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Start Over Author "Murphy, Tara" Journal monthly notices of the royal astronomical society
103 results on '"Murphy, Tara"'

3. Gaia GraL: Gaia DR2 gravitational lens systems – VIII. A radio census of lensed systems.

Author

Dobie, Dougal, Sluse, Dominique, Deller, Adam, Murphy, Tara, Krone-Martins, Alberto, Stern, Daniel, Wang, Ziteng, Wang, Yuanming, Bœhm, Céline, Djorgovski, S G, Galluccio, Laurent, Delchambre, Ludovic, Connor, Thomas, den Brok, Jakob Sebastiaan, Do Vale Cunha, Pedro H, Ducourant, Christine, Graham, Matthew J, Jalan, Priyanka, Klioner, Sergei A, and Klüter, Jonas

Subjects
OPTICAL measurements, CENSUS, RADIO technology, QUASARS, TELESCOPES, FEASIBILITY studies, GRAVITATIONAL lenses
Abstract

We present radio observations of 24 confirmed and candidate strongly lensed quasars identified by the Gaia Gravitational Lenses working group. We detect radio emission from eight systems in 5.5 and 9 GHz observations with the Australia Telescope Compact Array (ATCA), and 12 systems in 6 GHz observations with the Karl G. Jansky Very Large Array (VLA). The resolution of our ATCA observations is insufficient to resolve the radio emission into multiple lensed images, but we do detect multiple images from 11 VLA targets. We have analysed these systems using our observations in conjunction with existing optical measurements, including measuring offsets between the radio and optical positions for each image and building updated lens models. These observations significantly expand the existing sample of lensed radio quasars, suggest that most lensed systems are detectable at radio wavelengths with targeted observations, and demonstrate the feasibility of population studies with high-resolution radio imaging. [ABSTRACT FROM AUTHOR]

Published
2024
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4. Discovery of radio eclipses from 4FGL J1646.5−4406: a new candidate redback pulsar binary.

Author

Zic, Andrew, Wang, Ziteng, Lenc, Emil, Kaplan, David L, Murphy, Tara, Ridolfi, A, Sengar, Rahul, Hurley-Walker, Natasha, Dobie, Dougal, Leung, James K, Pritchard, Joshua, and Wang, Yuanming

Subjects
INTERSTELLAR medium, LOW mass stars, VARIABLE stars, BINARY pulsars, RADIO telescopes, ECLIPSING binaries, PULSARS
Abstract

Large widefield surveys make possible the serendipitous discovery of rare subclasses of pulsars. One such class are 'spider'-type pulsar binaries, comprised of a pulsar in a compact orbit with a low-mass (sub)stellar companion. In a search for circularly polarized radio sources in Australian Square Kilometre Array Pathfinder (ASKAP) Pilot Survey observations, we discovered highly variable and circularly polarized emission from a radio source within the error region of the γ-ray source 4FGL J1646.5−4406. The variability is consistent with the eclipse of a compact, steep-spectrum source behind ablated material from a companion in an ∼5.3 h binary orbit. Based on the eclipse properties and spatial coincidence with 4FGL J1646.5−4406, we argue that the source is likely a recycled pulsar in a 'redback' binary system. Using properties of the eclipses from ASKAP and Murchison Widefield Array observations, we provide broad constraints on the properties of the eclipse medium. We identified a potential optical/infrared counterpart in archival data consistent with a variable low-mass star. Using the Parkes radio telescope 'Murriyang' and the Meer Karoo Array Telescope (MeerKAT) , we searched extensively for radio pulsations but yielded no viable detections of pulsed emission. We suggest that the non-detection of pulses is due to scattering in the intra-binary material, but scattering from the interstellar medium can also plausibly explain the pulse non-detections if the interstellar dispersion measure exceeds ∼600 pc cm−3. Orbital constraints derived from optical observations of the counterpart would be highly valuable for future γ-ray pulsation searches, which may confirm the source nature as a pulsar. [ABSTRACT FROM AUTHOR]

