Radio Astronomy

Current research suggest super massive black holes are commonplace at the centers of active galaxies. The radio images of these galaxies often contain highly collimated jets emanating from the nucleus. Under high resolution these jets are observed to contain discrete ejecta or plasmons moving at highly relativistic velocities. An outburst of radio emission is associated with the ejection of these plasmons, the magnitude of which is extremely sensitive to the angle between the jet axis and the direction of the observer. Thus radio variability is a powerful diagnostic for detecting supermassive black holes with jets close to our line of sight. The same can be said for microquasars, stellar mass black holes or neutron stars accreting gas from a companion star which also exhibit relativistic jets.

Between 1977-84 we carried out a Galactic Radio Patrol to search for highly variable sources with the Green Bank 91 m telescope at a wavelength of 6 cm (Gregory, P. C. and Taylor, A. R., AJ, 92, 371, 1986 and references therein). With the development of a 7 feed 14 channel 6 cm receiver system, the patrol was extended to the entire Northern Celestial Sphere between declination 0 and 75 degrees for the years 1986-88. The telescope collapsed during our observing run in 1988 and the results for that year were not useable. The repeated surveys were combined to provide very sensitive maps (Condon, J. J., et al., AJ, 97, 1989 and AJ, 107, 1994) and two large catalogs of discrete radio sources (Gregory, P. C. and Condon, J. J., ApJS, 75, 1991 and Gregory, P. C. et al., ApJS, 103, 1996).

The same data yielded radio variability information on both a one year time base and on shorter time scales within each epoch. These variability catalogs can be down loaded from this site along with an explanatory README file and a Mathematica notebook for processing the catalogs.

Download the long term variability catalog (1 year time base).
    zipped ASCII file (4.4 MB)

Download the short term variability summary catalog.
    zipped ASCII file (2.0 MB)

Download the short term daily flux density measurements.
    zipped ASCII file (1.7 MB)

Download the README file.
    PDF file (330 kB)

Download the Mathematica 7 notebook to access variability catalogs.
    file (2.4 MB)

Download the Mathematica 10 notebook to access variability catalogs.
    file (2.4 MB)