ORCID Profile
0000-0002-8195-7562
Current Organisations
Curtin University
,
University of Leeds
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Astronomical and Space Sciences | Astronomy And Astrophysics | Astronomical and Space Instrumentation | Communications Technologies | Cosmology and Extragalactic Astronomy | Broadband Network Technology | Space and Solar Physics | Microwave And Millimetrewave Technology | Geology | Optical Physics | Antenna Technology | Digital Systems | Navigation And Position Fixing | Inorganic Geochemistry | Instruments And Techniques | Igneous and Metamorphic Petrology | Geodynamics | Information Storage, Retrieval And Management | Software Engineering | Photonics, Optoelectronics and Optical Communications | Lasers and Quantum Electronics | High Energy Astrophysics; Cosmic Rays | General Relativity and Gravitational Waves | Galactic Astronomy | Optical Fibre Communications | Particle Physics
ANZSRC Socio-Economic Objective (SEO)
Physical sciences | Expanding Knowledge in the Physical Sciences | Environmentally Sustainable Construction not elsewhere classified | Scientific instrumentation | Information Processing Services (incl. Data Entry and Capture) | Scientific Instruments | Application packages | Communication Networks and Services not elsewhere classified | Solar-photoelectric | Computer Hardware and Electronic Equipment not elsewhere classified | Industrial instrumentation | Integrated circuits and devices | Expanding Knowledge in Technology | Information services not elsewhere classified | Expanding Knowledge in the Earth Sciences | Expanding Knowledge in Engineering | Precious (Noble) Metal Ore Exploration |
Related Links
Publications
Some Intrinsic Properties of Parsec-scale Radio Jets
Publisher: Cambridge University Press (CUP)
Date: 1996
DOI: 10.1017/S1323358000020622
Abstract: A simple model for estimating the intrinsic flow direction and speed in the parsec-scale jets associated with extragalactic radio sources is presented. In this model, radio source brightness asymmetries are attributed to the apparent lification caused when a relativistic jet of radiating material is somewhat aligned with the observers line of sight. The knots of emission commonly seen in parsec-scale radio jets are interpreted as shocks in the relativistic fluid.
The VSOP 5 GHz AGN Survey I. Compilation and Observations
Publisher: Oxford University Press (OUP)
Date: 12-2000
Calibration database for the Murchison Widefield Array All-Sky Virtual Observatory
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.17
Abstract: We present a calibration component for the Murchison Widefield Array All-Sky Virtual Observatory (MWA ASVO) utilising a newly developed PostgreSQL database of calibration solutions. Since its inauguration in 2013, the MWA has recorded over 34 petabytes of data archived at the Pawsey Supercomputing Centre. According to the MWA Data Access policy, data become publicly available 18 months after collection. Therefore, most of the archival data are now available to the public. Access to public data was provided in 2017 via the MWA ASVO interface, which allowed researchers worldwide to download MWA uncalibrated data in standard radio astronomy data formats (CASA measurement sets or UV FITS files). The addition of the MWA ASVO calibration feature opens a new, powerful avenue for researchers without a detailed knowledge of the MWA telescope and data processing to download calibrated visibility data and create images using standard radio astronomy software packages. In order to populate the database with calibration solutions from the last 6 yr we developed fully automated pipelines. A near-real-time pipeline has been used to process new calibration observations as soon as they are collected and upload calibration solutions to the database, which enables monitoring of the interferometric performance of the telescope. Based on this database, we present an analysis of the stability of the MWA calibration solutions over long time intervals.
A 5 GH[CLC]z[/CLC] Southern Hemisphere VLBI Survey of Compact Radio Sources. II.
Publisher: American Astronomical Society
Date: 04-1998
DOI: 10.1086/300284
Absorption variability as a probe of the multiphase interstellar media surrounding active galaxies
Publisher: Oxford University Press (OUP)
Date: 16-05-2016
Pearson-Readhead Survey from Space
Publisher: Cambridge University Press (CUP)
Date: 2001
DOI: 10.1017/S0074180900220688
Abstract: We are using the VSOP space VLBI mission to observe a complete s le of Pearson-Readhead survey sources at 4.8 GHz to determine core brightness temperatures and pc-scale jet properties. To date we have imaged 27 of the 31 objects in our s le. Our preliminary results show that the majority of objects contain strong core components that remain unresolved on baselines of 30,000 km. The brightness temperatures of several cores significantly exceed 10 12 K, which is indicative of highly relativistically beamed emission. We also find that core brightness temperature is correlated with intraday variability in compact AGNs.
KM3NeT front-end and readout electronics system: hardware, firmware, and software
Publisher: SPIE-Intl Soc Optical Eng
Date: 23-12-2019
Identification of a new low-redshift GHz-peaked spectrum radio source and implications for the GHz-peaked spectrum class
Publisher: Oxford University Press (OUP)
Date: 21-11-2003
The Science and Technology of the Square Kilometre Array
Publisher: IOP Publishing
Date: 29-10-2014
The Parsec-Scale Structure and Evolution of PKS 0521−365
Publisher: American Astronomical Society
Date: 08-2002
DOI: 10.1086/341391
Wide-field VLBA observations of theChandradeep field South
Publisher: EDP Sciences
Date: 23-12-2010
TheChandra X‐Ray ObservatoryResolves the X‐Ray Morphology and Spectra of a Jet in PKS 0637−752
Publisher: American Astronomical Society
Date: 20-10-2000
DOI: 10.1086/317049
Pictor A (PKS 0518-45): From Nucleus to Lobes
Publisher: American Astronomical Society
Date: 08-1999
DOI: 10.1086/313243
THE EFFECT OF INTERPLANETARY SCINTILLATION ON EPOCH OF REIONIZATION POWER SPECTRA
Publisher: American Astronomical Society
Date: 05-2015
The first resolved imaging of milliarcsecond-scale jets in Circinus X-1
Publisher: Oxford University Press (OUP)
Date: 22-11-2011
Circadian Rhythms Confer a Higher Level of Fitness to Arabidopsis Plants
Publisher: Oxford University Press (OUP)
Date: 06-2002
DOI: 10.1104/PP.004374
Abstract: Circadian rhythms have been demonstrated in organisms across the taxonomic spectrum. In view of their widespread occurrence, the adaptive significance of these rhythms is of interest. We have previously shown that constitutive expression of theCCA1 (CIRCADIAN CLOCK ASSOCIATED 1) gene in Arabidopsis plants (CCA1-ox) results in loss of circadian rhythmicity. Here, we demonstrate that these CCA1-ox plants retain the ability to respond to diurnal changes in light. Thus, transcript levels of several circadian-regulated genes, as well as CCA1 itself and the closely related LHY, oscillate robustly if CCA1-ox plants are grown under diurnal conditions. However, in contrast with wild-type plants in which transcript levels change in anticipation of the dark/light transitions, the CCA1-ox plants have lost the ability to anticipate this daily change in their environment. We have used CCA1-ox lines to examine the effects of loss of circadian regulation on the fitness of an organism. CCA1-ox plants flowered later, especially under long-day conditions, and were less viable under very short-day conditions than their wild-type counterparts. In addition, we demonstrate that two other circadian rhythm mutants, LHY-ox and elf3, have low-viability phenotypes. Our findings demonstrate the adaptive advantage of circadian rhythms in Arabidopsis.
Limits on radio emission from meteors using the MWA
Publisher: Oxford University Press (OUP)
Date: 14-04-2018
DOI: 10.1093/MNRAS/STY930
The AuScope geodetic VLBI array
Publisher: Springer Science and Business Media LLC
Date: 14-03-2013
Constraining the 21 cm brightness temperature of the IGM at z = 6.6 around LAEs with the murchison widefield array
Publisher: Oxford University Press (OUP)
Date: 03-08-2021
Abstract: The locations of Ly α-emitting galaxies (LAEs) at the end of the Epoch of Reionization (EoR) are expected to correlate with regions of ionized hydrogen, traced by the redshifted 21 cm hyperfine line. Mapping the neutral hydrogen around regions with detected and localized LAEs offers an avenue to constrain the brightness temperature of the Universe within the EoR by providing an expectation for the spatial distribution of the gas, thereby providing prior information unavailable to power spectrum measurements. We use a test set of 12 h of observations from the Murchison Widefield Array (MWA) in extended array configuration, to constrain the neutral hydrogen signature of 58 LAEs, detected with the Subaru Hypersuprime Cam in the Silverrush survey, centred on z = 6.58. We assume that detectable emitters reside in the centre of ionized H ii bubbles during the end of reionization, and predict the redshifted neutral hydrogen signal corresponding to the remaining neutral regions using a set of different ionized bubble radii. A pre-whitening matched filter detector is introduced to assess detectability. We demonstrate the ability to detect, or place limits upon, the litude of brightness temperature fluctuations, and the characteristic H ii bubble size. With our limited data, we constrain the brightness temperature of neutral hydrogen to ΔTB & mK (& mK) at 95 per cent (99 per cent) confidence for lognormally distributed bubbles of radii, RB = 15 ± 2h−1 cMpc.
Nitric Oxide and Other Molecules: Molecular Modeling and Low-frequency Exploration Using the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 12-2020
Paving the way to simultaneous multi-wavelength astronomy
Publisher: Elsevier BV
Date: 11-2017
Very long baseline interferometry detection of an Infrared-Faint Radio Source
Publisher: Oxford University Press (OUP)
Date: 16-06-2007
The multifrequency parsec-scale structure of PKS 2254−367 (IC 1459): a luminosity-dependent break in morphology for the precursors of radio galaxies?
Publisher: Oxford University Press (OUP)
Date: 02-02-2015
The FR II Broad‐Line Seyfert 1 Galaxy: PKS J1037−2705
Publisher: American Astronomical Society
Date: 11-2008
DOI: 10.1086/591650
Constraining the radio properties of the z = 6.44 QSO VIK J2318−3113
Publisher: EDP Sciences
Date: 07-2022
DOI: 10.1051/0004-6361/202142733
Abstract: The recent detection of the quasi-stellar object (QSO) VIKING J231818.3−311346 (hereafter VIK J2318−3113) at redshift z = 6.44 in the Rapid ASKAP Continuum Survey (RACS) uncovered its radio-loud nature, making it one of the most distant known to date in this class. By using data from several radio surveys of the Galaxy And Mass Assembly 23 h field and from a dedicated follow-up, we were able to constrain the radio spectrum of VIK J2318−3113 in the observed range ∼0.1–10 GHz. At high frequencies (0.888–5.5 GHz in the observed frame) the QSO presents a steep spectrum ( α r = 1.24, with S ν ∝ ν − α r ), while at lower frequencies (0.4–0.888 GHz in the observed frame) it is nearly flat. The overall spectrum can be modelled by either a curved function with a rest-frame turnover around 5 GHz, or with a smoothly varying double power law that is flat below a rest-frame break frequency of about 20 GHz and above which it significantly steepens. Based on the model adopted, we estimated that the radio jets of VIK J2318−3113 must be a few hundred years old in the case of a turnover, or less than a few × 10 4 years in the case of a break in the spectrum. Having multiple observations at two frequencies (888 MHz and 5.5 GHz), we further investigated the radio variability previously reported for this source. We found that the marginally significant flux density variations are consistent with the expectations from refractive interstellar scintillation, even though relativistic effects related to the orientation of the source may still play a non-negligible role. Further radio and X-ray observations are required to conclusively discern the nature of this variation.
High-energy sources at low radio frequency: the Murchison Widefield Array view ofFermiblazars
Publisher: EDP Sciences
Date: 04-2016
Interplanetary scintillation studies with the Murchison Widefield Array – II. Properties of sub-arcsecond compact sources at low radio frequencies
Publisher: Oxford University Press (OUP)
Date: 06-11-2017
VLBI imaging throughout the primary beam using accurate UV shifting
Publisher: EDP Sciences
Date: 12-01-2011
New geodetic infrastructure for Australia
Publisher: Informa UK Limited
Date: 12-2008
e-VLBI observations of Circinus X-1: monitoring of the quiescent and flaring radio emission on au scales
Publisher: Oxford University Press (OUP)
Date: 17-05-2011
shygrl1 Is a Mutant Affected in Multiple Aspects of Photomorphogenesis
Publisher: Oxford University Press (OUP)
Date: 06-2001
DOI: 10.1104/PP.126.2.587
Abstract: We have used a counter-selection strategy based on aberrant phytochrome regulation of an Lhcb gene to isolate an Arabidopsis mutant designated shygrl1(shg1). shg1 seedlings have reduced phytochrome-mediated induction of the Lhcb gene family, but normal phytochrome-mediated induction of several other genes, including the rbcS1a gene. Additional phenotypes observed in shg1 plants include reduced chlorophyll in leaves and additional photomorphogenic abnormalities when the seedlings are grown on medium containing sucrose. Mutations in the TATA-proximal region of the Lhcb1*3 promoter that are known to be important for phytochrome regulation affected reporter gene expression in a manner similar to the shg1 mutation. Our results are consistent with the possibility that the mutation either leads to defective chloroplast development or to aberrant phytochrome regulation. They also add to the evidence of complex interactions between light- and sucrose-regulated pathways.
Observations of Low-frequency Radio Emission from Millisecond Pulsars and Multipath Propagation in the Interstellar Medium
Publisher: American Astronomical Society
Date: 23-08-2018
Simulations of orbital debris clouds due to breakup events and their characterisation using the Murchison Widefield Array radio telescope
Publisher: Springer Science and Business Media LLC
Date: 15-11-2021
A Search of TESS Full-frame Images for a Simultaneous Optical Counterpart to FRB 181228
Publisher: American Astronomical Society
Date: 09-08-2019
A Machine Learning Classifier for Fast Radio Burst Detection at the VLBA
Publisher: IOP Publishing
Date: 22-06-2016
The Pearson‐Readhead Survey of Compact Extragalactic Radio Sources from Space. I. The Images
Publisher: American Astronomical Society
Date: 20-06-2001
DOI: 10.1086/321429
A Search for Fast Radio Bursts at Low Frequencies with Murchison Widefield Array High Time Resolution Imaging
Publisher: American Astronomical Society
Date: 10-12-2015
Establishing the Capabilities of the Murchison Widefield Array as a Passive Radar for the Surveillance of Space
Publisher: MDPI AG
Date: 12-10-2017
DOI: 10.3390/RS14112571
Abstract: This paper describes the use of the Murchison Widefield Array, a low-frequency radio telescope at a radio-quiet Western Australian site, as a radar receiver forming part of a continent-spanning multistatic radar network for the surveillance of space. This paper details the system geometry employed, the orbit-specific radar signal processing, and the orbit determination algorithms necessary to ensure resident space objects are detected, tracked, and propagated. Finally, the paper includes the results processed after a short collection c aign utilising several FM radio transmitters across the country, up to a maximum baseline distance of over 2500 km. The results demonstrate the Murchison Widefield Array is able to provide widefield and persistent coverage of objects in low Earth orbit.
ATCA Monitoring Observations of 202 Compact Radio Sources in Support of the VSOP AGN Survey
Publisher: Oxford University Press (OUP)
Date: 25-04-2003
First limits on the 21 cm power spectrum during the Epoch of X-ray heating
Publisher: Oxford University Press (OUP)
Date: 19-05-2016
Performing a stellar autopsy using the radio-bright remnant of SN 1996cr
Publisher: Oxford University Press (OUP)
Date: 21-03-2013
DOI: 10.1093/MNRAS/STT340
The impact of tandem redundant/sky-based calibration in MWA Phase II data analysis
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.37
Abstract: Precise instrumental calibration is of crucial importance to 21-cm cosmology experiments. The Murchison Widefield Array’s (MWA) Phase II compact configuration offers us opportunities for both redundant calibration and sky-based calibration algorithms using the two in tandem is a potential approach to mitigate calibration errors caused by inaccurate sky models. The MWA Epoch of Reionization (EoR) experiment targets three patches of the sky (dubbed EoR0, EoR1, and EoR2) with deep observations. Previous work in Li et al. (2018) and (2019) studied the effect of tandem calibration on the EoR0 field and found that it yielded no significant improvement in the power spectrum (PS) over sky-based calibration alone. In this work, we apply similar techniques to the EoR1 field and find a distinct result: the improvements in the PS from tandem calibration are significant. To understand this result, we analyse both the calibration solutions themselves and the effects on the PS over three nights of EoR1 observations. We conclude that the presence of the bright radio galaxy Fornax A in EoR1 degrades the performance of sky-based calibration, which in turn enables redundant calibration to have a larger impact. These results suggest that redundant calibration can indeed mitigate some level of model incompleteness error.
Multiwavelength Monitoring of the Unusual Ultraluminous Supernova SN 1978K in NGC 1313 and the Search for an Associated Gamma‐Ray Burst
Publisher: American Astronomical Society
Date: 10-11-2007
DOI: 10.1086/521698
Search for non-standard neutrino interactions with 10 years of ANTARES data
Publisher: Springer Science and Business Media LLC
Date: 07-2022
Abstract: Non-standard interactions of neutrinos arising in many theories beyond the Standard Model can significantly alter matter effects in atmospheric neutrino propagation through the Earth. In this paper, a search for deviations from the prediction of the standard 3-flavour atmospheric neutrino oscillations using the data taken by the ANTARES neutrino telescope is presented. Ten years of atmospheric neutrino data collected from 2007 to 2016, with reconstructed energies in the range from ∼16 GeV to 100 GeV, have been analysed. A log-likelihood ratio test of the dimensionless coefficients ε μτ and ε ττ − ε μμ does not provide clear evidence of deviations from standard interactions. For normal neutrino mass ordering, the combined fit of both coefficients yields a value 1.7 σ away from the null result. However, the 68% and 95% confidence level intervals for ε μτ and ε ττ − ε μμ , respectively, contain the null value. Best fit values, one standard deviation errors and bounds at the 90% confidence level for these coefficients are given for both normal and inverted mass orderings. The constraint on ε μτ is among the most stringent to date and it further restrains the strength of possible non-standard interactions in the μ − τ sector.
