ORCID Profile
0000-0002-2686-438X
Current Organisation
University of Sydney
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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 | Cosmology and Extragalactic Astronomy | Galactic Astronomy | Astronomical and Space Instrumentation | High Energy Astrophysics; Cosmic Rays | Stellar Astronomy and Planetary Systems | Artificial Intelligence and Image Processing not elsewhere classified | Astronomical sciences | Space instrumentation | Pattern Recognition and Data Mining | General Relativity and Gravitational Waves | Cosmology and extragalactic astronomy | Lasers and quantum electronics | Image Processing | General relativity and gravitational waves |
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Physical Sciences | Education and Training not elsewhere classified | Information Processing Services (incl. Data Entry and Capture) | Network Infrastructure Equipment | Scientific Instruments | Command, Control and Communications |
Related Links
Publications
Serendipitous Discovery of PSR J1431-6328 as a Highly Polarized Point Source with the Australian SKA Pathfinder
Publisher: American Astronomical Society
Date: 14-10-2019
A new search for distant radio galaxies in the Southern hemisphere - I. Sample definition and radio properties
Publisher: Oxford University Press (OUP)
Date: 17-09-2007
AUTOCLASSIFICATION of the VARIABLE 3XMM SOURCES USING the RANDOM FOREST MACHINE LEARNING ALGORITHM
Publisher: American Astronomical Society
Date: 23-10-2015
GRB Orphan Afterglows in Present and Future Radio Transient Surveys
Publisher: Cambridge University Press (CUP)
Date: 2014
DOI: 10.1017/PASA.2014.14
Abstract: Orphan Afterglows (OA) are slow transients produced by Gamma Ray Bursts seen off–axis that become visible on timescales of days/years at optical/NIR and radio frequencies, when the prompt emission at high energies (X and γ rays) has already ceased. Given the typically estimated jet opening angle of GRBs θ jet ~ 3°, for each burst pointing to the Earth there should be a factor ~ 700 more GRBs pointing in other directions. Despite this, no secure OAs have been detected so far. Through a population synthesis code we study the emission properties of the population of OA at radio frequencies. OAs reach their emission peak on year-timescales and they last for a comparable amount of time. The typical peak fluxes (which depend on the observing frequency) are of few μJy in the radio band with only a few OA reaching the mJy level. These values are consistent with the upper limits on the radio flux of SN Ib/c observed at late times. We find that the OA radio number count distribution has a typical slope − 1.7 at high fluxes and a flatter ( − 0.4) slope at low fluxes with a break at a frequency–dependent flux. Our predictions of the OA rates are consistent with the (upper) limits of recent radio surveys and archive searches for radio transients. Future radio surveys like VAST/ASKAP at 1.4 GHz should detect ~ 3 × 10 − 3 OA deg − 2 yr − 1 , MeerKAT and EVLA at 8.4 GHz should see ~ 3 × 10 − 1 OA deg − 2 yr − 1 . The SKA, reaching the μJy flux limit, could see up to ~ 0.2 − 1.5 OA deg − 2 yr − 1 . These rates also depend on the duration of the OA above a certain flux limit and we discuss this effect with respect to the survey cadence.
Visibility stacking in the quest for type Ia supernova radio emission
Publisher: American Astronomical Society
Date: 21-06-2011
Blobcat: Software to catalogue flood-filled blobs in radio images of total intensity and linear polarization
Publisher: Oxford University Press (OUP)
Date: 14-08-2012
High-frequency radio properties of sources in the Fermi-LAT 1 year Point Source Catalog
Publisher: American Astronomical Society
Date: 02-07-2010
Periodic Radio Emission from the T8 Dwarf WISE J062309.94–045624.6
Publisher: American Astronomical Society
Date: 07-2023
Abstract: We present the detection of rotationally modulated, circularly polarized radio emission from the T8 brown dwarf WISE J062309.94−045624.6 between 0.9 and 2.0 GHz. We detected this high-proper-motion ultracool dwarf with the Australian SKA Pathfinder in 1.36 GHz imaging data from the Rapid ASKAP Continuum Survey. We observed WISE J062309.94−045624.6 to have a time and frequency averaged Stokes I flux density of 4.17 ± 0.41 mJy beam −1 , with an absolute circular polarization fraction of 66.3% ± 9.0%, and calculated a specific radio luminosity of L ν ∼ 10 14.8 erg s −1 Hz −1 . In follow-up observations with the Australian Telescope Compact Array and MeerKAT we identified a multipeaked pulse structure, used dynamic spectra to place a lower limit of B 0.71 kG on the dwarf’s magnetic field, and measured a P = 1.912 ± 0.005 hr periodicity, which we concluded to be due to rotational modulation. The luminosity and period we measured are comparable to those of other ultracool dwarfs observed at radio wavelengths. This implies that future megahertz to gigahertz surveys, with increased cadence and improved sensitivity, are likely to detect similar or later-type dwarfs. Our detection of WISE J062309.94−045624.6 makes this dwarf the coolest and latest-type star observed to produce radio emission.
GRB 110715A: Multiwavelength study of the first gamma-ray burst observed with ALMA
Publisher: EDP Sciences
Date: 2013
DOI: 10.1051/EAS/1361042
A matched-filter approach to radio variability and transients: searching for orphan afterglows in the VAST Pilot Survey
Publisher: Oxford University Press (OUP)
Date: 05-06-2023
Abstract: Radio transient searches using traditional variability metrics struggle to recover sources whose evolution time-scale is significantly longer than the survey cadence. Motivated by the recent observations of slowly evolving radio afterglows at gigahertz frequency, we present the results of a search for radio variables and transients using an alternative matched-filter approach. We designed our matched-filter to recover sources with radio light curves that have a high-significance fit to power-law and smoothly broken power-law functions light curves following these functions are characteristic of synchrotron transients, including ‘orphan’ gamma-ray burst afterglows, which were the primary targets of our search. Applying this matched-filter approach to data from Variables and Slow Transients Pilot Survey conducted using the Australian SKA Pathfinder, we produced five candidates in our search. Subsequent Australia Telescope Compact Array observations and analysis revealed that: one is likely a synchrotron transient one is likely a flaring active galactic nucleus, exhibiting a flat-to-steep spectral transition over 4 months one is associated with a starburst galaxy, with the radio emission originating from either star formation or an underlying slowly evolving transient and the remaining two are likely extrinsic variables caused by interstellar scintillation. The synchrotron transient, VAST J175036.1–181454, has a multifrequency light curve, peak spectral luminosity, and volumetric rate that is consistent with both an off-axis afterglow and an off-axis tidal disruption event interpreted as an off-axis afterglow would imply an average inverse beaming factor $\\langle f^{-1}_{\\text{b}} \\rangle = 860^{+1980}_{-710}$, or equivalently, an average jet opening angle of $\\langle \\theta _{\\textrm {j}} \\rangle = 3^{+4}_{-1}\\,$ deg.