Published
2024
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6. Radio variable and transient sources on minute time-scales in the ASKAP pilot surveys

Author

Wang, Yuanming, primary, Murphy, Tara, additional, Lenc, Emil, additional, Mercorelli, Louis, additional, Driessen, Laura, additional, Pritchard, Joshua, additional, Lao, Baoqiang, additional, Kaplan, David L, additional, An, Tao, additional, Bannister, Keith W, additional, Heald, George, additional, Lu, Shuoying, additional, Tuntsov, Artem, additional, Walker, Mark, additional, and Zic, Andrew, additional

Published
2023
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8. An off-axis relativistic jet seen in the long lasting delayed radio flare of the TDE AT 2018hyz.

Author

Sfaradi, Itai, Beniamini, Paz, Horesh, Assaf, Piran, Tsvi, Bright, Joe, Rhodes, Lauren, Williams, David R A, Fender, Rob, Leung, James K, Murphy, Tara, and Green, Dave A

Subjects
LIGHT curves, KINETIC energy
Abstract

The Tidal Disruption Event (TDE) AT 2018hyz exhibited a delayed radio flare almost three years after the stellar disruption. Here, we report new radio observations of the TDE AT 2018hyz with the AMI-LA and ATCA spanning from a month to more than four years after the optical discovery and 200 d since the last reported radio observation. We detected no radio emission from 30–220 d after the optical discovery in our observations at 15.5 GHz down to a 3σ level of <0.14 mJy. The fast-rising, delayed radio flare is observed in our radio data set and continues to rise almost ∼1580 d after the optical discovery. We find that the delayed radio emission, first detected 972 d after optical discovery, evolves as t 4.2 ± 0.9, at 15.5 GHz. Here, we present an off-axis jet model that can explain the full set of radio observations. In the context of this model, we require a powerful narrow jet with an isotropic equivalent kinetic energy E k, iso ∼ 1055 erg, an opening angle of ∼7°, and a relatively large viewing angle of ∼42°, launched at the time of the stellar disruption. Within our framework, we find that the minimal collimated energy possible for an off-axis jet from AT 2018hyz is Ek ≥ 3 × 1052 erg. Finally, we provide predictions based on our model for the light curve turnover time, and for the proper motion of the radio emitting source. [ABSTRACT FROM AUTHOR]

Published
2024
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9. An optimized transient detection pipeline for the ASKAP Variables and Slow Transients (VAST) survey.

Author

(安涛), Tao An, (劳保强), Baoqiang Lao, (徐志骏), Zhijun Xu, (卢铄迎), Shuoying Lu, (王远明), Yuanming Wang, Murphy, Tara, Kaplan, David L, and (郭绍光), Shaoguang Guo

Subjects
APPLICATION software, ELECTRONIC data processing, INTEGRATED software, BIG data, SCALABILITY
Abstract

In this paper, we present an optimized version of the detection pipeline for the ASKAP Variables and Slow Transients (VAST) survey, offering significant performance improvement. The key to this optimization is the replacement of the original w -projection algorithm integrated in the Common Astronomy Software Applications package with the w -stacking algorithm implemented in the WSClean software. Our experiments demonstrate that this optimization improves the overall processing efficiency of the pipeline by approximately a factor of 3. Moreover, the residual images generated by the optimized pipeline exhibit lower noise levels and fewer artefact sources, suggesting that our optimized pipeline not only enhances detection accuracy but also improves imaging fidelity. This optimized VAST detection pipeline is integrated into the Data Activated Liu Graph Engine (DALiuGE) execution framework, specifically designed for SKA-scale big data processing. Experimental results show that the performance and scalability advantages of the pipeline using DALiuGE over traditional MPI or BASH techniques increase with the data size. In summary, the optimized transient detection pipeline significantly reduces runtime, increases operational efficiency, and decreases implementation costs, offering a practical optimization solution for other ASKAP imaging pipelines as well. [ABSTRACT FROM AUTHOR]

