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151. The Murchison Widefield Array Correlator

Author

Ord, S M, Crosse, B, Emrich, David, Pallot, D, Wayth, Randall, Clark , M. A, Tremblay, S.E., Arcus, W, Barnes, David G, Bell, M, Bernardi, G, Bhat, N.D.R., Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, Bowman, J D, Bowman, Judd D, Deshpande, Avinash, Feng, Lu, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Kincaid, Barton B, Oberoi, D, Prabu, T, Rogers, Alan, Srivani, K. S., Webster, Rachel L, Whitney, Alan, Hindson, L, Jacobs, Daniel C., Kasper, J.C., Kasper, Justin, Procopio, P., Udaya Shankar, N., Williams, Christopher L, Waterson, Mark, Ord, S M, Crosse, B, Emrich, David, Pallot, D, Wayth, Randall, Clark , M. A, Tremblay, S.E., Arcus, W, Barnes, David G, Bell, M, Bernardi, G, Bhat, N.D.R., Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, Bowman, J D, Bowman, Judd D, Deshpande, Avinash, Feng, Lu, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Kincaid, Barton B, Oberoi, D, Prabu, T, Rogers, Alan, Srivani, K. S., Webster, Rachel L, Whitney, Alan, Hindson, L, Jacobs, Daniel C., Kasper, J.C., Kasper, Justin, Procopio, P., Udaya Shankar, N., Williams, Christopher L, and Waterson, Mark

Abstract

The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio-astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day-1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.

Published
2015

152. BROADBAND SPECTRAL MODELING of the EXTREME GIGAHERTZ-PEAKED SPECTRUM RADIO SOURCE PKS B0008-421

Author

Callingham, J, Gaensler, B M, Ekers, Ronald D, Tingay, S.J., Wayth, Randall, Morgan, J, Bernardi, Gianni, Bell, Martin E., Bhat, N.D.R., Bowman, J D, Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, Deshpande, Avinash, Ewall-Wice, Aaron, Feng, Lu, Greenhill, Lincoln, Oberoi, D, Prabu, T, Srivani, K. S., Callingham, J, Gaensler, B M, Ekers, Ronald D, Tingay, S.J., Wayth, Randall, Morgan, J, Bernardi, Gianni, Bell, Martin E., Bhat, N.D.R., Bowman, J D, Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, Deshpande, Avinash, Ewall-Wice, Aaron, Feng, Lu, Greenhill, Lincoln, Oberoi, D, Prabu, T, and Srivani, K. S.

Abstract

We present broadband observations and spectral modeling of PKS B0008-421 and identify it as an extreme gigahertz-peaked spectrum (GPS) source. PKS B0008-421 is characterized by the steepest known spectral slope below the turnover, close to the theoretical limit of synchrotron self-absorption, and the smallest known spectral width of any GPS source. Spectral coverage of the source spans from 0.118 to 22 GHz, which includes data from the Murchison Widefield Array and the wide bandpass receivers on the Australia Telescope Compact Array. We have implemented a Bayesian inference model fitting routine to fit the data with internal free-free absorption (FFA), single- and double-component FFA in an external homogeneous medium, FFA in an external inhomogeneous medium, or single- and double-component synchrotron self-absorption models, all with and without a high-frequency exponential break. We find that without the inclusion of a high-frequency break these models cannot accurately fit the data, with significant deviations above and below the peak in the radio spectrum. The addition of a high-frequency break provides acceptable spectral fits for the inhomogeneous FFA and double-component synchrotron self-absorption models, with the inhomogeneous FFA model statistically favored. The requirement of a high-frequency spectral break implies that the source has ceased injecting fresh particles. Additional support for the inhomogeneous FFA model as being responsible for the turnover in the spectrum is given by the consistency between the physical parameters derived from the model fit and the implications of the exponential spectral break, such as the necessity of the source being surrounded by a dense ambient medium to maintain the peak frequency near the gigahertz region. This implies that PKS B0008-421 should display an internal H i column density greater than 1020 cm-2. The discovery of PKS B0008-421 suggests that the next generation of low radio frequency surveys could reveal a

Published
2015

153. Measuring phased-array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137MHz ORBCOMM satellites

Author

Neben, A R, Bradley, R.F., Hewitt, Jacqueline N, Bernardi, G, Bowman, J D, Briggs, Franklin, Cappallo, R. J, Deshpande, Avinash, Goeke, R, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Lonsdale, Colin J, McWhirter, S.R., Mitchell, D.A., Morales, Miguel F, Morgan, Edward, Oberoi, D, Ord, S M, Prabu, T, Shankar, N.Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S.J., Wayth, Randall, B., Webster, Rachel L, Williams, Anne M., Williams, Christopher L, Neben, A R, Bradley, R.F., Hewitt, Jacqueline N, Bernardi, G, Bowman, J D, Briggs, Franklin, Cappallo, R. J, Deshpande, Avinash, Goeke, R, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Lonsdale, Colin J, McWhirter, S.R., Mitchell, D.A., Morales, Miguel F, Morgan, Edward, Oberoi, D, Ord, S M, Prabu, T, Shankar, N.Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S.J., Wayth, Randall, B., Webster, Rachel L, Williams, Anne M., and Williams, Christopher L

Abstract

Detection of the fluctuations in a 21cm line emission from neutral hydrogen during the Epoch of Reionization in thousand hour integrations poses stringent requirements on calibration and image quality, both of which necessitate accurate primary beam models. The Murchison Widefield Array (MWA) uses phased-array antenna elements which maximize collecting area at the cost of complexity. To quantify their performance, we have developed a novel beam measurement system using the 137MHz ORBCOMM satellite constellation and a reference dipole antenna. Using power ratio measurements, we measure the in situ beampattern of the MWA antenna tile relative to that of the reference antenna, canceling the variation of satellite flux or polarization with time. We employ angular averaging to mitigate multipath effects (ground scattering) and assess environmental systematics with a null experiment in which the MWA tile is replaced with a second-reference dipole. We achieve beam measurements over 30dB dynamic range in beam sensitivity over a large field of view (65% of the visible sky), far wider and deeper than drift scans through astronomical sources allow. We verify an analytic model of the MWA tile at this frequency within a few percent statistical scatter within the full width at half maximum. Toward the edges of the main lobe and in the sidelobes, we measure tens of percent systematic deviations. We compare these errors with those expected from known beamforming errors.