A Serendipitous MWA Search for Narrowband Signals from 'Oumuamua
Publisher: American Astronomical Society
Date: 09-04-2018
A sample of southern Compact Steep Spectrum radio sources: The VLBI observations
Publisher: EDP Sciences
Date: 09-2002
LIMITS ON THE EVENT RATES OF FAST RADIO TRANSIENTS FROM THE V-FASTR EXPERIMENT
Publisher: American Astronomical Society
Date: 26-06-2012
FIRST SEASON MWA EOR POWER SPECTRUM RESULTS AT REDSHIFT 7
Publisher: American Astronomical Society
Date: 09-12-2016
Science at Very High Angular Resolution with the Square Kilometre Array
Publisher: Cambridge University Press (CUP)
Date: 2012
DOI: 10.1071/AS11050
Abstract: Preliminary specifications for the Square Kilometre Array (SKA) call for 25% of the total collecting area of the dish array to be located at distances greater than 180 km from the core, with a maximum baseline of at least 3000 km. The array will provide angular resolution θ ≲ 40–2 mas at 0.5–10 GHz with image sensitivity reaching ≲50 nJy beam −1 in an 8-hour integration with 500-MHz bandwidth. Given these specifications, the high-angular-resolution component of the SKA will be capable of detecting brightness temperatures ≲200K with milliarcsecond-scale angular resolution. The aim of this article is to bring together in one place a discussion of the broad range of new and important high-angular-resolution science that will be enabled by the SKA, and in doing so, address the merits of long baselines as part of the SKA. We highlight the fact that high angular resolution requiring baselines greater than 1000 km provides a rich science case with projects from many areas of astrophysics, including important contributions to key SKA science.
Independent Discovery of a Nulling Pulsar with Unusual Subpulse Drifting Properties with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 07-2022
Abstract: We report the independent discovery of PSR J0026-1955 with the Murchison Widefield Array (MWA) in the ongoing Southern-sky MWA Rapid Two-metre pulsar survey. J0026-1955 has a period of ∼1.306 s, a dispersion measure of ∼20.869 pc cm −3 , and a nulling fraction of ∼77%. This pulsar highlights the advantages of the survey's long dwell times (∼80 minutes), which, when fully searched, will be sensitive to the expected population of similarly bright, intermittent pulsars with long nulls. A single-pulse analysis in the MWA's 140–170 MHz band also reveals a complex subpulse drifting behavior, including both rapid changes of the drift rate characteristic of mode switching pulsars, as well as a slow, consistent evolution of the drift rate within modes. In some longer drift sequences, interruptions in the otherwise smooth drift rate evolution occur preferentially at a particular phase, typically lasting a few pulses. These properties make this pulsar an ideal test bed for prevailing models of drifting behavior such as the carousel model.
An Opportunistic Search for Extraterrestrial Intelligence (SETI) with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 11-08-2016
A VOEvent-based automatic trigger system for the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2019.40
Abstract: The Murchison Widefield Array (MWA) is an electronically steered low-frequency ( MHz) radio interferometer, with a ‘slew’ time less than 8 s. Low-frequency (∼100 MHz) radio telescopes are ideally suited for rapid response follow-up of transients due to their large field of view, the inverted spectrum of coherent emission, and the fact that the dispersion delay between a 1 GHz and 100 MHz pulse is on the order of 1–10 min for dispersion measures of 100–2000 pc/cm 3 . The MWA has previously been used to provide fast follow-up for transient events including gamma-ray bursts (GRBs), fast radio bursts (FRBs), and gravitational waves, using systems that respond to gamma-ray coordinates network packet-based notifications. We describe a system for automatically triggering MWA observations of such events, based on Virtual Observatory Event standard triggers, which is more flexible, capable, and accurate than previous systems. The system can respond to external multi-messenger triggers, which makes it well-suited to searching for prompt coherent radio emission from GRBs, the study of FRBs and gravitational waves, single pulse studies of pulsars, and rapid follow-up of high-energy superflares from flare stars. The new triggering system has the capability to trigger observations in both the regular correlator mode (limited to ≥0.5 s integrations) and using the Voltage Capture System (VCS, 0.1 ms integration) of the MWA and represents a new mode of operation for the MWA. The upgraded standard correlator triggering capability has been in use since MWA observing semester 2018B (July–Dec 2018), and the VCS and buffered mode triggers will become available for observing in a future semester.
Science with the Murchison Widefield Array: Phase I results and Phase II opportunities
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2019.41
Abstract: The Murchison Widefield Array (MWA) is an open access telescope dedicated to studying the low-frequency (80–300 MHz) southern sky. Since beginning operations in mid-2013, the MWA has opened a new observational window in the southern hemisphere enabling many science areas. The driving science objectives of the original design were to observe 21 cm radiation from the Epoch of Reionisation (EoR), explore the radio time domain, perform Galactic and extragalactic surveys, and monitor solar, heliospheric, and ionospheric phenomena. All together $60+$ programs recorded 20 000 h producing 146 papers to date. In 2016, the telescope underwent a major upgrade resulting in alternating compact and extended configurations. Other upgrades, including digital back-ends and a rapid-response triggering system, have been developed since the original array was commissioned. In this paper, we review the major results from the prior operation of the MWA and then discuss the new science paths enabled by the improved capabilities. We group these science opportunities by the four original science themes but also include ideas for directions outside these categories.
The Pearson‐Readhead Survey of Compact Extragalactic Radio Sources from Space. II. Analysis of Source Properties
Publisher: American Astronomical Society
Date: 20-06-2001
DOI: 10.1086/321430
The SKA particle array prototype: The first particle detector at the Murchison Radio-astronomy Observatory
Publisher: Elsevier BV
Date: 09-2020
A Deep, High‐Resolution Survey of the Low‐Frequency Radio Sky
Publisher: American Astronomical Society
Date: 20-01-2008
DOI: 10.1086/524295
Proper Motions in the Knotty, Bipolar Jet in Henize 2-90
Publisher: American Astronomical Society
Date: 10-07-2002
DOI: 10.1086/341969
The VSOP 5 GHz Active Galactic Nucleus Survey. V. Imaging Results for the Remaining 140 Sources
Publisher: American Astronomical Society
Date: 04-2008
DOI: 10.1086/525025
A low-frequency blind survey of the low Earth orbit environment using non-coherent passive radar with the Murchison widefield array
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.40
Abstract: We have extended our previous work to use the Murchison widefield array (MWA) as a non-coherent passive radar system in the FM frequency band, using terrestrial FM transmitters to illuminate objects in low Earth orbit (LEO) and the MWA as the sensitive receiving element for the radar return. We have implemented a blind detection algorithm that searches for these reflected signals in difference images constructed using standard interferometric imaging techniques. From a large-scale survey using 20 h of archived MWA observations, we detect 74 unique objects over multiple passes, demonstrating the MWA to be a valuable addition to the global Space Domain Awareness network. We detected objects with ranges up to 977 km and as small as $0.03$ ${\\rm m}^2$ radar cross section. We found that 30 objects were either non-operational satellites or upper-stage rocket body debris. Additionally, we also detected FM reflections from Geminid meteors and aircraft flying over the MWA. Most of the detections of objects in LEO were found to lie within the parameter space predicted by previous feasibility studies, verifying the performance of the MWA for this application. We have also used our survey to characterise these reflected signals from LEO objects as a source of radio frequency interference (RFI) that corrupts astronomical observations. This has allowed us to undertake an initial analysis of the impact of this RFI on the MWA and the future square kilometer array (SKA). As part of this analysis, we show that the standard MWA RFI flagging strategy misses most of this RFI and that this should be a careful consideration for the SKA.
VLBI observations of Southern Hemisphere gamma-ray loud and quiet AGN
Publisher: AIP
Date: 1997
DOI: 10.1063/1.54055
Grain‐scale dependency of metamorphic reaction on crystal plastic strain
Publisher: Wiley
Date: 19-03-2019
DOI: 10.1111/JMG.12473
Abstract: The Breaksea Orthogneiss in Fiordland, New Zealand preserves water‐poor intermediate and mafic igneous rocks that were partially recrystallized to omphacite granulite and eclogite, respectively, at P ≈ 1.8 GP a and T ≈ 850°C. Metamorphic reaction consumed plagioclase and produced grossular‐rich garnet, jadeite‐rich omphacite, clinozoisite and kyanite. The extent of metamorphic reaction, identified by major and trace element composition and microstructural features, is patchy on the grain and outcrop scale. Domains of re‐equilibration coincide with areas that exhibit higher strain suggesting a causal link between crystal plastic strain and metamorphic reaction. Quantitative orientation analysis ( EBSD ) identifies gradual and stepped changes in crystal lattice orientations of igneous phenocrysts that are surrounded by homophase areas of neoblasts, characterized by high grain boundary to volume ratios and little to no internal lattice distortion. The narrow, peripheral compositional modification of less deformed garnet and omphacite phenocrysts reflects limited lattice diffusion in areas that lacked three‐dimensional networks of interconnected low‐angle boundaries. Low‐angle boundaries acted as elemental pathways (pipe diffusion) that enhanced in‐grain element diffusion. The scale of pipe diffusion is pronounced in garnet relatively to clinopyroxene. Strain‐induced mineral transformation largely controlled the extent of high‐ T metamorphic reaction under relatively fluid‐poor conditions.
LIMITS ON EINSTEIN’S EQUIVALENCE PRINCIPLE FROM THE FIRST LOCALIZED FAST RADIO BURST FRB 150418
Publisher: American Astronomical Society
Date: 23-03-2016
A Search for Extraterrestrial Intelligence (SETI) toward the Galactic Anticenter with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 22-03-2018
Prospects for the detection of fast radio bursts with the murchison widefield array
Publisher: American Astronomical Society
Date: 30-09-2013
Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 02-09-2015
Antenna array characterization via radio interferometry observation of astronomical sources
Publisher: IEEE
Date: 11-2014
A SETI survey of the Vela region using the Murchison Widefield Array: Orders of magnitude expansion in search space
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.27
Abstract: Following the results of our previous low-frequency searches for extraterrestrial intelligence (SETI) using the Murchison Widefield Array (MWA), directed towards the Galactic Centre and the Orion Molecular Cloud (Galactic Anticentre), we report a new large-scale survey towards the Vela region with the lowest upper limits thus far obtained with the MWA. Using the MWA in the frequency range 98–128 MHz over a 17-h period, a $400\\,\\textrm{deg}^{2}$ field centred on the Vela Supernova Remnant was observed with a frequency resolution of 10 kHz. Within this field, there are six known exoplanets. At the positions of these exoplanets, we searched for narrow-band signals consistent with radio transmissions from intelligent civilisations. No unknown signals were found with a 5 $\\sigma$ detection threshold. In total, across this work plus our two previous surveys, we have now examined 75 known exoplanets at low frequencies. In addition to the known exoplanets, we have included in our analysis the calculation of the Effective Isotropic Radiated Power (EIRP) upper limits towards over 10 million stellar sources in the Vela field with known distances from Gaia (assuming a 10-kHz transmission bandwidth). Using the methods of Wright, Kanodia, & Lubar (2018) to describe an eight-dimensional parameter space for SETI searches, our survey achieves the largest search fraction yet, two orders of magnitude higher than the previous highest (our MWA Galactic Anticentre survey), reaching a search fraction of $\\ \\sim2\\,{\\times}\\,10^{-16}$ . We also compare our results to previous SETI programs in the context of the $\\mbox{EIRP}_{\\textrm{min}}$ —Transmitter Rate plane. Our results clearly continue to demonstrate that SETI has a long way to go. But, encouragingly, the MWA SETI surveys also demonstrate that large-scale SETI surveys, in particular for telescopes with a large field-of-view, can be performed commensally with observations designed primarily for astrophysical purposes.
LOW-FREQUENCY OBSERVATIONS OF LINEARLY POLARIZED STRUCTURES IN THE INTERSTELLAR MEDIUM NEAR THE SOUTH GALACTIC POLE
Publisher: American Astronomical Society
Date: 10-10-2016
First Season MWA Phase II Epoch of Reionization Power Spectrum Results at Redshift 7
Publisher: American Astronomical Society
Date: 17-12-2019
The star-formation rate in the host of GRB 990712
Publisher: EDP Sciences
Date: 12-2001
TANAMI: Tracking Active Galactic Nuclei with Austral Milliarcsecond Interferometry
Publisher: EDP Sciences
Date: 02-2018
DOI: 10.1051/0004-6361/201731455
Abstract: Context. TANAMI is a multiwavelength program monitoring active galactic nuclei (AGN) south of − 30° declination including high-resolution very long baseline interferometry (VLBI) imaging, radio, optical/UV, X-ray, and γ -ray studies. We have previously published first-epoch8.4 GHz VLBI images of the parsec-scale structure of the initial s le. In this paper, we present images of 39 additional sources. The full s le comprises most of the radio- and γ -ray brightest AGN in the southern quarter of the sky, overlapping with the region from which high-energy ( 100 TeV) neutrino events have been found. Aims. We characterize the parsec-scale radio properties of the jets and compare them with the quasi-simultaneous Fermi /LAT γ -ray data. Furthermore, we study the jet properties of sources which are in positional coincidence with high-energy neutrino events compared to the full s le. We test the positional agreement of high-energy neutrino events with various AGN s les. Methods. TANAMI VLBI observations at 8.4 GHz are made with southern hemisphere radio telescopes located in Australia, Antarctica, Chile, New Zealand, and South Africa. Results. Our observations yield the first images of many jets below − 30° declination at milliarcsecond resolution. We find that γ -ray loud TANAMI sources tend to be more compact on parsec-scales and have higher core brightness temperatures than γ -ray faint jets, indicating higher Doppler factors. No significant structural difference is found between sources in positional coincidence with high-energy neutrino events and other TANAMI jets. The 22 γ -ray brightest AGN in the TANAMI sky show only a weak positional agreement with high-energy neutrinos demonstrating that the 100 TeV IceCube signal is not simply dominated by a small number of the γ -ray brightest blazars. Instead, a larger number of sources have to contribute to the signal with each in idual source having only a small Poisson probability for producing an event in multi-year integrations of current neutrino detectors.
The Murchison Widefield Array Commissioning Survey: A Low-Frequency Catalogue of 14 110 Compact Radio Sources over 6 100 Square Degrees
Publisher: Cambridge University Press (CUP)
Date: 2014
DOI: 10.1017/PASA.2014.40
Abstract: We present the results of an approximately 6 100 deg 2 104–196 MHz radio sky survey performed with the Murchison Widefield Array during instrument commissioning between 2012 September and 2012 December: the MWACS. The data were taken as meridian drift scans with two different 32-antenna sub-arrays that were available during the commissioning period. The survey covers approximately 20.5 h RA 8.5 h, − 58° Dec −14°over three frequency bands centred on 119, 150 and 180 MHz, with image resolutions of 6–3 arcmin. The catalogue has 3 arcmin angular resolution and a typical noise level of 40 mJy beam − 1 , with reduced sensitivity near the field boundaries and bright sources. We describe the data reduction strategy, based upon mosaicked snapshots, flux density calibration, and source-finding method. We present a catalogue of flux density and spectral index measurements for 14 110 sources, extracted from the mosaic, 1 247 of which are sub-components of complexes of sources.
Extragalactic Peaked-spectrum Radio Sources at Low Frequencies
Publisher: American Astronomical Society
Date: 17-02-2017
A digital-receiver for the MurchisonWidefield Array
Publisher: Springer Science and Business Media LLC
Date: 22-02-2015
Radio light curve of the galaxy possibly associated with FRB 150418
Publisher: Oxford University Press (OUP)
Date: 02-11-2016
e-VLBI observations of GHz-peaked spectrum radio sources in nearby galaxies from the AT20G survey
Publisher: Oxford University Press (OUP)
Date: 21-08-2009
Local partial melting of the lower crust triggered by hydration through melt-rock interaction: an example from Fiordland, New Zealand
Publisher: Wiley
Date: 18-11-2016
DOI: 10.1111/JMG.12229
ANTARES and IceCube Combined Search for Neutrino Point-like and Extended Sources in the Southern Sky
Publisher: American Astronomical Society
Date: 04-2020
SOURCE DETECTION IN INTERFEROMETRIC VISIBILITY DATA. I. FUNDAMENTAL ESTIMATION LIMITS
Publisher: American Astronomical Society
Date: 25-03-2011
A survey of spatially and temporally resolved radio frequency interference in the FM band at the Murchison Radio-astronomy Observatory
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.32
Abstract: We present the first survey of radio frequency interference (RFI) at the future site of the low frequency Square Kilometre Array (SKA), the Murchison Radio-astronomy Observatory (MRO), that both temporally and spatially resolves the RFI. The survey is conducted in a 1 MHz frequency range within the FM band, designed to encompass the closest and strongest FM transmitters to the MRO (located in Geraldton, approximately 300 km distant). Conducted over approximately three days using the second iteration of the Engineering Development Array in an all-sky imaging mode, we find a range of RFI signals. We are able to categorise the signals into: those received directly from the transmitters, from their horizon locations reflections from aircraft (occupying approximately 13% of the observation duration) reflections from objects in Earth orbit and reflections from meteor ionisation trails. In total, we analyse 33 994 images at 7.92 s time resolution in both polarisations with angular resolution of approximately 3.5 $^{\\circ}$ , detecting approximately forty thousand RFI events. This detailed breakdown of RFI in the MRO environment will enable future detailed analyses of the likely impacts of RFI on key science at low radio frequencies with the SKA.
VLBI of Southern EGRET Identifications
Publisher: Cambridge University Press (CUP)
Date: 1998
DOI: 10.1017/S025292110004450X
Abstract: We have undertaken VLBI observations of 8 Southern Hemisphere EGRET radio sources. Using our data as well as data obtained from the literature we have examined the difference in radio properties between gamma-ray loud and gamma-ray quiet radio sources. In particular, we find no evidence that gamma-ray loud radio sources lie preferentially in sources with straight radio jets as has been suggested.
