2017-B, Extended

Authors: S. J. McSweeney (Curtin; PI), N. D. R. Bhat (Curtin), A. A. Deshpande (RRI), S. E. Tremblay (Curtin)

Abstract: The past four decades of pulsar astronomy have successfully demonstrated a wide range of applications for physics and astrophysics. Still, the physical processes that govern the coherent emission of radio waves from these fascinating compact stellar objects remain not well understood. The rich and diverse phenomenology in pulsar emission on very short time scales (e.g., nulling, mode changing and sub-pulse drifting), coupled with the complexity in their observed polarisation properties as a function of the pulse phase and observing frequency, pose considerable challenges to both theorists and observers alike.

The phenomenon of sub-pulse drifting, manifesting as organised substructures marching in phase within the main pulse emission window, offers one of the most elegant and powerful means for relating observational data to action in the pulsar magnetosphere. Pulsars tend to be brighter and have wider emission beams at low radio frequencies, and therefore the frequency band of the MWA is extremely well suited to a systematic and thorough investigation of this phenomenon, particularly for pulsars in the southern hemisphere.

This project requests a modest 3.0 hr of VCS time to carry out MWA observations of PSR J0828-3417 simultaneously with GMRT observations scheduled during this semester. This pulsar is known to show interesting drifting behaviour from observations at higher frequencies. We will observe the target for a duration of ∼6000 rotation periods (2 sessions of 1.5 hrs). The success of this project will enable a study of a larger volume of a pulsar magnetosphere than is ordinarily possible, owing to this pulsar’s large duty cycle, and will form an important part of the overall project goal of understanding the physics of pulsar magnetospheres generally.

Authors: Ms Mengyao Xue (Curtin), Dr Ramesh Bhat (Curtin), Dr Steven Tremblay (Curtin), Dr Stephen Ord (CASS), Dr Charlotte Sobey (Curtin/CASS), Dr Franz Kirsten (Curtin)

Abstract: Up to April 2017, around 130 hours of high time resolution voltage data observed by MWA Voltage Capture System (VCS; Tremblay et al. 2015) have been archived on tapes in the Pawsey Supercomputing Centre. Among these VCS data , 77 hours (from 87 separate pointing) are observed between a continuum frequency range centered at 185 MHz and have a relatively long duration (larger than 400 s). These data cover a significant portion of a lot of the Southern sky and could be used for many science purposes including radio pulsars census and fast radio bursts (FRBs) searching. However, there are still some ’holes’ in the sky that haven’t covered by VCS 185 MHz data yet. We are proposing a set of MWA-VCS drift scan observations of 3 hours to fill some of these ’holes’ and help provide a more complete VCS 185 MHz data set. We will also census known (catalogued) pulsars in these areas. This project will form part of the PhD program of Mengyao Xue.

Authors: N. D. R. Bhat (Curtin; PI), K. Bannister (CASS), J.-P. Macquart (Curtin), R. Shannon (Curtin/CASS), R. Wayth (Curtin), A. Williams (Curtin), W. Arcus (Curtin)

Abstract: The field of Fast Radio Bursts (FRBs) has been rapidly gaining momentum over the past years. Since their discovery by Lorimer et al. (2007) and Thornton et al. (2013), the number of reported FRB detections has more than tripled, and measurements have been made of their scattering, scintillation, polarisation and Faraday rotation properties, all of which helped to establish their astrophysical nature. Observational evidence continues to mount in support of their extragalactic origin, and the world-wide competitive race is ramping up as a suite of new and existing instruments are gearing up to find them in large numbers. With its large field of view of ∼30 deg2 ASKAP presents a highly capable instrument for FRB hunt, and the MWA’s co-location at the site brings in unique opportunities for undertaking efficient co-observing and triggering. Simultaneous detection of even a single a self-same FRB would mean a huge science payoff and will yield the first unambiguous constraints on the spectral and scattering properties of FRBs, besides the prospects of sub-arc minute localisation that will be possible with the long baseline array of Phase 2 MWA. A low frequency detection will also help exclude certain classes of progenitor models that involve dense plasma surrounding FRB hosts and confirm their cosmological distances.

