Related papers: First Results from MASIV: The Micro-Arcsecond Scin…
We are undertaking a large-scale 5 GHz VLA survey of the northern sky to search for rapid intra-day variability (IDV). Over four observing epochs we found that 56% of the sources showed variability on timescales of hours to several days.…
We report on the variability of 443 flat spectrum, compact radio sources monitored using the VLA for 3 days in 4 epochs at ~ 4 month intervals at 5 GHz as part of the Micro-Arcsecond Scintillation-Induced Variability (MASIV) survey. Over…
Intraday variability (IDV) of the radio emission from active galactic nuclei is now known to be predominantly due to interstellar scintillation (ISS). The MASIV (The Micro-Arcsecond Scintillation-Induced Variability) survey of 443 flat…
The 4.9 GHz Micro-Arcsecond Scintillation-Induced Variability (MASIV) Survey detected a drop in Interstellar Scintillation (ISS) for sources at redshifts z > 2, indicating an apparent increase in angular diameter or a decrease in flux…
We investigate the relationship between 5 GHz interstellar scintillation (ISS) and 15 GHz intrinsic variability of compact, radio-selected AGNs drawn from the Microarcsecond Scintillation-Induced Variability (MASIV) Survey and the Owens…
Observations over the last two decades have shown that a significant fraction of all flat-spectrum, extragalactic radio sources exhibit flux density variations on timescales of a day or less at frequencies of several GHz. It has been…
From 1979--1996 the Green Bank Interferometer was used by the Naval Research Laboratory to monitor the flux density from 146 compact radio sources at frequencies near 2 and 8 GHz. We filter the ``light curves'' to separate intrinsic…
We report on the discovery of a source which exhibits over 300% amplitude changes in radio flux density on the period of hours. This source, J1819+3845, is the most extremely variable extragalactic source known in the radio sky. We believe…
Intraday variability (IDV) of compact extragalactic radio sources is a complex phenomenon and shows a wavelength dependent mixture of refractive interstellar scintillation (RISS) (dominant at long cm-wavelengths) and source-intrinsic…
We report on a search for low-frequency radio variability in 944 bright (> 4Jy at 154 MHz) unresolved, extragalactic radio sources monitored monthly for several years with the Murchison Widefield Array. In the majority of sources we find…
We present the first dedicated observations of Interplanetary Scintillation (IPS) with the Murchison Widefield Array (MWA). We have developed a synthesis imaging technique, tailored to the properties of modern "large-N" low-frequency radio…
We present the results of an Australia Telescope Compact Array (ATCA) survey for intra-day variability (IDV) of the total and polarized flux densities of 118 compact, flat spectrum, extragalactic radio sources from the Parkes 2.7 GHz…
We present the first unambiguous case of external variability of an extra-galactic radio source, the CLASS gravitational lens B1600+434, consisting of two images lensed by an edge-on disk galaxy. The VLA 8.5-GHz difference light curve of…
We have conducted the first systematic search for interday variability in a large sample of extragalactic radio sources at 15 GHz. From the sample of 1158 radio-selected blazars monitored over a $\sim$10 year span by the Owens Valley Radio…
The propagation of radio waves from distant compact radio sources through turbulent interstellar plasma in our Galaxy causes these sources to twinkle, a phenomenon called interstellar scintillation. Such scintillations are a unique probe of…
We summarize results from flux density monitoring campaigns performed with the 100 meter radio-telescope at Effelsberg and the VLA during the past 15 yrs. We briefly discuss some of the statistical properties of the rapid variability from…
Interstellar scintillation has been conclusively demonstrated to be the principal cause of the intraday variability (IDV) observed in the centimetre-wavelength emission of many AGN. A few sources show large amplitude modulation in their…
Comparing the asymmetry coefficients and scintillation indices for observed time variations of the intensity of the radiation of extragalactic sources and the predictions of theoretical models is a good test of the nature of the observed…
We report further results from our imaging survey at 15GHz (lambda=2 cm) with the Very Long Baseline Array. This paper presents single epoch images for 39 sources, bringing the total number of objects in the sample to 171. Our sample is…
Interstellar scintillation (ISS) has been established as the cause of the random variations seen at centimetre wavelengths in many compact radio sources on timescales of a day or less. Observations of ISS can be used to probe structure both…