Understanding instrumental Stokes leakage in Murchison Widefield Array polarimetry
Publisher: American Geophysical Union (AGU)
Date: 2015
DOI: 10.1002/2014RS005517
A HIGH RESOLUTION VIEW OF THE JET TERMINATION SHOCK IN A HOT SPOT OF THE NEARBY RADIO GALAXY PICTOR A: IMPLICATIONS FOR X-RAY MODELS OF RADIO GALAXY HOT SPOTS
Publisher: American Astronomical Society
Date: 13-11-2008
KM3NeT/ARCA expectations in view of a novel multimessenger study of starburst galaxies
Publisher: IOP Publishing
Date: 12-2021
DOI: 10.1088/1748-0221/16/12/C12016
Abstract: Starburst galaxies (SBGs) and more in general star-forming galaxies represent a class of galaxies with a high star formation rate (up to 100 M ⊙ /year). Despite their low luminosity, they can be considered as guaranteed “factories” of high energy neutrinos, being “reservoirs” of accelerated cosmic rays and hosting a high density target gas in the central region. In this contribution we present a novel multimessenger study of these sources and the possibility of observing their neutrino signals with the KM3NeT/ARCA telescope. The differential sensitivity for different SBG scenarios is reported considering track-like neutrino events in the 100 GeV–100 PeV energy range.
VLBI Observations of Gamma‐Ray–quiet Active Galactic Nuclei: Comparing Radio‐Core Brightness Temperatures
Publisher: American Astronomical Society
Date: 20-04-1998
DOI: 10.1086/305494
MWA rapid follow-up of gravitational wave transients: Prospects for detecting prompt radio counterparts
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.49
A Search of TESS Full-frame Images for an Optical Counterpart of the Repeating FRB 20180916B
Publisher: American Astronomical Society
Date: 08-2022
Abstract: Recently, an association between an optical transient, AT2020hur, and a repeating fast radio burst, FRB 20180916b, has been suggested, based on a strong positional coincidence on the sky and the temporal coincidence with one of the fast radio burst’s activity periods (∼6 days duration every ∼16 days). This suggestion is explored further and tested in this paper, utilizing full-frame images from the Transiting Exoplanet Survey Satellite (TESS) across three of its observing periods in 2019 and 2020 (Sectors 18, 24, and 25). The discovery observations of AT2020hur took place between Sectors 18 and 24, within 5 days of the commencement of Sector 24 observations. The TESS observations cover at least six activity periods for the FRB. Thus, the TESS data provide excellent temporal coverage close in time to the discovery of AT2020hur and at known times of FRB activity and radio detection. From the TESS data, no evidence is found for repeating optical transients with the suspected emission timescale of ⪆1000 s.
An overviewof the SKA project: Why take on this signal processing challenge?
Publisher: IEEE
Date: 04-2015
Combined search for neutrinos from dark matter self-annihilation in the Galactic Center with ANTARES and IceCube
Publisher: American Physical Society (APS)
Date: 27-10-2020
Maghemite soil nodules reveal the impact of fire on mineralogical and geochemical differentiation at the Earth’s surface
Publisher: Elsevier BV
Date: 03-2017
Measuring the Brightness Temperature Distribution of Extragalactic Radio Sources with Space VLBI
Publisher: American Astronomical Society
Date: 03-2001
DOI: 10.1086/319148
JPL contribution to the VSOP mission
Publisher: Elsevier BV
Date: 2000
Prospects for accurate distance measurements of pulsars with the Square Kilometre Array: Enabling fundamental physics
Publisher: EDP Sciences
Date: 10-03-2011
Report of a Management Program for Black Swans in South-Western Australia
Publisher: Informa UK Limited
Date: 10-1977
DOI: 10.1071/MU9770185
Agrobacterium tumefaciens‐mediated barley transformation
Publisher: Wiley
Date: 12-1997
Chemical signatures of melt-rock interaction in the root of a magmatic arc
Publisher: Oxford University Press (OUP)
Date: 02-2018
Robust statistics towards detection of the 21 cm signal from the Epoch of Reionization
Publisher: Oxford University Press (OUP)
Date: 17-05-2010
The Subparsec-Scale Structure and Evolution of Centaurus A. II. Continued Very Long Baseline Array Monitoring
Publisher: American Astronomical Society
Date: 10-2001
DOI: 10.1086/323097
An Investigation of Synchrotron Self-absorption and Free-Free Absorption Models in Explanation of the Gigahertz-peaked Spectrum of PKS 1718-649
Publisher: American Astronomical Society
Date: 08-2003
DOI: 10.1086/376600
Monte Carlo simulations for the ANTARES underwater neutrino telescope
Publisher: IOP Publishing
Date: 29-01-2021
Preliminary sensitivity verification of the SKA-Low AAVS2 prototype
Publisher: IEEE
Date: 22-03-2021
[ITAL]Chandra[/ITAL] Discovery of a 100 kiloparsec X-Ray Jet in PKS 0637−752
Publisher: American Astronomical Society
Date: 10-09-2000
DOI: 10.1086/312875
THE SUB-PARSEC SCALE RADIO PROPERTIES OF SOUTHERN STARBURST GALAXIES. II. SUPERNOVA REMNANTS, THE SUPERNOVA RATE, AND THE IONISED MEDIUM IN THE NGC 4945 STARBURST
Publisher: American Astronomical Society
Date: 19-12-2008
VLBI observations of southern egret identifications
Publisher: Springer Netherlands
Date: 1996
Inefficient high-temperature metamorphism in orthogneiss
Publisher: Mineralogical Society of America
Date: 2019
DOI: 10.2138/AM-2019-6503
Improved Techniques for the Surveillance of the Near Earth Space Environment with the Murchison Widefield Array
Publisher: IEEE
Date: 04-2019
The Phytochrome Response of the Lemna gibba NPR1 Gene Is Mediated Primarily through Changes in Abscisic Acid Levels1
Publisher: Oxford University Press (OUP)
Date: 04-1998
Abstract: Two important signaling systems involved in the growth and development of plants, those triggered by the photoreceptor phytochrome and the hormone abscisic acid (ABA), are involved in the regulation of expression of the NPR1 gene of Lemna gibba. We previously demonstrated that phytochrome action mediates changes in ABA levels in L. gibba, correlating with changes in gene expression evoked by stimulation of the phytochrome system. We have now further characterized phytochrome- and ABA-mediated regulation of L. gibba NPR1 gene expression using a transient particle bombardment assay, demonstrating that regulatory elements controlling responses to both stimuli reside within 156 nucleotides upstream of the transcription start. Linker scan (LS) analysis of the region from −156 to −70 was used to identify two specific requisite and nonredundant cis-acting promoter elements between −143 to −135 (LS2) and −113 to −101 (LS5). Mutation of either of these elements resulted in a coordinate loss of regulation by phytochrome and ABA. This suggests that, unlike theL. gibba Lhcb2*1 promoter, in which phytochrome and ABA regulatory elements are separable, the phytochrome response of theL. gibba NPR1 gene can be attributed to alterations in ABA levels.
The host galaxy of a fast radio burst
Publisher: Springer Science and Business Media LLC
Date: 02-2016
DOI: 10.1038/NATURE17140
Abstract: In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.
Event reconstruction for KM3NeT/ORCA using convolutional neural networks
Publisher: IOP Publishing
Date: 08-10-2020
The Sardinia Radio Telescope
Publisher: EDP Sciences
Date: 12-2017
Interplanetary scintillation studies with the Murchison Wide-field Array – IV. The hosts of sub-arcsecond compact sources at low radio frequencies
Publisher: Oxford University Press (OUP)
Date: 10-11-2018
The Phase II Murchison Widefield Array: Design overview
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/PASA.2018.37
Abstract: We describe the motivation and design details of the ‘Phase II’ upgrade of the Murchison Widefield Array radio telescope. The expansion doubles to 256 the number of antenna tiles deployed in the array. The new antenna tiles enhance the capabilities of the Murchison Widefield Array in several key science areas. Seventy-two of the new tiles are deployed in a regular configuration near the existing array core. These new tiles enhance the surface brightness sensitivity of the array and will improve the ability of the Murchison Widefield Array to estimate the slope of the Epoch of Reionisation power spectrum by a factor of ∼3.5. The remaining 56 tiles are deployed on long baselines, doubling the maximum baseline of the array and improving the array u, v coverage. The improved imaging capabilities will provide an order of magnitude improvement in the noise floor of Murchison Widefield Array continuum images. The upgrade retains all of the features that have underpinned the Murchison Widefield Array’s success (large field of view, snapshot image quality, and pointing agility) and boosts the scientific potential with enhanced imaging capabilities and by enabling new calibration strategies.
Crystallography of refractory metal nuggets in carbonaceous chondrites: A transmission Kikuchi diffraction approach
Publisher: Elsevier BV
Date: 11-2017
DiFX-2: A More Flexible, Efficient, Robust, and Powerful Software Correlator
Publisher: IOP Publishing
Date: 03-2011
DOI: 10.1086/658907
In situ measurement of MWA primary beam variation using ORBCOMM
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/PASA.2018.30
Abstract: We provide the first in situ measurements of antenna element beam shapes of the Murchison Widefield Array. Most current processing pipelines use an assumed beam shape, which can cause absolute and relative flux density errors and polarisation ‘leakage’. Understanding the primary beam is then of paramount importance, especially for sensitive experiments such as a measurement of the 21-cm line from the epoch of reionisation, where the calibration requirements are so extreme that tile to tile beam variations may affect our ability to make a detection. Measuring the primary beam shape from visibilities is challenging, as multiple instrumental, atmospheric, and astrophysical factors contribute to uncertainties in the data. Building on the methods of Neben et al. [Radio Sci., 50, 614], we tap directly into the receiving elements of the telescope before any digitisation or correlation of the signal. Using ORBCOMM satellite passes we are able to produce all-sky maps for four separate tiles in the XX polarisation. We find good agreement with the beam model of Sokolowski et al. [2017, PASA, 34, e062], and clearly observe the effects of a missing dipole from a tile in one of our beam maps. We end by motivating and outlining additional on-site experiments.
Hornblendite delineates zones of mass transfer through the lower crust
Publisher: Springer Science and Business Media LLC
Date: 22-08-2016
DOI: 10.1038/SREP31369
Abstract: Geochemical signatures throughout the layered Earth require significant mass transfer through the lower crust, yet geological pathways are under-recognized. Elongate bodies of basic to ultrabasic rocks are ubiquitous in exposures of the lower crust. Ultrabasic hornblendite bodies hosted within granulite facies gabbroic gneiss of the Pembroke Valley, Fiordland, New Zealand, are typical occurrences usually reported as igneous cumulate hornblendite. Their igneous features contrast with the metamorphic character of their host gabbroic gneiss. Both rock types have a common parent field relationships are consistent with modification of host gabbroic gneiss into hornblendite. This precludes any interpretation involving cumulate processes in forming the hornblendite these bodies are imposter cumulates. Instead, replacement of the host gabbroic gneiss formed hornblendite as a result of channeled high melt flux through the lower crust. High melt/rock ratios and disequilibrium between the migrating magma (granodiorite) and its host gabbroic gneiss induced dissolution (grain-scale magmatic assimilation) of gneiss and crystallization of mainly hornblende from the migrating magma. The extent of this reaction-replacement mechanism indicates that such hornblendite bodies delineate significant melt conduits. Accordingly, many of the ubiquitous basic to ultrabasic elongate bodies of the lower crust likely map the ‘missing’ mass transfer zones.
Search for secluded dark matter towards the Galactic Centre with the ANTARES neutrino telescope
Publisher: IOP Publishing
Date: 06-2022
DOI: 10.1088/1475-7516/2022/06/028
Abstract: Searches for dark matter (DM) have not provided any solid evidence for the existence of weakly interacting massive particles in the GeV-TeV mass range. Coincidentally, the scale of new physics is being pushed by collider searches well beyond the TeV domain. This situation strongly motivates the exploration of DM masses much larger than a TeV. Secluded scenarios contain a natural way around the unitarity bound on the DM mass, via the early matter domination induced by the mediator of its interactions with the Standard Model. High-energy neutrinos constitute one of the very few direct accesses to energy scales above a few TeV. An indirect search for secluded DM signals has been performed with the ANTARES neutrino telescope using data from 2007 to 2015. Upper limits on the DM annihilation cross section for DM masses up to 6 PeV are presented and discussed.
High-resolution structure of southern compact steep spectrum sources
Publisher: Springer Netherlands
Date: 1996
Constraining the contribution of Gamma-Ray Bursts to the high-energy diffuse neutrino flux with 10 yr of ANTARES data
Publisher: Oxford University Press (OUP)
Date: 25-11-2020
Abstract: Addressing the origin of the astrophysical neutrino flux observed by IceCube is of paramount importance. Gamma-Ray Bursts (GRBs) are among the few astrophysical sources capable of achieving the required energy to contribute to such neutrino flux through pγ interactions. In this work, ANTARES data have been used to search for upward going muon neutrinos in spatial and temporal coincidence with 784 GRBs occurred from 2007 to 2017. For each GRB, the expected neutrino flux has been calculated in the framework of the internal shock model and the impact of the lack of knowledge on the majority of source redshifts and on other intrinsic parameters of the emission mechanism has been quantified. It is found that the model parameters that set the radial distance where shock collisions occur have the largest impact on neutrino flux expectations. In particular, the bulk Lorentz factor of the source ejecta and the minimum variability time-scale are found to contribute significantly to the GRB-neutrino flux uncertainty. For the selected sources, ANTARES data have been analysed by maximizing the discovery probability of the stacking s le through an extended maximum-likelihood strategy. Since no neutrino event passed the quality cuts set by the optimization procedure, 90 per cent confidence level upper limits (with their uncertainty) on the total expected diffuse neutrino flux have been derived, according to the model. The GRB contribution to the observed diffuse astrophysical neutrino flux around 100 TeV is constrained to be less than 10 per cent.
RADIO OBSERVATIONS OF GRB 100418a: TEST OF AN ENERGY INJECTION MODEL EXPLAINING LONG-LASTING GRB AFTERGLOWS
Publisher: American Astronomical Society
Date: 27-11-2013
High-resolution Observations of Low-luminosity Gigahertz-Peaked Spectrum and Compact Steep Spectrum Sources
Publisher: Oxford University Press (OUP)
Date: 03-03-2018
DOI: 10.1093/MNRAS/STY564
Gridded and direct Epoch of Reionisation bispectrum estimates using the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2019.15
Abstract: We apply two methods to estimate the 21-cm bispectrum from data taken within the Epoch of Reionisation (EoR) project of the Murchison Widefield Array (MWA). Using data acquired with the Phase II compact array allows a direct bispectrum estimate to be undertaken on the multiple redundantly spaced triangles of antenna tiles, as well as an estimate based on data gridded to the uv -plane. The direct and gridded bispectrum estimators are applied to 21 h of high-band (167–197 MHz z = 6.2–7.5) data from the 2016 and 2017 observing seasons. Analytic predictions for the bispectrum bias and variance for point-source foregrounds are derived. We compare the output of these approaches, the foreground contribution to the signal, and future prospects for measuring the bispectra with redundant and non-redundant arrays. We find that some triangle configurations yield bispectrum estimates that are consistent with the expected noise level after 10 h, while equilateral configurations are strongly foreground-dominated. Careful choice of triangle configurations may be made to reduce foreground bias that hinders power spectrum estimators, and the 21-cm bispectrum may be accessible in less time than the 21-cm power spectrum for some wave modes, with detections in hundreds of hours.
Bright Giant Pulses from the Crab Nebula Pulsar: Statistical Properties, Pulse Broadening, and Scattering Due to the Nebula
Publisher: American Astronomical Society
Date: 04-2008
DOI: 10.1086/528735
A high reliability survey of discrete Epoch of Reionization foreground sources in the MWA EoR0 field
Publisher: Oxford University Press (OUP)
Date: 08-07-2016
Implications of a VLBI distance to the double pulsar J0737-3039A/B
Publisher: American Association for the Advancement of Science (AAAS)
Date: 06-03-2009
Abstract: The double pulsar J0737-3039A/B is a unique system with which to test gravitational theories in the strong-field regime. However, the accuracy of such tests will be limited by knowledge of the distance and relative motion of the system. Here we present very long baseline interferometry (VLBI) observations which reveal that the distance to PSR J0737-3039A/B is \\batchmode \\documentclass[fleqn,10pt,legalpaper]{article} \\usepackage{amssymb} \\usepackage{amsfonts} \\usepackage{amsmath} \\pagestyle{empty} \\begin{document} \\(1150_{-160}^{+220}\\) \\end{document} parsecs, more than double previous estimates, and confirm its low transverse velocity (∼9 kilometers per second). Combined with a decade of pulsar timing, these results will allow tests of gravitational radiation emission theories at the 0.01% uncertainty level, putting stringent constraints on theories that predict dipolar gravitational radiation. They also allow insight into the system's formation and the source of its high-energy emission.
A Review of Front-End Receivers for the INAF Radio Telescopes
Publisher: IEEE
Date: 05-2018
A Matched Filter Technique for Slow Radio Transient Detection and First Demonstration with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 07-02-2017
Interplanetary Scintillation with the Murchison Widefield Array V: An all-sky survey of compact sources using a modern low-frequency radio telescope
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2018.40
Abstract: We describe the parameters of a low-frequency all-sky survey of compact radio sources using Interplanetary Scintillation, undertaken with the Murchison Widefield Array. While this survey gives important complementary information to low-resolution survey, providing information on the sub-arsecond structure of every source, a survey of this kind has not been attempted in the era of low-frequency imaging arrays such as the Murchison Widefield Array and LOw Frequency Array. Here we set out the capabilities of such a survey, describing the limitations imposed by the heliocentric observing geometry and by the instrument itself. We demonstrate the potential for Interplanetary Scintillation measurements at any point on the celestial sphere and we show that at 160 MHz, reasonable results can be obtained within 30° of the ecliptic (2 π str: half the sky). We also suggest some observational strategies and describe the first such survey, the Murchison Widefield Array Phase I Interplanetary Scintillation survey. Finally we analyse the potential of the recently upgraded Murchison Widefield Array and discuss the potential of the Square Kilometre Array-low to use Interplanetary Scintillation to probe sub-mJy flux density levels at sub-arcsecond angular resolution.