Discovery of PSR J0523-7125 as a Circularly Polarized Variable Radio Source in the Large Magellanic Cloud
Publisher: American Astronomical Society
Date: 05-2022
Abstract: We report the discovery of a highly circularly polarized, variable, steep-spectrum pulsar in the Australian Square Kilometre Array Pathfinder (ASKAP) Variables and Slow Transients (VAST) survey. The pulsar is located about 1° from the center of the Large Magellanic Cloud, and has a significant fractional circular polarization of ∼20%. We discovered pulsations with a period of 322.5 ms, dispersion measure (DM) of 157.5 pc cm −3 , and rotation measure (RM) of +456 rad m −2 using observations from the MeerKAT and the Parkes telescopes. This DM firmly places the source, PSR J0523−7125, in the Large Magellanic Cloud (LMC). This RM is extreme compared to other pulsars in the LMC (more than twice that of the largest previously reported one). The average flux density of ∼1 mJy at 1400 MHz and ∼25 mJy at 400 MHz places it among the most luminous radio pulsars known. It likely evaded previous discovery because of its very steep radio spectrum (spectral index α ≈ −3, where S ν ∝ ν α ) and broad pulse profile (duty cycle ≳35%). We discuss implications for searches for unusual radio sources in continuum images, as well as extragalactic pulsars in the Magellanic Clouds and beyond. Our result highlighted the possibility of identifying pulsars, especially extreme pulsars, from radio continuum images. Future large-scale radio surveys will give us an unprecedented opportunity to discover more pulsars and potentially the most distant pulsars beyond the Magellanic Clouds.
A multiwavelength study of the radio source G296.7-0.9: Confirmation as a Galactic supernova remnant
Publisher: Oxford University Press (OUP)
Date: 18-11-2012
A survey of the Galactic plane for dispersed radio pulses with the Australian Square Kilometre Array Pathfinder
Publisher: Oxford University Press (OUP)
Date: 14-03-2019
DOI: 10.1093/MNRAS/STZ748
A Flare-type IV Burst Event from Proxima Centauri and Implications for Space Weather
Publisher: American Astronomical Society
Date: 09-12-2020
Data storage, processing, and visualization for the Australia telescope compact array
Publisher: Cambridge University Press (CUP)
Date: 2006
DOI: 10.1071/AS05033
Abstract: We present three Virtual Observatory tools developed at the Australia Telescope National Facility (ATNF) for the storage, processing and visualization of Australia Telescope Compact Array (ATCA) data. These are the Australia Telescope Online Archive, a prototype data-reduction pipeline, and the Remote Visualization System. These tools were developed in the context of the Virtual Observatory and were intended to be both useful for astronomers and technology demonstrators. We discuss the design and implementation of these tools, as well as issues that should be considered when developing similar systems for future telescopes.
Using the VO to Study the Time Domain
Publisher: Cambridge University Press (CUP)
Date: 09-2011
DOI: 10.1017/S1743921312000634
Abstract: Just as the astronomical “Time Domain” is a catch-phrase for a erse group of different science objectives involving time-varying phenomena in all astrophysical régimes from the solar system to cosmological scales, so the “Virtual Observatory” is a complex set of community-wide activities from archives to astroinformatics. This workshop touched on some aspects of adapting and developing those semantic and network technologies in order to address transient and time-domain research challenges. It discussed the VOEvent format for representing alerts and reports on celestial transient events, the SkyAlert and ATELstream facilities for distributing these alerts, and the IVOA time-series protocol and time-series tools provided by the VAO. Those tools and infrastructure are available today to address the real-world needs of astronomers.
A pilot ASKAP survey for radio transients towards the Galactic Centre
Publisher: Oxford University Press (OUP)
Date: 11-09-2022
Abstract: We present the results of a radio transient and polarization survey towards the Galactic Centre, conducted as part of the Australian Square Kilometre Array Pathfinder Variables and Slow Transients pilot survey. The survey region consisted of five fields covering $\sim 265\, {\rm deg}^2$ (350○ ≲ l ≲ 10○, |b| ≲ 10○). Each field was observed for 12 min, with between 7 and 9 repeats on cadences of between one day and four months. We detected eight highly variable sources and seven highly circularly polarized sources (14 unique sources in total). Seven of these sources are known pulsars including the rotating radio transient PSR J1739–2521 and the eclipsing pulsar PSR J1723–2837. One of them is a low-mass X-ray binary, 4U 1758–25. Three of them are coincident with optical or infrared sources and are likely to be stars. The remaining three may be related to the class of Galactic Centre Radio Transients (including a highly likely one, VAST J173608.2–321634, that has been reported previously), although this class is not yet understood. In the coming years, we expect to detect ∼40 bursts from this kind of source with the proposed 4-yr VAST survey if the distribution of the source is isotropic over the Galactic fields.
Hi Clouds in the Lower Halo. I. The Galactic All‐Sky Survey Pilot Region
Publisher: American Astronomical Society
Date: 20-11-2008
DOI: 10.1086/592188
An optimized transient detection pipeline for the ASKAP Variables and Slow Transients (VAST) survey
Publisher: Oxford University Press (OUP)
Date: 29-09-2023
Searching for stellar flares from low-mass stars using ASKAP and TESS
Publisher: Oxford University Press (OUP)
Date: 08-2022
Abstract: Solar radio emission at low frequencies (& GHz) can provide valuable information on processes driving flares and coronal mass ejections (CMEs). Radio emission has been detected from active M dwarf stars, suggestive of much higher levels of activity than previously thought. Observations of active M dwarfs at low frequencies can provide information on the emission mechanism for high energy flares and possible stellar CMEs. Here, we conducted two observations with the Australian Square Kilometre Array Pathfinder Telescope totalling 26 h and scheduled to overlap with the Transiting Exoplanet Survey Satellite Sector 36 field, utilizing the wide fields of view of both telescopes to search for multiple M dwarfs. We detected variable radio emission in Stokes I centred at 888 MHz from four known active M dwarfs. Two of these sources were also detected with Stokes V circular polarization. When examining the detected radio emission characteristics, we were not able to distinguish between the models for either electron cyclotron maser or gyrosynchrotron emission. These detections add to the growing number of M dwarfs observed with variable low-frequency emission.
An ASKAP Search for a Radio Counterpart to the First High-significance Neutron Star–Black Hole Merger LIGO/Virgo S190814bv
Publisher: American Astronomical Society
Date: 06-12-2019
Properties of luminous red galaxies in the Sloan Digital Sky Survey
Publisher: Oxford University Press (OUP)
Date: 11-05-2007
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.
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.
