2021-A Call for Proposals: Open
CFP-2021-A: Up to 500 hours of shared-risk observing time in the Guaranteed Time and Open Access categories, during the period 3rd May 2021 - 30 June 2021. This observing period is designated as 2021-A and is subject to the availability of the array as per the MWA Time Allocation Policy and the installation progress for the new MWAX correlator. The deadline for submission of proposals is 29th March 2021.
Observations are only open to experienced observers with the MWA and will be the first to access the new MWAX correlator. As such teams wishing to access MWAX just post technical commissioning will need to be willing and able to assist with the scientific testing and commissioning of the new MWAX correlator. Note that the array will be in the compact configuration for this semester.
Please see the 2021-A call for proposals document here.
SCHEDULING
Observing Time
The observing awards are listed below for every semester since MWA operations began in 2013.
Semester 2020-B, Ph II Extended
PI | Title | Science Theme | Triggered? | Visibility Time (Hours) | VCS Time (Hours) |
---|---|---|---|---|---|
Bhat | Timing and imaging follow-up of the first pulsar discovery from the MWA (details)
Abstract: We request 4 hr of MWA time for continued timing observations of PSR J0036-1033 – the first pulsar discovery from the MWA. The pulsar was discovered in the initial processing of data from the ongoing SMART pulsar survey (G0057), where ~3% of the data were searched out to DMs ~300pc cm3,reaching 30% of the full array sensitivity. Thanks to the virtues of the MWA’s large FoV and the voltage capture mode of our survey, we have been able to perform a number of immediate follow-up investigations, including the processing of archival data for candidate confirmation, initial positional determination, and a first attempt on polarimetry. The pulsar appears to be relatively faint, with inferred flux densities ~2-8 mJy at 150 MHz and an implied luminosity ( 0.1-0.3mJy kpc2at 1400 MHz)that would place it near the top end of the so-called low-luminosity pulsars, of which only a few are known. We have already commenced its timing observations (via the DDT proposal D0029), and the primary goal of this proposal is the continuation of that effort, in order to determine the pulsar’s spin and astrometric parameters. A secondary goal is to perform improved polarimetry, in an attempt to better constrain the pulsar’s emission geometry. The proposal will also complement the planned follow-up efforts with Parkes that will help constrain the pulsar’s spectral index and luminosity, alongside allowing us to study the spectral evolution of its emission properties. | Transients | No | 0 | 4 |
Bhat | Triggering on ASKAP FRB detections (details)
Abstract: Since the early discoveries by Lorimer et al. (2007) and Thornton et al. (2013), the field of Fast Radio Bursts (FRBs) has been through a number of significant developments: most notably, interferometric localisations of several, and an explosion in their tally with the CHIME/FRB project coming online. Measurements of their scattering, scintillation, polarisation and Faraday rotation properties are becoming routine, and theoretical efforts to understand their origin continues unabated. With its large field of view( 30deg2) and interferometric advantages, the Australian SKA Pathfinder (ASKAP) has proven to be a uniquely capable instrument for detecting them, and localising them with arcsecond (or better) precision. The MWA’s co-location at the MRO site provides unique opportunities for undertaking efficient co-observing and triggering observations. Our shadowing campaign in early years (2018-2019) has placed the most stringent constraints on the low-frequency emission of FRBs and their spectral indices. Starting the 2020A semester, we have shifted the focus to further development and testing of VCS triggering strategies and optimising them for improved efficiency. Simultaneous detection of even a single FRB would mean a huge payoff and will yield the first unambiguous constraints on the spectral and scattering properties of FRBs, besides putting an end to the long-unresolved puzzle relating to the lack of FRB emission at low frequencies. A detection within the MWA band (<300 MHz) will also help exclude certain classes of progenitor models that involve dense plasma surrounding FRB hosts, and thus narrow down on the plausible models for their origin. | Transients | Yes | 0 | 9 |
Bhat | Tracking Interstellar Space Weather Toward Timing-array Millisecond Pulsars (details)
Abstract: Searching for nanohertz gravitational waves (GWs) using a celestial array of extremely stable millisecond pulsars (MSPs) is amongst the high-profile science goals of the SKA and its pathfinders. The success of these Pulsar Timing Array (PTA) experiments will extend the spectrum of gravitational-wave astronomy that has been opened by the LIGO/VIRGO detections of kilohertz-frequency gravitational waves produced by black-hole and neutron-star mergers. PTAs exploit the clock-like stability of MSPs to make a direct detection of ultra-low frequency (nano-Hertz) gravitational waves, and the science is highly complementary to that possible with LIGO-like detectors. PTAs are most sensitive to GW signals produced by supermassive black-hole mergers. Interstellar propagation effects on pulsar signals are a major contributor to timing noise, which, if not accurately measured and corrected for in timing measurements, may ultimately limit the detection sensitivity of PTAs. The interstellar medium (ISM)effects are much stronger at low frequencies, and hence the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays. Here we propose continued regular observations of three promising PTA pulsars for which the MWA’s sensitivity and capabilities allow detailed studies. The primary goals include characterising the nature of the turbulent ISM through high-quality scintillation studies and investigating the chromatic (frequency-dependent) dispersion measures (DMs) via high precision DM determinations that are now possible with the MWA. Our success and accomplishments in this area will also help define the scope of a more ambitious program in the future, as upgrade plans move forward for the MWA and with the prospects of a pulsar monitoring capability with Phase3 MWA. This will also prove to be an excellent scientific niche for the MWA, and eventually for the SKA-low. | Transients | No | 0 | 5.5 |
Bouwhuis | MWA Follow-up of Neutrino Transient Candidates (details)