Fast response electromagnetic follow-ups from low latency GW triggers
Publisher: IOP Publishing
Date: 05-2016
BIGHORNS - Broadband Instrument for Global HydrOgen ReioNisation Signal
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.3
Abstract: The redshifted 21cm line of neutral hydrogen ( Hi ), potentially observable at low radio frequencies (~50–200 MHz), should be a powerful probe of the physical conditions of the inter-galactic medium during Cosmic Dawn and the Epoch of Reionisation (EoR). The sky-averaged Hi signal is expected to be extremely weak (~100 mK) in comparison to the foreground of up to 10 4 K at the lowest frequencies of interest. The detection of such a weak signal requires an extremely stable, well characterised system and a good understanding of the foregrounds. Development of a nearly perfectly (~mK accuracy) calibrated total power radiometer system is essential for this type of experiment. We present the BIGHORNS (Broadband Instrument for Global HydrOgen ReioNisation Signal) experiment which was designed and built to detect the sky-averaged Hi signal from the EoR at low radio frequencies. The BIGHORNS system is a mobile total power radiometer, which can be deployed in any remote location in order to collect radio frequency interference (RFI) free data. The system was deployed in remote, radio quiet locations in Western Australia and low RFI sky data have been collected. We present a description of the system, its characteristics, details of data analysis, and calibration. We have identified multiple challenges to achieving the required measurement precision, which triggered two major improvements for the future system.
The recognition of former melt flux through high‐strain zones
Publisher: Wiley
Date: 25-06-2018
DOI: 10.1111/JMG.12427
The High Time and Frequency Resolution Capabilities of the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.6
Abstract: The science cases for incorporating high time resolution capabilities into modern radio telescopes are as numerous as they are compelling. Science targets range from exotic sources such as pulsars, to our Sun, to recently detected possible extragalactic bursts of radio emission, the so-called fast radio bursts (FRBs). Originally conceived purely as an imaging telescope, the initial design of the Murchison Widefield Array (MWA) did not include the ability to access high time and frequency resolution voltage data. However, the flexibility of the MWA’s software correlator allowed an off-the-shelf solution for adding this capability. This paper describes the system that records the 100 μs and 10 kHz resolution voltage data from the MWA. Ex le science applications, where this capability is critical, are presented, as well as accompanying commissioning results from this mode to demonstrate verification.
VSOP Space VLBI and Geodetic VLBI Investigations of Southern Hemisphere Radio Sources
Publisher: American Astronomical Society
Date: 08-2002
DOI: 10.1086/340783
Overcoming real-world obstacles in 21 cm power spectrum estimation: A method demonstration and results from early Murchison Widefield Array data
Publisher: American Physical Society (APS)
Date: 15-01-2014
The Murchison Widefield Array Correlator
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.5
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.
The 154 MHz radio sky observed by the Murchison Widefield Array: Noise, confusion, and first source count analyses
Publisher: Oxford University Press (OUP)
Date: 12-04-2016
DOI: 10.1093/MNRAS/STW823
PARSEC-SCALE SHOCKS IN THE KILOPARSEC-SCALE JET OF CENTAURUS A
Publisher: American Astronomical Society
Date: 28-07-2009
The VSOP 5 GHz Active Galactic Nucleus Survey. III. Imaging Results for the First 102 Sources
Publisher: American Astronomical Society
Date: 11-2004
DOI: 10.1086/424819
A VLBI Study of Free-Free Absorbed Compact Radio Sources in the NGC 253 Starburst
Publisher: American Astronomical Society
Date: 2004
DOI: 10.1086/380234
VSOP Space VLBI observations of Pearson-Readhead survey sources
Publisher: Elsevier BV
Date: 11-1999
The VLBA fast radio transient experiment: Progress and early results
Publisher: Cambridge University Press (CUP)
Date: 09-2011
DOI: 10.1017/S1743921312001299
Abstract: Motivated by recent discoveries of isolated, dispersed radio pulses of possible extragalactic origin, we are performing a commensal search for short-duration (ms) continuum radio pulses using the Very Long Baseline Array (VLBA). The geographically separated antennæ of the VLBA make the system robust to local RFI and allow events to be verified and localised on the sky with milli-arcsec accuracy. We report sky coverage and detection limits from the experiment to date.
Discovery of a Steep-spectrum Low-luminosity Pulsar with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 04-2021
Abstract: We report the discovery of the first new pulsar with the Murchison Widefield Array (MWA), PSR J0036−1033, a long-period (0.9 s) nonrecycled pulsar with a dispersion measure (DM) of 23.1 pc cm −3 . It was found after processing only a small fraction (∼1%) of data from an ongoing all-sky pulsar survey. Follow-up observations have been made with the MWA, the upgraded Giant Metrewave Radio Telescope (uGMRT), and the Parkes 64 m telescopes, spanning a frequency range from ∼150 MHz to 4 GHz. The pulsar is faint, with an estimated flux density ( S ) of ∼1 mJy at 400 MHz and a spectrum , where ν is frequency. The DM-derived distance implies that it is also a low-luminosity source (∼0.1 mJy kpc 2 at 1400 MHz). The analysis of archival MWA observations reveals that the pulsar’s mean flux density varies by up to a factor of ∼5–6 on timescales of several weeks to months. By combining MWA and uGMRT data, the pulsar position was determined to arcsecond precision. We also report on polarization properties detected in the MWA and Parkes bands. The pulsar’s nondetection in previous pulsar and continuum imaging surveys, the observed high variability, and its detection in a small fraction of the survey data searched to date, all hint at a larger population of pulsars that await discovery in the southern hemisphere, with the MWA and the future low-frequency Square Kilometre Array.
LIMITS ON FAST RADIO BURSTS FROM FOUR YEARS OF THE V-FASTR EXPERIMENT
Publisher: American Astronomical Society
Date: 02-08-2016
e-VLBI observations of GRB 080409 afterglow with an Australasian radio telescope network
Publisher: IOP Publishing
Date: 11-2016
An international survey of front-end receivers and observing performance of telescopes for radio astronomy
Publisher: IOP Publishing
Date: 02-07-2019
Abstract: This paper presents a survey of microwave front-end receivers installed at radio telescopes throughout the world. This unprecedented analysis was conducted as part of a review of front-end developments for Italian radio telescopes, initiated by the Italian National Institute for Astrophysics in 2016. Fifteen international radio telescopes have been selected to be representative of the instrumentation used for radio astronomical observations in the frequency domain from 300 MHz to 116 GHz. A comprehensive description of the existing receivers is presented and their characteristics are compared and discussed. The observing performances of the complete receiving chains are also presented. An overview of ongoing developments illustrates and anticipates future trends in front-end projects to meet the most ambitious scientific research goals.
Optical and radio astrometry of the galaxy associated with FRB 150418
Publisher: Oxford University Press (OUP)
Date: 30-07-2016
Constraints on dark matter annihilation in dwarf spheroidal galaxies from low frequency radio observations
Publisher: American Physical Society (APS)
Date: 08-2019
Mass transfer in the lower crust: Evidence for incipient melt assisted flow along grain boundaries in the deep arc granulites of Fiordland, New Zealand
Publisher: American Geophysical Union (AGU)
Date: 09-2016
DOI: 10.1002/2015GC006236
MODELLING OF AN INEXPENSIVE 9M SATELLITE DISH FROM 3D POINT CLOUDS CAPTURED BY TERRESTRIAL LASER SCANNERS
Publisher: Copernicus GmbH
Date: 05-09-2012
DOI: 10.5194/ISPRSARCHIVES-XXXVIII-5-W12-313-2011
Abstract: Abstract. This paper presents the use of Terrestrial laser scanners (TLS) to model the surface of satellite dish. In this case, the dish was an inexpensive 9m parabolic satellite dish with a mesh surface, and was to be utilised in radio astronomy. The aim of the modelling process was to determine the deviation of the surface away from its true parabolic shape, in order to estimate the surface efficiency with respect to its principal receiving frequency. The main mathematical problems were the optimal and unbiased estimation the orientation of the dish and the fitting of a parabola to the local orientation or coordinate system, which were done by both orthogonal and algebraic minimization using the least-squares method. Due to the mesh structure of the dish, a classification method was also applied to filter out erroneous points being influenced by the supporting structure behind the dish. Finally, a comparison is performed between the ideal parabolic shape, and the data collected from three different temporal intervals.
Parallax measurements of pulsars with the Square Kilometre Array
Publisher: AIP
Date: 2011
DOI: 10.1063/1.3615153
A framework for interpreting fast radio transients search experiments: Application to the V-FASTR experiment
Publisher: American Astronomical Society
Date: 19-03-2013
The Counterjet in the Nucleus of Centaurus A
Publisher: Cambridge University Press (CUP)
Date: 1998
DOI: 10.1017/S0252921100044687
Abstract: We have observed the nucleus of Centaurus A with the VLBA and the SHEVE arrays, in idually and in combination. In sensitive experiments at 8.4 GHz which use both arrays together we have detected components in a sub-parsec-scale counterjet. The counterjet is also seen in 2.3 and 22 GHz images. The nuclear region appears to be partially obscured by a free-free absorbing structure of about 1 pc in extent. The jet axis appears to lie at a 50°–70° angle to our line of sight.
The 2003 radio outburst of a new X-ray transient: XTE J1720-318
Publisher: Oxford University Press (OUP)
Date: 2005
MWAX: A new correlator for the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.15
Abstract: We describe the design, validation, and commissioning of a new correlator termed ‘MWAX’ for the Murchison Widefield Array (MWA) low-frequency radio telescope. MWAX replaces an earlier generation MWA correlator, extending correlation capabilities and providing greater flexibility, scalability, and maintainability. MWAX is designed to exploit current and future Phase II/III upgrades to MWA infrastructure, most notably the simultaneous correlation of all 256 of the MWA’s antenna tiles (and potentially more in future). MWAX is a fully software-programmable correlator based around an ethernet multicast architecture. At its core is a cluster of 24 high-performance GPU-enabled commercial-off-the-shelf compute servers that together process in real-time up to 24 coarse channels of 1.28 MHz bandwidth each. The system is highly flexible and scalable in terms of the number of antenna tiles and number of coarse channels to be correlated, and it offers a wide range of frequency/time resolution combinations to users. We conclude with a roadmap of future enhancements and extensions that we anticipate will be progressively rolled out over time.
Equivalent Widths for 54 Red Giants in 47 Tucanae, omega Centauri, NGC 6397, M22, and NGC 6752
Publisher: American Astronomical Society
Date: 08-1995
DOI: 10.1086/192200
Radio Spectral Variability of the Nearby GPS Galaxy PKS 1718–649
Publisher: Cambridge University Press (CUP)
Date: 2003
DOI: 10.1071/AS02045
Abstract: Data from new Australia Telescope Compact Array observations of a nearby gigahertz peaked spectrum radio source, PKS 1718–649, show significant variability both below and above the spectral turnover frequency during a nine month period. Simple models of synchrotron self-absorption (SSA) and free–free absorption (FFA) cannot explain the in idual spectra or the spectral variability. Novel SSA or FFA models will need to be investigated in order to explain the complex variability in this source. Some potential explanations for the spectral variability are explored here but we can make no strong conclusion about which of SSA or FFA (or alternative mechanisms) causes the peaked spectrum in PKS 1718–649.
VLBI properties of compact interplanetary scintillators detected by the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 20-10-2021
Abstract: Interplanetary scintillation (IPS) provides an approach for identifying the presence of sub-arcsec structures in radio sources, and very long baseline interferometry (VLBI) technique can help verify whether the IPS sources have fine structures on milli-arcsec (mas) scales. We searched the available VLBI archive for the 244 IPS sources detected by the Murchison Widefield Array at 162 MHz and found 63 cross-matches. We analysed the VLBI data of the 63 sources and characterised the compactness index in terms of the ratio R of the VLBI-measured flux density at 4.3 GHz to the flux density estimated using the Very Large Array Sky Survey (VLASS) at 3 GHz and NRAO VLA Sky Survey (NVSS) at 1.4 GHz (SVLBI/SSA). Eleven sources are identified as blazars according to their flat spectra and strong variability. They show high compactness indices with R & 0.4, compact core-jet structure, and a broad distribution of normalised scintillation index (NSI). Other sources show erse morphologies (compact core, core and one-sided jet, core and two-sided jets), but there is a correlation between R and NSI with a correlation coefficient r = 0.47. A similar R–NSI correlation is found in sources showing single steep power-law or convex spectra. After excluding blazars (which are already known to be compact sources) from the VLBI-detected IPS sources, a strong correlation is found between the compactness and scintillation index of the remaining s les, indicating that stronger scintillating sources are more compact. This pilot study shows that IPS offers a convenient method to identify compact radio sources without the need to invoke high-resolution imaging observations, which often require significant observational time.
The first VLBI image of an infrared-faint radio source
Publisher: EDP Sciences
Date: 17-09-2008
A 5-GHz Southern Hemishere VLBI Survey of Compact Radio Sources.I.
Publisher: American Astronomical Society
Date: 11-1997
DOI: 10.1086/118621
Wavelet-based Characterization of Small-scale Solar Emission Features at Low Radio Frequencies
Publisher: American Astronomical Society
Date: 27-06-2017
Performance of a small array of Imaging Air Cherenkov Telescopes sited in Australia
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.29
Abstract: As TeV gamma-ray astronomy progresses into the era of the Cherenkov Telescope Array (CTA), there is a desire for the capacity to instantaneously follow up on transient phenomena and continuously monitor gamma-ray flux at energies above $10^{12}\\,\\mathrm{eV}$ . To this end, a worldwide network of Imaging Air Cherenkov Telescopes (IACTs) is required to provide triggers for CTA observations and complementary continuous monitoring. An IACT array sited in Australia would contribute significant coverage of the Southern Hemisphere sky. Here, we investigate the suitability of a small IACT array and how different design factors influence its performance. Monte Carlo simulations were produced based on the Small-Sized Telescope (SST) and Medium-Sized Telescope (MST) designs from CTA. Angular resolution improved with larger baseline distances up to 277 m between telescopes, and energy thresholds were lower at 1 000 m altitude than at 0 m. The ${\\sim} 300\\,\\mathrm{GeV}$ energy threshold of MSTs proved more suitable for observing transients than the ${\\sim}1.2\\,\\mathrm{TeV}$ threshold of SSTs. An array of four MSTs at 1 000 m was estimated to give a 5.7 $\\sigma$ detection of an RS Ophiuchi-like nova eruption from a 4-h observation. We conclude that an array of four MST-class IACTs at an Australian site would ideally complement the capabilities of CTA.
Atom probe tomography analysis of the reference zircon gj-1: An interlaboratory study
Publisher: Elsevier BV
Date: 09-2018
Early-Time searches for coherent radio emission from short GRBs with the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2019
DOI: 10.1017/PASA.2021.58
Abstract: Many short gamma-ray bursts (GRBs) originate from binary neutron star mergers, and there are several theories that predict the production of coherent, prompt radio signals either prior, during, or shortly following the merger, as well as persistent pulsar-like emission from the spin-down of a magnetar remnant. Here we present a low frequency (170–200 MHz) search for coherent radio emission associated with nine short GRBs detected by the Swift and/or Fermi satellites using the Murchison Widefield Array (MWA) rapid-response observing mode. The MWA began observing these events within 30–60 s of their high-energy detection, enabling us to capture any dispersion delayed signals emitted by short GRBs for a typical range of redshifts. We conducted transient searches at the GRB positions on timescales of 5 s, 30 s, and 2 min, resulting in the most constraining flux density limits on any associated transient of 0.42, 0.29, and 0.084 Jy, respectively. We also searched for dispersed signals at a temporal and spectral resolution of 0.5 s and 1.28 MHz, but none were detected. However, the fluence limit of 80–100 Jy ms derived for GRB 190627A is the most stringent to date for a short GRB. Assuming the formation of a stable magnetar for this GRB, we compared the fluence and persistent emission limits to short GRB coherent emission models, placing constraints on key parameters including the radio emission efficiency of the nearly merged neutron stars ( $\\epsilon_r\\lesssim10^{-4}$ ), the fraction of magnetic energy in the GRB jet ( $\\epsilon_B\\lesssim2\\times10^{-4}$ ), and the radio emission efficiency of the magnetar remnant ( $\\epsilon_r\\lesssim10^{-3}$ ). Comparing the limits derived for our full GRB s le (along with those in the literature) to the same emission models, we demonstrate that our fluence limits only place weak constraints on the prompt emission predicted from the interaction between the relativistic GRB jet and the interstellar medium for a subset of magnetar parameters. However, the 30-min flux density limits were sensitive enough to theoretically detect the persistent radio emission from magnetar remnants up to a redshift of $z\\sim0.6$ . Our non-detection of this emission could imply that some GRBs in the s le were not genuinely short or did not result from a binary neutron star merger, the GRBs were at high redshifts, these mergers formed atypical magnetars, the radiation beams of the magnetar remnants were pointing away from Earth, or the majority did not form magnetars but rather collapse directly into black holes.