Published
2015

154. CONFIRMATION OF WIDE-FIELD SIGNATURES IN REDSHIFTED 21 cm POWER SPECTRA

Author

Thyagarajan, Nithyanandan, Jacobs, Daniel C., Bowman, J D, Barry, N, Beardsley, A, Bernardi, G, Briggs, Franklin, Cappallo, Roger C, Carroll, P, Deshpande, Avinash, de Oliveira-Costa,, A, Dillon, Joshua, Ewall-Wice, Aaron, McKinley, Benjamin, Offringa, Andre, Bowman, Judd D, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Loeb, Abraham, Oberoi, D, Prabu, T, Srivani, K. S., Webster, Rachel L, Wyithe, J Stuart B, Thyagarajan, Nithyanandan, Jacobs, Daniel C., Bowman, J D, Barry, N, Beardsley, A, Bernardi, G, Briggs, Franklin, Cappallo, Roger C, Carroll, P, Deshpande, Avinash, de Oliveira-Costa,, A, Dillon, Joshua, Ewall-Wice, Aaron, McKinley, Benjamin, Offringa, Andre, Bowman, Judd D, Greenhill, Lincoln, Hazelton, B, Johnston-Hollitt, M, Kaplan, D L, Loeb, Abraham, Oberoi, D, Prabu, T, Srivani, K. S., Webster, Rachel L, and Wyithe, J Stuart B

Abstract

We confirm our recent prediction of the "pitchfork" foreground signature in power spectra of high-redshift 21 cm measurements where the interferometer is sensitive to large-scale structure on all baselines. This is due to the inherent response of a wide-field instrument and is characterized by enhanced power from foreground emission in Fourier modes adjacent to those considered to be the most sensitive to the cosmological H i signal. In our recent paper, many signatures from the simulation that predicted this feature were validated against Murchison Widefield Array (MWA) data, but this key pitchfork signature was close to the noise level. In this paper, we improve the data sensitivity through the coherent averaging of 12 independent snapshots with identical instrument settings and provide the first confirmation of the prediction with a signal-to-noise ratio >10. This wide-field effect can be mitigated by careful antenna designs that suppress sensitivity near the horizon. Simple models for antenna apertures that have been proposed for future instruments such as the Hydrogen Epoch of Reionization Array and the Square Kilometre Array indicate they should suppress foreground leakage from the pitchfork by ∼40 dB relative to the MWA and significantly increase the likelihood of cosmological signal detection in these critical Fourier modes in the three-dimensional power spectrum.

Published
2015

155. The spectral variability of the GHZ-peaked spectrum radio source PKS 1718-649 and a comparison of absorption models

Author

Tingay, S. J., Macquart, J.-P., Collier, J. D., Rees, G., Callingham, J. R., Stevens, J., Carretti, E., Wayth, R. B., Wong, G. F., Trott, C. M., McKinley, B., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Tingay, S. J., Macquart, J.-P., Collier, J. D., Rees, G., Callingham, J. R., Stevens, J., Carretti, E., Wayth, R. B., Wong, G. F., Trott, C. M., McKinley, B., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

Using the new wideband capabilities of the ATCA, we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked 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 spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of active galactic nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free–free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free–free absorption model characterized by a power-law distribution of free–free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free–free and synchrotron self-absorption) that are based on simple homogenous structures.

Published
2015

157. A SEARCH FOR FAST RADIO BURSTS AT LOW FREQUENCIES WITH MURCHISON WIDEFIELD ARRAY HIGH TIME RESOLUTION IMAGING

Author

Tingay, S. J., primary, Trott, C. M., additional, Wayth, R. B., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Feng, L., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hancock, P. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Murphy, T., additional, Oberoi, D., additional, Prabu, T., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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159. Parity nonconservation in neutron resonances in238U

Author

TRIPLE Collaboration, Crawford, B. E., Bowman, J. D., Delheij, P. P. J., Frankle, C. M., Iinuma, Masataka, Knudson, J. N., Lowie, L. Y., Masaike, Akira, Matsuda, Yasuyuki, Mitchell, G. E., Penttilä, S. I., Postma, H., Roberson, N. R., Seestrom, S. J., Sharapov, E. I., Stephenson, S. L., Yen, Y.-F., and Yuan, V. W.

Subjects
Physics, Nuclear and High Energy Physics, Particle physics, Uranium-238, Total neutron, Neutron, Matrix element, Parity (physics), Symmetry breaking, Random variable, Helicity
Abstract

Parity nonconservation (PNC) was studied for 24 p-wave neutron resonances in ${}^{238}\mathrm{U}$ from 10 to 300 eV by measuring the helicity dependence of the total neutron cross section with an improved experimental apparatus. Six resonances show statistically significant (greater than $2.9\ensuremath{\sigma})$ parity violation. An analysis treating the PNC matrix elements as random variables yields a root-mean-square PNC matrix element ${M=0.67}_{\ensuremath{-}0.16}^{+0.24}$ meV. The corresponding weak spreading width ${\ensuremath{\Gamma}}_{w}{=(1.35}_{\ensuremath{-}0.64}^{+0.97})\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$ eV.

Published
1998
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161. A new layout optimization technique for interferometric arrays, applied to the Murchison Widefield Array

Author

Beardsley, A. P., Hazelton, B. J., Morales, M. F., Capallo, R.J., Goeke, Robert F, Emrich, D., Lonsdale, Colin John, Arcus, W., Barnes, D., Bernardi, G., Bowman, J. D., Bunton, J. D., Corey, Brian E, Deshpande, A., deSouza, L., Gaensler, B. M., Greenhill, L. J., Herne, D., Hewitt, Jacqueline N, Kaplan, D. L., Kasper, J. C., Kincaid, Barton B., Koenig, R., Kratzenberg, Eric W, Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morgan, Edward H, Oberoi, Divya, Ord, S. M., Pathikulangara, J., Prabu, T., Rogers, Alan E E, Roshi, A., Salah, Joseph E., Sault, R. J., Shankar, N. Udaya, Srivani, K. S., Stevens, J., Subrahmanyan, R., Tingay, S. J., Wayth, R. B., Waterson, M., Webster, R. L., Whitney, Alan R, Williams, A., Williams, C. L., Wyithe, J. S. B., Remillard, Ronald A, Haystack Observatory, and MIT Kavli Institute for Astrophysics and Space Research

Abstract

Antenna layout is an important design consideration for radio interferometers because it determines the quality of the snapshot point spread function (PSF, or array beam). This is particularly true for experiments targeting the 21-cm Epoch of Reionization signal as the quality of the foreground subtraction depends directly on the spatial dynamic range and thus the smoothness of the baseline distribution. Nearly all sites have constraints on where antennas can be placed - even at the remote Australian location of the Murchison Widefield Array (MWA) there are rock outcrops, flood zones, heritages areas, emergency runways and trees. These exclusion areas can introduce spatial structure into the baseline distribution that enhances the PSF sidelobes and reduces the angular dynamic range. In this paper we present a new method of constrained antenna placement that reduces the spatial structure in the baseline distribution. This method not only outperforms random placement algorithms that avoid exclusion zones, but surprisingly outperforms random placement algorithms without constraints to provide what we believe are the smoothest constrained baseline distributions developed to date. We use our new algorithm to determine antenna placements for the originally planned MWA, and present the antenna locations, baseline distribution and snapshot PSF for this array choice., U.S. National Science Foundation (grants AST CAREER-0847753, AST-0457585, AST-0908884 and PHY-0835713), Australian Research Council (grants LE0775621 and LE0882938), U.S. Air Force Office of Scientific Research (grant FA9550-0510247)