Abstract: We request MWA follow-up of neutrino transient candidates detected by the ANTARES and IceCube neutrino telescopes. These follow-up observations will either lead to the strongest limits to date on prompt radio emission from neutrino transients, or to the detection of a correlated radio signal. The latter will lead to the localization of the astrophysical sources that emit high-energy neutrinos. In addition, the combined particle and radio detection from a common astrophysical source will contribute to evidence for the origin of cosmic rays. For around 30% of the ANTARES and IceCube neutrino alerts, the source is expected to be visible immediately from the MWA site. We expect to receive and follow up three or four neutrino triggers during 2020-B. The follow-up observations would be disruptive target of opportunity observations. We request 30 minutes of prompt follow-up of each trigger, followed by a second epoch 1–2 weeks later for each trigger (matched in LST range) for comparison. | Transients | Yes | 4 | 0 |
Chauhan* | Monitoring of X-ray binary transient outbursts with the MWA (details)
Abstract: We propose pointed observations with the MWA of any nearby bright (≥ 50 mJy) outbursting X-ray binary (XRB) during the 2020-B observing semester. The low-frequency regime of radio jets in XRBs is still not fully explored, especially at frequencies < 500 MHz. XRBs can produce two different types of radio jets over the course of a single outburst. Optically thick, at-spectrum, compact steady jets are observed during the hard state whereas steep-spectrum, relativistically-moving transient jets are detected near the peak of the outburst, when the source undergoes a transition from the hard to the soft X-ray spectral state. Both types of jets can be observed in the low-frequency regime. We aim to study both types of radio jets using MWA observations to constrain the radio spectrum in the low-frequency band. The prime aim of this proposal is to detect the possible low-frequency turn-over in the compact jets. The turn-over frequency along with the spectral slope below the turn-over frequency will put observational constraints on the electron energy distribution and magnetic field strength. Simultaneous high-cadence monitoring of transient jets at low and high frequencies will provide observational measurements essential for constraining the low-frequency emission geometry and thereby constrain various theoretical jet models. To the end, we aim to provide high-quality low- frequency radio light curves of XRBs covering a few epochs in the hard state, and denser sampling over the hard-to-soft state transition. | Transients | No | 30 | 0 |
Hancock | Demonstrating advanced space domain awareness capability with the MWA (details)
Abstract: Over the last 7 years we have shown that the MWA can be used to detect and monitor satellites and space debris in low Earth orbit. The initial detection of the international space station (ISS, Tingay et al. 2013) used correlated observations and image-based searches to track the ISS as it transited the MWA in elevation and azimuth. Subsequent work was done with voltages to perform traditional radar processing (Palmer et al. 2017, Hennessey et al. 2019) to also recover line of sight range, velocity, and acceleration. Since these two demonstrations, we have used the MWA as a passive bi-static radar receiver station to detect aircraft, meteor trails, satellites, and space debris (Zhang et al. 2018). Our most recent work (Prabu et al. 2020, Prabu et al. 2021 submitted) focuses on the development of an image-based processing workflow that automates the detection and monitoring of resident space objects in Low Earth Orbit (LEO). Work to date has focused on demonstration of capability using archival observations from the MWA. In this proposal we are requesting a modest 8h12m of observations to test and develop an advanced capability of the MWA using observing modes that are not present in the archive (specifically the choice of frequency channels and low elevations). The proposed observations will coincide with activities leading up to and including the Space Fest event that is a civilian activity run by the Australian Airforce at the end of November, and the Hayabusa-2 capsule re-entry in early December. | Transients | No | 8 | 0 |
Hurley-Walker | GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey (details)
Abstract: We propose the second half of observations of an extension to the highly successful GaLactic and Extragalactic MWA (GLEAM) survey. The aim is to create a legacy data set for innovative low-frequency science which will serve many astronomers overcoming years. This proposal covers an RA range of 20 to 06h, concluding the observation program initiated in 2018-A. The optimal time for our observations is a month between mid-September and mid-November, which straddles 2020-A and B, so we are submitting this proposal now for ease of scheduling. A deeper all-sky survey at higher resolution will enable a legion of science capabilities, whilst maintaining advantages over LOFAR including larger field-of-view (and survey speed), wider frequency coverage, and better sensitivity to extended emission. We propose to cover the GLEAM frequency range of 72—231 MHz and use repeated drift scans to observe 8,000 deg2, which in combination with the 20,000 deg2 observed in2018-A, will cover the entire southern sky. We will continue the successful snapshot imaging and image-plane combination strategy of GLEAM. We will utilise calibration strategies we have developed over the last year of research. The GLEAM extragalactic sky catalogue improves the prospects for good ionospheric calibration in this new regime, as well as trivialising absolute flux density calibration. Extrapolating from GLEAM, GLEAM-X will have lower noise, higher surface brightness sensitivity, and considerably wider bandwidth than TGSS. These properties will enable a wide range of science, such as: ●Detecting and characterising cluster relics and haloes beyond z = 0.45; ●Measuring the low-frequency luminosity function to z~0.5 (particularly the bright end); ●Characterising the low-frequency polarised sky; ●Investigating the spectral energy distributions (SEDs) of selected AGN to characterise jet activity; ●Providing broad-band radio SEDs of up to 1 million radio sources (especially in combination with the Rapid ASKAP Continuum Survey (RACS)); ●Better constraining the typical ionospheric diffractive scale and weather at the MRO, feeding into SKA_Low calibration strategies. In addition, the proposal is designed to be commensally used for transients science. | GEG | No | 280 | 0 |
Hu* | An MWA Probe of Radio Bridges in Merging Galaxy Cluster Pairs in the Low-Frequency Radio Band (details)