Published
2023
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10. Radio transients and variables in the tenth Deeper, Wider, Faster observing run

Author

Dobie, D, primary, Pritchard, J, additional, Wang, Y, additional, Graham, L W, additional, Freeburn, J, additional, Qiu, H, additional, White, T R, additional, O’Brien, A, additional, Lenc, E, additional, Leung, J K, additional, Lynch, C, additional, Murphy, Tara, additional, Stewart, A J, additional, Wang, Z, additional, Zic, A, additional, Abbott, T M C, additional, Cai, C, additional, Cooke, J, additional, Dobiecki, M, additional, Goode, S, additional, Jia, S, additional, Li, C, additional, Möller, A, additional, Webb, S, additional, Zhang, J, additional, and Zhang, S N, additional

Published
2022
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11. A pilot ASKAP survey for radio transients towards the Galactic Centre

Author

Wang, Ziteng, primary, Murphy, Tara, additional, Kaplan, David L, additional, Bannister, Keith W, additional, Lenc, Emil, additional, Leung, James K, additional, O’Brien, Andrew, additional, Pintaldi, Sergio, additional, Pritchard, Joshua, additional, Stewart, Adam J, additional, and Zic, Andrew, additional

Published
2022
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13. Radio transients and variables in the tenth Deeper, Wider, Faster observing run.

Author

Dobie, D, Pritchard, J, (王远明), Y Wang, Graham, L W, Freeburn, J, (邱昊), H Qiu, White, T R, O'Brien, A, Lenc, E, (梁), J K Leung, Lynch, C, Murphy, Tara, Stewart, A J, (王子腾), Z Wang, Zic, A, Abbott, T M C, (蔡策), C Cai, Cooke, J, Dobiecki, M, and Goode, S

Subjects
SOLAR radio bursts, RADIO telescopes, X-ray telescopes, HARD X-rays, OPTICAL rotation, ELECTROMAGNETIC spectrum, DARK energy
Abstract

The Deeper, Wider, Faster (DWF) program coordinates observations with telescopes across the electromagnetic spectrum, searching for transients on time-scales of milliseconds to days. The tenth DWF observing run was carried out in near real-time during September 2021, and consisted of six consecutive days of observations of the NGC 6744 galaxy group and a field containing the repeating fast radio burst FRB 190711 with the Australian Square Kilometre Array Pathfinder, the Dark Energy Camera, the Hard X-ray Modulation Telescope, and the Parkes 64-m 'Murriyang' radio telescope. In this work, we present the results of an image-domain search for transient, variable, and circularly polarized sources carried out with ASKAP, using data from the observing run along with test observations prior to the run and follow-up observations carried out during and after the run. We identified eight variable radio sources, consisting of one pulsar, six stellar systems (five of which exhibit circularly polarized emission), and one previously uncatalogued source. Of particular interest is the detection of pulses from the ultra-cool dwarf SCR J1845–6357 with a period of 14.2 ± 0.3 h in good agreement with the known optical rotation period, making this the slowest rotating radio-loud ultra-cool dwarf discovered. [ABSTRACT FROM AUTHOR]

Published
2023
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14. A comprehensive search for the radio counterpart of GW190814 with the Australian Square Kilometre Array Pathfinder

Author

Dobie, D, primary, Stewart, A, additional, Hotokezaka, K, additional, Murphy, Tara, additional, Kaplan, D L, additional, Buckley, D A H, additional, Cooke, J, additional, Ho, A Y Q, additional, Lenc, E, additional, Leung, J K, additional, Gromadzki, M, additional, O’Brien, A, additional, Pintaldi, S, additional, Pritchard, J, additional, Wang, Y, additional, and Wang, Z, additional

Published
2021
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17. A search for radio afterglows from gamma-ray bursts with the Australian Square Kilometre Array Pathfinder

