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Extreme Scattering Events: An Observational Summary

Published online by Cambridge University Press:  12 April 2016

T. Joseph ,
W. Lazio ,
Alan L. Fey  and
R.A. Gaume
T. Joseph
Affiliation:
Naval Research Laboratory. E-mail: lazio@rsd.nrl.navy.mil
W. Lazio
Affiliation:
Naval Research Laboratory. E-mail: lazio@rsd.nrl.navy.mil
Alan L. Fey
Affiliation:
Naval Research Laboratory. E-mail: lazio@rsd.nrl.navy.mil
R.A. Gaume
Affiliation:
Naval Research Laboratory. E-mail: lazio@rsd.nrl.navy.mil

Abstract

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We review observational constraints on the structures responsible for extreme scattering events, focussing on a series of observations of the quasar PKS 1741–038. VLA observations were conducted to search for changes in the rotation measure and HI absorption during the ESE, while VLBI observations sought ESE-induccd changes in the source’s image. No RM changes were found implying B‖ < 12 mG, and no HI opacity changes were found implying N(HI) < 6.4 × 1017 cm−2. No multiple imaging was observed, but the diameter of the source increased by 0.7 mas, contrary to what is predicted by simple refractive lens modeling of ESEs. We summarize what these limits imply about the structure responsible for this ESE.

Type
Chapter Four Extreme Scattering Events, Distribution of Material and IPS
Information
International Astronomical Union Colloquium , Volume 182: Sources and Scintillations: Refraction and Scattering in Radio Astronomy , 2001 , pp. 155 - 158
Copyright
Copyright © Kluwer 2001

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