Abstract: Mpc-scale radio halos and radio relics have been frequently observed in galaxy clusters with merger signatures, showing a higher prevalence in luminous systems (see van Weeren et al. 2019, for a recent review). On the contrary, radio bridges, which appear as a giant filamentary source of diffuse radio emission that links two merging clusters, are rarely seen, possibly due to their low luminosities in the radio band. As of today, only two cases, i.e., the radio bridges in Abell 399 - Abell 401 (Govoni et al. 2019) and Abell 1758 (Botteon et al. 2020) have been detected by LOFAR with a threshold of 3σ at about 140 MHz, and both the bridges show a tight spatial correlation with a hot ( ~ 7 keV) and dense X-ray emitting region between the merging members. A possible explanation for the formation of radio bridges is that a population of in situ relativistic electrons are re-accelerated by either shock or turbulence. However, the form of the radio spectra of the radio bridge, the origin of the relativistic electrons, and the strength of the magnetic field, as well as the details of the electron acceleration processes are still unclear, due to the lack of observational evidence. Therefore, we propose to utilize the advantages of the MWA, i.e., the wide field of view, the good coverage of the low frequency band and the intermediate spatial resolution, to carry out deep pointing observations of two pairs of galaxy clusters (Abell 3016 - Abell 3017 and Abell 222 - Abell 223) across full MWA Phase II band 72-231 MHz for a total of 170 hrs (17 hrs per frequency band per source). Each of the two pairs of contain massive clusters in a clear dynamically disturbed state that are evolving and are seen in a pre-merger stage, as indicated by hot X-ray gas bridges between the two merging members. All these properties are highly similar to those of the two proto-typical radio bridge systems already detected with LOFAR. Radio bridges are expected to be detected in the two targets above 3σ with a spatial resolution of 1.5’, assuming that they have the same radio flux density as two proto-typical sources (~ 3 mJy beam-1 at about 140 MHz). The spectral slopes will also be measured with 5 spectral points. By jointly analysing the MWA radio data and the high-quality archival X-ray data acquired with Chandra and XMM-Newton, we will able to study the pre-merger stage dynamics in the virial region, and better constrain the origin and mechanism of the radio bridges. | GEG | No | 170 | 0 |
Lynch | Follow-up to the Long Baseline Epoch of Reionisation Survey (details)
Abstract: One of the principal systematic constraints on the Epoch of Reionisation (EoR) experiment using the Murchison Widefield Array (MWA) is the accuracy and depth of the foreground calibration model. Given the large field of view of the MWA, the MWA EoR fields contain several bright, extended sources located towards the edge of the primary beam and in the sidelobes. Recent results have shown that accurately modelling and removing bright sources at the edges of the field and in the sidelobes, removes more contaminating signal than just removing sources at the centre of the primary beam. In an effort to improve the models of sources in the MWA primary beam sidelobes of the EoR0 and EoR1 fields, we are conducting the Long Baseline Epoch of Reionisation Survey (LoBES). This survey consists of multi-frequency (between 103 --230 MHz) observations of EoR0, EoR1, and their eight neighbouring fields using the MWA Phase II extended array. Here we proposeto re-observe key LoBES fields to replace bad data taken during the original LoBE survey. | EoR | No | 3 | 0 |
Morgan | An Interplanetary Scintillation Survey with the extended Phase II MWA (details)
Abstract: In 2019A and 2020A we proposed (and were awarded) daily observations of Interplanetary Scintillation (IPS). We can use these observations for both space weather monitoring, and for determining the arcsecond-scale structure of the detected sources. With 8⨉10 minute observations per day we covered all solar elongations where we can make optimum IPS measurements, broadly following the survey methodology used in 2019A. We propose to continue these observations in 2020B with 10✕10 minute observations per day, since with the Sun in the Southern Hemisphere over 2020B we will be able to cover areas further to the North of the Sun while observing at a reasonable elevation. Overall, this semester will double our coverage. Observing later in the year than was possible in 2019/20A will allow us to access parts of the sky for which we have no prior data. Much of this area is particularly interesting as they cover high Galactic latitude fields well studied by other radio surveys such as FIRST. However, we will also be able to make IPS measurements in the Galactic Plane near the Galactic Centre for the first time with the MWA. Our observations in 2019A of the Galactic anticentre have demonstrated the unique ability of the MWA to probe scattering due to the ISM along a very large number of lines of sight. With an additional measurement above our standard observing frequency of 162MHz, we will be able to separate scatter broadening from source structure, and so we propose to observe some Galactic centre fields at the top GLEAM band. In summary, we request 190 hours to continue the survey started in 2019A and 2020A, and a further 20 hours to observe ~10 fields ~20 times at 200-230MHz. | SHI / GEG | No | 210 | 0 |
Oberoi | MWA Observations of the Sun (details)
Abstract: Two hundred hours of observing time for solar observations is requested during the 2020-B observing semester. These data will be used to address science objectives for solar burst science(Goal A); studies of weak non-thermal radiation (Goal B); quiet sun science (Goal C), imaging of CME plasma (Goal D); and observations coordinated with various spacecraft (Goal E). Goal A will focus on detailed investigations of individual events seen in the MWA data, using the unsurpassed spectroscopic snapshot imaging ability of the MWA to address some key solar physics questions. Detailed observations of type II bursts and type III bursts will be one focus. Goal B will address studies of the numerous short lived and narrow band emission features, significantly weaker than those seen by most other instruments revealed by the MWA. These emission features do not resemble any known types of solar bursts, but are possible radio signatures of the “nanoflares' which have long been suspected to play a role in coronal heating. A large database of these events is needed to be able explore this possibility and to reliably estimate their contribution to coronal heating. These observations will contribute to this database. Goal C will focus on characterising the Sun’s background thermal emissions, their short and long term variability and look for evidence of a scattering disc around the Sun. Goal D makes use of our high dynamic range capability to directly image the gyrosynchrotron emission from the CME plasma. Goal E proposes opportunistic coordinated observations with the Parker Solar Probe, the Solar Orbiter and the Chandrayaan-2. | SHI | No | 200 | 0 |
Oberoi | High Time Resolution Observations of the Sun using the Voltage Capture System (details)