Evaluating the importance of metamorphism in the foundering of continental crust
Publisher: Springer Science and Business Media LLC
Date: 12-10-2017
DOI: 10.1038/S41598-017-13221-6
Abstract: The metamorphic conditions and mechanisms required to induce foundering in deep arc crust are assessed using an ex le of representative lower crust in SW New Zealand. Composite plutons of Cretaceous monzodiorite and gabbro were emplaced at ~1.2 and 1.8 GPa are parts of the Western Fiordland Orthogneiss (WFO) ex les of the plutons are tectonically juxtaposed along a structure that excised ~25 km of crust. The 1.8 GPa Breaksea Orthogneiss includes suitably dense minor components (e.g. eclogite) capable of foundering at peak conditions. As the eclogite facies boundary has a positive dP/dT , cooling from supra-solidus conditions ( T 950 ºC) at high- P should be accompanied by omphacite and garnet growth. However, a high monzodioritic proportion and inefficient metamorphism in the Breaksea Orthogneiss resulted in its positive buoyancy and preservation. Metamorphic inefficiency and compositional relationships in the 1.2 GPa Malaspina Pluton meant it was never likely to have developed densities sufficiently high to founder. These relationships suggest that the deep arc crust must have primarily involved significant igneous accumulation of garnet–clinopyroxene (in proportions %). Crustal dismemberment with or without the development of extensional shear zones is proposed to have induced foundering of excised cumulate material at P 1.2 GPa.
No Low-frequency Emission from Extremely Bright Fast Radio Bursts
Publisher: American Astronomical Society
Date: 29-10-2018
The VSOP 5 GHz Active Galactic Nucleus Survey. II. Data Calibration and Imaging
Publisher: American Astronomical Society
Date: 11-2004
DOI: 10.1086/424820
Multiwavelength Observations of the Unusual Ultraluminous Supernova SN 1978K in NGC 1313 and the Search for an Associated Gamma-Ray Burst
Publisher: AIP
Date: 2009
DOI: 10.1063/1.3155895
VLBI observations of southern gamma-ray sources. III
Publisher: Cambridge University Press (CUP)
Date: 2018
DOI: 10.1017/PASA.2018.4
Abstract: We report the results of Long Baseline Array observations made in 2001 of ten southern sources proposed by Mattox et al. as counterparts to EGRET MeV gamma-ray sources. Source structures are compared with published data where available and possible superluminal motions identified in several cases. The associations are examined in the light of Fermi observations, indicating that the confirmed counterparts tend to have radio properties consistent with other identifications, including flat radio spectral index, high brightness temperature, greater radio variability, and higher core dominance.
VLBI observations of low-redshift radio galaxies
Publisher: Springer Netherlands
Date: 1996
An Ultra-High Time Resolution Cosmic-Ray Detection Mode for the Murchison Widefield Array
Publisher: World Scientific Pub Co Pte Ltd
Date: 24-02-2021
DOI: 10.1142/S2251171721500033
Abstract: The radio-wavelength detection of extensive air showers (EASs) initiated by cosmic-ray interactions in the Earth’s atmosphere is a promising technique for investigating the origin of these particles and the physics of their interactions. The Low-frequency Array (LOFAR) and the Owens Valley Long Wavelength Array (OVRO-LWA) have both demonstrated that the dense cores of low-frequency radio telescope arrays yield detailed information on the radiation ground pattern, which can be used to reconstruct key EAS properties and infer the primary cosmic-ray composition. Here, we demonstrate a new observation mode of the Murchison Widefield Array (MWA), tailored to the observation of the sub-microsecond coherent bursts of radiation produced by EAS. We first show how an aggregate 30.72[Formula: see text]MHz bandwidth ([Formula: see text][Formula: see text]kHz frequency channels) recorded at 0.1[Formula: see text]ms resolution with the MWA’s voltage capture system (VCS) can be synthesized back to the full bandwidth Nyquist resolution of 16.3[Formula: see text]ns. This process, which involves “inverting” two sets of polyphase filterbanks, retains 90.5% of the signal-to-noise of a cosmic-ray signal. We then demonstrate the timing and positional accuracy of this mode by resolving the location of a calibrator pulse to within 5[Formula: see text]m. Finally, preliminary observations show that the rate of nanosecond radio-frequency interference (RFI) events is 0.1[Formula: see text]Hz, much lower than that found at the sites of other radio telescopes that study cosmic rays. We conclude that the identification of cosmic rays at the MWA, and hence with the low-frequency component of the Square Kilometre Array, is feasible with minimal loss of efficiency due to RFI.
EMC certification of a digital radio astronomy receiver: A case study
Publisher: IEEE
Date: 09-2012
Dual-frequency VLBI study of Centaurus A on sub-parsec scales
Publisher: EDP Sciences
Date: 20-05-2011
A MULTI-RESOLUTION, MULTI-EPOCH LOW RADIO FREQUENCY SURVEY OF THEKepler K2MISSION CAMPAIGN 1 FIELD
Publisher: American Astronomical Society
Date: 09-09-2016
CHIPS: THE COSMOLOGICAL H i POWER SPECTRUM ESTIMATOR
Publisher: American Astronomical Society
Date: 18-02-2016
ANTARES upper limits on the multi-TeV neutrino emission from the GRBs detected by IACTs
Publisher: IOP Publishing
Date: 03-2021
DOI: 10.1088/1475-7516/2021/03/092
Abstract: The first gamma-ray burst detections by Imaging Atmospheric Cherenkov Telescopes have been recently announced: GRB 190114C, detected by MAGIC, GRB 180720B and GRB 190829A, observed by H.E.S.S. A dedicated search for neutrinos in space and time coincidence with the gamma-ray emission observed by IACTs has been performed using ANTARES data. The search covers both the prompt and afterglow phases, yielding no neutrinos in coincidence with the three GRBs studied. Upper limits on the energetics of the neutrino emission are inferred. The resulting upper limits are several orders of magnitude above the observed gamma-ray emission, and they do not allow to constrain the available models.
What is the SKA-Low sensitivity for your favourite radio source?
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2021.63
Abstract: The Square Kilometre Array (SKA) will be the largest radio astronomy observatory ever built, providing unprecedented sensitivity over a very broad frequency band from 50 MHz to 15.3 GHz. The SKA’s low frequency component (SKA-Low), which will observe in the 50–350 MHz band, will be built at the Murchison Radio-astronomy Observatory (MRO) in Western Australia. It will consist of 512 stations each composed of 256 dual-polarised antennas, and the sensitivity of an in idual station is pivotal to the performance of the entire SKA-Low telescope. The answer to the question in the title is, it depends. The sensitivity of a low frequency array, such as an SKA-Low station, depends strongly on the pointing direction of the digitally formed station beam and the local sidereal time (LST), and is different for the two orthogonal polarisations of the antennas. The accurate prediction of the SKA-Low sensitivity in an arbitrary direction in the sky is crucial for future observation planning. Here, we present a sensitivity calculator for the SKA-Low radio telescope, using a database of pre-computed sensitivity values for two realisations of an SKA-Low station architecture. One realisation uses the log-periodic antennas selected for SKA-Low. The second uses a known benchmark, in the form of the bowtie dipoles of the Murchison Widefield Array. Prototype stations of both types were deployed at the MRO in 2019, and since then have been collecting commissioning and verification data. These data were used to measure the sensitivity of the stations at several frequencies and over at least 24 h intervals, and were compared to the predictions described in this paper. The sensitivity values stored in the SQLite database were pre-computed for the X, Y, and Stokes I polarisations in 10 MHz frequency steps, $\\scriptsize{1/2}$ hour LST intervals, and $5^\\circ$ resolution in pointing directions. The database allows users to quickly and easily estimate the sensitivity of SKA-Low for arbitrary observing parameters (your favourite object) using interactive web-based or command line interfaces. The sensitivity can be calculated using publicly available web interface ( sensitivity.skalow.link ) or a command line python package ( arcinsokolowski/station_beam ), which can also be used to calculate the sensitivity for arbitrary pointing directions, frequencies, and times without interpolations.
THE MURCHISON WIDEFIELD ARRAY 21 cm POWER SPECTRUM ANALYSIS METHODOLOGY
Publisher: American Astronomical Society
Date: 11-07-2016
Overview and Initial Results of the Very Long Baseline Interferometry Space Observatory Programme
Publisher: American Association for the Advancement of Science (AAAS)
Date: 18-09-1998
DOI: 10.1126/SCIENCE.281.5384.1825
Abstract: High angular resolution images of extragalactic radio sources are being made with the Highly Advanced Laboratory for Communications and Astronomy (HALCA) satellite and ground-based radio telescopes as part of the Very Long Baseline Interferometry (VLBI) Space Observatory Programme (VSOP). VSOP observations at 1.6 and 5 gigahertz of the milli–arc-second–scale structure of radio quasars enable the quasar core size and the corresponding brightness temperature to be determined, and they enable the motions of jet components that are close to the core to be studied. Here, VSOP images of the gamma-ray source 1156+295, the quasar 1548+056, the ultraluminous quasar 0014+813, and the superluminal quasar 0212+735 are presented and discussed.
Extended X-ray emission in PKS 1718−649
Publisher: EDP Sciences
Date: 04-2018
DOI: 10.1051/0004-6361/201833064
Abstract: PKS 1718−649 is one of the closest and most comprehensively studied candidates of a young active galactic nucleus (AGN) that is still embedded in its optical host galaxy. The compact radio structure, with a maximal extent of a few parsecs, makes it a member of the group of compact symmetric objects (CSO). Its environment imposes a turnover of the radio synchrotron spectrum towards lower frequencies, also classifying PKS 1718−649 as gigahertz-peaked radio spectrum (GPS) source. Its close proximity has allowed the first detection of extended X-ray emission in a GPS/CSO source with Chandra that is for the most part unrelated to nuclear feedback. However, not much is known about the nature of this emission. By co-adding all archival Chandra data and complementing these datasets with the large effective area of XMM-Newton , we are able to study the detailed physics of the environment of PKS 1718−649. Not only can we confirm that the bulk of the ≲kiloparsec-scale environment emits in the soft X-rays, but we also identify the emitting gas to form a hot, collisionally ionized medium. While the feedback of the central AGN still seems to be constrained to the inner few parsecs, we argue that supernovae are capable of producing the observed large-scale X-ray emission at a rate inferred from its estimated star formation rate.
The Pearson-Readhead Survey from space
Publisher: Elsevier BV
Date: 2000
Search for solar atmospheric neutrinos with the ANTARES neutrino telescope
Publisher: IOP Publishing
Date: 06-2022
DOI: 10.1088/1475-7516/2022/06/018
Abstract: Solar Atmospheric Neutrinos (SA ν s) are produced by the interaction of cosmic rays with the solar medium. The detection of SA ν s would provide useful information on the composition of primary cosmic rays as well as the solar density. These neutrinos represent an irreducible source of background for indirect searches for dark matter towards the Sun and the measurement of their flux would allow for a better assessment of the uncertainties related to these searches. In this paper we report on the analysis performed, based on an unbinned likelihood maximisation, to search for SA ν s with the ANTARES neutrino telescope. After analysing the data collected over 11 years, no evidence for a solar atmospheric neutrino signal has been found. An upper limit at 90% confidence level on the flux of solar atmospheric neutrinos has been obtained, equal to 7×10 -11 [ TeV -1 cm -2 s -1 ] at E ν = 1 TeV for the reference cosmic ray model assumed.
A search for long-time-scale, low-frequency radio transients
Publisher: Oxford University Press (OUP)
Date: 30-11-2016
The Engineering Development Array: A Low Frequency Radio Telescope Utilising SKA Precursor Technology
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.27
Abstract: We describe the design and performance of the Engineering Development Array, which is a low-frequency radio telescope comprising 256 dual-polarisation dipole antennas working as a phased array. The Engineering Development Array was conceived of, developed, and deployed in just 18 months via re-use of Square Kilometre Array precursor technology and expertise, specifically from the Murchison Widefield Array radio telescope. Using drift scans and a model for the sky brightness temperature at low frequencies, we have derived the Engineering Development Array’s receiver temperature as a function of frequency. The Engineering Development Array is shown to be sky-noise limited over most of the frequency range measured between 60 and 240 MHz. By using the Engineering Development Array in interferometric mode with the Murchison Widefield Array, we used calibrated visibilities to measure the absolute sensitivity of the array. The measured array sensitivity matches very well with a model based on the array layout and measured receiver temperature. The results demonstrate the practicality and feasibility of using Murchison Widefield Array-style precursor technology for Square Kilometre Array-scale stations. The modular architecture of the Engineering Development Array allows upgrades to the array to be rolled out in a staged approach. Future improvements to the Engineering Development Array include replacing the second stage beamformer with a fully digital system, and to transition to using RF-over-fibre for the signal output from first stage beamformers.
High time resolution search for prompt radio emission from the long GRB 210419A with the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 30-05-2022
Abstract: We present a low-frequency (170–200 MHz) search for prompt radio emission associated with the long GRB 210419A using the rapid-response mode of the Murchison Widefield Array (MWA), triggering observations with the Voltage Capture System for the first time. The MWA began observing GRB 210419A within 89 s of its detection by Swift, enabling us to capture any dispersion delayed signal emitted by this gamma-ray burst (GRB) for a typical range of redshifts. We conducted a standard single pulse search with a temporal and spectral resolution of $100\\, \\mu$s and 10 kHz over a broad range of dispersion measures from 1 to $5000\\, \\text{pc}\\, \\text{cm}^{-3}$, but none were detected. However, fluence upper limits of 77–224 Jy ms derived over a pulse width of 0.5–10 ms and a redshift of 0.6 & z & 4 are some of the most stringent at low radio frequencies. We compared these fluence limits to the GRB jet–interstellar medium interaction model, placing constraints on the fraction of magnetic energy (ϵB ≲ [0.05–0.1]). We also searched for signals during the X-ray flaring activity of GRB 210419A on minute time-scales in the image domain and found no emission, resulting in an intensity upper limit of $0.57\\, \\text{Jy}\\, \\text{beam}^{-1}$, corresponding to a constraint of ϵB ≲ 10−3. Our non-detection could imply that GRB 210419A was at a high redshift, there was not enough magnetic energy for low-frequency emission, or the radio waves did not escape from the GRB environment.
A High-Resolution Foreground Model for the MWA EoR1 Field: Model and Implications for EoR Power Spectrum Analysis
Publisher: Cambridge University Press (CUP)
Date: 2017
DOI: 10.1017/PASA.2017.26
Abstract: The current generation of experiments aiming to detect the neutral hydrogen signal from the Epoch of Reionisation (EoR) is likely to be limited by systematic effects associated with removing foreground sources from target fields. In this paper, we develop a model for the compact foreground sources in one of the target fields of the MWA’s EoR key science experiment: the ‘EoR1’ field. The model is based on both the MWA’s GLEAM survey and GMRT 150 MHz data from the TGSS survey, the latter providing higher angular resolution and better astrometric accuracy for compact sources than is available from the MWA alone. The model contains 5 049 sources, some of which have complicated morphology in MWA data, Fornax A being the most complex. The higher resolution data show that 13% of sources that appear point-like to the MWA have complicated morphology such as double and quad structure, with a typical separation of 33 arcsec. We derive an analytic expression for the error introduced into the EoR two-dimensional power spectrum due to peeling close double sources as single point sources and show that for the measured source properties, the error in the power spectrum is confined to high k ⊥ modes that do not affect the overall result for the large-scale cosmological signal of interest. The brightest 10 mis-modelled sources in the field contribute 90% of the power bias in the data, suggesting that it is most critical to improve the models of the brightest sources. With this hybrid model, we reprocess data from the EoR1 field and show a maximum of 8% improved calibration accuracy and a factor of two reduction in residual power in k -space from peeling these sources. Implications for future EoR experiments including the SKA are discussed in relation to the improvements obtained.
Limits on Fast Radio Bursts and other transient sources at 182 MHz using the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 03-2016
DOI: 10.1093/MNRAS/STW451
The parsec-scale morphology of Southern GPS Sources
Publisher: Cambridge University Press (CUP)
Date: 2016
DOI: 10.1017/PASA.2016.57
Abstract: Multi-frequency, multi-epoch ATCA observations of a s le of AGN resulted in the identification of nine new candidate Giga-hertz Peaked Spectrum sources. Here, we present Long Baseline Array observations at 4.8 GHz of the four candidates with no previously published VLBI image, and consider these together with previously published VLBI images of the other five sources. We find core-jet or compact double morphologies dominate, with further observations required to distinguish between these two possibilities for some sources. One of the nine candidates, PKS 1831–711, displays appreciable variability, suggesting its GPS spectrum is more ephemeral in nature. We focus in particular on the apparent relationship between a narrow spectral width and ‘compact double’ parsec-scale morphology, finding further ex les, but also exceptions to this trend. An examination of the VLBI morphologies high-redshift ( z 3) sub-class of GPS sources suggests that core-jet morphologies predominate in this class.
THE IMPORTANCE OF JET BENDING IN GAMMA-RAY AGNs—REVISITED
Publisher: American Astronomical Society
Date: 18-03-2014
A DEEP SEARCH FOR PROMPT RADIO EMISSION FROM THE SHORT GRB 150424A WITH THE MURCHISON WIDEFIELD ARRAY
Publisher: American Astronomical Society
Date: 24-11-2015
Search for neutrino counterparts of gravitational-wave events detected by LIGO and Virgo during run O2 with the ANTARES telescope
Publisher: Springer Science and Business Media LLC
Date: 05-2020
DOI: 10.1140/EPJC/S10052-020-8015-6
Abstract: An offline search for a neutrino counterpart to gravitational-wave (GW) events detected during the second observation run (O2) of Advanced-LIGO and Advanced-Virgo performed with ANTARES data is presented. In addition to the search for long tracks induced by $$\\nu _\\mu $$ ν μ ( $${\\overline{\\nu }}_{\\mu }$$ ν ¯ μ ) charged current interactions, a search for showering events induced by interactions of neutrinos of any flavour is conducted. The severe spatial and time coincidence provided by the gravitational-wave alert allows regions above the detector horizon to be probed, extending the ANTARES sensitivity over the entire sky. The results of this all-neutrino-flavour and all-sky time dependent analysis are presented. The search for prompt neutrino emission within ±500 s around the time of six GW events yields no neutrino counterparts. Upper limits on the neutrino spectral fluence and constraints on the isotropic energy radiated via high-energy neutrinos (from a few TeV to a few tens of PeV) are set for each GW event analysed.