Published
2012

162. Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array

Author

Loi, Shyeh Tjing, primary, Murphy, Tara, additional, Bell, Martin E., additional, Kaplan, David L., additional, Lenc, Emil, additional, Offringa, André R., additional, Hurley-Walker, Natasha, additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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163. BROADBAND SPECTRAL MODELING OF THE EXTREME GIGAHERTZ-PEAKED SPECTRUM RADIO SOURCE PKS B0008-421

Author

Callingham, J. R., primary, Gaensler, B. M., additional, Ekers, R. D., additional, Tingay, S. J., additional, Wayth, R. B., additional, Morgan, J., additional, Bernardi, G., additional, Bell, M. E., additional, Bhat, R., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Ewall-Wice, A., additional, Feng, L., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hindson, L., additional, Hurley-Walker, N., additional, Jacobs, D. C., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kudrayvtseva, N., additional, Lenc, E., additional, Lonsdale, C. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S. M., additional, Pindor, B., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Shankar, N. Udaya, additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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164. MURCHISON WIDEFIELD ARRAY OBSERVATIONS OF ANOMALOUS VARIABILITY: A SERENDIPITOUS NIGHT-TIME DETECTION OF INTERPLANETARY SCINTILLATION

Author

Kaplan, D. L., primary, Tingay, S. J., additional, Manoharan, P. K., additional, Macquart, J. P., additional, Hancock, P., additional, Morgan, J., additional, Mitchell, D. A., additional, Ekers, R. D., additional, Wayth, R. B., additional, Trott, C., additional, Murphy, T., additional, Oberoi, D., additional, Cairns, I. H., additional, Feng, L., additional, Kudryavtseva, N., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hurley Walker, N., additional, Hazelton, B. J., additional, Johnston Hollitt, M., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Morales, M. F., additional, Morgan, E., additional, Ord, S. M., additional, Prabu, T., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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165. Measuring phased-array antenna beampatterns with high dynamic range for the Murchison Widefield Array using 137 MHz ORBCOMM satellites

Author

Neben, A. R., primary, Bradley, R. F., additional, Hewitt, J. N., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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166. Power spectrum analysis of ionospheric fluctuations with the Murchison Widefield Array

Author

Loi, Shyeh Tjing, primary, Trott, Cathryn M., additional, Murphy, Tara, additional, Cairns, Iver H., additional, Bell, Martin, additional, Hurley-Walker, Natasha, additional, Morgan, John, additional, Lenc, Emil, additional, Offringa, A. R., additional, Feng, L., additional, Hancock, P. J., additional, Kaplan, D. L., additional, Kudryavtseva, N., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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167. An analysis of the halo and relic radio emission from Abell 3376 from Murchison Widefield Array observations

Author

George, L. T., primary, Dwarakanath, K. S., additional, Johnston-Hollitt, M., additional, Hurley-Walker, N., additional, Hindson, L., additional, Kapińska, A. D., additional, Tingay, S. J., additional, Bell, M., additional, Callingham, J. R., additional, For, Bi-Qing, additional, Hancock, P. J., additional, Lenc, E., additional, McKinley, B., additional, Morgan, J., additional, Offringa, A., additional, Procopio, P., additional, Staveley-Smith, L., additional, Wayth, R. B., additional, Wu, Chen, additional, Zheng, Q., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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168. Empirical covariance modeling for 21 cm power spectrum estimation: A method demonstration and new limits from early Murchison Widefield Array 128-tile data

Author

Dillon, Joshua S., primary, Neben, Abraham R., additional, Hewitt, Jacqueline N., additional, Tegmark, Max, additional, Barry, N., additional, Beardsley, A. P., additional, Bowman, J. D., additional, Briggs, F., additional, Carroll, P., additional, de Oliveira-Costa, A., additional, Ewall-Wice, A., additional, Feng, L., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hernquist, L., additional, Hurley-Walker, N., additional, Jacobs, D. C., additional, Kim, H. S., additional, Kittiwisit, P., additional, Lenc, E., additional, Line, J., additional, Loeb, A., additional, McKinley, B., additional, Mitchell, D. A., additional, Morales, M. F., additional, Offringa, A. R., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Procopio, P., additional, Riding, J., additional, Sethi, S., additional, Shankar, N. Udaya, additional, Subrahmanyan, R., additional, Sullivan, I., additional, Thyagarajan, Nithyanandan, additional, Tingay, S. J., additional, Trott, C., additional, Wayth, R. B., additional, Webster, R. L., additional, Wyithe, S., additional, Bernardi, G., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Lonsdale, C. J., additional, McWhirter, S. R., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Srivani, K. S., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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169. Real‐time imaging of density ducts between the plasmasphere and ionosphere

Author

Loi, Shyeh Tjing, primary, Murphy, Tara, additional, Cairns, Iver H., additional, Menk, Frederick W., additional, Waters, Colin L., additional, Erickson, Philip J., additional, Trott, Cathryn M., additional, Hurley‐Walker, Natasha, additional, Morgan, John, additional, Lenc, Emil, additional, Offringa, André R., additional, Bell, Martin E., additional, Ekers, Ronald D., additional, Gaensler, B. M., additional, Lonsdale, Colin J., additional, Feng, Lu, additional, Hancock, Paul J., additional, Kaplan, David L., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Deshpande, A. A., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston‐Hollitt, M., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Wayth, R. B., additional, Webster, R. L., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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170. Measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

Author

Grammer, K. B., primary, Alarcon, R., additional, Barrón-Palos, L., additional, Blyth, D., additional, Bowman, J. D., additional, Calarco, J., additional, Crawford, C., additional, Craycraft, K., additional, Evans, D., additional, Fomin, N., additional, Fry, J., additional, Gericke, M., additional, Gillis, R. C., additional, Greene, G. L., additional, Hamblen, J., additional, Hayes, C., additional, Kucuker, S., additional, Mahurin, R., additional, Maldonado-Velázquez, M., additional, Martin, E., additional, McCrea, M., additional, Mueller, P. E., additional, Musgrave, M., additional, Nann, H., additional, Penttilä, S. I., additional, Snow, W. M., additional, Tang, Z., additional, and Wilburn, W. S., additional

Published
2015
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172. THE SPECTRAL VARIABILITY OF THE GHZ-PEAKED SPECTRUM RADIO SOURCE PKS 1718-649 AND A COMPARISON OF ABSORPTION MODELS