Abstract: The MWA Solar physics group has recently reported the discovery of ubiquitous weak impulsive nonthermal emissions from the quiet Sun. So far, they satisfy all of the requirements for being relevant for heating of the quiet corona. The median duration of these “events” was found to be close to the time resolution of the interferometric data, and most of these events remain unresolved intime. The objective of this proposal is to seek a small amount of VCS data (1 hour) to carry out high time resolution observations of these events. The present times of low solar activity and the MWA being in the extended configuration are particularly well suited for these observations. An hour of correlator observations for calibration is also requested. | SHI | No | 1 | 1 |
Tian* | Rapid-response MWA observations of Swift and Fermi gamma-ray bursts (details)
Abstract: We request the use of the MWA rapid-response mode to perform triggered standard correlator and VCS observations of Swift and Fermi gamma-ray bursts (GRBs) during the 2020B semester. The prompt and early-time radio emission associated with GRBs is still a poorly explored regime, particularly at MHz frequencies. Short-duration GRBs (SGRBs), one of the two main classes of GRBs, are a hot topic in astronomy as they are linked with the compact binary coalescence of binary neutron stars (BNS), or a neutron star (NS) - black hole (BH) binary. BNS mergers are the main classes of gravitational wave events known to have electromagnetic counterparts (Abbott et al. 2017). Several theories predict such mergers should produce prompt, coherent emission (such as fast radio bursts, FRBs; Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014) the detection of which would allow us to distinguish between different binary merger models and scenarios. It is also possible that low-frequency pulsed radio emission could be generated by long-duration GRBs (LGRB; the other main GRB class resulting from stellar collapse; Usov & Katz, 2000).As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with GRBs may not arrive for seconds up to several minutes following the initial burst alerts at MWA frequencies. Given that the MWA rapid-response mode can automatically repoint the telescope within 14 seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. An additional advantage of the MWA is its large field-of-view, making it possible to follow-up Fermi detected GRB events, which have poor position constraints (order of ~10deg). Such rapid-response MWA observations have the sensitivities necessary to rule out some GRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low. | Transients | Yes | 1 | 4 |
Trott | Detecting ionised bubbles in the early Universe with stacked observations around Lyman-Alpha Emitting Galaxies (details)
Abstract: Measuring the evolution of the ionisation state of the intergalactic medium provides key insights into the growth of structure in the early Universe. Multiple observational probes have constrained the neutral fraction at a given redshift (e.g., sightlines to distant quasars, quasar proximity zones)or as an integrated quantity (e.g., Thomson scattering of CMB photons), yielding limits on the duration and endpoint of reionisation. The Silverrush Survey using the Subaru Hypersuprime Cam detected 282 bright Lyman-α Emitting Galaxies (LAEs) at z = 5.7, 6.6 in the UD-SXDS field (RA=34deg, Dec=-5deg). Strong Ly-αemission at the tail end of reionisation is suggested to be evidence for the host galaxy residing inside ionised regions of the IGM. Theoretical and simulation studies show an anti-correlation of21cm emission and Ly-α emission on scales of 5-50 cMpc (2-10’), as the 21cm traces neutral IGM while the Ly-α traces ionised bubbles. The expected brightness temperature contrast between neutral and ionised regions at z = 6.6 is2-10 mK, depending on the hydrogen neutral fraction. This is inaccessible without hundreds of hours of observations with the MWA for a single LAE. However, stacking 21cm images at known LAE spatial and redshift locations improves the signal-to-noise ratio leading to a statistical constraint on the IGM neutral fraction. Combined compact and extended array MWA observations of the UD-SXDS field at redshifted 21cm emission in these bands will produce images with sufficient angular resolution and surface brightness sensitivity to perform this stacking experiment. We have previously obtained 20.5 hours of data with the Compact configuration and propose to observe the same field with 40 hours of LST-matched observations with the Extended Array to complete the dataset. An IGM neutral fraction exceeding 25% at z = 6.6, should be detectable with SNR ≅ 3 using the 58 catalogued LAEs in the field. | EoR | No | 40 | 0 |
Williamson* | Detecting cosmic-ray extensive air showers (details)
Abstract: The goal of this project is to detect cosmic rays interacting in the atmosphere above the MWA. Using time granted in the previous allocation, we: • detected 7 cosmic ray candidates and are able to differentiate these from standard RFI events (Figure1); • have streamlined the processing pipeline to increase the rate at which data is processed; • have demonstrated that the data can be processed and deleted within the necessary timeline. Our goals for this proposal are to: • gather more data to increase our sample of cosmic ray candidates and further characterise these events; • continue to investigate the RFI on site at nanosecond timescales. The verification of the first cosmic ray event at the MWA opens up opportunities in the development of cosmic ray reconstruction and analysis techniques and benefits transient science at nanosecond timescales. There have been two Australian Research Council grants (ARC Discovery Project DP200102643, Detecting cosmic rays using precision radio imaging; and ARC LIEF grant LE200100078, A particle detector array forth Murchison Widefield Array) awarded towards cosmic ray science at the MWA with the specific purpose of detecting and analysing many cosmic ray events, where this work will allow for a better understanding of the view that the MWA has of cosmic ray air showers. | Transients | No | 0 | 24 |
Xu | Searching for the FRB121102 at low radio frequencies (details)
Abstract: Since the first discovered FRB in 2007, more than 100 sources have been published. The majority of the FRBs are observed not to repeat. However, the discovery of FRB 121102 revealed that at least a subset of FRBs exhibits a repeating nature. FRB 121102 has been studied extensively over the past five years. Recently a trial period P0 = 157 ± 7 day was found. The extension of the periodicity to the future time predicts that the next activity period is from 2020 November 5 to 2021 February 1. Till now, there is no FRB detection at frequencies <300 MHz; a detection of FRB at low radio frequencies would mean a vast science payoff. We expect to detect FRB 121102 with the MWA in the middle of the next active period and compare its low-frequency properties with the FAST observational results. In addition, we will use Machine Learning methods to process the data to increase the potential of detecting weak FRBs. | Transients | No | 0 | 2 |
*Student PI; †Open Access proposal
Semester 2020-A, Ph II Extended