The impact of point-source subtraction residuals on 21cm epoch of reionization estimation
Publisher: American Astronomical Society
Date: 06-09-2012
DUG Insight: A software package for big-data analysis and visualisation, and its demonstration for passive radar space situational awareness using radio telescopes
Publisher: Elsevier BV
Date: 07-2022
ON THE DETECTION AND TRACKING OF SPACE DEBRIS USING THE MURCHISON WIDEFIELD ARRAY. I. SIMULATIONS AND TEST OBSERVATIONS DEMONSTRATE FEASIBILITY
Publisher: American Astronomical Society
Date: 16-09-2013
The first very long baseline interferometric seti experiment
Publisher: American Astronomical Society
Date: 28-06-2012
Sensitivity of a low-frequency polarimetric radio interferometer
Publisher: EDP Sciences
Date: 02-2021
DOI: 10.1051/0004-6361/202039445
Abstract: Context. The sensitivity of a radio interferometer is a key figure of merit (FoM) for a radio telescope. The sensitivity of a single polarized interferometer is typically given as an antenna effective area over a system temperature, A e / T sys , assuming an unpolarized source. For a dual-polarized polarimetric interferometer intended to observe sources of unknown polarization, the state of polarization must not be assumed a priori. Furthermore, in contrast to the narrow field of view (FoV) of dish-based interferometers, the sensitivity of a polarimetric low-frequency radio interferometer warrants a careful review because of the very wide FoV of the dual-polarized antennas. A revision of this key FoM is particularly needed in the context of the Low-Frequency Square Kilometre Array (SKA-Low) where the sensitivity requirements are currently stated using A e / T sys for a single-polarized antenna system, which produces ambiguity for off-zenith angles. Aims. This paper aims to derive an expression for the sensitivity of a polarimetric radio interferometer that is valid for all-sky observations of arbitrarily polarized sources, with neither a restriction on FoV nor with any a priori assumption regarding the polarization state of the source. We verify the resulting formula with an all-sky observation using the Murchison Widefield Array telescope. Methods. The sensitivity expression was developed from first principles by applying the concept of system equivalent flux density (SEFD) to a polarimetric radio interferometer (not by computing A e / T sys ). The SEFD was calculated from the standard deviation of the noisy flux density estimate for a target source due to system noise. Results. The SEFD for a polarimetric radio interferometer is generally not 1/√2 of a single-polarized interferometer as is often assumed for narrow FoV. This assumption can lead to significant errors for a dual-polarized dipole based system, which is common in low-frequency radio astronomy: up to ∼15% for a zenith angle with a coverage of 45° and up to ∼45% for 60° coverage. The worst case errors occur in the diagonal planes of the dipole for very wide FoV. This is demonstrated through theory, simulation, and observations. Furthermore, using the resulting formulation, the calculation of the off-zenith sensitivity is straightforward and unambiguous. Conclusions. For wide FoV observations pertinent to a low-frequency radio interferometer such as SKA-Low, the narrow FoV and the single-polarized sensitivity expressions are not correct and should be replaced by the formula derived in this paper.
Geodetic VLBI correlation in software
Publisher: Springer Science and Business Media LLC
Date: 10-06-2009
High-cadence optical transient searches using drift scan imaging I: Proof of concept with a pre-prototype system
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.7
Abstract: An imaging technique with sensitivity to short duration optical transients is described. The technique is based on the use of wide-field cameras operating in a drift scanning mode, whereby persistent objects produce trails on the sensor and short duration transients occupy localised groups of pixels. A benefit of the technique is that sensitivity to short duration signals is not accompanied by massive data rates, because the exposure time is much greater than the transient duration. The technique is demonstrated using a pre-prototype system composed of readily available and inexpensive commercial components, coupled with common coding environments, commercially available software, and free web-based services. The performance of the technique and the pre-prototype system is explored, including aspects of photometric and astrometric calibration, detection sensitivity, characterisation of candidate transients, and the differentiation of astronomical signals from non-astronomical signals (primarily glints from satellites in Earth orbit and cosmic ray hits on sensor pixels). Test observations were made using the pre-prototype system, achieving sensitivity to transients with 21-ms duration, resulting in the detection of five candidate transients. An investigation of these candidates concludes they are most likely due to cosmic ray hits on the sensor and/or satellites. The sensitivity obtained with the pre-prototype system is such that, under some models for the optical emission from fast radio bursts (FRBs), the detection of a typical FRB, such as FRB181228, to a distance of approximately 100 Mpc is plausible. Several options for improving the system/technique in the future are described.
Microstructurally controlled trace element (Zr, U–Pb) concentrations in metamorphic rutile: An example from the amphibolites of the Bergen Arcs
Publisher: Wiley
Date: 25-11-2019
DOI: 10.1111/JMG.12514
Radio and gamma-ray properties of extragalactic jets from the TANAMI sample
Publisher: EDP Sciences
Date: 04-05-2016
PKS 1018-42: A Powerful, Kinetically Dominated Quasar
Publisher: American Astronomical Society
Date: 28-02-2006
DOI: 10.1086/503277
The development of non-coherent passive radar techniques for space situational awareness with the Murchison Widefield Array
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.1
Abstract: The number of active and non active satellites in Earth orbit has dramatically increased in recent decades, requiring the development of novel surveillance techniques to monitor and track them. In this paper, we build upon previous non-coherent passive radar space surveillance demonstrations undertaken using the Murchison Widefield Array (MWA). We develop the concept of the Dynamic Signal to Noise Ratio Spectrum (DSNRS) in order to isolate signals of interest (reflections of FM transmissions of objects in orbit) and efficiently differentiate them from direct path reception events. We detect and track Alouette-2, ALOS, UKube-1, the International Space Station, and Duchifat-1 in this manner. We also identified out-of-band transmissions from Duchifat-1 and UKube-1 using these techniques, demonstrating the MWA’s capability to look for spurious transmissions from satellites. We identify an offset from the locations predicted by the cataloged orbital parameters for some of the satellites, demonstrating the potential of using MWA for satellite catalog maintenance. These results demonstrate the capability of the MWA for Space Situational Awareness and we describe future work in this area.
Hunting for Radio Emission from the Intermittent Pulsar J1107-5907 at Low Frequencies
Publisher: American Astronomical Society
Date: 19-12-2018
Low Altitude Solar Magnetic Reconnection, Type III Solar Radio Bursts, and X-ray Emissions
Publisher: Springer Science and Business Media LLC
Date: 26-01-2018
DOI: 10.1038/S41598-018-19195-3
Abstract: Type III solar radio bursts are the Sun’s most intense and frequent nonthermal radio emissions. They involve two critical problems in astrophysics, plasma physics, and space physics: how collective processes produce nonthermal radiation and how magnetic reconnection occurs and changes magnetic energy into kinetic energy. Here magnetic reconnection events are identified definitively in Solar Dynamics Observatory UV-EUV data, with strong upward and downward pairs of jets, current sheets, and cusp-like geometries on top of time-varying magnetic loops, and strong outflows along pairs of open magnetic field lines. Type III bursts imaged by the Murchison Widefield Array and detected by the Learmonth radiospectrograph and STEREO B spacecraft are demonstrated to be in very good temporal and spatial coincidence with specific reconnection events and with bursts of X-rays detected by the RHESSI spacecraft. The reconnection sites are low, near heights of 5–10 Mm. These images and event timings provide the long-desired direct evidence that semi-relativistic electrons energized in magnetic reconnection regions produce type III radio bursts. Not all the observed reconnection events produce X-ray events or coronal or interplanetary type III bursts thus different special conditions exist for electrons leaving reconnection regions to produce observable radio, EUV, UV, and X-ray bursts.
The Halo, Hot Spots, and Jet/Cloud Interaction of PKS 2153−69
Publisher: American Astronomical Society
Date: 04-2005
DOI: 10.1086/428280
Erratum: Science with the murchison widefield array: Phase I results and phase II opportunities (Publications of the Astronomical Society of Australia (2019) 36 (1-30) DOI: 10.1017/pasa.2019.41)
Publisher: Cambridge University Press (CUP)
Date: 2020
DOI: 10.1017/PASA.2020.4
Capturing the electromagnetic counterparts of binary neutron star mergers through low-latency gravitational wave triggers
Publisher: Oxford University Press (OUP)
Date: 11-03-2016
DOI: 10.1093/MNRAS/STW576
THE IMPACT OF FREQUENCY STANDARDS ON COHERENCE IN VLBI AT THE HIGHEST FREQUENCIES
Publisher: American Astronomical Society
Date: 14-09-2012
Testing Potential New Sites for Optical Telescopes in Australia
Publisher: Cambridge University Press (CUP)
Date: 2013
Abstract: In coming years, Australia may find the need to build new optical telescopes to continue local programmes, contribute to global survey projects, and form a local multi-wavelength connection for the new radio telescopes being built. In this study, we refine possible locations for a new optical telescope by studying remotely sensed meteorological infrared data to ascertain expected cloud coverage rates across Australia, and combine these data with a digital elevation model using a geographic information system. We find that the best sites within Australia for building optical telescopes are likely to be on the highest mountains in the Hamersley Range in northwest Western Australia, while the MacDonnell Ranges in the Northern Territory may also be appropriate. We believe that similar seeing values to Siding Spring should be obtainable and with significantly more observing time at the identified sites. We expect to find twice as many clear nights as at current telescope sites. These sites are thus prime locations for future on-site testing.
The 1997 hard-state outburst of the X-ray transient GS 1354-64/BW Cir
Publisher: Oxford University Press (OUP)
Date: 11-05-2001
The KM3NeT multi-PMT optical module
Publisher: IOP Publishing
Date: 07-2022
DOI: 10.1088/1748-0221/17/07/P07038
Abstract: The optical module of the KM3NeT neutrino telescope is an innovative multi-faceted large area photodetection module. It contains 31 three-inch photomultiplier tubes in a single 0.44 m diameter pressure-resistant glass sphere. The module is a sensory device also comprising calibration instruments and electronics for power, readout and data acquisition. It is capped with a breakout-box with electronics for connection to an electro-optical cable for power and long-distance communication to the onshore control station. The design of the module was qualified for the first time in the deep sea in 2013. Since then, the technology has been further improved to meet requirements of scalability, cost-effectiveness and high reliability. The module features a sub-nanosecond timing accuracy and a dynamic range allowing the measurement of a single photon up to a cascade of thousands of photons, suited for the measurement of the Cherenkov radiation induced in water by secondary particles from interactions of neutrinos with energies in the range of GeV to PeV. A distributed production model has been implemented for the delivery of more than 6000 modules in the coming few years with an average production rate of more than 100 modules per month. In this paper a review is presented of the design of the multi-PMT KM3NeT optical module with a proven effective background suppression and signal recognition and sensitivity to the incoming direction of photons.
THE IMPACT OF THE IONOSPHERE ON GROUND-BASED DETECTION OF THE GLOBAL EPOCH OF REIONIZATION SIGNAL
Publisher: American Astronomical Society
Date: 22-10-2015
The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey - II. Survey status, pulsar census, and first pulsar discoveries
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.18
Abstract: In Paper I, we presented an overview of the Southern-sky MWA Rapid Two-metre (SMART) survey, including the survey design and search pipeline. While the combination of MWA’s large field-of-view and the voltage capture system brings a survey speed of ${\\sim} 450\\, {\\textrm{deg}}^{2}\\,\\textrm{h}^{-1}$ , the progression of the survey relies on the availability of compact configuration of the Phase II array. Over the past few years, by taking advantage of multiple windows of opportunity when the compact configuration was available, we have advanced the survey to 75% of the planned sky coverage. To date, about 10% of the data collected thus far have been processed for a first-pass search, where 10 min of observation is processed for dispersion measures out to 250 ${\\textrm{pc cm}}^{-3}$ , to realise a shallow survey that is largely sensitive to long-period pulsars. The ongoing analysis has led to two new pulsar discoveries, as well as an independent discovery and a rediscovery of a previously incorrectly characterised pulsar, all from ${\\sim} 3\\% $ of the data for which candidate scrutiny is completed. In this sequel to Paper I, we describe the strategies for further detailed follow-up including improved sky localisation and convergence to timing solution, and illustrate them using ex le pulsar discoveries. The processing has also led to re-detection of 120 pulsars in the SMART observing band, bringing the total number of pulsars detected to date with the MWA to 180, and these are used to assess the search sensitivity of current processing pipelines. The planned second-pass (deep survey) processing is expected to yield a three-fold increase in sensitivity for long-period pulsars, and a substantial improvement to millisecond pulsars by adopting optimal de-dispersion plans. The SMART survey will complement the highly successful Parkes High Time Resolution Universe survey at 1.2–1.5 GHz, and inform future large survey efforts such as those planned with the low-frequency Square Kilometre Array (SKA-Low).
The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey - I. Survey design and processing pipeline
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.17
Abstract: We present an overview of the Southern-sky MWA Rapid Two-metre (SMART) pulsar survey that exploits the Murchison Widefield Array’s large field of view and voltage-capture system to survey the sky south of 30 $^{\\circ}$ in declination for pulsars and fast transients in the 140–170 MHz band. The survey is enabled by the advent of the Phase II MWA’s compact configuration, which offers an enormous efficiency in beam-forming and processing costs, thereby making an all-sky survey of this magnitude tractable with the MWA. Even with the long dwell times employed for the survey (4800 s), data collection can be completed in $ $ 100 h of telescope time, while still retaining the ability to reach a limiting sensitivity of $\\sim$ 2–3 mJy (at 150 MHz, near zenith), which is effectively 3–5 times deeper than the previous-generation low-frequency southern-sky pulsar survey, completed in the 1990s. Each observation is processed to generate $\\sim$ 5000–8000 tied-array beams that tessellate the full $\\sim 610\\, {\\textrm{deg}^{2}}$ field of view (at 155 MHz), which are then processed to search for pulsars. The voltage-capture recording of the survey also allows a multitude of post hoc processing options including the reprocessing of data for higher time resolution and even exploring image-based techniques for pulsar candidate identification. Due to the substantial computational cost in pulsar searches at low frequencies, the survey data processing is undertaken in multiple passes: in the first pass, a shallow survey is performed, where 10 min of each observation is processed, reaching about one-third of the full-search sensitivity. Here we present the system overview including details of ongoing processing and initial results. Further details including first pulsar discoveries and a census of low-frequency detections are presented in a companion paper. Future plans include deeper searches to reach the full sensitivity and acceleration searches to target binary and millisecond pulsars. Our simulation analysis forecasts $\\sim$ 300 new pulsars upon the completion of full processing. The SMART survey will also generate a complete digital record of the low-frequency sky, which will serve as a valuable reference for future pulsar searches planned with the low-frequency Square Kilometre Array.
Source Detection with Interferometric Datasets
Publisher: Cambridge University Press (CUP)
Date: 09-2011
DOI: 10.1017/S1743921312001263
Abstract: The detection of sources in interferometric radio data typically relies on extracting information from images, formed by Fourier transform of the underlying visibility dataset, and CLEANed of contaminating sidelobes through iterative deconvolution. Variable and transient radio sources span a large range of variability timescales, and their study has the potential to enhance our knowledge of the dynamic universe. Their detection and classification involve large data rates and non-stationary PSFs, commensal observing programs and ambitious science goals, and will demand a paradigm shift in the deployment of next-generation instruments. Optimal source detection and classification in real time requires efficient and automated algorithms. On short time-scales variability can be probed with an optimal matched filter detector applied directly to the visibility dataset. This paper shows the design of such a detector, and some preliminary detection performance results.
First results of VSOP imaging of strong GPS sources
Publisher: Elsevier BV
Date: 2000
Detection of compact radio emission from Circinus X-1 with the first Southern hemisphere e-VLBI experiment
Publisher: Oxford University Press (OUP)
Date: 09-2007
Search for dark matter towards the Galactic Centre with 11 years of ANTARES data
Publisher: Elsevier BV
Date: 06-2020
VSOP monitoring of the quasar 1928+738
Publisher: Elsevier BV
Date: 2000
The Murchison Widefield Array Transients Survey (MWATS). A search for low frequency variability in a bright Southern hemisphere sample
Publisher: Oxford University Press (OUP)
Date: 18-10-2018
Multi-scale feedback and feeding in the closest radio galaxy Centaurus A
Publisher: Springer Science and Business Media LLC
Date: 22-12-2021
Ten Milliparsec-Scale Structure of the Nucleus Region in Centaurus A
Publisher: Oxford University Press (OUP)
Date: 25-04-2006
Precision Southern Hemisphere pulsar vlbi astrometry: Techniques and results for PSR J1559-4438
Publisher: American Astronomical Society
Date: 12-2009
Engineering Development Array 2: design, performance, and lessons from an SKA-Low prototype station
Publisher: SPIE-Intl Soc Optical Eng
Date: 20-12-2022
Parametrizing Epoch of Reionization foregrounds: a deep survey of low-frequency point-source spectra with the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 11-02-2016
DOI: 10.1093/MNRAS/STW310
High-cadence optical transient searches using drift scan imaging III: Development of an inexpensive drive control system and characterisation and correction of drive system periodic errors
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.28
Abstract: In order to further develop and implement novel drift scan imaging experiments to undertake wide-field, high time resolution surveys for millisecond optical transients, an appropriate telescope drive system is required. This paper describes the development of a simple and inexpensive hardware and software system to monitor, characterise, and correct the primary category of telescope drive errors and periodic errors due to imperfections in the drive and gear chain. A model for the periodic errors is generated from direct measurements of the telescope drive shaft rotation, verified by comparison to astronomical measurements of the periodic errors. The predictive model is generated and applied in real time in the form of corrections to the drive rate. A demonstration of the system shows that inherent periodic errors of peak-to-peak litude ${\\sim}{100}''$ are reduced to below the seeing limit of ${\\sim}3''$ . This demonstration allowed an estimate of the uncertainties on the transient sensitivity timescales of the prototype survey of Tingay $\\& $ Joubert (2021), with the nominal timescale sensitivity of 21 ms revised to be in the range of $20\\!-\\!22$ ms, which does not significantly affect the results of the experiment. The correction system will be adopted into the final version of high-cadence imaging experiment, which is currently under construction. The correction system is inexpensive ( $ \\!{\\$}$ A100) and composed of readily available hardware and is readily adaptable to other applications. Design details and codes are therefore made publicly available.