Author

Leung, James K, primary, Murphy, Tara, additional, Ghirlanda, Giancarlo, additional, Kaplan, David L, additional, Lenc, Emil, additional, Dobie, Dougal, additional, Banfield, Julie, additional, Hale, Catherine, additional, Hotan, Aidan, additional, McConnell, David, additional, Moss, Vanessa A, additional, Pritchard, Joshua, additional, Raja, Wasim, additional, Stewart, Adam J, additional, and Whiting, Matthew, additional

Published
2021
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18. A circular polarization survey for radio stars with the Australian SKA Pathfinder

Author

Pritchard, Joshua, primary, Murphy, Tara, additional, Zic, Andrew, additional, Lynch, Christene, additional, Heald, George, additional, Kaplan, David L, additional, Anderson, Craig, additional, Banfield, Julie, additional, Hale, Catherine, additional, Hotan, Aidan, additional, Lenc, Emil, additional, Leung, James K, additional, McConnell, David, additional, Moss, Vanessa A, additional, Raja, Wasim, additional, Stewart, Adam J, additional, and Whiting, Matthew, additional

Published
2021
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20. A population analysis of pulse broadening in ASKAP fast radio bursts

Author

Qiu, Hao, primary, Shannon, Ryan M, additional, Farah, Wael, additional, Macquart, Jean-Pierre, additional, Deller, Adam T, additional, Bannister, Keith W, additional, James, Clancy W, additional, Flynn, Chris, additional, Day, Cherie K, additional, Bhandari, Shivani, additional, and Murphy, Tara, additional

Published
2020
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22. The LBA Calibrator Survey of Southern Compact Extragalactic Radio Sources - LCS1

Author

Petrov, Leonid, Phillips, Chris, Bertarini, Alessandra, Murphy, Tara, and Sadler, Elaine M

Subjects
Astronomy
Abstract

We present a catalogue of accurate positions and correlated flux densities for 410 flat-spectrum, compact extragalactic radio sources previously detected in the Australia Telescope 20 GHz (AT20G) survey. The catalogue spans the declination range [-90deg, -40deg] and was constructed from four 24-h very long baseline interferometry (VLBI) observing sessions with the Australian Long Baseline Array at 8.3 GHz. The VLBI detection rate in these experiments is 97 per cent, the median uncertainty of the source positions is 2.6 mas and the median correlated flux density on projected baselines longer than 1000 km is 0.14 Jy. The goals of this work are (1) to provide a pool of southern sources with positions accurate to a few milliarcsec, which can be used for phase-referencing observations, geodetic VLBI and space navigation; (2) to extend the complete flux-limited sample of compact extragalactic sources to the Southern hemisphere; and (3) to investigate the parsec-scale properties of high-frequency selected sources from the AT20G survey. As a result of this VLBI campaign, the number of compact radio sources south of declination -40deg which have measured VLBI correlated flux densities and positions known to milliarcsec accuracy has increased by a factor of 3.5.

Published
2011
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26. The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample

Author

Bell, M E, primary, Murphy, Tara, additional, Hancock, P J, additional, Callingham, J R, additional, Johnston, S, additional, Kaplan, D L, additional, Hunstead, R W, additional, Sadler, E M, additional, Croft, S, additional, White, S V, additional, Hurley-Walker, N, additional, Chhetri, R, additional, Morgan, J S, additional, Edwards, P G, additional, Rowlinson, A, additional, Offringa, A R, 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, Hazelton, B J, additional, Johnston-Hollitt, M, 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
2018
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30. A search for long-time-scale, low-frequency radio transients

Author

Murphy, Tara, primary, Kaplan, David L., additional, Croft, Steve, additional, Lynch, Christene, additional, Callingham, J. R., additional, Bannister, Keith, additional, Bell, Martin E., additional, Hurley-Walker, Natasha, additional, Hancock, Paul, additional, Line, Jack, additional, Rowlinson, Antonia, additional, Lenc, Emil, additional, Intema, H. T., additional, Jagannathan, P., additional, Ekers, Ronald D., additional, Tingay, Steven, additional, Yuan, Fang, additional, Wolf, Christian, additional, Onken, Christopher A., additional, Dwarakanath, K. S., additional, For, B.-Q., additional, Gaensler, B. M., additional, Hindson, L., 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, Wayth, R., additional, Wu, C., additional, and Zheng, Q., additional

Published
2016
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31. survey of the Galactic plane for dispersed radio pulses with the Australian Square Kilometre Array Pathfinder.