PI | Title | Science Theme | Triggered? | Visibility Time (Hours) | VCS Time (Hours) |
---|---|---|---|---|---|
Anderson | Catching the low frequency radio component of stellar X-ray superflares (details)
Abstract: We request the use of the new MWA rapid-response mode to perform triggered observations of X-ray/gamma-ray flaring magnetically active stars detected with the Swift Burst Alert Telescope and the Monitor of All-sky X-ray Image (MAXI) instrument during the 2020A observing semester. Flare stars, such as rapidly rotating M dwarfs (dMe) and tidally-locked RS Canum Venaticorum binaries (RS CVn), are known to produce coherent, highly-circularly polarised flares at low radio frequencies (<5 GHz), particularly in the MHz range (Spangler et al. 1974a). These low frequency flares are indicative of unusual emission mechanisms such as electron-cyclotron masers or plasma radiation (Dulk 1985). The MWA has already proven to be a sensitive instrument for low frequency flare star studies through the detection of flares at 154 MHz from UV Ceti in Stokes V maps, which are thermal noise (rather than confusion noise) limited. These flares were likely generated via the electron-cyclotron maser mechanism (Lynch et al. 2017). dMe and RS CVn also experience extreme flaring events via incoherent emission mechanisms, producing synchrotron X-ray/gamma-ray “superflares” that are bright enough to trigger high-energy satellites such as Swift . Rapid-response radio observations performed with the Arcminute Microkelvin Imager (AMI) at high (15 GHz) radio frequencies have demonstrated that such superflares are accompanied by giant radio gyrosynchrotron flares peaking within a few minutes of the high-energy trigger (Fender et al. 2015). However, it is unknown whether X-ray/gamma-ray superflares can also be temporally coincident with low-frequency (coherent) radio bursts. By using the MWA rapid-response mode to trigger on Swift- and MAXI -detected high-energy superflares, we can investigate whether the same magnetic event that produces these bright, incoherent X-ray/gamma-ray superflares could also trigger the emission mechanisms responsible for bright, coherent low-frequency radio flares, providing a more unified understanding of the plasma physics in these stellar systems. | Transients | Yes | 4.5 | 0 |
Anderson | Negative-latency triggering on gravitational wave events with the Murchison Widefield Array (details)
Abstract: We request the use of the Murchison Widefield Array (MWA) rapid-response mode to perform VCS triggered observations of negative latency gravitational wave alerts of binary neutron star (BNS) and neutron star (NS) - black hole (BH) mergers detected by Advanced LIGO/Virgo (LV). While the prompt and early-time radio emission associated with BNS mergers is an unexplored regime, leading theories suggest that fast radio bursts (FRBs; extreme radio transients of unknown origin) are related to these events (Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014). The best chance to detect a prompt FRB-like event associated with a BNS merger requires that LV rapidly disseminate alerts of GW events. However, the estimated delay between merger and alert generation for the current LV O3 run, combined with the response times of most radio telescopes, is too slow to catch a simultaneous FRB. However, by sending negative latency GW triggers to the MWA (response times <14s; Hancock et al. 2019), it is possible to be on-target before an associated FRB arrives. The current O3 LV run has been detecting GW mergers involving at least one NS at a rate of ~1 per month. Using the high-time resolution capabilities of the MWA VCS, we therefore request to trigger on up to 2 events during the remainder of the O3 LV run (April and May 2020), of which we estimate up to 1 will be an MWA-detectable GW-FRB event. | Transients | Yes | 0 | 0.3 |
Bhat | Tracking Interstellar Space Weather Toward Timing-array Millisecond Pulsars (details)
Abstract: Searching for nanohertz gravitational waves (GWs) using a celestial array of extremely stable millisecond pulsars (MSPs) is amongst the high-profile science goals of the SKA and its pathfinders. The success of these Pulsar Timing Array (PTA) experiments will extend the spectrum of gravitational-wave astronomy that has been opened by the LIGO/VIRGO detections of kilohertz-frequency gravitational waves produced by black-hole and neutron-star mergers. PTAs exploit the clock-like stability of MSPs to make a direct detection of ultra-low frequency (nano-Hertz) gravitational waves, and the science is highly complementary to that possible with LIGO-like detectors. PTAs are most sensitive to GW signals produced by supermassive black-hole mergers. Interstellar propagation effects on pulsar signals are a major contributor to timing noise, which, if not accurately measured and corrected for in timing measurements, may ultimately limit the detection sensitivity of PTAs. The interstellar medium (ISM) effects are much stronger at low frequencies, and hence the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays. Here we propose continued regular observations of three promising PTA pulsars that we have already demonstrated to be most suitable for detailed studies using the MWA. The primary goals include characterising the nature of the turbulent ISM through high-quality scintillation and dispersion studies, including the investigation of chromatic (frequency-dependent) dispersion measures (DMs) and high-precision DM determinations that are now possible with the MWA. Our success and accomplishments in this area will also help define the scope of a more ambitious program in the future, as upgrade plans move forward for the MWA and with the prospects of a pulsar monitoring capability in the horizon in the era of Phase 3 MWA. This will also prove to be an excellent scientific niche for the MWA, and eventually for the SKA-low. | Pulsars and Fast Transients | No | 0 | 15.5 |
Bhat | Triggering on ASKAP FRB Detections (details)
Abstract: The Fast Radio Bursts (FRB) research is a rapidly emerging frontier of radio astronomy. Since their early discoveries by Lorimer et al. (2007) and Thornton et al. (2013), there have been a number of significant developments, including an explosion in their tally with the CHIME/FRB project coming online. Measurements of their scattering, scintillation, polarisation and Faraday rotation properties are becoming routine, and theoretical efforts to understand their origin continues unabated. As observational evidence continues to mount in support of their extragalactic origin, the world-wide competitive race is on, with a suite of new generation instruments geared up to find them in large numbers, and efforts are in earnest to localise them. With its large field of view of _30 deg2 and interferometric advantages, ASKAP has proven to be a uniquely capable instrument for detecting them, as well as localising them on sky with arcsecond (or better) precision. TheMWA’s co-location at the MRO site enables unique opportunities for undertaking efficient co-observing and triggering obseravtions. Our shadowing campaign in 2018-2019 has placed the most stringent constraints on low-frequency emission of FRBs and their spectral indices. For the 2020A semester, we intend to shift the focus to further development and testing of VCS triggering strategies and optimising them for improved efficiency. Simultaneous ASKAP+MWA detection of even a single FRB would mean a huge science payoff and will yield the first unambiguous constraints on the spectral and scattering properties of FRBs, besides putting an end to the long-unresolved puzzle relating to the lack of FRB emission at low frequencies. A detection within the MWA band (<300 MHz) will also help exclude certain classes of progenitor models that involve dense plasma surrounding FRB hosts, and confirm their cosmological distances. | Pulsars and Fast Transients | Yes | 0 | 15 |