Ionospheric Modelling using GPS to Calibrate the MWA. I: Comparison of First Order Ionospheric Effects between GPS Models and MWA Observations
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.29
Abstract: We compare first-order (refractive) ionospheric effects seen by the MWA with the ionosphere as inferred from GPS data. The first-order ionosphere manifests itself as a bulk position shift of the observed sources across an MWA field of view. These effects can be computed from global ionosphere maps provided by GPS analysis centres, namely the CODE. However, for precision radio astronomy applications, data from local GPS networks needs to be incorporated into ionospheric modelling. For GPS observations, the ionospheric parameters are biased by GPS receiver instrument delays, among other effects, also known as receiver DCBs. The receiver DCBs need to be estimated for any non-CODE GPS station used for ionosphere modelling. In this work, single GPS station-based ionospheric modelling is performed at a time resolution of 10 min. Also the receiver DCBs are estimated for selected Geoscience Australia GPS receivers, located at Murchison Radio Observatory, Yarragadee, Mount Magnet and Wiluna. The ionospheric gradients estimated from GPS are compared with that inferred from MWA. The ionospheric gradients at all the GPS stations show a correlation with the gradients observed with the MWA. The ionosphere estimates obtained using GPS measurements show promise in terms of providing calibration information for the MWA.
Spectral Flattening at Low Frequencies in Crab Giant Pulses
Publisher: American Astronomical Society
Date: 06-12-2017
GLEAM: The GaLactic and Extragalactic All-Sky MWA Survey
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.26
Abstract: GLEAM, the GaLactic and Extragalactic All-sky MWA survey, is a survey of the entire radio sky south of declination + 25° at frequencies between 72 and 231 MHz, made with the MWA using a drift scan method that makes efficient use of the MWA’s very large field-of-view. We present the observation details, imaging strategies, and theoretical sensitivity for GLEAM. The survey ran for two years, the first year using 40-kHz frequency resolution and 0.5-s time resolution the second year using 10-kHz frequency resolution and 2 s time resolution. The resulting image resolution and sensitivity depends on observing frequency, sky pointing, and image weighting scheme. At 154 MHz, the image resolution is approximately 2.5 × 2.2/cos (δ + 26.7°) arcmin with sensitivity to structures up to ~ 10° in angular size. We provide tables to calculate the expected thermal noise for GLEAM mosaics depending on pointing and frequency and discuss limitations to achieving theoretical noise in Stokes I images. We discuss challenges, and their solutions, that arise for GLEAM including ionospheric effects on source positions and linearly polarised emission, and the instrumental polarisation effects inherent to the MWA’s primary beam.
Nanobeacon: A time calibration device for the KM3NeT neutrino telescope
Publisher: Elsevier BV
Date: 10-2022
A Molecular Line Survey around Orion at Low Frequencies with the MWA
Publisher: American Astronomical Society
Date: 21-06-2018
Multi-epoch Low-radio-frequency Surveys of the Kepler K2 Mission Campaign Fields 3, 4, and 5 with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 25-06-2019
DiFX: A software correlator for very long baseline interferometry using multiprocessor computing environments
Publisher: IOP Publishing
Date: 03-2007
DOI: 10.1086/513572
The 1997 hard state outburst of the X-ray transient GS 1354-64/BW Cir
Publisher: Springer Science and Business Media LLC
Date: 2001
The jet/wind outflow in Centaurus A: A local laboratory for AGN feedback
Publisher: Oxford University Press (OUP)
Date: 09-11-2018
A high-resolution wide-field radio survey of M51
Publisher: Oxford University Press (OUP)
Date: 07-2015
Ultimate precision in cosmic-ray radio detection — the SKA
Publisher: EDP Sciences
Date: 2017
First results from AAVS 0.5: A prototype array for next-generation radio astronomy
Publisher: IEEE
Date: 09-2013
MULTI-EPOCH VERY LONG BASELINE INTERFEROMETRIC OBSERVATIONS OF THE NUCLEAR STARBURST REGION OF NGC 253: IMPROVED MODELING OF THE SUPERNOVA AND STAR FORMATION RATES
Publisher: American Astronomical Society
Date: 22-11-2013
Indigenous Australian artists and astrophysicists come together to communicate science and culture via art
Publisher: Sissa Medialab Srl
Date: 17-12-2018
DOI: 10.22323/2.17040302
Abstract: During the International Year of Astronomy in 2009, we initiated a collaboration between astrophysicists in Western Australia working toward building the largest telescope on Earth, the Square Kilometre Array (SKA), and Indigenous artists living in the region where the SKA is to be built. We came together to explore deep traditions in Indigenous culture, including perspectives of the night sky, and the modern astrophysical understanding of the Universe. Over the course of the year, we travelled as a group and c ed at the SKA site, we sat under the stars and shared stories about the constellations, and we talked about the telescopes we wanted to build and how they could sit on the Indigenous traditional country. We found lots of interesting points of connection in our discussions and both artists and astronomers found inspiration. The artists then produced original works of art, curated as an exhibition called “Ilgarijiri — Things belonging to the Sky” in the language of the Wadjarri Yamatji people. This was exhibited in Geraldton, Perth, Canberra, South Africa, Brussels, the U.S.A., and Germany over the course of the next few years. In 2015, the concept went further, connecting with Indigenous artists from South Africa, resulting in the “Shared Sky” exhibition, which now tours the ten SKA member countries. The exhibitions communicate astrophysics and traditional Indigenous stories, as well as carry to the world Indigenous culture and art forms. The process behind the collaboration is an ex le of the Reconciliation process in Australia, successful through thoughtful and respectful engagements, built around common human experiences and points of contact (the night sky). This Commentary briefly describes the collaboration, its outcomes, and future work.
Search for Spatial Correlations of Neutrinos with Ultra-high-energy Cosmic Rays
Publisher: American Astronomical Society
Date: 08-2022
Abstract: For several decades, the origin of ultra-high-energy cosmic rays (UHECRs) has been an unsolved question of high-energy astrophysics. One approach for solving this puzzle is to correlate UHECRs with high-energy neutrinos, since neutrinos are a direct probe of hadronic interactions of cosmic rays and are not deflected by magnetic fields. In this paper, we present three different approaches for correlating the arrival directions of neutrinos with the arrival directions of UHECRs. The neutrino data are provided by the IceCube Neutrino Observatory and ANTARES, while the UHECR data with energies above ∼50 EeV are provided by the Pierre Auger Observatory and the Telescope Array. All experiments provide increased statistics and improved reconstructions with respect to our previous results reported in 2015. The first analysis uses a high-statistics neutrino s le optimized for point-source searches to search for excesses of neutrino clustering in the vicinity of UHECR directions. The second analysis searches for an excess of UHECRs in the direction of the highest-energy neutrinos. The third analysis searches for an excess of pairs of UHECRs and highest-energy neutrinos on different angular scales. None of the analyses have found a significant excess, and previously reported overfluctuations are reduced in significance. Based on these results, we further constrain the neutrino flux spatially correlated with UHECRs.
The VLBI Space Observatory Programme and the Radio-Astronomical Satellite HALCA
Publisher: Oxford University Press (OUP)
Date: 12-2000
DELAY SPECTRUM WITH PHASE-TRACKING ARRAYS: EXTRACTING THE H i POWER SPECTRUM FROM THE EPOCH OF REIONIZATION
Publisher: American Astronomical Society
Date: 19-12-2016
A Southern-Hemisphere all-sky radio transientmonitor for SKA-Low prototype stations
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.16
Abstract: We present the first Southern-Hemisphere all-sky imager and radio-transient monitoring system implemented on two prototype stations of the low-frequency component of the Square Kilometre Array (SKA-Low). Since its deployment, the system has been used for real-time monitoring of the recorded commissioning data. Additionally, a transient searching algorithm has been executed on the resulting all-sky images. It uses a difference imaging technique to enable identification of a wide variety of transient classes, ranging from human-made radio-frequency interference to genuine astrophysical events. Observations at the frequency 159.375 MHz and higher in a single coarse channel ( $\\approx$ 0.926 MHz) were made with 2 s time resolution, and multiple nights were analysed generating thousands of images. Despite having modest sensitivity ( $\\sim$ few Jy beam –1 ), using a single coarse channel and 2-s imaging, the system was able to detect multiple bright transients from PSR B0950+08, proving that it can be used to detect bright transients of an astrophysical origin. The unusual, extreme activity of the pulsar PSR B0950+08 (maximum flux density $\\sim$ 155 Jy beam –1 ) was initially detected in a ‘blind’ search in the 2020 April 10/11 data and later assigned to this specific pulsar. The limitations of our data, however, prevent us from making firm conclusions of the effect being due to a combination of refractive and diffractive scintillation or intrinsic emission mechanisms. The system can routinely collect data over many days without interruptions the large amount of recorded data at 159.375 and 229.6875 MHz allowed us to determine a preliminary transient surface density upper limit of $1.32 \\times 10^{-9} \\text{deg}^{-2}$ for a timescale and limiting flux density of 2 s and 42 Jy, respectively. In the future, we plan to extend the observing bandwidth to tens of MHz and improve time resolution to tens of milliseconds in order to increase the sensitivity and enable detections of fast radio bursts below 300 MHz.
Remnant radio galaxies discovered in a multi-frequency survey
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2020.49
Abstract: The remnant phase of a radio galaxy begins when the jets launched from an active galactic nucleus are switched off. To study the fraction of radio galaxies in a remnant phase, we take advantage of a $8.31$ deg $^2$ subregion of the GAMA 23 field which comprises of surveys covering the frequency range 0.1–9 GHz. We present a s le of 104 radio galaxies compiled from observations conducted by the Murchison Widefield Array (216 MHz), the Australia Square Kilometer Array Pathfinder (887 MHz), and the Australia Telescope Compact Array (5.5 GHz). We adopt an ‘absent radio core’ criterion to identify 10 radio galaxies showing no evidence for an active nucleus. We classify these as new candidate remnant radio galaxies. Seven of these objects still display compact emitting regions within the lobes at 5.5 GHz at this frequency the emission is short-lived, implying a recent jet switch off. On the other hand, only three show evidence of aged lobe plasma by the presence of an ultra-steep-spectrum ( $\\alpha -1.2$ ) and a diffuse, low surface brightness radio morphology. The predominant fraction of young remnants is consistent with a rapid fading during the remnant phase. Within our s le of radio galaxies, our observations constrain the remnant fraction to $4\\%\\lesssim f_{\\mathrm{rem}} \\lesssim 10\\%$ the lower limit comes from the limiting case in which all remnant candidates with hotspots are simply active radio galaxies with faint, undetected radio cores. Finally, we model the synchrotron spectrum arising from a hotspot to show they can persist for 5–10 Myr at 5.5 GHz after the jets switch of—radio emission arising from such hotspots can therefore be expected in an appreciable fraction of genuine remnants.
The Parsec-Scale Structure and Evolution of the Nearby Fanaroff-Riley Type II Radio Galaxy Pictor A
Publisher: American Astronomical Society
Date: 04-2000
DOI: 10.1086/301283
Murchison Widefield Array rapid-response observations of the short GRB 180805A
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.15
Abstract: Here we present stringent low-frequency (185 MHz) limits on coherent radio emission associated with a short-duration gamma-ray burst (SGRB). Our observations of the short gamma-ray burst (GRB) 180805A were taken with the upgraded Murchison Widefield Array (MWA) rapid-response system, which triggered within 20s of receiving the transient alert from the Swift Burst Alert Telescope, corresponding to 83.7 s post-burst. The SGRB was observed for a total of 30 min, resulting in a $3\\sigma$ persistent flux density upper limit of 40.2 mJy beam –1 . Transient searches were conducted at the Swift position of this GRB on 0.5 s, 5 s, 30 s and 2 min timescales, resulting in $3\\sigma$ limits of 570–1 830, 270–630, 200–420, and 100–200 mJy beam –1 , respectively. We also performed a dedispersion search for prompt signals at the position of the SGRB with a temporal and spectral resolution of 0.5 s and 1.28 MHz, respectively, resulting in a $6\\sigma$ fluence upper-limit range from 570 Jy ms at DM $=3\\,000$ pc cm –3 ( $z\\sim 2.5$ ) to 1 750 Jy ms at DM $=200$ pc cm –3 ( $z\\sim 0.1)$ , corresponding to the known redshift range of SGRBs. We compare the fluence prompt emission limit and the persistent upper limit to SGRB coherent emission models assuming the merger resulted in a stable magnetar remnant. Our observations were not sensitive enough to detect prompt emission associated with the alignment of magnetic fields of a binary neutron star just prior to the merger, from the interaction between the relativistic jet and the interstellar medium (ISM) or persistent pulsar-like emission from the spin-down of the magnetar. However, in the case of a more powerful SGRB (a gamma-ray fluence an order of magnitude higher than GRB 180805A and/or a brighter X-ray counterpart), our MWA observations may be sensitive enough to detect coherent radio emission from the jet-ISM interaction and/or the magnetar remnant. Finally, we demonstrate that of all current low- frequency radio telescopes, only the MWA has the sensitivity and response times capable of probing prompt emission models associated with the initial SGRB merger event.
A High Time-resolution Study of the Millisecond Pulsar J2241−5236 at Frequencies Below 300 MHz
Publisher: American Astronomical Society
Date: 10-09-2019
Centaurus A, the core of the problem.
Publisher: CSIRO Publishing
Date: 1994
DOI: 10.1071/PH940619
Abstract: The bright, peculiar elliptical galaxy Centaurus A (NGC 5128, PKS 1322-427) was one of the first extragalactic radio sources to be optically identified (Bolton et al 1949). At a distance of 4 Mpc, Centaurus A is the closest active radio galaxy and affords the highest linear imaging resolution (1 mas ~ 0�02 pc) and hence the best prospects for studying an active nucleus close to the central radio source. We present the results of multi-epoch, 8� 4-G Hz, very long baseline interferometry (VLBI), imaging observations of the nucleus made over the past three years. The nucleus possesses a core-jet structure where the inner portion of the jet shows apparent linear motion with a velocity substantially less than the speed of light.
An analysis of the halo and relic radio emission from Abell 3376 from Murchison Widefield Array observations
Publisher: Oxford University Press (OUP)
Date: 30-06-2015
Architecture and performance of the KM3NeT front-end firmware
Publisher: SPIE-Intl Soc Optical Eng
Date: 07-01-2021
The Parsec-Scale Jet of PKS 0637−752
Publisher: Oxford University Press (OUP)
Date: 25-04-2006
High cadence optical transient searches using drift scan imaging II: Event rate upper limits on optical transients of duration <21 ms and magnitude <6.6
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2020.53
Abstract: We have realised a simple prototype system to perform searches for short timescale optical transients, utilising the novel drift scan imaging technique described by Tingay (2020). We used two coordinated and aligned cameras, with an overlap field of view of approximately 3.7 deg $^2$ , to capture over $34\\,000 \\times 5$ second images during approximately 24 h of observing. The system is sensitive to optical transients, due to an effective exposure time per pixel of 21 ms, brighter than a V magnitude of 6.6. In our 89.7 deg $^2$ h of observations, we find no candidate astronomical transients, giving an upper limit to the rate of these transients of 0.8 per deg $^2$ per day, competitive with other experiments of this type. The system is triggered by reflections from satellites and various instrumental effects, which are easily identifiable due to the two camera system. The next step in the development of this promising technique is to move to a system with larger apertures and wider fields of view.
VLBI Observations of Southern EGRET Identifications. II. VLBA Observations and the Importance of Jet Bending in Gamma‐Ray Sources
Publisher: American Astronomical Society
Date: 20-06-1998
DOI: 10.1086/305759
Characterization of a Low-Frequency Radio Astronomy Prototype Array in Western Australia
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 12-2015
The Subparsec-Scale Radio Properties of Southern Starburst Galaxies. I. Supernova Remnants, the Supernova Rate, and the Ionized Medium in the NGC 253 Starburst
Publisher: American Astronomical Society
Date: 10-08-2006
DOI: 10.1086/506475
X-ray magnitude of the 4 November 2003 solar flare inferred from the ionospheric attenuation of the galactic radio background
Publisher: American Geophysical Union (AGU)
Date: 09-2005
DOI: 10.1029/2004JA010960
The unusual multiwavelength properties of the gamma-ray source PMN J1603−4904
Publisher: EDP Sciences
Date: 30-01-2014
Uncued Detection and Initial Orbit Determination From Short Observations With the Murchison Widefield Array
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 10-2021
TANAMI: tracking active galactic nuclei with austral milliarcsecond interferometry
Publisher: EDP Sciences
Date: 09-2010
Search for magnetic monopoles with ten years of the ANTARES neutrino telescope
Publisher: Elsevier BV
Date: 06-2022
Improved sensitivity for space domain awareness observations with the murchison widefield array
Publisher: Elsevier BV
Date: 08-2022
GaLactic and Extragalactic All-sky Murchison Widefield Array survey eXtended (GLEAM-X) I: Survey description and initial data release
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.17
Abstract: We describe a new low-frequency wideband radio survey of the southern sky. Observations covering 72–231 MHz and Declinations south of $+30^\\circ$ have been performed with the Murchison Widefield Array “extended” Phase II configuration over 2018–2020 and will be processed to form data products including continuum and polarisation images and mosaics, multi-frequency catalogues, transient search data, and ionospheric measurements. From a pilot field described in this work, we publish an initial data release covering 1,447 $\\mathrm{deg}^2$ over $4\\,\\mathrm{h}\\leq \\mathrm{RA}\\leq 13\\,\\mathrm{h}$ , $-32.7^\\circ \\leq \\mathrm{Dec} \\leq -20.7^\\circ$ . We process twenty frequency bands s ling 72–231 MHz, with a resolution of 2′–45 ′′ , and produce a wideband source-finding image across 170–231 MHz with a root mean square noise of $1.27\\pm0.15\\,\\mathrm{mJy\\,beam}^{-1}$ . Source-finding yields 78,967 components, of which 71,320 are fitted spectrally. The catalogue has a completeness of 98% at ${{\\sim}}50\\,\\mathrm{mJy}$ , and a reliability of 98.2% at $5\\sigma$ rising to 99.7% at $7\\sigma$ . A catalogue is available from Vizier images are made available via the PASA datastore, AAO Data Central, and SkyView. This is the first in a series of data releases from the GLEAM-X survey.