Author

Tingay, S. J., primary, Macquart, J.-P., additional, Collier, J. D., additional, Rees, G., additional, Callingham, J. R., additional, Stevens, J., additional, Carretti, E., additional, Wayth, R. B., additional, Wong, G. F., additional, Trott, C. M., additional, McKinley, B., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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173. The Low-Frequency Environment of the Murchison Widefield Array: Radio-Frequency Interference Analysis and Mitigation

Author

Offringa, A. R., primary, Wayth, R. B., additional, Hurley-Walker, N., additional, Kaplan, D. L., additional, Barry, N., additional, Beardsley, A. P., additional, Bell, M. E., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Callingham, J. R., additional, Cappallo, R. J., additional, Carroll, P., additional, Deshpande, A. A., additional, Dillon, J. S., additional, Dwarakanath, K. S., additional, Ewall-Wice, A., additional, Feng, L., additional, For, B.-Q., additional, Gaensler, B. M., additional, Greenhill, L. J., additional, Hancock, P., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Hindson, L., additional, Jacobs, D. C., additional, Johnston-Hollitt, M., additional, Kapińska, A. D., additional, Kim, H.-S., additional, Kittiwisit, P., additional, Lenc, E., additional, Line, J., additional, Loeb, A., additional, Lonsdale, C. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Morgan, J., additional, Neben, A. R., additional, Oberoi, D., additional, Ord, S. M., additional, Paul, S., additional, Pindor, B., additional, Pober, J. C., additional, Prabu, T., additional, Procopio, P., additional, Riding, J., additional, Udaya Shankar, N., additional, Sethi, S., additional, Srivani, K. S., additional, Staveley-Smith, L., additional, Subrahmanyan, R., additional, Sullivan, I. S., additional, Tegmark, M., additional, Thyagarajan, N., additional, Tingay, S. J., additional, Trott, C. M., additional, Webster, R. L., additional, Williams, A., additional, Williams, C. L., additional, Wu, C., additional, Wyithe, J. S., additional, and Zheng, Q., additional

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2015
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174. The High Time and Frequency Resolution Capabilities of the Murchison Widefield Array

Author

Tremblay, S. E., primary, Ord, S. M., additional, Bhat, N. D. R., additional, Tingay, S. J., additional, Crosse, B., additional, Pallot, D., additional, Oronsaye, S. I., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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175. Ionospheric Modelling using GPS to Calibrate the MWA. I: Comparison of First Order Ionospheric Effects between GPS Models and MWA Observations

Author

Arora, B. S., primary, Morgan, J., additional, Ord, S. M., additional, Tingay, S. J., additional, Hurley-Walker, N., additional, Bell, M., additional, Bernardi, G., additional, Bhat, N. D. R., additional, Briggs, F., additional, Callingham, J. R., additional, Deshpande, A. A., additional, Dwarakanath, K. S., additional, Ewall-Wice, A., additional, Feng, L., additional, For, B.-Q., additional, Hancock, P., additional, Hazelton, B. J., additional, Hindson, L., additional, Jacobs, D., additional, Johnston-Hollitt, M., additional, Kapińska, A. D., additional, Kudryavtseva, N., additional, Lenc, E., additional, McKinley, B., additional, Mitchell, D., additional, Oberoi, D., additional, Offringa, A. R., additional, Pindor, B., additional, Procopio, P., additional, Riding, J., additional, Staveley-Smith, L., additional, Wayth, R. B., additional, Wu, C., additional, Zheng, Q., additional, Bowman, J. D., additional, Cappallo, R. J., additional, Corey, B. E., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Morales, M. F., additional, Morgan, E., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, and C. L., additional

Published
2015
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176. GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey

Author

Wayth, R. B., primary, Lenc, E., additional, Bell, M. E., additional, Callingham, J. R., additional, Dwarakanath, K. S., additional, Franzen, T. M. O., additional, For, B.-Q., additional, Gaensler, B., additional, Hancock, P., additional, Hindson, L., additional, Hurley-Walker, N., additional, Jackson, C. A., additional, Johnston-Hollitt, M., additional, Kapińska, A. D., additional, McKinley, B., additional, Morgan, J., additional, Offringa, A. R., additional, Procopio, P., additional, Staveley-Smith, L., additional, Wu, C., additional, Zheng, Q., additional, Trott, C. M., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2015
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177. The Murchison Widefield Array Correlator

Author

Ord, S. M., primary, Crosse, B., additional, Emrich, D., additional, Pallot, D., additional, Wayth, R. B., additional, Clark, M. A., additional, Tremblay, S. E., additional, Arcus, W., additional, Barnes, D., additional, Bell, M., additional, Bernardi, G., additional, Bhat, N. D. R., additional, Bowman, J. D., additional, Briggs, F., additional, Bunton, J. D., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, deSouza, L., additional, Ewell-Wice, A., additional, Feng, L., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Herne, D., additional, Hewitt, J. N., additional, Hindson, L., additional, Hurley-Walker, N., additional, Jacobs, D., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kincaid, B. B., additional, Koenig, R., additional, Kratzenberg, E., additional, Kudryavtseva, N., additional, Lenc, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McKinley, B., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Offringa, A., additional, Pathikulangara, J., additional, Pindor, B., additional, Prabu, T., additional, Procopio, P., additional, Remillard, R. A., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Salah, J. E., additional, Sault, R. J., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Stevens, J., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, Williams, C. L., additional, and Wyithe, J. S. B., additional

Published
2015
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178. First Look Murchison Widefield Array observations of Abell 3667

Author

Hindson, L., Johnston-Hollitt, M., Hurley-Walker, N., Buckley, K., Morgan, J., Carretti, E., Dwarakanath, K. S., Bell, M., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., McKinley, B., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Procopio, P., Offringa, A. R., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Hindson, L., Johnston-Hollitt, M., Hurley-Walker, N., Buckley, K., Morgan, J., Carretti, E., Dwarakanath, K. S., Bell, M., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., McKinley, B., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Procopio, P., Offringa, A. R., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

The Murchison Widefield Array (MWA) is a new low frequency interferometric radio telescope, operating in the remote Murchison Radio Observatory in Western Australia. In this paper we present the first MWA observations of the well known radio relics in Abell 3667 (A3667) between 120 and 226 MHz. We clearly detect the radio relics in A3667 and present flux estimates and spectral indices for these features. The average spectral index of the north-west (NW) and south-east (SE) relics is -0.9 +/- 0.1 between 120 and 1400 MHz. We are able to resolve spatial variation in the spectral index of the NW relic from -1.7 to -0.4, which is consistent with results found at higher frequencies., Comment: 4 pages, 4 figures, accepted for the 31st URSI General Assembly Proceedings to be published in IEEE Xplore

Published
2014
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179. The first Murchison Widefield Array low frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Author

