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Paper: Intraday Variability of Flat-Spectrum Radio Sources
Volume: 144, Radio Emission from Galactic and Extragalactic Compact Sources, IAU Colloquium 164
Page: 257
Authors: Wagner, S. J.
Abstract: The characteristics of rapid variability of flat-spectrum radio sources are reviewed. A large fraction of the blazar population is found to show variability on timescales shorter than one day throughout the entire electromagnetic spectrum. The spectral indices and polarization characteristics change equally fast. Structure functions of the well-monitored sources show pronounced breaks on scales of about 10 to 50 hours, with flatter slopes towards the fast end. This illustrates that Intraday Variability (IDV), \ie\ the high frequency end of the power spectrum is qualitatively different and requires different mechanisms than slower variations. While intrinsic IDV provides direct clues on small-scale structure over fifteen decades in frequency, extrinsic contributions from interstellar scattering contributes at the lowest frequencies, and remains difficult to disentangle from the intrinsic effects.
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