Chauhan* | Monitoring of X-ray binary transient outbursts with the MWA (details)
Abstract: We propose pointed observations with the MWA of any nearby bright (&50 mJy) outbursting X-ray binary (XRB) during the 2020{A observing semester. The low-frequency regime of radio jets in XRBs is still not fully explored, especially at frequencies < 500 MHz. XRBs can produce two different types of radio jets over the course of a single outburst. Optically thick, at-spectrum, compact steady jets are observed during the hard state whereas steep-spectrum, relativistically-moving transient jets are detected near the peak of the outburst, when the source undergoes a transition from the hard to the soft X-ray spectral state. Both types of jets can be observed in the low-frequency regime. We aim to study both types of radio jets using MWA observations to constrain the radio spectrum in the low-frequency band. The prime aim of this proposal is to detect the possible low-frequency turn-over in the compact jets. The turn-over frequency along with the spectral slope below the turn-over frequency will put observational constraints on the electron energy distribution and magnetic field strength. Simultaneous high-cadence monitoring of transient jets at low and high frequencies will provide observational measurements essential for constraining the low-frequency emission geometry and thereby constrain various theoretical jet models. To the end, we aim to provide high-quality low- frequency radio light curves of XRBs covering a few epochs in the hard state, and denser sampling over the hard-to-soft state transition. | Transients | Yes | 30 | 0 |
Croft | MWA Follow-up of Neutrino Transient Candidates (details)
Abstract: We request MWA follow-up of neutrino transient candidates detected by the ANTARES/KM3NeT and IceCube telescopes during 2020-A. These observations would be disruptive target of opportunity observations. Around 30% of ANTARES/KM3NeT triggers are expected to be visible immediately from the MWA site (Adrian-Martinez et al. 2015). IceCube alerts favouring high-energy events are also more likely to originate from the Southern Hemisphere (https://icecube.wisc.edu/science/data/TXS0506_alerts), and approximately 30% are likely to be visible to the MWA. We expect to follow up three or four triggers during the semester. We request 30 min of prompt follow-up of each trigger, followed by a second epoch 1 – 2 weeks later (matched in LST range) for comparison. These will allow the strongest limits to date on prompt radio emission from neutrino transients and may aid in localization of these new astrophysical probes. We expect ANTARES to be decommissioned part-way through the semester, and to implement parsing software to accept IceCube alerts prior to the beginning of the semester. | Transients | Yes | 4 | 0 |
Hurley-Walker | GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey (details)
Abstract: We propose the second half of observations of an extension to the highly successful GaLactic and Extragalactic MWA (GLEAM) survey. The aim is to create a legacy data set for innovative low-frequency science which will serve many astronomers overcoming years. This proposal covers an RA range of 20 to 06h, concluding the observation program initiated in 2018-A. The optimal time for our observations is a month between mid-September and mid-November, which straddles 2020-A and B, so we are submitting this proposal now for ease of scheduling. A deeper all-sky survey at higher resolution will enable a legion of science capabilities, whilst maintaining advantages over LOFAR including larger field-of-view (and survey speed), wider frequency coverage, and better sensitivity to extended emission. We propose to cover the GLEAM frequency range of 72—231 MHz and use repeated drift scans to observe 8,000 deg2, which in combination with the 20,000 deg2 observed in2018-A, will cover the entire southern sky. We will continue the successful snapshot imaging and image-plane combination strategy of GLEAM. We will utilise calibration strategies we have developed over the last year of research. The GLEAM extragalactic sky catalogue improves the prospects for good ionospheric calibration in this new regime, as well as trivialising absolute flux density calibration. Extrapolating from GLEAM, GLEAM-X will have lower noise, higher surface brightness sensitivity, and considerably wider bandwidth than TGSS. These properties will enable a wide range of science, such as: ●Detecting and characterising cluster relics and haloes beyond z = 0.45; ●Measuring the low-frequency luminosity function to z~0.5 (particularly the bright end); ●Characterising the low-frequency polarised sky; ●Investigating the spectral energy distributions (SEDs) of selected AGN to characterise jet activity; ●Providing broad-band radio SEDs of up to 1 million radio sources (especially in combination with the Rapid ASKAP Continuum Survey (RACS)); ●Better constraining the typical ionospheric diffractive scale and weather at the MRO, feeding into SKA_Low calibration strategies. In addition, the proposal is designed to be commensally used for transients science. | GEG | No | 280 | 0 |
Janagal† | Investigation of sub-pulse drifting properties for three pulsars (details)