Hindson, L., Johnston-Hollitt, M., Hurley-Walker, N., Buckley, K., Morgan, J., Carretti, E., Dwarakanath, K. S., Bell, M., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., McKinley, B., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Procopio, P., Offringa, A. R., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Hindson, L., Johnston-Hollitt, M., Hurley-Walker, N., Buckley, K., Morgan, J., Carretti, E., Dwarakanath, K. S., Bell, M., Bernardi, G., Bhat, N. D. R., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., McKinley, B., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Procopio, P., Offringa, A. R., Riding, J., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origins of radio halos, relics and bridges is still unclear, however galaxy cluster mergers seems to be an important factor. We clearly detect the North-West (NW) and South-East (SE) radio relics in A3667 and find an integrated flux density at 149 MHz of 28.1 +/- 1.7 and 2.4 +/- 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of -0.9 +/- 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. How- ever, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features., Comment: 17 pages, 11 figures

Published
2014
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180. WSClean: an implementation of a fast, generic wide-field imager for radio astronomy

Author

Offringa, A. R., McKinley, B., Hurley-Walker, N., Briggs, F. H., Wayth, R. B., Kaplan, D. L., Bell, M. E., Feng, L., Neben, A. R., Hughes, J. D., Rhee, J., Murphy, T., Bhat, N. D. R., Bernardi, G., Bowman, J. D., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hindson, L., Johnston-Hollitt, M., Jacobs, D. C., Kasper, J. C., Kratzenberg, E., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Kudryavtseva, N., Oberoi, D., Ord, S. M., Pindor, B., Procopio, P., Prabu, T., Riding, J., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Offringa, A. R., McKinley, B., Hurley-Walker, N., Briggs, F. H., Wayth, R. B., Kaplan, D. L., Bell, M. E., Feng, L., Neben, A. R., Hughes, J. D., Rhee, J., Murphy, T., Bhat, N. D. R., Bernardi, G., Bowman, J. D., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hindson, L., Johnston-Hollitt, M., Jacobs, D. C., Kasper, J. C., Kratzenberg, E., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Kudryavtseva, N., Oberoi, D., Ord, S. M., Pindor, B., Procopio, P., Prabu, T., Riding, J., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

Astronomical widefield imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new widefield interferometric imager that uses the w-stacking algorithm and can make use of the w-snapshot algorithm. The performance dependencies of CASA's w-projection and our new imager are analysed and analytical functions are derived that describe the required computing cost for both imagers. On data from the Murchison Widefield Array, we find our new method to be an order of magnitude faster than w-projection, as well as being capable of full-sky imaging at full resolution and with correct polarisation correction. We predict the computing costs for several other arrays and estimate that our imager is a factor of 2-12 faster, depending on the array configuration. We estimate the computing cost for imaging the low-frequency Square-Kilometre Array observations to be 60 PetaFLOPS with current techniques. We find that combining w-stacking with the w-snapshot algorithm does not significantly improve computing requirements over pure w-stacking. The source code of our new imager is publicly released., Comment: Accepted for publication in MNRAS

Published
2014
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181. Observing the Sun with the Murchison Widefield Array

Author

Oberoi, D., Sharma, R., Bhatnagar, S., Lonsdale, C. J., Matthews, L. D., Cairns, I. H., Tingay, S. J., Benkevitch, L., Donea, A., White, S. M., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Offringa, A. R., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Salah, J. E., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., William, A., Williams, C. L., Oberoi, D., Sharma, R., Bhatnagar, S., Lonsdale, C. J., Matthews, L. D., Cairns, I. H., Tingay, S. J., Benkevitch, L., Donea, A., White, S. M., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Offringa, A. R., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Salah, J. E., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., William, A., and Williams, C. L.

Abstract

The Sun has remained a difficult source to image for radio telescopes, especially at the low radio frequencies. Its morphologically complex emission features span a large range of angular scales, emission mechanisms involved and brightness temperatures. In addition, time and frequency synthesis, the key tool used by most radio interferometers to build up information about the source being imaged is not effective for solar imaging, because many of the features of interest are short lived and change dramatically over small fractional bandwidths. Building on the advances in radio frequency technology, digital signal processing and computing, the kind of instruments needed to simultaneously capture the evolution of solar emission in time, frequency, morphology and polarization over a large spectral span with the requisite imaging fidelity, and time and frequency resolution have only recently begun to appear. Of this class of instruments, the Murchison Widefield Array (MWA) is best suited for solar observations. The MWA has now entered a routine observing phase and here we present some early examples from MWA observations., Comment: 4 pages, 3 figures, submitted for the 31st URSI General Assembly and Scientific Symposium, to be held in Bejing, China from 16-23, August, 2014

Published
2014

182. The Low-frequency Characteristics of PSR J0437-4715 Observed with the Murchison Wide-field Array

Author

Bhat, N.D.R., Ord, S M, Tremblay, S.E., Tingay, S. J., Deshpande, Avinash, Van Straten, William, Oronsaye, S. I., Bernardi, Gianni, Bowman, J D, Briggs, Franklin, Cappallo, R. J, Waterson, Mark, Bhat, N.D.R., Ord, S M, Tremblay, S.E., Tingay, S. J., Deshpande, Avinash, Van Straten, William, Oronsaye, S. I., Bernardi, Gianni, Bowman, J D, Briggs, Franklin, Cappallo, R. J, and Waterson, Mark

Abstract

We report on the detection of the millisecond pulsar PSR J0437-4715 with the Murchison Wide-field Array (MWA) at a frequency of 192 MHz. Our observations show rapid modulations of pulse intensity in time and frequency that arise from diffractive scintillation effects in the interstellar medium (ISM), as well as prominent drifts of intensity maxima in the time-frequency plane that arise from refractive effects. Our analysis suggests that the scattering screen is located at a distance of ~80-120 pc from the Sun, in disagreement with a recent claim that the screen is closer (~10 pc). Comparisons with higher frequency data from Parkes reveal a dramatic evolution of the pulse profile with frequency, with the outer conal emission becoming comparable in strength to that from the core and inner conal regions. As well as demonstrating the high time resolution science capabilities currently possible with the MWA, our observations underscore the potential to conduct low-frequency investigations of timing-array millisecond pulsars, which may lead to increased sensitivity in the detection of nanoHertz gravitational waves via the accurate characterization of ISM effects.