Optical properties of high-frequency radio sources from the Australia Telescope 20 GHz (AT20G) Survey
Publisher: Oxford University Press (OUP)
Date: 10-10-2011
New galactic ISM results and progress towards low-frequency spectroscopy
Publisher: Cambridge University Press (CUP)
Date: 08-2006
DOI: 10.1017/S1743921307011027
Abstract: We dicuss new Galactic ISM results and progress towards low-frequency spectroscopy
Learning multilingual named entity recognition from Wikipedia
Publisher: Elsevier BV
Date: 2013
ASKAP observations of multiple rapid scintillators reveal a degrees-long plasma filament
Publisher: Oxford University Press (OUP)
Date: 21-01-2021
Abstract: We present the results from an Australian Square Kilometre Array Pathfinder search for radio variables on timescales of hours. We conducted an untargeted search over a 30 deg2 field, with multiple 10-h observations separated by days to months, at a central frequency of 945 MHz. We discovered six rapid scintillators from 15-min model-subtracted images with sensitivity of $\\sim\\! 200\\, \\mu$Jy/beam two of them are extreme intra-hour variables with modulation indices up to $\\sim 40{{\\ \\rm per\\ cent}}$ and timescales as short as tens of minutes. Five of the variables are in a linear arrangement on the sky with angular width ∼1 arcmin and length ∼2 degrees, revealing the existence of a huge plasma filament in front of them. We derived kinematic models of this plasma from the annual modulation of the scintillation rate of our sources, and we estimated its likely physical properties: a distance of ∼4 pc and length of ∼0.1 pc. The characteristics we observe for the scattering screen are incompatible with published suggestions for the origin of intra-hour variability leading us to propose a new picture in which the underlying phenomenon is a cold tidal stream. This is the first time that multiple scintillators have been detected behind the same plasma screen, giving direct insight into the geometry of the scattering medium responsible for enhanced scintillation.
Automatic classification of time-variable x-ray sources
Publisher: American Astronomical Society
Date: 10-04-2014
Deep 20-GHz survey of the Chandra deep field south and SDSS stripe 82: Source catalogue and spectral properties
Publisher: Oxford University Press (OUP)
Date: 11-02-2014
Erratum: A 22-yr southern sky survey for transient and variable radio sources using the Molonglo Observatory Synthesis Telescope
Publisher: Oxford University Press (OUP)
Date: 24-11-2011
Wide-field imaging and polarimetry for the biggest and brightest in the 20-GHz southern sky
Publisher: Oxford University Press (OUP)
Date: 05-2009
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
GASS: the Parkes Galactic all-sky survey
Publisher: EDP Sciences
Date: 10-2010
Radio detections of southern ultracool dwarfs
Publisher: Oxford University Press (OUP)
Date: 02-2016
DOI: 10.1093/MNRAS/STW050
The Second Epoch Molonglo Galactic Plane Survey: Images and Candidate Supernova Remnants
Publisher: Cambridge University Press (CUP)
Date: 2014
DOI: 10.1017/PASA.2014.37
Abstract: The second epoch Molonglo Galactic Plane Survey covers the area 245° ⩽ l ⩽ 365° and | b | ⩽ 10° at a frequency of 843 MHz and an angular resolution of 45 arcsec × 45 arcsec cosec(δ). The sensitivity varies between 1–2 mJy beam − 1 depending on the presence of strong extended sources. This survey is currently the highest resolution and most sensitive large-scale continuum survey of the southern Galactic plane. In this paper, we present the images of the complete survey, including postage st s of some new supernova remnant (SNR) candidates and a discussion of the highly structured features detected in the interstellar medium. The intersection of these two types of features is discussed in the context of the ‘missing’ SNR population in the Galaxy.
ERRATUM: “H I CLOUDS IN THE LOWER HALO. I. THE GALACTIC ALL-SKY SURVEY PILOT REGION” (2008, ApJ, 688, 290)
Publisher: American Astronomical Society
Date: 03-02-2010
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
A Non-equipartition Shock Wave Traveling in a Dense Circumstellar Environment around SN 2020oi
Publisher: American Astronomical Society
Date: 11-2020
Abstract: We report the discovery and panchromatic follow-up observations of the young Type Ic supernova (SN Ic) SN 2020oi in M100, a grand-design spiral galaxy at a mere distance of 14 Mpc. We followed up with observations at radio, X-ray, and optical wavelengths from only a few days to several months after explosion. The optical behavior of the supernova is similar to those of other normal SNe Ic. The event was not detected in the X-ray band but our radio observations revealed a bright mJy source ( L ν ≈ 1.2 × 10 27 erg s − 1 Hz − 1 ). Given the relatively small number of stripped envelope SNe for which radio emission is detectable, we used this opportunity to perform a detailed analysis of the comprehensive radio data set we obtained. The radio-emitting electrons initially experience a phase of inverse Compton cooling, which leads to steepening of the spectral index of the radio emission. Our analysis of the cooling frequency points to a large deviation from equipartition at the level of ϵ e / ϵ B ≳ 200, similar to a few other cases of stripped envelope SNe. Our modeling of the radio data suggests that the shock wave driven by the SN ejecta into the circumstellar matter (CSM) is moving at ∼ 3 × 10 4 km s − 1 . Assuming a constant mass loss from the stellar progenitor, we find that the mass-loss rate is M ̇ ≈ 1.4 × 10 − 4 M ⊙ yr − 1 for an assumed wind velocity of 1000 km s − 1 . The temporal evolution of the radio emission suggests a radial CSM density structure steeper than the standard r −2 .
Is the observed high-frequency radio luminosity distribution of QSOs bimodal?
Publisher: American Astronomical Society
Date: 28-06-2012
The Panchromatic Afterglow of GW170817: The Full Uniform Data Set, Modeling, Comparison with Previous Results, and Implications
Publisher: American Astronomical Society
Date: 26-11-2021
Abstract: We present the full panchromatic afterglow light-curve data of GW170817, including new radio data as well as archival optical and X-ray data, between 0.5 and 940 days post-merger. By compiling all archival data and reprocessing a subset of it, we have evaluated the impact of differences in data processing or flux determination methods used by different groups and attempted to mitigate these differences to provide a more uniform data set. Simple power-law fits to the uniform afterglow light curve indicate a t 0.86±0.04 rise, a t −1.92±0.12 decline, and a peak occurring at 155 ± 4 days. The afterglow is optically thin throughout its evolution, consistent with a single spectral index (−0.584 ± 0.002) across all epochs. This gives a precise and updated estimate of the electron power-law index, p = 2.168 ± 0.004. By studying the diffuse X-ray emission from the host galaxy, we place a conservative upper limit on the hot ionized interstellar medium density, .01 cm −3 , consistent with previous afterglow studies. Using the late-time afterglow data we rule out any long-lived neutron star remnant having a magnetic field strength between 10 10.4 and 10 16 G. Our fits to the afterglow data using an analytical model that includes Very Long Baseline Interferometry proper motion from Mooley et al., and a structured jet model that ignores the proper motion, indicates that the proper-motion measurement needs to be considered when seeking an accurate estimate of the viewing angle.