Author

Qiu(邱昊), Hao, Bannister, K W, Shannon, R M, Murphy, Tara, Bhandari, Shivani, Agarwal, Devansh, Lorimer, D R, and Bunton, J D

Subjects
SOLAR radio bursts, ELECTRON density, RADIOS, PULSARS, INTERSTELLAR medium, SURVEYING (Engineering)
Abstract

We report the results from a survey of the Galactic plane for dispersed single pulses using the Australian SKA Pathfinder (ASKAP). We searched for rare bright dispersed radio pulses comprising 160 pointings covering 4800 deg2 of the Galactic plane within |b| < 7°, each pointing with an exposure time of 10 h. We detected one fast radio burst, FRB 180430, and single pulses from 11 pulsars. No rotating radio transients were detected. We detected FRB 180430 in the Galactic plane in the anticentre direction with a fluence of 216 ± 5 Jy ms a dispersion measure (DM) of 264.1 pc cm−3. We estimate the extragalactic DM of the object to be less than 86.7 pc cm−3 depending on the electron density model. One model suggests that this FRB may be a giant pulse within our galaxy; we discuss how this may not correctly represent the line-of-sight DM. Based on the single detection of FRB 180430 in |$3.47 \times 10^{4}\deg ^2 \text{h}$| we derive an FRB event rate in the Galactic plane at the 20 Jy ms threshold to be in the range 2–140 per sky per day at 95 per cent confidence. Despite the necessarily large uncertainties from this single detection, this is consistent with the current ASKAP all-sky detection rate. [ABSTRACT FROM AUTHOR]

Published
2019
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32. Low-frequency GMRT observations of ultra-cool dwarfs.

Author

Zic, Andrew, Lynch, Christene, Murphy, Tara, Kaplan, David L, and Chandra, Poonam

Subjects
DWARF stars, STELLAR magnetic fields, STARS, COSMIC magnetic fields, MAGNETIC fields
Abstract

Observations of radio emission in about 10 per cent of ultra-cool dwarfs (UCDs) indicate the presence of strong, persistent magnetic fields in these stars. These results are in contrast to early theoretical expectations on fully convective dynamos, and to other tracers of magnetic activity, such as |$\mathrm{H}\, \alpha$| and X-ray luminosity. Radio-frequency observations have been key to physically characterizing UCD magnetospheres, although explaining the diverse behaviour within them remains challenging. Most radio-frequency studies of UCDs have been conducted in the 4–8 GHz band, where traditional radio interferometers are typically most sensitive. Hence, the nature of UCD radio emission at low frequencies (⁠|${\lesssim } 1.4\, {\rm GHz}$|⁠) remains relatively unexplored, but can probe optically thick emission, and regions of lower magnetic field strengths – regimes not accessible to higher-frequency observations. In this work, we present the results from Giant Metrewave Radio Telescope observations of nine UCDs taken at ∼610 and |$1300\, {\rm MHz}$|⁠. These are the first observations of UCDs in this frequency range to be published in the literature. Using these observations, we are able to constrain the coronal magnetic field strength and electron number density of one of the targets to |$1 \lesssim B \lesssim 90\, \mathrm{G}$| and 4 ≲ log (Ne) ≲ 10, respectively. We do not detect the flaring emission observed at higher frequencies, to a limit of a few millijansky. These results show that some UCDs can produce low-frequency radio emission and highlight the need for simultaneous multiwavelength radio observations to tightly constrain the coronal and magnetospheric properties of these stars. [ABSTRACT FROM AUTHOR]

Published
2019
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33. GRB 110715A: the peculiar multiwavelength evolution of the first afterglow detected by ALMA