Authors: Nicole Barry (Washington), Dr Adam Beardsley (Arizona State), Prof Judd Bowman (Arizona State), Prof Frank Briggs (ANU), Ruby Byrne (Washington), Dr Patti Carroll (Washington), Dr Bryna Hazelton, (Washington), Dr Danny Jacobs (Arizona State), Dr Chris Jordan (ICRAR-Curtin), Piyanat Kittiwisit (Arizona State), Kenji Kubota (Kumamoto), Adam Lanman (Brown), Dr Emil Lenc (Sydney), Wenyang Li (Brown), Jack Line (Melbourne), Dr Ben McKinley (Melbourne), Dr Daniel Mitchell (CSIRO), Prof Miguel Morales (Washington), Dr Steven Murray (ICRAR-Curtin), Sourabh Paul (RRI), Dr Bart Pindor (Melbourne), Prof Jonathan Pober (Brown), Mahsa Rahimi (Melbourne), Jenny Riding (Melbourne), Dr Shiv Sethi (RRI), Prof Udaya Shankar (RRI), Prof Ravi Subrahmanyan (RRI), Dr Ian Sullivan (Washington), Prof Keitaro Takahashi (Kumamoto), Dr Nithyanandan Thyagarajan (Arizona State), Prof Steven Tingay (ICRAR-Curtin), Dr Cathryn Trott (ICRAR-Curtin), Assoc Prof Randall Wayth (ICRAR-Curtin), Prof Rachel Webster (Melbourne), Prof Stuart Wyithe (Melbourne), Shintaro Yoshiura (Kumamoto)

Abstract: The Epoch of Reionisation science program (G0009) has operated since 2014, collecting data and publishing 21cm power spectrum limits. One of its principal systematic constraints is the accuracy and depth of the foreground calibration and signal model (Beardsley et al. 2016, Barry et al. 16). The science experiment requires the compact configuration to sample the relevant angular scales of the EoR signal. In the extended configuration, we propose to undertake deep pointed observations of the two primary EoR fields (EoR0, EoR1), and their flanking fields, to obtain a higher resolution foreground model, and provide independent data (uv-coverage) to the current foreground and calibration model. Observation of the flanking fields will improve the ability to calibrate and remove contaminating sources in the main field sidelobes, and provide high-resolution information about extended sources within the fields. Combination of data from Phase I, Phase II (compact) and Phase II (extended, this proposal) will provide complete uv-coverage of the envisioned 256- tile Phase III array.

Authors: Dr. Christene Lynch (U. Sydney/CAASTRO), Dr. Emil Lenc (U. Sydney/ CAASTRO), Dr. Tara Murphy (U. Sydney/CAASTRO), Dr. David Kaplan (UW-Milwaukee), Dr. Gemma Anderson (Curtin), Mr. Andrew Zic (U. Sydney/CAASTRO)

Abstract: To better constrain stellar flare rates of magnetically active M dwarf stars at 154 MHz, we used the Murchison Widefield Array (MWA) to carry out an observational campaign of UV Ceti (through ac- cepted DDT proposals) in 2015-B and 2016-B observational periods. This campaign revealed flares with two very different set of characteristics: (1) four faint periodic flares with durations of 30 minutes and flat spectrum across the MWA band; and (2) a single bright short-duration flare with complex fre- quency structure. These tantalising results hint that UV Ceti might be host to a large variety of flaring activity. Further long timescale variation of the observed flare characteristics, including the stability of periodic signals, can inform our understanding of UV Ceti’s ability to generate and sustain the magnet- ic structures that produce the observed radio emission. Thus we are proposing a large observational campaign targeting UV Ceti, involving 100 hours of observation to fully characterise the flaring activi- ty of this source and investigate the periodicity of observed flares.

