Statistics of the MASIV 5 GHZ VLA Scintillation Survey

We are undertaking a large-scale VLA 5 GHz variability survey of the northern sky searching for rapid intra-day variability. From four epochs of observations spread over a year we find 56% of the flat-spectrum sources showed significant variability on time-scales from hours to days, with many sources varying episodically on only one epoch during the year. We find that the weaker sources show more frequent variability as well as fractionally larger amplitude variability. Fewer sources were detected at high Galactic latitude, demonstrating that inter-stellar scintillation is the principal mechanism responsible for this IDV. We also see a significant dependence on spectral index with the flatter and more inverted sources more frequently exhibiting scintillation.
Presented at the conference entitled "From Planets to Dark Energy: The Modern Radio Universe," held in Manchester, UK, on 1-5 Oct 2007. Published in Proceedings of Science, PoS (MRU) 040, p1-5, 2007. Prepared in collaboration with Australia Telescope National Facility, Epping, Australia; University of Tasmania, Hobart, Australia; University of California, San Diego, CA; and others. The original document contains color images.