Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 438, Issue 1, Pages 352-367Publisher
OXFORD UNIV PRESS
DOI: 10.1093/mnras/stt2200
Keywords
instrumentation: interferometers; techniques: image processing; catalogues; radio continuum: general
Categories
Funding
- US National Science Foundation [AST-0457585, PHY-0835713, CAREER-0847753, AST-0908884]
- Australian Research Council (LIEF grants) [LE0775621, LE0882938]
- US Air Force Office of Scientific Research [FA9550-0510247]
- Centre for All-sky Astrophysics (CAASTRO)
- Australian Research Council Centre of Excellence [CE110001020]
- Science Leveraging Fund of the New South Wales Department of Trade and Investment
- Smithsonian Astrophysical Observatory
- MIT School of Science
- Raman Research Institute
- Australian National University
- Victoria University of Wellington from the New Zealand Ministry of Economic Development [MED-E1799]
- Victoria University of Wellington (via IBM Shared University Research Grant)
- Australian Federal government
- NVIDIA at Harvard University
- International Centre for Radio Astronomy Research (ICRAR), a Joint Venture of Curtin University
- International Centre for Radio Astronomy Research (ICRAR), a Joint Venture of University of Western Australia
- Western Australian State government
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We present a search for transient and variable radio sources at 154 MHz with the Murchison Widefield Array 32-tile prototype. 51 images were obtained that cover a field of view of 1430 deg(2) centred on Hydra A. The observations were obtained over three days in 2010 March and three days in 2011 April and May. The mean cadence of the observations was 26 min and there was additional temporal information on day and year time-scales. We explore the variability of a sample of 105 low-frequency radio sources within the field. Four bright (S > 6 Jy) candidate variable radio sources were identified that displayed low levels of short time-scale variability (26 min). We conclude that this variability is likely caused by simplifications in the calibration strategy or ionospheric effects. On the time-scale of 1 yr we find two sources that show significant variability. We attribute this variability to either refractive scintillation or intrinsic variability. No radio transients were identified and we place an upper limit on the surface density of sources rho < 7.5 x 10(-5) deg(-2) with flux densities > 5.5 Jy, and characteristic time-scales of both 26 min and 1 yr.
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