B. M. Gaensler , R. W. Hunstead ,, PASA, 17 (1), 72.
Next Section: Introduction
Long-term Monitoring of Molonglo Calibrators
B. M. Gaensler 1,2,3
R. W. Hunstead 2
1 Center for Space Research, Massachusetts Institute of Technology, 70 Vassar Street,
Cambridge MA 02139, USA; bmg@space.mit.edu
2 School of Physics, University of Sydney, NSW 2006, Australia; rwh@physics.usyd.edu.au
3 Hubble Fellow
Abstract:
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 58000 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: general -- quasars: general -- radio continuum: galaxies
- Introduction
- Observations and Data Analysis
- Results
- Discussion
- Conclusions
- Acknowledgements
- References
б© Copyright Astronomical Society of Australia 1997