Published
2014

183. STUDY OF REDSHIFTED H i FROM THE EPOCH OF REIONIZATION WITH DRIFT SCAN

Author

Paul, S, Sethi, Shiv K, Subrahmanyan, Ravi, Shankar, N.Udaya, Dwarakanath, K S, Deshpande, Avinash, Bernardi, Gianni, Bowman, J D, Briggs, Franklin, Waterson, Mark, Paul, S, Sethi, Shiv K, Subrahmanyan, Ravi, Shankar, N.Udaya, Dwarakanath, K S, Deshpande, Avinash, Bernardi, Gianni, Bowman, J D, Briggs, Franklin, and Waterson, Mark

Abstract

Detection of the epoch of reionization (EoR) in the redshifted 21 cm line is a challenging task. Here, we formulate the detection of the EoR signal using the drift scan strategy. This method potentially has better instrumental stability compared to the case where a single patch of sky is tracked. We demonstrate that the correlation time between measured visibilities could extend up to 1-2 hr for an interferometer array such as the Murchison Widefield Array, which has a wide primary beam. We estimate the EoR power based on a cross-correlation of visibilities over time and show that the drift scan strategy is capable of detecting the EoR signal with a signal to noise that is comparable/better compared to the tracking case. We also estimate the visibility correlation for a set of bright point sources and argue that the statistical inhomogeneity of bright point sources might allow their separation from the EoR signal

Published
2014

184. The FirstMurchisonWidefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Author

Hindson, L, Johnston-Hollitt, M, Hurley-Walker, Natasha, Buckley, K, Morgan, John, Carretti, Ettore, Dwarakanath, K S, Bell, M. E., Bernardi, G, Bhat, N.D.R., Bowman, J D, Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, Waterson, Mark, Hindson, L, Johnston-Hollitt, M, Hurley-Walker, Natasha, Buckley, K, Morgan, John, Carretti, Ettore, Dwarakanath, K S, Bell, M. E., Bernardi, G, Bhat, N.D.R., Bowman, J D, Briggs, Franklin, McKinley, Benjamin, Offringa, Andre, and Waterson, Mark

Abstract

We present the first Murchison Widefield Array observations of the well-known cluster of galaxies Abell 3667 (A3667) between 105 and 241 MHz. A3667 is one of the best known examples of a galaxy cluster hosting a double radio relic and has been reported to contain a faint radio halo and bridge. The origin of radio haloes, relics and bridges is still unclear, however galaxy cluster merger seems to be an important factor. We clearly detect the north-west (NW) and south-east radio relics in A3667 and find an integrated flux density at 149MHz of 28.1 ± 1.7 and 2.4 ± 0.1 Jy, respectively, with an average spectral index, between 120 and 1400 MHz, of -0.9 ± 0.1 for both relics. We find evidence of a spatial variation in the spectral index across the NW relic steepening towards the centre of the cluster, which indicates an ageing electron population. These properties are consistent with higher frequency observations. We detect emission that could be associated with a radio halo and bridge. However, due to the presence of poorly sampled large-scale Galactic emission and blended point sources we are unable to verify the exact nature of these features.

Published
2014

185. WSCLEAN: an implementation of a fast, generic wide-field imager for radio astronomy

Author

Offringa, Andre, McKinley, Benjamin, Hurley-Walker, Natasha, Briggs, Franklin, Wayth, Randall, Kaplan, D L, Bell, M. E., Feng, Lu, Neben, A R, Hughes, J D, Rhee, Jonghwan, Murphy, Tara, Bhat, N.D.R., Bernardi, Gianni, Bowman, J D, Deshpande, Avinash, Ewall-Wice, Aaron, Offringa, Andre, McKinley, Benjamin, Hurley-Walker, Natasha, Briggs, Franklin, Wayth, Randall, Kaplan, D L, Bell, M. E., Feng, Lu, Neben, A R, Hughes, J D, Rhee, Jonghwan, Murphy, Tara, Bhat, N.D.R., Bernardi, Gianni, Bowman, J D, Deshpande, Avinash, and Ewall-Wice, Aaron

Abstract

Astronomical wide-field imaging of interferometric radio data is computationally expensive, especially for the large data volumes created by modern non-coplanar many-element arrays. We present a new wide-field interferometric imager that uses the w-stacking algorithm and can make use of the w-snapshot algorithm. The performance dependences of CASA's w-projection and our new imager are analysed and analytical functions are derived that describe the required computing cost for both imagers. On data from the Murchison Widefield Array, we find our new method to be an order of magnitude faster than w-projection, as well as being capable of full-sky imaging at full resolution and with correct polarization correction. We predict the computing costs for several other arrays and estimate that our imager is a factor of 2-12 faster, depending on the array configuration. We estimate the computing cost for imaging the lowfrequency Square Kilometre Array observations to be 60 PetaFLOPS with current techniques. We find that combining w-stacking with the w-snapshot algorithm does not significantly improve computing requirements over pure w-stacking. The source code of our new imager is publicly released.

Published
2014

186. The Spectral Variability of the GHz-Peaked Spectrum Radio Source PKS 1718-649 and a Comparison of Absorption Models

Author

Tingay, S. J., Macquart, J. -P., Collier, J. D., Rees, G., Callingham, J. R., Stevens, J., Carretti, E., Wayth, R. B., Wong, G. F., Trott, C. M., McKinley, B., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Tingay, S. J., Macquart, J. -P., Collier, J. D., Rees, G., Callingham, J. R., Stevens, J., Carretti, E., Wayth, R. B., Wong, G. F., Trott, C. M., McKinley, B., Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Gaensler, B. M., Goeke, R., Greenhill, L. J., Hazelton, B. J., Johnston-Hollitt, M., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

Using the new wideband capabilities of the Australia Telescope Compact Array (ATCA), we obtain spectra for PKS 1718-649, a well-known gigahertz-peaked spectrum radio source. The observations, between approximately 1 and 10 GHz over three 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 spectral peak) and the adiabatic expansion of the radio source itself at high frequencies (above the spectral peak). The optical depth variations are found to be plausible when X-ray continuum absorption variability seen in samples of Active Galactic Nuclei is considered. We find that the cause of the peaked spectrum in PKS 1718-649 is most likely due to free-free absorption. In agreement with previous studies, we find that the spectrum at each epoch of observation is best fit by a free-free absorption model characterised by a power-law distribution of free-free absorbing clouds. This agreement is extended to frequencies below the 1 GHz lower limit of the ATCA by considering new observations with Parkes at 725 MHz and 199 MHz observations with the newly operational Murchison Widefield Array. These lower frequency observations argue against families of absorption models (both free-free and synchrotron self-absorption) that are based on simple homogenous structures., Comment: Accepted for publication in The Astronomical Journal

Published
2014
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187. Limits on low frequency radio emission from southern exoplanets with the Murchison Widefield Array

Author

Murphy, Tara, Bell, Martin E., Kaplan, David L., Gaensler, B. M., Offringa, Andre R., Lenc, Emil, Hurley-Walker, Natasha, Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hewitt, J. N., Johnston-Hollitt, M., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., Murphy, Tara, Bell, Martin E., Kaplan, David L., Gaensler, B. M., Offringa, Andre R., Lenc, Emil, Hurley-Walker, Natasha, Bernardi, G., Bowman, J. D., Briggs, F., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hewitt, J. N., Johnston-Hollitt, M., Kasper, J. C., Kratzenberg, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Prabu, T., Rogers, A. E. E., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Tingay, S. J., Waterson, M., Wayth, R. B., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