Crates: An all-sky survey of flat-spectrum radio sources
Publisher: American Astronomical Society
Date: 07-2007
DOI: 10.1086/513742
A comprehensive search for the radio counterpart of GW190814 with the Australian Square Kilometre Array Pathfinder
Publisher: Oxford University Press (OUP)
Date: 14-12-2021
Abstract: We present results from a search for the radio counterpart to the possible neutron star–black hole merger GW190814 with the Australian Square Kilometre Array Pathfinder. We have carried out 10 epochs of observation spanning 2–655 d post-merger at a frequency of 944 MHz. Each observation covered 30 deg2, corresponding to 87 per cent of the posterior distribution of the merger’s sky location. We conducted an untargeted search for radio transients in the field, as well as a targeted search for transients associated with known galaxies. We find one radio transient, ASKAP J005022.3−230349, but conclude that it is unlikely to be associated with the merger. We use our observations to place constraints on the inclination angle of the merger and the density of the surrounding environment by comparing our non-detection to model predictions for radio emission from compact binary coalescences. This survey is also the most comprehensive widefield search (in terms of sensitivity and both areal and temporal coverage) for radio transients to-date and we calculate the radio transient surface density at 944 MHz.
Discovery of ASKAP J173608.2–321635 as a Highly Polarized Transient Point Source with the Australian SKA Pathfinder
Publisher: American Astronomical Society
Date: 10-2021
The AT20G view of Swift/BAT selected AGN: high-frequency radio waves meet hard X-rays
Publisher: Oxford University Press (OUP)
Date: 21-03-2013
DOI: 10.1093/MNRAS/STT343
154 MHz Detection of Faint, Polarized Flares from UV Ceti
Publisher: American Astronomical Society
Date: 21-02-2017
Observations and modelling of pulsed radio emission from CU Virginis
Publisher: Oxford University Press (OUP)
Date: 05-03-2012
Low-frequency GMRT observations of ultra-cool dwarfs
Publisher: Oxford University Press (OUP)
Date: 22-11-2019
Two populations of gamma-ray burst radio afterglows
Publisher: American Astronomical Society
Date: 04-10-2013
The Rapid ASKAP Continuum Survey IV: continuum imaging at 1367.5 MHz and the first data release of RACS-mid
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.31
Abstract: The Australian SKA Pathfinder (ASKAP) is being used to undertake a c aign to rapidly survey the sky in three frequency bands across its operational spectral range. The first pass of the Rapid ASKAP Continuum Survey (RACS) at 887.5 MHz in the low band has already been completed, with images, visibility datasets, and catalogues made available to the wider astronomical community through the CSIRO ASKAP Science Data Archive (CASDA). This work presents details of the second observing pass in the mid band at 1367.5 MHz, RACS-mid, and associated data release comprising images and visibility datasets covering the whole sky south of $\\delta_{\\text{J2000}}=+49^\\circ$ . This data release incorporates selective peeling to reduce artefacts around bright sources, as well as accurately modelled primary beam responses. The Stokes I images reach a median noise of 198 $\\mu$ Jy PSF $^{-1}$ with a declination-dependent angular resolution of 8.1–47.5 arcsec that fills a niche in the existing ecosystem of large-area astronomical surveys. We also supply Stokes V images after application of a widefield leakage correction, with a median noise of 165 $\\mu$ Jy PSF $^{-1}$ . We find the residual leakage of Stokes I into V to be $\\lesssim 0.9$ – $2.4$ % over the survey. This initial RACS-mid data release will be complemented by a future release comprising catalogues of the survey region. As with other RACS data releases, data products from this release will be made available through CASDA.
First Results from the COLA Project: The Radio–Far‐Infrared Correlation and Compact Radio Cores in Southern COLA Galaxies
Publisher: American Astronomical Society
Date: 10-01-2002
DOI: 10.1086/324281
Quantifying ionospheric effects on time-domain astrophysics with the Murchison Widefield Array
Publisher: Oxford University Press (OUP)
Date: 02-09-2015
SUMSS: A wide-field radio imaging survey of the southern sky - II. The source catalogue
Publisher: Oxford University Press (OUP)
Date: 11-07-2003
LOW-FREQUENCY OBSERVATIONS OF LINEARLY POLARIZED STRUCTURES IN THE INTERSTELLAR MEDIUM NEAR THE SOUTH GALACTIC POLE
Publisher: American Astronomical Society
Date: 10-10-2016
The second epoch Molonglo Galactic Plane Survey: Compact source catalogue
Publisher: Oxford University Press (OUP)
Date: 21-11-2007
A population analysis of pulse broadening in ASKAP fast radio bursts
Publisher: Oxford University Press (OUP)
Date: 06-07-2020
Abstract: The pulse morphology of fast radio bursts (FRBs) provides key information in both understanding progenitor physics and the plasma medium through which the burst propagates. We present a study of the profiles of 33 bright FRBs detected by the Australian Square Kilometre Array Pathfinder. We identify seven FRBs with measureable intrinsic pulse widths, including two FRBs that have been seen to repeat. In our modest s le, we see no evidence for bimodality in the pulse width distribution. We also identify five FRBs with evidence of millisecond time-scale pulse broadening caused by scattering in inhomogeneous plasma. We find no evidence for a relationship between pulse broadening and extragalactic dispersion measure. The scattering could be either caused by extreme turbulence in the host galaxy or chance propagation through foreground galaxies. With future high time resolution observations and detailed study of host galaxy properties, we may be able to probe line-of-sight turbulence on gigaparsec scales.
Detection of radio emission from stars via proper-motion searches
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.26
Abstract: We present a method for identifying radio stellar sources using their proper-motion. We demonstrate this method using the FIRST, VLASS, RACS-low and RACS-mid radio surveys, and astrometric information from Gaia Data Release 3. We find eight stellar radio sources using this method, two of which have not previously been identified in the literature as radio stars. We determine that this method probes distances of $\\sim$ 90pc when we use FIRST and RACS-mid, and $\\sim$ 250pc when we use FIRST and VLASS. We investigate the time baselines required by current and future radio sky surveys to detect the eight sources we found, with the SKA (6.7 GHz) requiring $ $ 3 yr between observations to find all eight sources. We also identify nine previously known and 43 candidate variable radio stellar sources that are detected in FIRST (1.4 GHz) but are not detected in RACS-mid (1.37 GHz). This shows that many stellar radio sources are variable, and that surveys with multiple epochs can detect a more complete s le of stellar radio sources.
