Radio Intra-Day Variability: Answers and Questions |
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| Authors: | David L Jauncey Lucyna Kedziora-Chudczer James EJ Lovell Jean-Pierre Macquart George D Nicolson Rick A Perley John E Reynolds Anastasios K Tzioumis Mark H Wieringa Hayley E Bignall |
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| Institution: | (1) Australia Telescope National Facility, CSIRO, Australia;(2) Australia Telescope National Facility, and Anglo-Australian Observatory, Epping, NSW, Australia;(3) Australia Telescope National Facility, CSIRO, Australia;(4) RCfTA, School of Physics, University of Sydney, NSW, Australia;(5) Hartebeesthoek Radio Astronomy Observatory, Krugersdorp, South Africa;(6) National Radio Astronomy Observatory, Socorro, NM, U.S.A.;(7) Australia Telescope National Facility, CSIRO, Australia;(8) Australia Telescope National Facility, CSIRO, Australia;(9) Australia Telescope National Facility, CSIRO, Australia;(10) Department of Physics and Mathematical Physics, University of Adelaide, SA, Australia |
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| Abstract: | Intra-day variability (IDV) of active galactic nuclei (AGN) has been detected from gamma-ray energies to radio wavelengths.
At high energies, such variability appears to be intrinsic to the sources themselves. However, at radio wavelengths, brightness
temperatures as high as1018 to 1021 K are encountered if the IDV is intrinsic to the source. We discuss here the accumulating evidence showing that, at radio
wavelengths where the highest brightness temperatures are encountered, interstellar scintillation (ISS) is the principal mechanism
causing IDV. While ISS reduces the implied brightness temperatures, they still remain uncomfortably high.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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