Author

Sánchez-Ramírez, R., primary, Hancock, P. J., additional, Jóhannesson, G., additional, Murphy, Tara, additional, de Ugarte Postigo, A., additional, Gorosabel, J., additional, Kann, D. A., additional, Krühler, T., additional, Oates, S. R., additional, Japelj, J., additional, Thöne, C. C., additional, Lundgren, A., additional, Perley, D. A., additional, Malesani, D., additional, de Gregorio Monsalvo, I., additional, Castro-Tirado, A. J., additional, D'Elia, V., additional, Fynbo, J. P. U., additional, Garcia-Appadoo, D., additional, Goldoni, P., additional, Greiner, J., additional, Hu, Y.-D., additional, Jelínek, M., additional, Jeong, S., additional, Kamble, A., additional, Klose, S., additional, Kuin, N. P. M., additional, Llorente, A., additional, Martín, S., additional, Nicuesa Guelbenzu, A., additional, Rossi, A., additional, Schady, P., additional, Sparre, M., additional, Sudilovsky, V., additional, Tello, J. C., additional, Updike, A., additional, Wiersema, K., additional, and Zhang, B.-B., additional

Published
2016
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34. Time-domain and spectral properties of pulsars at 154 MHz

Author

Bell, M. E., primary, Murphy, Tara, additional, Johnston, S., additional, Kaplan, D. L., additional, Croft, S., additional, Hancock, P., additional, Callingham, J. R., additional, Zic, A., additional, Dobie, D., additional, Swiggum, J. K., additional, Rowlinson, A., additional, Hurley-Walker, N., additional, Offringa, A. R., 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, Hazelton, B. J., additional, Johnston-Hollitt, M., 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
2016
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35. A pilot ASKAP survey of radio transient events in the region around the intermittent pulsar PSR J1107−5907

Author

Hobbs, G., primary, Heywood, I., additional, Bell, M. E., additional, Kerr, M., additional, Rowlinson, A., additional, Johnston, S., additional, Shannon, R. M., additional, Voronkov, M. A., additional, Ward, C., additional, Banyer, J., additional, Hancock, P. J., additional, Murphy, Tara, additional, Allison, J. R., additional, Amy, S. W., additional, Ball, L., additional, Bannister,  K., additional, Bock, D. C.-J., additional, Brodrick, D., additional, Brothers, M., additional, Brown, A. J., additional, Bunton, J. D., additional, Chapman, J., additional, Chippendale, A. P., additional, Chung, Y., additional, DeBoer, D., additional, Diamond, P., additional, Edwards, P. G., additional, Ekers, R., additional, Ferris, R. H., additional, Forsyth, R., additional, Gough, R., additional, Grancea, A., additional, Gupta, N., additional, Harvey-Smith, L., additional, Hay, S., additional, Hayman, D. B., additional, Hotan, A. W., additional, Hoyle, S., additional, Humphreys, B., additional, Indermuehle, B., additional, Jacka, C. E., additional, Jackson, C. A., additional, Jackson, S., additional, Jeganathan, K., additional, Joseph, J, additional, Kendall, R., additional, Kiraly, D., additional, Koribalski, B., additional, Leach, M., additional, Lenc, E., additional, MacLeod, A., additional, Mader, S., additional, Marquarding, M., additional, Marvil, J., additional, McClure-Griffiths, N., additional, McConnell, D., additional, Mirtschin, P., additional, Neuhold, S., additional, Ng, A., additional, Norris, R. P., additional, O'Sullivan, J., additional, Pearce, S., additional, Phillips, C. J., additional, Popping, A., additional, Qiao, R. Y., additional, Reynolds, J. E., additional, Roberts, P., additional, Sault, R. J., additional, Schinckel, A. E. T., additional, Serra, P., additional, Shaw, R., additional, Shimwell, T. W., additional, Storey, M., additional, Sweetnam, A. W., additional, Tzioumis, A., additional, Westmeier, T., additional, Whiting, M., additional, and Wilson, C. D., additional

Published
2016
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36. 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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38. GRB 110715A: the peculiar multiwavelength evolution of the first afterglow detected by ALMA.

