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Long-term Monitoring of Molonglo Calibrators

Published online by Cambridge University Press:  05 March 2013

B. M. Gaensler  and
R. W. Hunstead
B. M. Gaensler
Affiliation:
Center for Space Research, Massachusetts Institute of Technology, 70 Vassar Street, Cambridge, MA 02139, USA; bmg@space.mit.edu School of Physics, University of Sydney, NSW 2006, Australia
R. W. Hunstead
Affiliation:
School of Physics, University of Sydney, NSW 2006, Australia; rwh@physics.usyd.edu.au
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Abstract

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Before and after every 12 hour synthesis observation, the Molonglo Observatory Synthesis Telescope (MOST) measures the flux densities of ∼5 compact extragalactic radio sources, chosen from a list of 55 calibrators. From 1984 to 1996, the MOST made some 58,000 such measurements. We have developed an algorithm to process this dataset to produce a light curve for each source spanning this thirteen-year period. We find that 18 of the 55 calibrators are variable, on time scales between one and ten years. There is the tendency for sources closer to the Galactic Plane to be more likely to vary, which suggests that the variability is a result of refractive scintillation in the Galactic interstellar medium. The sources with the flattest radio spectra show the highest levels of variability, an effect possibly resulting from differing orientations of the radio axes to the line of sight.

Keywords

ISM: generalquasars: generalradio continuum: galaxies
Type
Research Article
Information
Publications of the Astronomical Society of Australia , Volume 17 , Issue 1 , 2000 , pp. 72 - 82
Copyright
Copyright © Astronomical Society of Australia 2000

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