hundred of the brightest radio sources in one of the 30×30MWA Epoch of Reionization fields using the Murchison Widefield Array (MWA) at 155 MHz. Afterrejecting intrinsic, instrumental, and ionospheric origins we consider the most likely explanation forthis variability to be interplanetary scintillation (IPS), likely the result of a large coronal mass ejectionpropagating from the Sun. This is confirmed by roughly contemporaneous observations with the OotyRadio Telescope. We see evidence for structure on spatial scales ranging from<1000 km to>106km.The serendipitous night-time nature of these detections illustrates the new regime that the MWA hasopened for IPS studies with sensitive night-time, wide-field, low-frequency observations. This regimecomplements traditional dedicated strategies for observing IPS and can be utilized in real-time to fa-cilitate dedicated follow-up observations. At the same time, it allows large-scale surveys for compact(arcsec) structures in low-frequency radio sources despite the 20resolution of the array.Subject headings:scattering — techniques: interferometric — Sun: coronal mass ejections (CMEs) —Sun: heliosphere — radio continuum: galaxies1.INTRODUCTIONInterplanetary scintillation (IPS) — the rapid (<1 s–10 s) flux density variability of distant compact radio1Department of Physics, University of Wisconsin–Milwaukee,Milwaukee, WI 53201, USA; [email protected]2International Centre for Radio Astronomy Research, CurtinUniversity, Bentley, WA 6102, Australia3ARC Centre of Excellence for All-sky Astrophysics (CAAS-TRO)4Radio Astronomy Centre, National Centre for Radio Astro-physics, Tata Institute of Fundamental Research, Ooty 643001,India5CSIRO Astronomy and Space Science (CASS), PO Box 76,Epping, NSW 1710, Australia6Sydney Institute for Astronomy, School of Physics, The Uni-versity of Sydney, NSW 2006, Australia7Kavli Institute for Astrophysics and Space Research, Mas-sachusetts Institute of Technology, Cambridge, MA 02139, USA8SKA SA, 3rd Floor, The Park, Park Road, Pinelands, 7405,South Africa9Department of Physics and Electronics, Rhodes University,PO Box 94, Grahamstown 6140, South Africa10

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Term
Winter
Professor
Dr.Rotella
Tags
The Road, MWA, Radio astronomy

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