Abstract: A significant population of pulsars exhibits the extremely intriguing drifting subpulse phenomenon. When individual pulses are stacked vertically to form a two-dimensional pulse stack, the individual components of pulses, termed subpulses, are observed to undergo a regular modulation pattern in both amplitude and phase, which visually resemble a set of discrete diagonally-oriented burst regions called drift bands. The study of this phenomenon is essential for unlocking the mystery of radio pulsar emission mechanisms. A systematic single pulse study with enhanced sensitivities of a sample of pulsars exhibiting subpulse drifting can provide a better understanding of this phenomenon. We selected a sample of three pulsars, PSR J1543+0929, PSR J1820-0427, and PSR J1834-0426, for investigation of subpulse drifting properties with the MWA. A separate proposal to observe these targets (among others) at higher frequencies has been recently submitted in Cycle-38 of uGMRT. These pulsars have high flux at both uGMRT (Band-3 and 4) and MWA frequencies. There is evidence that each of these pulsars exhibit subpulse drifting (Weltevrede et al., 2006,2007), but no studies have yet been conducted using single pulse data. These sources lie in the field of view of MWA and are nightly targets for the 2020Asemester, hence providing low RFI conditions. Also, the new MWA beamformer equips the instrument to study the listed sources, some of which are at high DM, with better sensitivity. The sample of pulsars selected has previously indicated the presence of subpulse drifting at different frequencies (Weltevrede et al., 2006, 2007) and requires further detailed multi-frequency investigation. Since the target pulsars have different profile shapes with multi-component profiles generated from varied emission geometry, our study will probe the connection between subpulse drift properties of various emission components. The lower frequency and high sensitivity of our targets at MWA frequencies will provide a useful platform to study the subpulse behavior, mode switching and fluctuation spectra. In addition, MWA has also demonstrated the capability for high-quality single pulse work through multiple recent publications (McSweeney et al. 2017, 2019). | Pulsars and Fast Transients | No | 0 | 6.7 |
Kaplan | Searching for Prompt Emission from Binary Neutron Star Mergers (details)
Abstract: We propose a triggered search for prompt emission from up to three binary neutron stars discovered through gravitational waves with the LIGO/Virgo detectors. A detection of such emission would immediately yield enormous insight into the physics of the explosion, the cosmic baryon distribution, and other topics, and would open up a new avenue for multi-messenger exploitation of these amazing events. | Transients | Yes | 1 | 0 |
Morgan | An Interplanetary Scintillation Survey with the extended Phase II MWA (details)
Abstract: We propose to conduct daily observations of Interplanetary Scintillation (IPS). We can use these observations for both space weather monitoring, and for determining the arcsecond-scale structure of the detected sources. With 8⨉10 minute observations per day we can cover all solar elongations where we can make optimum IPS measurements, broadly following the survey methodology used in 2019A. In the first part of the 2020A we will be re-observing the same sky areas from 2019A. However, these will be independent observations from a space weather point of view; and this is also useful for improving our astrophysical modelling, since multiple independent observations reduce uncertainty introduced by space weather variations. Observing later in the year than was possible in 2019A will allow us to access parts of the sky for which we have no prior data. The parts of the sky opened up are particularly interesting as they cover high Galactic latitude fields well studied by other radio surveys such as FIRST. In contrast to most other projects using the long-baseline MWA, IPS is not strongly affected by bandwidth smearing and we can accept 40kHz frequency resolution, reducing the archive volume of our observations by a factor of 4. | SHI | No | 240 | 0 |
Oberoi | MWA Observations of the Sun (details)
Abstract: Two hundred hours of observing time for solar observations is requested during the 2020-A observing semester. These data will be used to address science objectives for solar burst science (Goal A); studies of weak non-thermal radiation (Goal B); quiet sun science (Goal C), imaging of CME plasma (Goal D); observations coordinated with the trajectory of the Parker Solar Probe (Goal E); and measuring CME magnetic fields (Goal F). Goal A will focus on detailed investigations of individual events seen in the MWA data, using the unsurpassed spectroscopic imaging ability of the MWA to address some key solar physics questions. Detailed observations of type II bursts, of which MWA has observed two, and type III bursts will be one focus. Goal B will address studies of the numerous short lived and narrow band emission features, significantly weaker than those seen by most other instruments revealed by the MWA. These emission features do not resemble any known types of solar bursts, but are possible radio signatures of the “nanoflares' which have long been suspected to play a role in coronal heating. A large database of these events is needed to be able explore this possibility and to reliably estimate their contribution to coronal heating. These observations will contribute to this database. Goal C will focus on characterizing the Sun’s background thermal emissions, their short and long term variability and look for evidence of a scattering disc around the Sun. Goal D makes use of our high dynamic range capability to directly image the gyrosynchrotron emission from the CME plasma. Goal E proposes opportunistic observations during the perihelion of PSP. Finally, Goal F will explore the use of Faraday rotation of linearly polarised light from background radio source due CME plasma to build a 3D model for the CME magnetic field. | SHI | No | 200 | 0 |
Ross* | Low-Frequency Variability Monitoring of Peaked Spectrum Sources (details)
Abstract: Gigahertz-peaked spectrum (GPS) radio sources are a unique subset of active galactic nuclei (AGN) which can display compact, double-lobe morphology. GPS sources are identified by a spectral peak in their radio spectral energy distributions (SED) in the gigahertz regime, typically have sizes of 1-20 kpc, and show little to no polarisation or variability. As compact radio galaxies can also peak at MHz frequencies (often referred to as Megahertz-peaked spectrum (MPS) sources) we refer collectively to all sources displaying a peak in their SED as peaked spectrum sources (PSS), regardless of peak frequency. PSS have played a pivotal role in shaping our understanding evolutionary paths of radio galaxies as they are hypothesised to be the progenitors to massive, radio-loud AGN (O'Dea, 1998). We have performed a comparison of ˞500 peaked spectrum sources identified from the GaLactic and Extragalactic All-sky MWA Survey (GLEAM; Hurley-Walker et al., 2017; Wayth et al., 2015), by Callingham et al. (2017) with the second year of GLEAM observations (Franzen et al. in prep). We find ˞ 25 sources (˞ 30% of the variable population and ˞ 5% of the PSS population) which show significant variability across the two years of observation but, unexpectedly, maintain their peaked spectrum classification. Furthermore, we have discovered extreme variability in the SEDs of 10 peaked-spectrum sources (˞ 12% of the variable population) that maintained their curved or peaked spectral classification over both epochs. Year-long variability, much shorter than the expected evolution variation of these sources, suggests a fundamental misunderstanding of the physical mechanisms causing the spectral peak and/or a departure from the stereotypical structure of peaked-spectrum sources. We aim to conduct year-long monitoring of 15 of these sources with both the MWA and ATCA in order to detect and classify any observed variability across the entire SED. Our ATCA proposal was 100% awarded in the OCT19 semester for which we obtained matching DDT MWA observations. We have a follow-up APR20 ATCA proposal under review to continue these observations for a further five epochs of 2.1GHz, 5GHz and 9GHz imaging spread across the semester. We request simultaneous (subject to availability, otherwise within 2 days) MWA time with the APR20 ATCA observations. | GEG | No | 62.5 | 0 |