Author

Sánchez-Ramírez, R., Hancock, P. J., Jóhannesson, G., Murphy, Tara, de Ugarte Postigo, A., Gorosabel, J., Kann, D. A., Krühler, T., Oates, S. R., Japelj, J., Thöne, C. C., Lundgren, A., Perley, D. A., Malesani, D., de Gregorio Monsalvo, I., Castro-Tirado, A. J., D'Elia, V., Fynbo, J. P. U., Garcia-Appadoo, D., and Goldoni, P.

Subjects
WAVELENGTHS, NEAR infrared spectroscopy, X-ray astronomy, RADIO frequency, IONIZATION (Atomic physics)
Abstract

We present the extensive follow-up campaign on the afterglowof GRB 110715A at 17 different wavelengths, from X-ray to radio bands, starting 81 s after the burst and extending up to 74 d later. We performed for the first time aGRBafterglowobservationwith theALMAobservatory. We find that the afterglow of GRB 110715A is very bright at optical and radio wavelengths. We use the optical and near-infrared spectroscopy to provide further information about the progenitor's environment and its host galaxy. The spectrum shows weak absorption features at a redshift z = 0.8225, which reveal a host-galaxy environment with low ionization, column density, and dynamical activity. Late deep imaging shows a very faint galaxy, consistent with the spectroscopic results. The broad-band afterglow emission is modelled with synchrotron radiation using a numerical algorithm and we determine the best-fitting parameters using Bayesian inference in order to constrain the physical parameters of the jet and the medium in which the relativistic shock propagates. We fitted our data with a variety of models, including different density profiles and energy injections. Although the general behaviour can be roughly described by thesemodels, none of them are able to fully explain all data points simultaneously. GRB 110715A shows the complexity of reproducing extensive multiwavelength broad-band afterglow observations, and the need of good sampling in wavelength and time and more complex models to accurately constrain the physics of GRB afterglows. [ABSTRACT FROM AUTHOR]

Published
2017
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41. Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array.

Author

Tjing Loi, Shyeh, Murphy, Tara, Bell, Martin E., Kaplan, David L., Lenc, Emil, Offringa, Andr'e R., Hurley-Walker, Natasha, 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., and Kasper, J. C.

Subjects
*IONOSPHERE, *TIME-domain analysis, *ASTROPHYSICS, *RADIO wave diffraction, *ASTRONOMICAL refraction, *RADIO sources (Astronomy)
Abstract

Refraction and diffraction of incoming radio waves by the ionosphere induce time variability in the angular positions, peak amplitudes and shapes of radio sources, potentially complicating the automated cross-matching and identification of transient and variable radio sources. In this work, we empirically assess the effects of the ionosphere on data taken by the Murchison Widefield Array (MWA) radio telescope. We directly examine 51 h of data observed over 10 nights under quiet geomagnetic conditions (global storm index Kp < 2), analysing the behaviour of short-time-scale angular position and peak flux density variations of around ten thousand unresolved sources. We find that while much of the variation in angular position can be attributed to ionospheric refraction, the characteristic displacements (10-20 arcsec) at 154 MHz are small enough that search radii of 1-2 arcmin should be sufficient for crossmatching under typical conditions. By examining bulk trends in amplitude variability, we place upper limits on the modulation index associated with ionospheric scintillation of 1-3 per cent for the various nights. For sources fainter than ~1 Jy, this variation is below the image noise at typical MWA sensitivities. Our results demonstrate that the ionosphere is not a significant impediment to the goals of time-domain science with the MWA at 154 MHz. [ABSTRACT FROM AUTHOR]

Published
2015
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44. The Australia Telescope 20 GHz (AT20G) Survey: analysis of the extragalactic source sample