A Large-Scale, Low-Frequency Murchison Widefield Array Survey of Galactic H ii Regions between 260 < l < 340
Publisher: Cambridge University Press (CUP)
Date: 2016
DOI: 10.1017/PASA.2016.19
Abstract: We have compiled a catalogue of H ii regions detected with the Murchison Widefield Array between 72 and 231 MHz. The multiple frequency bands provided by the Murchison Widefield Array allow us identify the characteristic spectrum generated by the thermal Bremsstrahlung process in H ii regions. We detect 306 H ii regions between 260° l 340° and report on the positions, sizes, peak, integrated flux density, and spectral indices of these H ii regions. By identifying the point at which H ii regions transition from the optically thin to thick regime, we derive the physical properties including the electron density, ionised gas mass, and ionising photon flux, towards 61 H ii regions. This catalogue of H ii regions represents the most extensive and uniform low frequency survey of H ii regions in the Galaxy to date.
100 μas RESOLUTION VLBI IMAGING OF ANISOTROPIC INTERSTELLAR SCATTERING TOWARD PULSAR B0834+06
Publisher: American Astronomical Society
Date: 09-12-2009
Archival VLBA Observations of the Cygnus A Nuclear Radio Transient (Cyg A-2) Strengthen the Tidal Disruption Event Interpretation
Publisher: American Astronomical Society
Date: 23-09-2020
Space VLBI observations of southern hemisphere gamma-ray and non-gamma-ray AGN: First results for PKS 0637-752
Publisher: Elsevier BV
Date: 2000
V-FASTR: The VLBA fast radio transients experiment
Publisher: American Astronomical Society
Date: 22-06-2011
Improving the Epoch of Reionization Power Spectrum Results from Murchison Widefield Array Season 1 Observations
Publisher: American Astronomical Society
Date: 07-10-2019
Detection of fast radio transients with multiple stations: A case study using the very long baseline array
Publisher: American Astronomical Society
Date: 22-06-2011
Dark matter annihilation in ω Centauri: Astrophysical implications derived from the MWA radio data
Publisher: Elsevier BV
Date: 12-2020
A VLBA SEARCH FOR BINARY BLACK HOLES IN ACTIVE GALACTIC NUCLEI WITH DOUBLE-PEAKED OPTICAL EMISSION LINE SPECTRA
Publisher: American Astronomical Society
Date: 15-04-2011
The Sub-Parsec-Scale Structure and Evolution of Centaurus A at 8.4 and 22.2 GHz
Publisher: Cambridge University Press (CUP)
Date: 1998
DOI: 10.1017/S0252921100044663
Abstract: We have been observing the sub-parsec-scale radio jet in the nucleus of Centaurus A, the closest active radio galaxy, at 8.4 GHz over the last 6 years with the SHEVE array and most recently with the VLBA at 8.4 and 22.2 GHz. In this paper we will review the results of these observations and give a brief summary of our interpretation, concentrating on the evolution of the sub-parsec-scale jet structure with time subluminal component motions and rapid short timescale evolution. A full description of this work is soon to be published in a major journal article.
Comparing Redundant and Sky-model-based Interferometric Calibration: A First Look with Phase II of the MWA
Publisher: American Astronomical Society
Date: 22-08-2018
Deep multiredshift limits on Epoch of Reionization 21 cm power spectra from four seasons of Murchison Widefield Array observations
Publisher: Oxford University Press (OUP)
Date: 12-02-2020
Abstract: We compute the spherically averaged power spectrum from four seasons of data obtained for the Epoch of Reionization (EoR) project observed with the Murchison Widefield Array (MWA). We measure the EoR power spectrum over k = 0.07–3.0 h Mpc−1 at redshifts $z$ = 6.5–8.7. The largest aggregation of 110 h on EoR0 high band (3340 observations), yields a lowest measurement of (43 mK)2 = 1.8 × 103 mK2 at k = 0.14 h Mpc−1 and $z$ = 6.5 (2σ thermal noise plus s le variance). Using the Real-Time System to calibrate and the CHIPS pipeline to estimate power spectra, we select the best observations from the central five pointings within the 2013–2016 observing seasons, observing three independent fields and in two frequency bands. This yields 13 591 2-min snapshots (453 h), based on a quality assurance metric that measures ionospheric activity. We perform another cut to remove poorly calibrated data, based on power in the foreground-dominated and EoR-dominated regions of the two-dimensional power spectrum, reducing the set to 12 569 observations (419 h). These data are processed in groups of 20 observations, to retain the capacity to identify poor data, and used to analyse the evolution and structure of the data over field, frequency, and data quality. We subsequently choose the cleanest 8935 observations (298 h of data) to form integrated power spectra over the different fields, pointings, and redshift ranges.
Implementation and first results of the KM3NeT real-time core-collapse supernova neutrino search
Publisher: Springer Science and Business Media LLC
Date: 04-2022
DOI: 10.1140/EPJC/S10052-022-10137-Y
Abstract: The KM3NeT research infrastructure is unconstruction in the Mediterranean Sea. KM3NeT will study atmospheric and astrophysical neutrinos with two multi-purpose neutrino detectors, ARCA and ORCA, primarily aimed at GeV–PeV neutrinos. Thanks to the multi-photomultiplier tube design of the digital optical modules, KM3NeT is capable of detecting the neutrino burst from a Galactic or near-Galactic core-collapse supernova. This potential is already exploitable with the first detection units deployed in the sea. This paper describes the real-time implementation of the supernova neutrino search, operating on the two KM3NeT detectors since the first months of 2019. A quasi-online astronomy analysis is introduced to study the time profile of the detected neutrinos for especially significant events. The mechanism of generation and distribution of alerts, as well as the integration into the SNEWS and SNEWS 2.0 global alert systems, are described. The approach for the follow-up of external alerts with a search for a neutrino excess in the archival data is defined. Finally, an overview of the current detector capabilities and a report after the first two years of operation are given.
On the Origin of Radio Emission in the X-Ray States of XTE J1650-500 during the 2001-2002 Outburst
Publisher: American Astronomical Society
Date: 20-12-2004
DOI: 10.1086/425650
A search for technosignatures toward the Galactic Centre at 150 MHz
Publisher: Cambridge University Press (CUP)
Date: 2022
DOI: 10.1017/PASA.2022.5
Abstract: This paper is the fourth in a series of low-frequency searches for technosignatures. Using the Murchison Widefield Array over two nights, we integrate 7 h of data toward the Galactic Centre (centred on the position of Sagittarius $\\mathrm{A}^{*}$ ) with a total field-of-view of $200\\,\\mathrm{deg}^{2}$ . We present a targeted search toward 144 exoplanetary systems, at our best yet angular resolution (75 arcsec). This is the first technosignature search at a central frequency of 155 MHz toward the Galactic Centre (our previous central frequencies have been lower). A blind search toward in excess of 3 million stars toward the Galactic Centre and Galactic bulge is also completed, placing an equivalent isotropic power limit $ \\!1.1\\times10^{19}\\,\\mathrm{W}$ at the distance to the Galactic Centre. No plausible technosignatures are detected.
Measuring the global 21-cm signal with the MWA-I: improved measurements of the Galactic synchrotron background using lunar occultation
Publisher: Oxford University Press (OUP)
Date: 06-09-2018
PKS 1622-253: A Weakly Accreting, Powerful Gamma-Ray Source
Publisher: American Astronomical Society
Date: 19-10-2005
DOI: 10.1086/498307
PKS 0743-67: An Ultraluminous Accretion Disk and a High Kinetic Luminosity Jet
Publisher: American Astronomical Society
Date: 31-10-2005
DOI: 10.1086/498429
Deep-sea deployment of the KM3NeT neutrino telescope detection units by self-unrolling
Publisher: IOP Publishing
Date: 19-11-2020
The MWA long baseline Epoch of reionisation survey - I. Improved source catalogue for the EoR 0 field
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.50
Abstract: One of the principal systematic constraints on the Epoch of Reionisation (EoR) experiment is the accuracy of the foreground calibration model. Recent results have shown that highly accurate models of extended foreground sources, and including models for sources in both the primary beam and its sidelobes, are necessary for reducing foreground power. To improve the accuracy of the source models for the EoR fields observed by the Murchison Widefield Array (MWA), we conducted the MWA Long Baseline Epoch of Reionisation Survey (LoBES). This survey consists of multi-frequency observations of the main MWA EoR fields and their eight neighbouring fields using the MWA Phase II extended array. We present the results of the first half of this survey centred on the MWA EoR0 observing field (centred at RA (J2000) $0^\\mathrm{h}$ , Dec (J2000) $-27^{\\circ}$ ). This half of the survey covers an area of 3 069 degrees $^2$ , with an average rms of 2.1 mJy beam –1 . The resulting catalogue contains a total of 80 824 sources, with 16 separate spectral measurements between 100 and 230 MHz, and spectral modelling for 78 $\\%$ of these sources. Over this region we estimate that the catalogue is 90 $\\%$ complete at 32 mJy, and 70 $\\%$ complete at 10.5 mJy. The overall normalised source counts are found to be in good agreement with previous low-frequency surveys at similar sensitivities. Testing the performance of the new source models we measure lower residual rms values for peeled sources, particularly for extended sources, in a set of MWA Phase I data. The 2-dimensional power spectrum of these data residuals also show improvement on small angular scales—consistent with the better angular resolution of the LoBES catalogue. It is clear that the LoBES sky models improve upon the current sky model used by the Australian MWA EoR group for the EoR0 field.
SN 1978K: An evolved supernova outside our Local Group detected at millimetre wavelengths
Publisher: EDP Sciences
Date: 11-2016
A broadband radio view of transient jet ejecta in the black hole candidate X-ray binary MAXI J1535–571
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.38
Abstract: We present a broadband radio study of the transient jets ejected from the black hole candidate X-ray binary MAXI J1535–571, which underwent a prolonged outburst beginning on 2017 September 2. We monitored MAXI J1535–571 with the Murchison Widefield Array (MWA) at frequencies from 119 to 186 MHz over six epochs from 2017 September 20 to 2017 October 14. The source was quasi-simultaneously observed over the frequency range 0.84–19 GHz by UTMOST (the Upgraded Molonglo Observatory Synthesis Telescope) the Australian Square Kilometre Array Pathfinder (ASKAP), the Australia Telescope Compact Array (ATCA), and the Australian Long Baseline Array (LBA). Using the LBA observations from 2017 September 23, we measured the source size to be $34\\pm1$ mas. During the brightest radio flare on 2017 September 21, the source was detected down to 119 MHz by the MWA, and the radio spectrum indicates a turnover between 250 and 500 MHz, which is most likely due to synchrotron self-absorption (SSA). By fitting the radio spectrum with a SSA model and using the LBA size measurement, we determined various physical parameters of the jet knot (identified in ATCA data), including the jet opening angle ( $\\phi_{\\rm op} = 4.5\\pm1.2^{\\circ}$ ) and the magnetic field strength ( $B_{\\rm s} = 104^{+80}_{-78}$ mG). Our fitted magnetic field strength agrees reasonably well with that inferred from the standard equipartition approach, suggesting the jet knot to be close to equipartition. Our study highlights the capabilities of the Australian suite of radio telescopes to jointly probe radio jets in black hole X-ray binaries via simultaneous observations over a broad frequency range, and with differing angular resolutions. This suite allows us to determine the physical properties of X-ray binary jets. Finally, our study emphasises the potential contributions that can be made by the low-frequency part of the Square Kilometre Array (SKA-Low) in the study of black hole X-ray binaries.
Assessment of Ionospheric Activity Tolerances for Epoch of Reionization Science with the Murchison Widefield Array
Publisher: American Astronomical Society
Date: 25-10-2018
VSOP monitoring of the Quasar 1928+738
Publisher: Elsevier BV
Date: 11-1999
Real-time adaptive event detection in astronomical data streams
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 2014
DOI: 10.1109/MIS.2013.10
VLBI OH maser polarimetry with the Australian Long Baseline Array: the star-forming region G340.054 0.244
Publisher: Cambridge University Press (CUP)
Date: 03-2007
DOI: 10.1017/S1743921307012574
Abstract: Until recently, high spatial resolution full Stokes maser polarimetry was the sole domain of northern interferometers and a wealth of sources in the far south remained unexplored due to a lack of suitable instrumentation having both high spatial and high velocity resolution. The Australia Telescope Long Baseline Array (LBA) has now switched to disk-based software correlation, permitting full Stokes observing in spectral line mode with velocity channels which are sufficiently narrow to s le usefully the polarization structure. To illustrate the utility of this valuable addition to radio astronomy, we present preliminary results of the first such polarimetric observation, the subject of which are the OH masers in the star-forming region G340.054–0.244.
Measurement of the atmospheric ν and ν energy spectra with the ANTARES neutrino telescope
Publisher: Elsevier BV
Date: 05-2021
Extremely high precision VLBI astrometry of PSR J0437-4715 and implications for theories of gravity
Publisher: American Astronomical Society
Date: 26-08-2008
DOI: 10.1086/592401
Radiation efficiency calculation of the murchison widefield array using a power wave based framework
Publisher: IEEE
Date: 07-2019
Spectral Energy Distribution and Radio Halo of NGC 253 at Low Radio Frequencies
Publisher: American Astronomical Society
Date: 27-03-2017
Orthopyroxene-omphacite- and garnet-omphacite-bearing magmatic assemblages, Breaksea Orthogneiss, New Zealand: Oxidation state controlled by high-P oxide fractionation
Publisher: Elsevier BV
Date: 02-2015
Estimates of the Free‐Free Optical Depth toward the Subparsec‐Scale Radio Source in Centaurus A
Publisher: American Astronomical Society
Date: 2001
DOI: 10.1086/318247
A wide and collimated radio jet in 3C84 on the scale of a few hundred gravitational radii
Publisher: Springer Science and Business Media LLC
Date: 02-04-2018
Observation of the cosmic ray shadow of the Sun with the ANTARES neutrino telescope
Publisher: American Physical Society (APS)
Date: 28-12-2020
Sensitivity to light sterile neutrino mixing parameters with KM3NeT/ORCA
Publisher: Springer Science and Business Media LLC
Date: 10-2021
Abstract: KM3NeT/ORCA is a next-generation neutrino telescope optimised for atmospheric neutrino oscillations studies. In this paper, the sensitivity of ORCA to the presence of a light sterile neutrino in a 3+1 model is presented. After three years of data taking, ORCA will be able to probe the active-sterile mixing angles θ 14 , θ 24 , θ 34 and the effective angle θ μe , over a broad range of mass squared difference $$ \\Delta {m}_{41}^2 $$ ∆ m 41 2 ∼ [10 − 5 , 10] eV 2 , allowing to test the eV-mass sterile neutrino hypothesis as the origin of short baseline anomalies, as well as probing the hypothesis of a very light sterile neutrino, not yet constrained by cosmology. ORCA will be able to explore a relevant fraction of the parameter space not yet reached by present measurements.
New candidate GHz peaked spectrum and compact steep spectrum sources
Publisher: EDP Sciences
Date: 17-08-2004
Precision southern hemisphere vlbi pulsar astrometry. ii. measurement of seven parallaxes
Publisher: American Astronomical Society
Date: 30-07-2009
EVOLUTION OF THE PARSEC-SCALE STRUCTURE OF PKS 1934–638 REVISITED: FIRST SCIENCE WITH THE ASKAP AND NEW ZEALAND TELESCOPES
Publisher: American Astronomical Society
Date: 15-10-2010
The radio spectral energy distribution of infrared-faint radio sources
Publisher: EDP Sciences
Date: 09-2016
Wide-field vlbi observations of M31: A unique probe of the ionized interstellar medium of a nearby Galaxy
Publisher: American Astronomical Society
Date: 09-04-2013
The Control Unit of the KM3NeT Data Acquisition System
Publisher: Elsevier BV
Date: 11-2020
Combined sensitivity of JUNO and KM3NeT/ORCA to the neutrino mass ordering
Publisher: Springer Science and Business Media LLC
Date: 03-2022
Abstract: This article presents the potential of a combined analysis of the JUNO and KM3NeT/ORCA experiments to determine the neutrino mass ordering. This combination is particularly interesting as it significantly boosts the potential of either detector, beyond simply adding their neutrino mass ordering sensitivities, by removing a degeneracy in the determination of ∆ $$ {m}_{31}^2 $$ m 31 2 between the two experiments when assuming the wrong ordering. The study is based on the latest projected performances for JUNO, and on simulation tools using a full Monte Carlo approach to the KM3NeT/ORCA response with a careful assessment of its energy systematics. From this analysis, a 5 σ determination of the neutrino mass ordering is expected after 6 years of joint data taking for any value of the oscillation parameters. This sensitivity would be achieved after only 2 years of joint data taking assuming the current global best-fit values for those parameters for normal ordering.
Multiwavelength Observations of PKS 2255−282
Publisher: American Astronomical Society
Date: 09-1999
DOI: 10.1086/301019
Improving the Murchison Widefield Array tile model for polarimetry
Publisher: IEEE
Date: 07-2014
Tectonic significance of deformation patterns in granitoid rocks of the Menderes nappes, Anatolide belt, southwest Turkey
Publisher: Springer Science and Business Media LLC
Date: 26-04-2001
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