Authors:

MWA members: Lister Staveley-Smith (ICRAR/UWA; GEG-MCL leader), Miroslav Filipovic (UWS), Ramesh Bhat (ICRAR/Curtin), Roland Crocker (ANU), John Dickey (U. Tasmania), Bi-Qing For (ICRAR/UWA), Bryan Gaensler (U.Toronto; GEG-POL leader), Natasha Hurley-Walker (ICRAR/UWA; GEG-SNR leader), Naomi McClure-Griffiths (ANU), Maria Rioja (ICRAR/UWA), Nick Seymour (ICRAR/Curtin) (GEG leader), on behalf of the GEG team.

External members: Juergen Kerp (U.Bonn), Manami Sasaki (University of Erlangen-Nuremberg)

Abstract: We propose a deep survey (MAGE-X) of the Large and Small Magellanic Clouds with the extended configuration of the MWA. The survey will allow us to quantify the energy spectrum of cosmic ray electrons at the highest physical resolution in an external galaxy, including spatial variation arising from shock re-acceleration, spectral aging, and absorption effects. The survey will use the existing phase 1 GLEAM short-baseline data already processed (Callingham et al. 2016; Hurley-Walker et al. 2017; For et al., in prep), but the angular resolution of the combined data set will closely match higher- frequency radio observations (e.g. 1 arcmin for the ATCA LMC HI and continuum survey - Kim et al. 2003, Hughes et al. 2007), and will be within a factor of two of the high-surface-brightness sensitivity observations that will be forthcoming from the eROSITA X-ray mission (for which CAASTRO and eROSITA_DE have a data access partnership) and the ASKAP local HI and radio continuum radio surveys, GASKAP and EMU. This combination will be powerful in identifying sources of non-thermal emission. Combination with HESS and Fermi data will allow us to better separate leptonic and hadronic cosmic ray processes. Combination of MAGE-X with the large-scale Spitzer and Herschel (SAGE and HERITAGE) mid and far-infrared surveys (Meixner et al. 2006, 2013) and the ongoing VISTA near-infrared surveys of the Clouds (Cioni et al., 2013; Ivanov et al., 2016) will be powerful in identifying sources of thermal and stellar emission.

Authors: A/Prof. Tara Murphy (University of Sydney), Dr. Emil Lenc (University of Sydney), Prof. David Kaplan (UW – Milwaukee), Mr Andrew Zic (University of Sydney), Dr. Jean-Pierre Macquart (Curtin University), Prof. Ron Ekers (Curtin University / CSIRO), Dr Christene Lynch (University of Sydney).

Abstract: We propose pilot observations to explore the possibility of an imaging survey to detect pulsars through diffractive interstellar scintillation. In this project we will observe a sample of eight pulsars that have scintillation bandwidths and timescales in the observable range of the MWA. By taking data with continuous time coverage (2 hours) on each source, in the highest MWA frequency band (215 MHz), we will be able to experiment with image-domain detection techniques that we have developed as part of Andrew Zic’s honours thesis work.

This modest request of 32 hours observing time will serve as a pilot for a project targeting a larger sample of known pulsars, and ultimately a blind survey for new pulsars.

Authors: Dr. A. R. Offringa (ASTRON), Assoc. Prof. Randall Wayth (Curtin University), Dr. Thomas Franzen (Curtin University), Dr. Cathryn Trott (Curtin University)

Abstract: In this project we seek to make images at the confusion limit of the new extended array, thereby analysing the sky at MWA’s new sensitivity limit.

One of the main goals of the MWA is to investigate the Epoch of Reionization (EoR). In this project, we seek to test a new pointing for EoR studies, which has shown to be easy to calibrate, has little Galactic foregrounds and has no complicated sources in the beam. Additionally, with this project we will gain knowledge about the faint extragalactic sources that are foregrounds in EoR experiments. To separate signals from the EoR from the foregrounds, such accurate knowledge of the foreground sources is required. Increasing the accuracy of the foregrounds will lower the systematics and therefore result in more sensitive EoR analyses.