Gaia GraL: Gaia DR2 Gravitational Lens Systems. VI. Spectroscopic Confirmation and Modeling of Quadruply Imaged Lensed Quasars
Publisher: American Astronomical Society
Date: 28-10-2021
MURCHISON WIDEFIELD ARRAY LIMITS ON RADIO EMISSION FROM ANTARES NEUTRINO EVENTS
Publisher: American Astronomical Society
Date: 22-03-2016
Classical novae in the ASKAP pilot surveys
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.21
Abstract: We present a systematic search for radio counterparts of novae using the Australian Square Kilometer Array Pathfinder (ASKAP). Our search used the Rapid ASKAP Continuum Survey, which covered the entire sky south of declination $+41^{\\circ}$ ( $\\sim$ $34000$ square degrees) at a central frequency of 887.5 MHz, the Variables and Slow Transients Pilot Survey, which covered $\\sim$ $5000$ square degrees per epoch (887.5 MHz), and other ASKAP pilot surveys, which covered $\\sim$ 200–2000 square degrees with 2–12 h integration times. We crossmatched radio sources found in these surveys over a two–year period, from 2019 April to 2021 August, with 440 previously identified optical novae, and found radio counterparts for four novae: V5668 Sgr, V1369 Cen, YZ Ret, and RR Tel. Follow-up observations with the Australian Telescope Compact Array confirm the ejecta thinning across all observed bands with spectral analysis indicative of synchrotron emission in V1369 Cen and YZ Ret. Our light-curve fit with the Hubble Flow model yields a value of $1.65\\pm 0.17 \\times 10^{-4} \\rm \\:M_\\odot$ for the mass ejected in V1369 Cen. We also derive a peak surface brightness temperature of $250\\pm80$ K for YZ Ret. Using Hubble Flow model simulated radio lightcurves for novae, we demonstrate that with a 5 $\\sigma$ sensitivity limit of 1.5 mJy in 15-min survey observations, we can detect radio emission up to a distance of 4 kpc if ejecta mass is in the range $10^{-3}\\rm \\:M_\\odot$ , and upto 1 kpc if ejecta mass is in the range $10^{-5}$ – $10^{-3}\\rm \\:M_\\odot$ . Our study highlights ASKAP’s ability to contribute to future radio observations for novae within a distance of 1 kpc hosted on white dwarfs with masses $0.4$ – $1.25\\:\\rm M_\\odot$ , and within a distance of 4 kpc hosted on white dwarfs with masses $0.4$ – $1.0\\:\\rm M_\\odot$ .
Erratum: “AT2018cow: A Luminous Millimeter Transient” (2019, ApJ, 871, 73)
Publisher: American Astronomical Society
Date: 08-2022
MURCHISON WIDEFIELD ARRAY OBSERVATIONS OF ANOMALOUS VARIABILITY: A SERENDIPITOUS NIGHT-TIME DETECTION OF INTERPLANETARY SCINTILLATION
Publisher: American Astronomical Society
Date: 07-08-2015
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
Erratum: Visibility stacking in the quest for type Ia supernova radio emission (Astrophysical Journal Letters (2011) 735 (L35))
Publisher: American Astronomical Society
Date: 04-10-2011
A 20-yr radio light curve for the young supernova remnant G1.9+0.3
Publisher: Oxford University Press (OUP)
Date: 09-2008
A circular polarization survey for radio stars with the Australian SKA Pathfinder
Publisher: Oxford University Press (OUP)
Date: 05-02-2021
Abstract: We present results from a circular polarization survey for radio stars in the Rapid ASKAP Continuum Survey (RACS). RACS is a survey of the entire sky south of δ = +41○ being conducted with the Australian Square Kilometre Array Pathfinder telescope (ASKAP) over a 288 MHz wide band centred on 887.5 MHz. The data we analyse include Stokes I and V polarization products to an RMS sensitivity of 250 μJy PSF−1. We searched RACS for sources with fractional circular polarization above 6 per cent, and after excluding imaging artefacts, polarization leakage, and known pulsars we identified radio emission coincident with 33 known stars. These range from M-dwarfs through to magnetic, chemically peculiar A- and B-type stars. Some of these are well-known radio stars such as YZ CMi and CU Vir, but 23 have no previous radio detections. We report the flux density and derived brightness temperature of these detections and discuss the nature of the radio emission. We also discuss the implications of our results for the population statistics of radio stars in the context of future ASKAP and Square Kilometre Array surveys.
GASS: THE PARKES GALACTIC ALL-SKY SURVEY. I. SURVEY DESCRIPTION, GOALS, AND INITIAL DATA RELEASE
Publisher: American Astronomical Society
Date: 12-03-2009
The local radio-galaxy population at 20 GHz
Publisher: Oxford University Press (OUP)
Date: 12-2014
A search for radio afterglows from gamma-ray bursts with the Australian Square Kilometre Array Pathfinder
Publisher: Oxford University Press (OUP)
Date: 06-02-2021
Abstract: We present a search for radio afterglows from long gamma-ray bursts using the Australian Square Kilometre Array Pathfinder (ASKAP). Our search used the Rapid ASKAP Continuum Survey, covering the entire celestial sphere south of declination +41○, and three epochs of the Variables and Slow Transients Pilot Survey (Phase 1), covering ∼5000 square degrees per epoch. The observations we used from these surveys spanned a nine-month period from 2019 April 21 to 2020 January 11. We cross-matched radio sources found in these surveys with 779 well-localized (to ≤15 arcsec) long gamma-ray bursts occurring after 2004 and determined whether the associations were more likely afterglow- or host-related through the analysis of optical images. In our search, we detected one radio afterglow candidate associated with GRB 171205A, a local low-luminosity gamma-ray burst with a supernova counterpart SN 2017iuk, in an ASKAP observation 511 d post-burst. We confirmed this detection with further observations of the radio afterglow using the Australia Telescope Compact Array at 859 and 884 d post-burst. Combining this data with archival data from early-time radio observations, we showed the evolution of the radio spectral energy distribution alone could reveal clear signatures of a wind-like circumburst medium for the burst. Finally, we derived semi-analytical estimates for the microphysical shock parameters of the burst: electron power-law index p = 2.84, normalized wind-density parameter A* = 3, fractional energy in electrons ϵe = 0.3, and fractional energy in magnetic fields ϵB = 0.0002.