We present the results of a survey for low frequency radio emission from 17 known exoplanetary systems with the Murchison Widefield Array. This sample includes 13 systems that have not previously been targeted with radio observations. We detected no radio emission at 154 MHz, and put 3 sigma upper limits in the range 15.2-112.5 mJy on this emission. We also searched for circularly polarised emission and made no detections, obtaining 3 sigma upper limits in the range 3.4-49.9 mJy. These are comparable with the best low frequency radio limits in the existing literature and translate to luminosity limits of between 1.2 x 10^14 W and 1.4 x 10^17 W if the emission is assumed to be 100% circularly polarised. These are the first results from a larger program to systematically search for exoplanetary emission with the MWA., Comment: Accepted for publication in MNRAS. Updated author list from last revision

Published
2014
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188. Modelling of the Spectral Energy Distribution of Fornax A: Leptonic and Hadronic Production of High Energy Emission from the Radio Lobes

Author

McKinley, B., Yang, R., López-Caniego, M., Briggs, F., Hurley-Walker, N., Wayth, R. B., Offringa, A. R., Crocker, R., Bernardi, G., Procopio, P., Gaensler, B. M., Tingay, S. J., Johnston-Hollitt, M., McDonald, M., Bell, M., Bhat, N. D. R., Bowman, J. D., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hewitt, J. N., Hindson, L., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Riding, J., Rogers, A. E. E., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., Williams, C. L., McKinley, B., Yang, R., López-Caniego, M., Briggs, F., Hurley-Walker, N., Wayth, R. B., Offringa, A. R., Crocker, R., Bernardi, G., Procopio, P., Gaensler, B. M., Tingay, S. J., Johnston-Hollitt, M., McDonald, M., Bell, M., Bhat, N. D. R., Bowman, J. D., Cappallo, R. J., Corey, B. E., Deshpande, A. A., Emrich, D., Ewall-Wice, A., Feng, L., Goeke, R., Greenhill, L. J., Hazelton, B. J., Hewitt, J. N., Hindson, L., Jacobs, D., Kaplan, D. L., Kasper, J. C., Kratzenberg, E., Kudryavtseva, N., Lenc, E., Lonsdale, C. J., Lynch, M. J., McWhirter, S. R., Mitchell, D. A., Morales, M. F., Morgan, E., Oberoi, D., Ord, S. M., Pindor, B., Prabu, T., Riding, J., Rogers, A. E. E., Roshi, D. A., Shankar, N. Udaya, Srivani, K. S., Subrahmanyan, R., Waterson, M., Webster, R. L., Whitney, A. R., Williams, A., and Williams, C. L.

Abstract

We present new low-frequency observations of the nearby radio galaxy Fornax A at 154 MHz with the Murchison Widefield Array, microwave flux-density measurements obtained from WMAP and Planck data, and gamma-ray flux densities obtained from Fermi data. We also compile a comprehensive list of previously published images and flux-density measurements at radio, microwave and X-ray energies. A detailed analysis of the spectrum of Fornax A between 154 MHz and 1510 MHz reveals that both radio lobes have a similar spatially-averaged spectral index, and that there exists a steep-spectrum bridge of diffuse emission between the lobes. Taking the spectral index of both lobes to be the same, we model the spectral energy distribution of Fornax A across an energy range spanning eighteen orders of magnitude, to investigate the origin of the X-ray and gamma-ray emission. A standard leptonic model for the production of both the X-rays and gamma-rays by inverse-Compton scattering does not fit the multi-wavelength observations. Our results best support a scenario where the X-rays are produced by inverse-Compton scattering and the gamma-rays are produced primarily by hadronic processes confined to the filamentary structures of the Fornax A lobes., Comment: 16 pages, 11 figures

Published
2014
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189. Modelling of the spectral energy distribution of Fornax A: leptonic and hadronic production of high-energy emission from the radio lobes

Author

McKinley, B., primary, Yang, R., additional, López-Caniego, M., additional, Briggs, F., additional, Hurley-Walker, N., additional, Wayth, R. B., additional, Offringa, A. R., additional, Crocker, R., additional, Bernardi, G., additional, Procopio, P., additional, Gaensler, B. M., additional, Tingay, S. J., additional, Johnston-Hollitt, M., additional, McDonald, M., additional, Bell, M., additional, Bhat, N. D. R., additional, Bowman, J. D., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Hindson, L., additional, Jacobs, D., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Kudryavtseva, N., additional, Lenc, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Pindor, B., additional, Prabu, T., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, D. A., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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191. Improved measurement of the spectral index of the diffuse radio background between 90 and 190 MHz.

Author

Mozdzen, T. J., Bowman, J. D., Monsalve, R. A., and Rogers, A. E. E.

Subjects
*DIPOLE antennas, *SOLAR radio emission, *ASTRONOMICAL observations, *UNCERTAINTY (Information theory), *ASTRONOMICAL surveys
Abstract

We report absolutely calibrated measurements of diffuse radio emission between 90 and 190MHz from the Experiment to Detect the Global EoR Signature (EDGES). EDGESemploys a wide beam zenith-pointing dipole antenna centred on a declination of -26.7°. We measure the sky brightness temperature as a function of frequency averaged over the EDGES beam from 211 nights of data acquired from 2015 July to 2016 March. We derive the spectral index, ß, as a function of local sidereal time (LST) and find -2.60 > ß > -2.62 ± 0.02 between 0 and 12 h LST. When the Galactic Centre is in the sky, the spectral index flattens, reaching ß = -2.50 ± 0.02 at 17.7 h. The EDGES instrument is shown to be very stable throughout the observations with night-to-night reproducibility of sß < 0.003. Including systematic uncertainty, the overall uncertainty of ß is 0.02 across all LST bins. These results improve on the earlier findings of Rogers & Bowman by reducing the spectral index uncertainty from 0.10 to 0.02 while considering more extensive sources of errors. We compare our measurements with spectral index simulations derived from the Global Sky Model (GSM) of de Oliveira-Costa et al. and with fits between the Guzmán et al. 45MHz and Haslam et al. 408 MHz maps. We find good agreement at the transit of the Galactic Centre. Away from transit, the GSM tends to overpredict (GSM less negative) by 0.05<Δß = ßGSM - ßEDGES < 0.12, while the 45-408 MHz fits tend to overpredict by Δß < 0.05. [ABSTRACT FROM AUTHOR]

Published
2017
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192. Occupational carcinogens: ELF MFs (multiple letters) [1]

Author

Mild, K. H., Mattsso, M. -O., Hardell, L., Bowman, J. D., Kundi, M., Straif, K., Cardis, E., Boffetta, P., Rousseau, M. -C., Siemiatycki, J., Mild, K.H., Mattsso, M.-O., Hardell, L., Bowman, J.D., Kundi, M., Straif, K., Cardis, E., Boffetta, P., Rousseau, M.-C., and Siemiatycki, J.