Apart from producing an accurate foreground model, we also intend to perform a low-frequency population and spectral characterization study of faint sources. While the extended MWA will not reach the sensitivity of LOFAR deep surveys, it has a phenomenal field of view, thereby allowing the census to cover an extremely large number of sources. If the confusion limit is reached, we can perform a P(D) analysis to probe the data below the 5 sigma limit and deduce the probable source count behaviour.

Performing deep imaging is an excellent way to learn how to calibrate and image the extended MWA in the best possible way. Our previous comparable project with the MWA (offringa et al. 2016a) has delivered the deepest MWA image so far, as well as tools which have increased the productivity of the MWA substantially. These tools (e.g. Cotter, WSClean, Mitchcal, autoprocess) are now widely used, and amongst other have formed the basis for the GLEAM pipeline. We will also test out a different pointing mechanism.

Authors: Q.Zheng (VUW, Shanghai Astronomical Observatory, Peripety Scientific Ltd), X.-P. Wu (Shanghai Astronomical Observatory, National Astronomical Observatories of China), M.Johnston-Hollitt (VUW, Peripety Scientific Ltd), R.Wayth (Curtin University), Q.Guo (Shanghai Astronomical Observatory), H.-Y. Shan (Argelander-Institut fr Astronomie), S.Duchesne (VUW, Peripety Scientific Ltd), X.-Y. Hong (Shanghai Astronomical Observatory)

Abstract: Deep imaging of the ionization structures of the IGM during EoR is one of the key science goals for SKA1-low. Detecting the EoR will require removal of all foregrounds, a task which is most easily done first by minimizing the foregrounds present by observing ‘quiet’ fields. We have used the radio source catalog (Hurley-Walker et al. 2017) and the diffuse source catalog (Johnston-Hollitt et al. in prep) of the GLEAM survey, the Haslam 408MHz All-Sky Map, ROSAT images, combined with the optical/X-ray catalog of galaxy clusters, WISE images, and 30GHz and 857GHz Planck datasets, to select the two ‘quietest’ sky fields with a radius of 7.5 degrees for deep EoR observations (Field centers: F1 (69deg, -43deg), F2 (41deg, -44deg)). We request to observe the two fields at five frequency bands over 30 hours for each field. Our deep observations of the selected fields may provide the simplest MWA fields from which foregrounds can be removed. The lack of radio sources also presents our best hope of achieving the highest possible dynamic range imaging the MWA is capable of. This is a “pathfinding” observation looking at finding potential EoR fields for SKA-Low, not specifically for the current MWA EoR program.

Authors: Prof. David Kaplan (UW – Milwaukee), A/Prof. Tara Murphy (University of Sydney), Dr Christene Lynch (University of Sydney), Dr Steve Croft (University of California, Berkeley), Dr. Emil Lenc (University of Sydney), and the MWA transients collaboration.

Abstract: We propose to conduct commensal transients searches through data collected for the MAGE-X project: deep, multi-wavelength observations of the Magellanic Clouds with the extended MWA. The techniques used will be similar to have so far resulted in the best limits yet on radio transient rates (Rowlinson et al. 2016).

Many types of variable and transient sources are predicted and observed at low frequencies. For example, flares from low-mass stars and brown dwarfs, magnetars, and flares associated with state transitions in accreting stellar-mass and intermediate-mass black holes. In addition, possible non-repeating transient sources, such as merging black holes and tidal disruption events, are expected to emit at MWA frequencies. The MWA is extremely well-suited for blind transient surveys due to its large instantaneous field of view and high sensitivity. We propose to survey for transient and variable sources in the Magellanic Cloud fields, which will include both significant Galactic foreground as well as nearby extragalactic sources. This is a commensal project, sharing data with the MAGE-X collaboration and targets transient events on time scales from 0.5 seconds to years, enabling us to search for both short duration coherent emission (e.g. Fast Radio Bursts, FRBs) and moderate duration incoherent sources over multiple days.