A radio counterpart to a neutron star merger
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-12-2017
Abstract: The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths. Science , this issue p. 1565 , p. 1579 , p. 1559 see also p. 1554
A Strong Jet Signature in the Late-time Light Curve of GW170817
Publisher: American Astronomical Society
Date: 16-11-2018
Online classification for time-domain astronomy
Publisher: IEEE
Date: 12-2013
Illuminating gravitational waves: A concordant picture of photons from a neutron star merger
Publisher: American Association for the Advancement of Science (AAAS)
Date: 22-12-2017
Abstract: The gravitational wave event GW170817 was caused by the merger of two neutron stars (see the Introduction by Smith). In three papers, teams associated with the GROWTH (Global Relay of Observatories Watching Transients Happen) project present their observations of the event at wavelengths from x-rays to radio waves. Evans et al. used space telescopes to detect GW170817 in the ultraviolet and place limits on its x-ray flux, showing that the merger generated a hot explosion known as a blue kilonova. Hallinan et al. describe radio emissions generated as the explosion slammed into the surrounding gas within the host galaxy. Kasliwal et al. present additional observations in the optical and infrared and formulate a model for the event involving a cocoon of material expanding at close to the speed of light, matching the data at all observed wavelengths. Science , this issue p. 1565 , p. 1579 , p. 1559 see also p. 1554
Radio afterglows from compact binary coalescences: prospects for next-generation telescopes
Publisher: Oxford University Press (OUP)
Date: 22-05-2021
Abstract: The detection of gravitational waves from a neutron star merger, GW170817, marked the dawn of a new era in time-domain astronomy. Monitoring of the radio emission produced by the merger, including high-resolution radio imaging, enabled measurements of merger properties including the energetics and inclination angle. In this work, we compare the capabilities of current and future gravitational wave facilities to the sensitivity of radio facilities to quantify the prospects for detecting the radio afterglows of gravitational wave events. We consider three observing strategies to identify future mergers – wide field follow-up, targeting galaxies within the merger localization and deep monitoring of known counterparts. We find that while planned radio facilities like the Square Kilometre Array will be capable of detecting mergers at gigaparsec distances, no facilities are sufficiently sensitive to detect mergers at the range of proposed third-generation gravitational wave detectors that would operate starting in the 2030s.
HIGH-VELOCITY CLOUDS IN THE GALACTIC ALL SKY SURVEY. I. CATALOG
Publisher: American Astronomical Society
Date: 23-10-2013
The Rapid ASKAP Continuum Survey III: Spectra and Polarisation In Cutouts of Extragalactic Sources (SPICE-RACS) first data release
Publisher: Cambridge University Press (CUP)
Date: 2023
DOI: 10.1017/PASA.2023.38
Abstract: The Australian SKA Pathfinder (ASKAP) radio telescope has carried out a survey of the entire Southern Sky at 887.5 MHz. The wide area, high angular resolution, and broad bandwidth provided by the low-band Rapid ASKAP Continuum Survey (RACS-low) allow the production of a next-generation rotation measure (RM) grid across the entire Southern Sky. Here we introduce this project as Spectral and Polarisation in Cutouts of Extragalactic sources from RACS (SPICE-RACS). In our first data release, we image 30 RACS-low fields in Stokes I , Q , U at 25 $^{\\prime\\prime}$ angular resolution, across 744–1032 MHz with 1 MHz spectral resolution. Using a bespoke, highly parallelised, software pipeline we are able to rapidly process wide-area spectro-polarimetric ASKAP observations. Notably, we use ‘postage st ’ cutouts to assess the polarisation properties of 105912 radio components detected in total intensity. We find that our Stokes Q and U images have an rms noise of $\\sim$ 80 $\\unicode{x03BC}$ Jy PSF $^{-1}$ , and our correction for instrumental polarisation leakage allows us to characterise components with $\\gtrsim$ 1% polarisation fraction over most of the field of view. We produce a broadband polarised radio component catalogue that contains 5818 RM measurements over an area of $\\sim$ 1300 deg $^{2}$ with an average error in RM of $1.6^{+1.1}_{-1.0}$ rad m $^{-2}$ , and an average linear polarisation fraction $3.4^{+3.0}_{-1.6}$ %. We determine this subset of components using the conditions that the polarised signal-to-noise ratio is $ $ 8, the polarisation fraction is above our estimated polarised leakage, and the Stokes I spectrum has a reliable model. Our catalogue provides an areal density of $4\\pm2$ RMs deg $^{-2}$ an increase of $\\sim$ 4 times over the previous state-of-the-art (Taylor, Stil, Sunstrum 2009, ApJ, 702, 1230). Meaning that, having used just 3% of the RACS-low sky area, we have produced the 3rd largest RM catalogue to date. This catalogue has broad applications for studying astrophysical magnetic fields notably revealing remarkable structure in the Galactic RM sky. We will explore this Galactic structure in a follow-up paper. We will also apply the techniques described here to produce an all-Southern-sky RM catalogue from RACS observations. Finally, we make our catalogue, spectra, images, and processing pipeline publicly available.
ASKAP detection of periodic and elliptically polarized radio pulses from UV Ceti
Publisher: Oxford University Press (OUP)
Date: 28-06-2019
Abstract: Active M dwarfs are known to produce bursty radio emission, and multiwavelength studies have shown that solar-like magnetic activity occurs in these stars. However, coherent bursts from active M dwarfs have often been difficult to interpret in the solar activity paradigm. We present Australian Square Array Pathfinder (ASKAP) observations of UV Ceti at a central frequency of 888 MHz. We detect several periodic, coherent pulses occurring over a time-scale consistent with the rotational period of UV Ceti. The properties of the pulsed emission show that they originate from the electron cyclotron maser instability, in a cavity at least 7 orders of magnitude less dense than the mean coronal density at the estimated source altitude. These results confirm that auroral activity can occur in active M dwarfs, suggesting that these stars mark the beginning of the transition from solar-like to auroral magnetospheric behaviour. These results demonstrate the capabilities of ASKAP for detecting polarized, coherent bursts from active stars and other systems.
Ultra- and hyper-compact H ii regions at 20 GHz
Publisher: Oxford University Press (OUP)
Date: 04-2010
Discovery of an Extremely Short Duration Flare from Proxima Centauri Using Millimeter through Far-ultraviolet Observations
Publisher: American Astronomical Society
Date: 04-2021
Abstract: We present the discovery of an extreme flaring event from Proxima Cen by the Australian Square Kilometre Array Pathfinder (ASKAP), Atacama Large Millimeter/submillimeter Array (ALMA), Hubble Space Telescope (HST), Transiting Exoplanet Survey Satellite (TESS), and the du Pont Telescope that occurred on 2019 May 1. In the millimeter and FUV, this flare is the brightest ever detected, brightening by a factor of and ,000 as seen by ALMA and HST, respectively. The millimeter and FUV continuum emission trace each other closely during the flare, suggesting that millimeter emission could serve as a proxy for FUV emission from stellar flares and become a powerful new tool to constrain the high-energy radiation environment of exoplanets. Surprisingly, optical emission associated with the event peaks at a much lower level with a time delay. The initial burst has an extremely short duration, lasting for s. Taken together with the growing s le of millimeter M dwarf flares, this event suggests that millimeter emission is actually common during stellar flares and often originates from short burst-like events.
