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Paper: The microarcsecond properties of J1819+385
Volume: 290, Active Galactic Nuclei: from Central Engine to Host Galaxy
Page: 349
Authors: Macquart, J.-P.; de Bruyn, A. G.; Dennett-Thorpe, J.
Abstract: With intensity modulations > 30% on a timescale less than 0.5 hr, the quasar J1819+385 is the most extreme variable intra-day variable radio source known. This source continues to show very high modulations, indicating a lack of expansion (v/c < 0.1). This is puzzling in light of the brightness temperature, well in excess of 1012 K. Annual modulations in the variability timescale, combined with a direct measurement of the scintillation speed, indicate that the scintillation pattern of this source is highly elongated. This is either due to an elongated source and/or anisotropic scattering. Furthermore, comparison of the 3 and 6 cm lightcurves indicates the source is comprised of at least two distinct components. Short-timescale structure is observed in the 21 cm lightcurves which, if real, indicates diffractive scintillation from an extremely compact region of the source. The source also exhibits polarization variations, showing that a portion of the source is linearly and circularly(?) polarized on microarcsecond scales. This information is assembled into a coherent picture of the source.
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