Serendipitous VLBI detection of rapid, large-amplitude, intraday variability in QSO 1156+295 release_3g7z2kcc5vagpeh6s6bsxooknq

by T. Savolainen Max-Planck-Institut fuer Radioastronomie, Bonn, Germany, Astro Space Center of Lebedev Physical Institute, Moscow, Russia)

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2008  

Abstract

We report a serendipitous detection of rapid, large amplitude flux density variations in the highly core-dominated, flat-spectrum radio quasar 1156+295 during an observing session at the Very Long Baseline Array (VLBA). The source was observed as a part of the MOJAVE survey programme with the VLBA at 15 GHz on February 5, 2007. Large amplitude variability in the correlated flux density, unexplainable in terms of the source structure, was first discovered while processing the data, and later confirmed by calibrating the antenna gains using 24 other sources observed in the experiment. The source shows variations in the correlated flux density as high as 40% on a timescale of only 2.7 hours. This places 1156+295 between the classical IDV sources and the so-called intra-hour variables. The observed variability timescale and the modulation index of 13% are consistent with interstellar scintillation by a nearby, highly turbulent scattering screen. The large modulation index at 15 GHz implies a scattering measure that is atypically high for a high galactic latitude source such as 1156+295.
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Date   2008-09-02
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arXiv  0809.0451v1
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