Author

Massardi, Marcella, primary, Ekers, Ronald D., additional, Murphy, Tara, additional, Mahony, Elizabeth, additional, Hancock, Paul J., additional, Chhetri, Rajan, additional, De Zotti, Gianfranco, additional, Sadler, Elaine M., additional, Burke-Spolaor, Sarah, additional, Calabretta, Mark, additional, Edwards, Philip G., additional, Ekers, Jennifer A., additional, Jackson, Carole A., additional, Kesteven, Michael J., additional, Newton-McGee, Katherine, additional, Phillips, Chris, additional, Ricci, Roberto, additional, Roberts, Paul, additional, Sault, Robert J., additional, Staveley-Smith, Lister, additional, Subrahmanyan, Ravi, additional, Walker, Mark A., additional, and Wilson, Warwick E., additional

Published
2011
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46. The Australia Telescope 20 GHz Survey: the source catalogue

Author

Murphy, Tara, primary, Sadler, Elaine M., additional, Ekers, Ronald D., additional, Massardi, Marcella, additional, Hancock, Paul J., additional, Mahony, Elizabeth, additional, Ricci, Roberto, additional, Burke-Spolaor, Sarah, additional, Calabretta, Mark, additional, Chhetri, Rajan, additional, De Zotti, Gianfranco, additional, Edwards, Philip G., additional, Ekers, Jennifer A., additional, Jackson, Carole A., additional, Kesteven, Michael J., additional, Lindley, Emma, additional, Newton-McGee, Katherine, additional, Phillips, Chris, additional, Roberts, Paul, additional, Sault, Robert J., additional, Staveley-Smith, Lister, additional, Subrahmanyan, Ravi, additional, Walker, Mark A., additional, and Wilson, Warwick E., additional

Published
2010
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47. The Australia Telescope 20-GHz (AT20G) Survey: the Bright Source Sample

Author

Massardi, Marcella, primary, Ekers, Ronald D., additional, Murphy, Tara, additional, Ricci, Roberto, additional, Sadler, Elaine M., additional, Burke, Sarah, additional, De Zotti, Gianfranco, additional, Edwards, Philip G., additional, Hancock, Paul J., additional, Jackson, Carole A., additional, Kesteven, Michael J., additional, Mahony, Elizabeth, additional, Phillips, Christopher J., additional, Staveley-Smith, Lister, additional, Subrahmanyan, Ravi, additional, Walker, Mark A., additional, and Wilson, Warwick E., additional

Published
2008
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49. 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, André R., 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., and Kratzenberg, E.

Subjects
*LUMINOSITY, *ASTRONOMICAL observations, *EXTRASOLAR planets, *RADIO frequency, *CIRCULAR polarization
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 3s upper limits in the range 15.2-112.5 mJy on this emission. We also searched for circularly polarized emission and made no detections, obtaining 3s 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 × 1014 and 1.4 × 1017 W if the emission is assumed to be 100 percent circularly polarized. These are the first results from a larger program to systematically search for exoplanetary emission with the MWA. [ABSTRACT FROM AUTHOR]

Published
2015
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50. Radio sources in the 2dF Galaxy Redshift Survey - II. Local radio luminosity functions for AGN and star-forming galaxies at 1.4 GHz

Author

Sadler, Elaine M., primary, Jackson, Carole A., additional, Cannon, Russell D., additional, McIntyre, Vincent J., additional, Murphy, Tara, additional, Bland-Hawthorn, Joss, additional, Bridges, Terry, additional, Cole, Shaun, additional, Colless, Matthew, additional, Collins, Chris, additional, Couch, Warrick, additional, Dalton, Gavin, additional, De Propris, Roberto, additional, Driver, Simon P., additional, Efstathiou, George, additional, Ellis, Richard S., additional, Frenk, Carlos S., additional, Glazebrook, Karl, additional, Lahav, Ofer, additional, Lewis, Ian, additional, Lumsden, Stuart, additional, Maddox, Steve, additional, Madgwick, Darren, additional, Norberg, Peder, additional, Peacock, John A., additional, Peterson, Bruce A., additional, Sutherland, Will, additional, and Taylor, Keith, additional

Published
2002
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