THE SEVENTH DATA RELEASE OF THE SLOAN DIGITAL SKY SURVEY
Publisher: American Astronomical Society
Date: 18-05-2009
A 22-yr southern sky survey for transient and variable radio sources using the Molonglo Observatory Synthesis Telescope
Publisher: Oxford University Press (OUP)
Date: 13-01-2011
A polarization survey of bright extragalactic AT20G sources
Publisher: Oxford University Press (OUP)
Date: 30-10-2013
An Interaction of a Magellanic Leading Arm High-Velocity Cloud with the Milky Way Disk
Publisher: American Astronomical Society
Date: 08-01-2008
DOI: 10.1086/528683
Radio variable and transient sources on minute time-scales in the ASKAP pilot surveys
Publisher: Oxford University Press (OUP)
Date: 08-06-2023
Abstract: We present results from a radio survey for variable and transient sources on 15-min time-scales, using the Australian SKA Pathfinder (ASKAP) pilot surveys. The pilot surveys consist of 505 h of observations conducted at around 1 GHz observing frequency, with a total sky coverage of 1476 deg2. Each observation was tracked for approximately 8 – 10 h, with a typical rms sensitivity of ∼30 μJy beam−1 and an angular resolution of ∼12 arcsec. The variability search was conducted within each 8 – 10 h observation on a 15-min time-scale. We detected 38 variable and transient sources. Seven of them are known pulsars, including an eclipsing millisecond pulsar, PSR J2039−5617. Another eight sources are stars, only one of which has been previously identified as a radio star. For the remaining 23 objects, 22 are associated with active galactic nuclei or galaxies (including the five intra-hour variables that have been reported previously), and their variations are caused by discrete, local plasma screens. The remaining source has no multiwavelength counterparts and is therefore yet to be identified. This is the first large-scale radio survey for variables and transient sources on minute time-scales at a sub-mJy sensitivity level. We expect to discover ∼1 highly variable source per day using the same technique on the full ASKAP surveys.
The Rapid ASKAP Continuum Survey Paper II: First Stokes I Source Catalogue Data Release
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.47
Abstract: The Rapid ASKAP Continuum Survey (RACS) is the first large sky survey using the Australian Square Kilometre Array Pathfinder (ASKAP), covering the sky south of $+41^\circ$ declination. With ASKAP’s large, instantaneous field of view, ${\sim}31\,\mathrm{deg}^2$ , RACS observed the entire sky at a central frequency of 887.5 MHz using 903 in idual pointings with 15 minute observations. This has resulted in the deepest radio survey of the full Southern sky to date at these frequencies. In this paper, we present the first Stokes I catalogue derived from the RACS survey. This catalogue was assembled from 799 tiles that could be convolved to a common resolution of $25^{\prime\prime}$ , covering a large contiguous region in the declination range $\delta=-80^{\circ}$ to $+30^\circ$ . The catalogue provides an important tool for both the preparation of future ASKAP surveys and for scientific research. It consists of $\sim$ 2.1 million sources and excludes the $|b| ^{\circ}$ region around the Galactic plane. This provides a first extragalactic catalogue with ASKAP covering the majority of the sky ( $\delta +30^{\circ}$ ). We describe the methods to obtain this catalogue from the initial RACS observations and discuss the verification of the data, to highlight its quality. Using simulations, we find this catalogue detects 95% of point sources at an integrated flux density of $\sim$ 5 mJy. Assuming a typical sky source distribution model, this suggests an overall 95% point source completeness at an integrated flux density $\sim$ 3 mJy. The catalogue will be available through the CSIRO ASKAP Science Data Archive (CASDA).
Hunting Gravitational Waves with Multi-Messenger Counterparts: Australia's Role
Publisher: Cambridge University Press (CUP)
Date: 2015
DOI: 10.1017/PASA.2015.49
Abstract: The first observations by a worldwide network of advanced interferometric gravitational wave detectors offer a unique opportunity for the astronomical community. At design sensitivity, these facilities will be able to detect coalescing binary neutron stars to distances approaching 400 Mpc, and neutron star–black hole systems to 1 Gpc. Both of these sources are associated with gamma-ray bursts which are known to emit across the entire electromagnetic spectrum. Gravitational wave detections provide the opportunity for ‘multi-messenger’ observations, combining gravitational wave with electromagnetic, cosmic ray, or neutrino observations. This review provides an overview of how Australian astronomical facilities and collaborations with the gravitational wave community can contribute to this new era of discovery, via contemporaneous follow-up observations from the radio to the optical and high energy. We discuss some of the frontier discoveries that will be made possible when this new window to the Universe is opened.
Classification of ASKAP VAST radio light curves
Publisher: Cambridge University Press (CUP)
Date: 09-2011
DOI: 10.1017/S1743921312001196
Abstract: The VAST survey is a wide-field survey that observes with unprecedented instrument sensitivity (0.5 mJy or lower) and repeat cadence (a goal of 5 seconds) that will enable novel scientific discoveries related to known and unknown classes of radio transients and variables. Given the unprecedented observing characteristics of VAST, it is important to estimate source classification performance, and determine best practices prior to the launch of ASKAP's BETA in 2012. The goal of this study is to identify light-curve characterization and classification algorithms that are best suited for archival VAST light-curve classification. We perform our experiments on light-curve simulations of eight source types and achieve best-case performance of approximately 90% accuracy. We note that classification performance is most influenced by light-curve characterization rather than classifier algorithm.
Limits on prompt, dispersed radio pulses from gamma-ray bursts
Publisher: American Astronomical Society
Date: 04-09-2012
ATPMN: Accurate positions and flux densities at 5 and 8GHz for 8385 sources from the PMN survey
Publisher: Oxford University Press (OUP)
Date: 19-03-2012
The properties of extragalactic radio sources selected at 20 GHz
Publisher: Oxford University Press (OUP)
Date: 11-09-2006
AT2018cow: A Luminous Millimeter Transient
Publisher: American Astronomical Society
Date: 23-01-2019
The radio continuum structure of centaurus a at 1.4GHz
Publisher: American Astronomical Society
Date: 20-09-2011
Compact continuum source finding for next generation radio surveys
Publisher: Oxford University Press (OUP)
Date: 04-04-2012
The australia telescope 20 GHz (AT20G) survey
Publisher: Cambridge University Press (CUP)
Date: 08-2009
DOI: 10.1017/S1743921310006411
Abstract: The recently completed AT20G survey provides the largest and most complete s le of high-frequency selected radio sources yet obtained, and offers new insights into the nature of the high-frequency active galaxy population. Here we focus on the optical properties of this survey which highlights the difference of the AT20G source population compared to other radio-selected AGN s les.
