Extreme Scattering Events: An Observational Summary
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We review observational constraints on the structures responsible for extreme scatteringevents, focussing on a series of observations of the quasar PKS 1741-038. VLA observations wereconducted to search for changes in the rotation measure and HI absorption during the ESE, whileVLBI observations sought ESE-induced changes in the source’s image. No RM changes were foundimplying B∥ < 12 mG, and no HI opacity changes were found implying (HI) < 6.4 x 1017 cm-2.No multiple imaging was observed, but the diameter of the source increased by 0.7 mas, contrary towhat is predicted by simple refractive lens modeling of ESEs. We summarize what these limits implyabout the structure responsible for this ESE.
KeywordsColumn Density Multiple Imaging Faraday Rotation Observational Constraint Angular Diameter
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