ORCID Profile
0000-0002-9449-4384
Current Organisation
Alcoa (Australia)
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Publisher: Oxford University Press (OUP)
Date: 10-01-2015
Publisher: Oxford University Press (OUP)
Date: 06-07-2016
Publisher: Oxford University Press (OUP)
Date: 19-05-2016
Publisher: Elsevier BV
Date: 03-2018
Publisher: Oxford University Press (OUP)
Date: 30-07-2016
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).
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.
Publisher: Oxford University Press (OUP)
Date: 19-12-2015
Publisher: Oxford University Press (OUP)
Date: 30-09-2015
Publisher: Oxford University Press (OUP)
Date: 19-06-2015
Publisher: De Gruyter
Date: 18-11-2019
Publisher: Oxford University Press (OUP)
Date: 02-2016
Publisher: Informa UK Limited
Date: 20-11-2018
Publisher: SAGE Publications
Date: 12-04-2018
Abstract: This study takes a systemic functional multimodal social semiotic approach to the analysis and discussion of image and text relations in two sets of data. First, patterns of contextualisation of images and text in the online magazines Dabiq and Rumiyah produced by the Islamic extremist organisation which refers to itself as Islamic State (referred to here as ISIS) are examined. The second data set consists of a s le of texts from Western online news and blog sites which include recontextualisations of images found in the first data set. A s le of ex les of the use and re-use of images is discussed in order to identify patterns of similarity and difference when images and text are recontextualised. It is argued that the ISIS material tends to foreground the interpersonal metafunction in combination with the textual metafunction (i.e. the stance towards the content and the organisation of the message for this purpose), while the other data set tends to foreground the ideational metafunction (the participants, processes and circumstances of what is being reported). These inferences indicate that further exploration of a larger data set is worth pursuing. Such studies would provide deeper insights helping to distinguish between online material which supports terrorism and that which opposes it, as well as facilitating the further development of multimodal social semiotic approaches to image and text relations.
Publisher: SPIE
Date: 09-06-2011
DOI: 10.1117/12.890973
Publisher: Routledge
Date: 08-09-2017
Publisher: Oxford University Press (OUP)
Date: 23-12-2016
Publisher: SPIE
Date: 09-06-2011
DOI: 10.1117/12.890088
Publisher: Oxford University Press (OUP)
Date: 12-04-2016
DOI: 10.1093/MNRAS/STW832
Publisher: Elsevier BV
Date: 09-2014
Publisher: Oxford University Press (OUP)
Date: 03-12-2015
Publisher: Springer Science and Business Media LLC
Date: 09-03-2013
Publisher: Oxford University Press (OUP)
Date: 09-09-2015
Location: United Kingdom of Great Britain and Northern Ireland
No related grants have been discovered for Rebecca Lange.