Large amplitude intraday variability in 1156 295 observed during a VLBI experiment

T. Savolainen, Y. Kovalev

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientific


We present here the discovery of rapid, large amplitude intraday variability in the compact flat-spectrum radio quasar 1156+295. The detection of 40% flux density variations at 15 GHz on a timescale of only 2.7 hours was serendipitously made when the source was observed with the Very Long Baseline Array as a part of the MOJAVE survey programme on February 5, 2007. Intraday variability on timescales of a few hours or less is rare, and there exist very few sources that show large-amplitude variations on a timescale as short as what is now observed for 1156+295. The shape of the visibility function of the source changes very little during the observation, although the correlated flux density changes by 40%. This suggests that the variability occurs in a single dominant compact component. The observed variability characteristics are consistent with interstellar scintillation in nearby, highly turbulent medium. The rms amplitude of modulation at 15 GHz is unusually large and it implies a rather high scattering measure along the line-of-sight towards 1156+295.
Original languageEnglish
Title of host publicationProceedings of the Workshop on Blazar Variability across the Electromagnetic Spectrum. April 22-25, 2008 Palaiseau, France. Proceedings of Science
Publication statusPublished - 2008
MoE publication typeB3 Non-refereed conference publication


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