Subjects
Occupational carcinogens
Abstract

No abstract

Published
2005

194. Limits on low-frequency radio emission from southern exoplanets with the Murchison Widefield Array

Author

Murphy, T., primary, Bell, M. E., additional, Kaplan, D. L., additional, Gaensler, B. M., additional, Offringa, A. R., additional, Lenc, E., additional, Hurley-Walker, N., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Johnston-Hollitt, M., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, D. A., additional, Shankar, N. U., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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195. The First Murchison Widefield Array low-frequency radio observations of cluster scale non-thermal emission: the case of Abell 3667

Author

Hindson, L., primary, Johnston-Hollitt, M., additional, Hurley-Walker, N., additional, Buckley, K., additional, Morgan, J., additional, Carretti, E., additional, Dwarakanath, K. S., additional, Bell, M., additional, Bernardi, G., additional, Bhat, N. D. R., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Ewall-Wice, A., additional, Feng, L., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Jacobs, D., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Kudryavtseva, N., additional, Lenc, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, McKinley, B., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Ord, S. M., additional, Pindor, B., additional, Prabu, T., additional, Procopio, P., additional, Offringa, A. R., additional, Riding, J., additional, Rogers, A. E. E., additional, Roshi, A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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196. wsclean: an implementation of a fast, generic wide-field imager for radio astronomy

Author

Offringa, A. R., primary, McKinley, B., additional, Hurley-Walker, N., additional, Briggs, F. H., additional, Wayth, R. B., additional, Kaplan, D. L., additional, Bell, M. E., additional, Feng, L., additional, Neben, A. R., additional, Hughes, J. D., additional, Rhee, J., additional, Murphy, T., additional, Bhat, N. D. R., additional, Bernardi, G., additional, Bowman, J. D., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A. A., additional, Emrich, D., additional, Ewall-Wice, A., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hindson, L., additional, Johnston-Hollitt, M., additional, Jacobs, D. C., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lenc, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Kudryavtseva, N., additional, Oberoi, D., additional, Ord, S. M., additional, Pindor, B., additional, Procopio, P., additional, Prabu, T., additional, Riding, J., additional, Roshi, D. A., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Tingay, S. J., additional, Waterson, M., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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197. THE LOW-FREQUENCY CHARACTERISTICS OF PSR J0437–4715 OBSERVED WITH THE MURCHISON WIDE-FIELD ARRAY

Author

Bhat, N. D. R., primary, Ord, S. M., additional, Tremblay, S. E., additional, Tingay, S. J., additional, Deshpande, A. A., additional, van Straten, W., additional, Oronsaye, S., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Emrich, D., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Hewitt, J. N., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lonsdale, C. J., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Oberoi, D., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, D. A., additional, Udaya Shankar, N., additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, Williams, A., additional, and Williams, C. L., additional

Published
2014
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198. Observing the Sun with the Murchison Widefield Array

Author

Oberoi, D., primary, Sharma, R., additional, Bhatnagar, S., additional, Lonsdale, C. J., additional, Matthews, L. D., additional, Cairns, I. H., additional, Tingay, S. J., additional, Benkevitch, L., additional, Donea, A., additional, White, S. M., additional, Bernardi, G., additional, Bowman, J. D., additional, Briggs, F., additional, Cappallo, R. J., additional, Corey, B. E., additional, Deshpande, A., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L. J., additional, Hazelton, B. J., additional, Johnston-Hollitt, M., additional, Kaplan, D. L., additional, Kasper, J. C., additional, Kratzenberg, E., additional, Lynch, M. J., additional, McWhirter, S. R., additional, Mitchell, D. A., additional, Morales, M. F., additional, Morgan, E., additional, Offringa, A. R., additional, Ord, S. M., additional, Prabu, T., additional, Rogers, A. E. E., additional, Roshi, A., additional, Salah, J. E., additional, Shankar, N. Udaya, additional, Srivani, K. S., additional, Subrahmanyan, R., additional, Waterson, M., additional, Wayth, R. B., additional, Webster, R. L., additional, Whitney, A. R., additional, William, A., additional, and Williams, C. L., additional

Published
2014
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199. First look Murchison Widefield Array observations of Abell 3667

Author

Hindson, L., primary, Johnston-Hollitt, M., additional, Hurley-Walker, N., additional, Morgan, J., additional, Buckley, K., additional, Carretti, E., additional, Dwarakanath, K.S., additional, Bell, M., additional, Bernardi, G., additional, Bhat, R., additional, Briggs, F., additional, Deshpande, A. A., additional, Ewall-Wice, A., additional, Feng, L., additional, Hazelton, B., additional, Jacobs, D., additional, Kaplan, D., additional, Kudryavtseva, N., additional, Lenc, E., additional, McKinley, B., additional, Mitchell, D., additional, Pindor, B., additional, Procopio, P., additional, Oberoi, D., additional, Offringa, A. R., additional, Ord, S., additional, Riding, J., additional, Bowman, J. D., additional, Cappallo, R., additional, Corey, B., additional, Emrich, D., additional, Gaensler, B. M., additional, Goeke, R., additional, Greenhill, L., additional, Kasper, J., additional, Kratzenberg, E., additional, Lonsdale, C., additional, Lynch, M., additional, McWhirter, R., additional, Morales, M., additional, Morgan, E., additional, Prabu, T., additional, Rogers, A., additional, Roshi, A., additional, Shankar, U., additional, Srivani, K., additional, Subrahmanyan, R., additional, Tingay, S., additional, Waterson, M., additional, Webster, R., additional, Whitney, A., additional, Williams, A., additional, and Williams, C., additional

Published
2014
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200. Storage of ultracold neutrons in the magneto-gravitational trap of theUCNτexperiment

Author

Salvat, D. J., primary, Adamek, E. R., additional, Barlow, D., additional, Bowman, J. D., additional, Broussard, L. J., additional, Callahan, N. B., additional, Clayton, S. M., additional, Cude-Woods, C., additional, Currie, S., additional, Dees, E. B., additional, Fox, W., additional, Geltenbort, P., additional, Hickerson, K. P., additional, Holley, A. T., additional, Liu, C.-Y., additional, Makela, M., additional, Medina, J., additional, Morley, D. J., additional, Morris, C. L., additional, Penttilä, S. I., additional, Ramsey, J., additional, Saunders, A., additional, Seestrom, S. J., additional, Sharapov, E. I., additional, Sjue, S. K. L., additional, Slaughter, B. A., additional, Vanderwerp, J., additional, VornDick, B., additional, Walstrom, P. L., additional, Wang, Z., additional, Womack, T. L., additional, and Young, A. R., additional

Published
2014
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