The completeness and reliability of threshold and false-discovery rate source extraction algorithms for compact continuum sources
Publisher: Cambridge University Press (CUP)
Date: 2012
DOI: 10.1071/AS11026
Abstract: The process of determining the number and characteristics of sources in astronomical images is so fundamental to a large range of astronomical problems that it is perhaps surprising that no standard procedure has ever been defined that has well-understood properties with a high degree of statistical rigour on completeness and reliability. The Evolutionary Map of the Universe (EMU) survey with the Australian Square Kilometre Array Pathfinder (ASKAP), a continuum survey of the Southern Hemisphere up to declination +30°, aims to utilise an automated source identification and measurement approach that is demonstrably optimal, to maximise the reliability, utility and robustness of the resulting radio source catalogues. A key stage in source extraction methods is the background estimation (background level and noise level) and the choice of a threshold high enough to reject false sources, yet not so high that the catalogues are significantly incomplete. In this analysis, we present results from testing the SExtractor, Selavy (Duch ), and SFIND source extraction tools on simulated data. In particular, the effects of background estimation, threshold and false-discovery rate settings are explored. For parameters that give similar completeness, we find the false-discovery rate method employed by SFIND results in a more reliable catalogue compared to the peak threshold methods of SExtractor and Selavy.
Characterizing Pulsars Detected in the Rapid ASKAP Continuum Survey
Publisher: American Astronomical Society
Date: 10-2023
Reflections on a week in Oxford
Publisher: Cambridge University Press (CUP)
Date: 09-2011
DOI: 10.1017/S1743921312001342
Abstract: When Bob asked me a couple of days ago to give this talk, he said it should be “pithy and wise.” When I spoke to Aris the next day he said it should be “informal and funny.” Then Elizabeth spoke to me and said it would be great if it was “controversial and challenging.” I mentioned to Aris just before dinner that I had put a talk together, and he said “Oh, you've written a talk—I thought it would be something more spontaneous!” Faced with an obviously impossible spec, I did what any reasonable programmer would do and rewrote the spec myself. So what I'm going to talk about this evening is a reflection on my week in Oxford.
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
FARADAY ROTATION STRUCTURE ON KILOPARSEC SCALES IN THE RADIO LOBES OF CENTAURUS A
Publisher: American Astronomical Society
Date: 18-11-2009
Radio transients and variables in the tenth Deeper, Wider, Faster observing run
Publisher: Oxford University Press (OUP)
Date: 24-12-2022
Abstract: The Deeper, Wider, Faster (DWF) program coordinates observations with telescopes across the electromagnetic spectrum, searching for transients on time-scales of milliseconds to days. The tenth DWF observing run was carried out in near real-time during September 2021, and consisted of six consecutive days of observations of the NGC 6744 galaxy group and a field containing the repeating fast radio burst FRB 190711 with the Australian Square Kilometre Array Pathfinder, the Dark Energy Camera, the Hard X-ray Modulation Telescope, and the Parkes 64-m ‘Murriyang’ radio telescope. In this work, we present the results of an image-domain search for transient, variable, and circularly polarized sources carried out with ASKAP, using data from the observing run along with test observations prior to the run and follow-up observations carried out during and after the run. We identified eight variable radio sources, consisting of one pulsar, six stellar systems (five of which exhibit circularly polarized emission), and one previously uncatalogued source. Of particular interest is the detection of pulses from the ultra-cool dwarf SCR J1845–6357 with a period of 14.2 ± 0.3 h in good agreement with the known optical rotation period, making this the slowest rotating radio-loud ultra-cool dwarf discovered.
An Upper Limit on the Linear Polarization Fraction of the GW170817 Radio Continuum
Publisher: American Astronomical Society
Date: 03-07-2018
Constraining properties of neutron star merger outflows with radio observations
Publisher: Oxford University Press (OUP)
Date: 17-04-2020
Abstract: The jet opening angle and inclination of GW170817 – the first detected binary neutron star merger – were vital to understand its energetics, relation to short gamma-ray bursts, and refinement of the standard siren-based determination of the Hubble constant, H0. These basic quantities were determined through a combination of the radio light curve and Very Long Baseline Interferometry (VLBI) measurements of proper motion. In this paper, we discuss and quantify the prospects for the use of radio VLBI observations and observations of scintillation-induced variability to measure the source size and proper motion of merger afterglows, and thereby infer properties of the merger including inclination angle, opening angle, and energetics. We show that these techniques are complementary as they probe different parts of the circum-merger density/inclination angle parameter space and different periods of the temporal evolution of the afterglow. We also find that while VLBI observations will be limited to the very closest events it will be possible to detect scintillation for a large fraction of events beyond the range of current gravitational wave detectors. Scintillation will also be detectable with next-generation telescopes such as the Square Kilometre Array, 2000 antenna Deep Synoptic Array, and the next-generation Very Large Array, for a large fraction of events detected with third-generation gravitational wave detectors. Finally, we discuss prospects for the measurement of the H0 with VLBI observations of neutron star mergers and compare this technique to other standard siren methods.
A Turnover in the Radio Light Curve of GW170817
Publisher: American Astronomical Society
Date: 09-05-2018
The ASKAP Variables and Slow Transients (VAST) Pilot Survey
Publisher: Cambridge University Press (CUP)
Date: 2021
DOI: 10.1017/PASA.2021.44
Abstract: The Variables and Slow Transients Survey (VAST) on the Australian Square Kilometre Array Pathfinder (ASKAP) is designed to detect highly variable and transient radio sources on timescales from 5 s to $\\sim\\!5$ yr. In this paper, we present the survey description, observation strategy and initial results from the VAST Phase I Pilot Survey. This pilot survey consists of $\\sim\\!162$ h of observations conducted at a central frequency of 888 MHz between 2019 August and 2020 August, with a typical rms sensitivity of $0.24\\ \\mathrm{mJy\\ beam}^{-1}$ and angular resolution of $12-20$ arcseconds. There are 113 fields, each of which was observed for 12 min integration time, with between 5 and 13 repeats, with cadences between 1 day and 8 months. The total area of the pilot survey footprint is 5 131 square degrees, covering six distinct regions of the sky. An initial search of two of these regions, totalling 1 646 square degrees, revealed 28 highly variable and/or transient sources. Seven of these are known pulsars, including the millisecond pulsar J2039–5617. Another seven are stars, four of which have no previously reported radio detection (SCR J0533–4257, LEHPM 2-783, UCAC3 89–412162 and 2MASS J22414436–6119311). Of the remaining 14 sources, two are active galactic nuclei, six are associated with galaxies and the other six have no multi-wavelength counterparts and are yet to be identified.
Erratum: Constraining properties of neutron star merger outflows with radio observations
Publisher: Oxford University Press (OUP)
Date: 03-06-2021
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