Journal article
THE SPECTRAL VARIABILITY OF THE GHZ-PEAKED SPECTRUM RADIO SOURCE PKS 1718-649 AND A COMPARISON OF ABSORPTION MODELS
SJ Tingay, J-P Macquart, JD Collier, G Rees, JR Callingham, J Stevens, E Carretti, RB Wayth, GF Wong, CM Trott, B McKinley, G Bernardi, JD Bowman, F Briggs, RJ Cappallo, BE Corey, AA Deshpande, D Emrich, BM Gaensler, R Goeke Show all
ASTRONOMICAL JOURNAL | IOP PUBLISHING LTD | Published : 2015
Abstract
Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertzpeaked spectrum radio source. The observations, between approximately 1 and 10 GHz over 3 epochs spanning approximately 21 months, reveal variability both above the spectral peak at ∼3 GHz and below the peak. The combination of the low- and high-frequency variability cannot be easily explained using a single absorption mechanism, such as free-free absorption or synchrotron self-absorption. We find that the PKS 1718-649 spectrum and its variability are best explained by variations in the free-free optical depth on our line of sight to the radio source at low frequencies (below the spectr..
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Grants
Awarded by U.S. National Science Foundation
Awarded by Australian Research Council
Awarded by U.S. Air Force Office of Scientific Research
Awarded by Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence)
Awarded by Victoria University of Wellington (New Zealand Ministry of Economic Development)
Awarded by Victoria University of Wellington (IBM Shared University Research Grant)
Funding Acknowledgements
This scientific work makes use of the Murchison Radio-astronomy Observatory, operated by the Commonwealth Scientific and Industrial Research Organisation (CSIRO). We acknowledge the Wajarri Yamatji people as the traditional owners of the Observatory site. Support for the MWA comes from the U.S. National Science Foundation (grants AST-0457585, PHY-0835713, CAREER-0847753, and AST-0908884), the Australian Research Council (LIEF grants LE0775621 and LE0882938), the U.S. Air Force Office of Scientific Research (grant FA9550-0510247), and the Centre for All-sky Astrophysics (an Australian Research Council Centre of Excellence funded by grant CE110001020). Support is also provided by the Smithsonian Astrophysical Observatory, the MIT School of Science, the Raman Research Institute, the Australian National University, and the Victoria University of Wellington (via grant MED-E1799 from the New Zealand Ministry of Economic Development and an IBM Shared University Research Grant). The Australian Federal government provides additional support via the CSIRO, National Collaborative Research Infrastructure Strategy, Education Investment Fund, the Australia India Strategic Research Fund, and Astronomy Australia Limited, under contract to Curtin University. We acknowledge the iVEC Petabyte Data Store, the Initiative in Innovative Computing and the CUDA Center for Excellence sponsored by NVIDIA at Harvard University, and the International Centre for Radio Astronomy Research (ICRAR), a Joint Venture of Curtin University and The University of Western Australia, funded by the Western Australian State government. SJT acknowledges support from the Western Australian Government via a Premier's Research Fellowship. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO. The Parkes Radio Telescope is part of the Australia Telescope National Facility which is funded by the Commonwealth of Australia for operation as a National Facility managed by CSIRO.