Seymour | Observing HI in Absorption Against a Luminous z ∼ 10 Radio Galaxy (details)
Abstract: We have been conducting a search for high redshift (z >5:5) radio galaxies in order to investigate the formation and evolution of super-massive black holes in the early Universe. In addition to studying super-massive black holes, we can use these sources to study the formation of massive host galaxies and their environments. Of particular interest is how the host galaxy interacts with its environment. The HI/ 1420.4 MHz hyperfine transition is a tracer of the cold neutral hydrogen, but this line is too weak to detect in emission at this redshift. However, it should in theory be detectable in absorption with a bright enough background source. We propose a long observation to obtain a spectrum of a newly confirmed powerful radio galaxy at z= 10:154. At the HI observed frame frequency, 127 MHz, this galaxy has a flux density of ˞600 mJy. We estimate that a 100-hour observation would detect HI with an optical depth of ˠ= 0:1 with a SNR of ˞6 over one 10 kHz channel. We estimate the HI to be 710 channels wide boosting our SNR. Such an observation naturally pushes the capability of the MWA regarding systematics, but we argue that this is a great example of a high-risk/high-reward project. At minimum we would obtain an upper limit for the HI optical depth in this galaxy. We may see intervening absorption from neutral HI along the line sight within the Epoch of Reionisation. | GEG | No | 100 | 0 |
Sobey | Targeted MWA pulsar search towards promising candidates identified in radio surveys (details)
Abstract: We propose a pilot targeted pulsar search towards five promising pulsar candidates. These were identified as polarised sources in POGS (POlarised GLEAM Survey; MWA imaging data), or steep spectrum sources in TGSS, and have properties consistent with those of the pulsar polulation. This is a proof-of-concept study that presents the opportunity to efficiently discover more pulsars, which are powerful probes of a range of physics. We request 5 h of observing time using the MWA in the extended configuration, mostly utilising the high-time and -frequency resolution VCS mode. | Pulsars and Fast Transients | No | 0.8 | 4.2 |
Tian* | Rapid-response MWA observations of Swift and Fermi gamma-ray bursts (details)
Abstract: We request the use of the MWA rapid-response mode to perform triggered standard correlator and VCS observations of Swift and Fermi gamma-ray bursts (GRBs) during the 2020A semester. The prompt and early-time radio emission associated with GRBs is still a poorly explored regime, particularly at MHz frequencies. Short-duration GRBs (SGRBs), one of the two main classes of GRBs, are a hot topic in astronomy as they are linked with the compact binary coalescence of binary neutron stars (BNS), or a neutron star (NS) -black hole (BH) binary. BNS mergers are the main classes of gravitational wave events known to have electromagnetic counterparts (Abbott et al. 2017). Several theories predict such mergers should produce prompt, coherent emission (such as fast radio bursts, FRBs; Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014) the detection of which would allow us to distinguish between different binary merger models and scenarios. It is also possible that low-frequency pulsed radio emission could be generated by long-duration GRBs (LGRB; the other main GRB class resulting from stellar collapse; Usov & Katz, 2000).As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with GRBs may not arrive for seconds up to several minutes following the initial burst alerts at MWA frequencies. Given that the MWA rapid-response mode can automatically repoint the telescope within 20seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. An additional advantage of the MWA is its large field-of-view, making it possible to follow-up Fermi detected GRB events, which have poor position constraints (order of ~10 deg). Such rapid-response MWA observations have the sensitivities necessary to rule out some GRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low. | Transients | Yes | 8 | 1 |
Williamson* | Detecting cosmic-ray extensive air showers (details)
Abstract: Following the request for DDT last year, the purpose of this proposal is to use the improved methods developed through the DDT to detect the first radio emission from cosmic ray air showers at the MWA. The aims for this observation proposal are: • To detect the first cosmic ray event using the MWA • To further investigate the RFI at nanosecond timescales • To monitor the cosmic ray detector on site in conjunction with MWA data for any concurrent cosmic ray detections • To limit the impact of these observations on the limited space available on the archive. (See Part C for more details). The detection of the first cosmic ray event at the MWA would open up opportunities in the development of cosmic ray reconstruction and analysis techniques and would benefit transient science at nano second timescales. There have been two ARC grants (ARC Discovery Project DP200102643, Detecting cosmic rays using precision radio imaging; and ARC LIEF grant LE200100078, A particle detector array for the Murchison Widefield Array) awarded towards cosmic ray science at the MWA with the specific purpose of detecting and analysing many cosmic ray events, where this work will allow for a better understanding of the view that the MWA has of cosmic ray air showers. Using the DDT data we achieved: • The inverse Polyphase Filter Bank software was further optimized and benchmarked • The inversion was validated through an experiment conducted on site with a gas lighter (see Part Cand Figures 2 and 3). | Transients | No | 0 | 24 |
*Student PI; †Open Access proposal
Semester 2019-B, Ph II Compact
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0002 | Oberoi, Divya | (continuation) MWA Observations of the Sun (details)
Abstract: A hundred hours of observing time for solar observations is requested during the 2019-B observing semester. These data will be used to address science objectives for solar burst science (Goal A); studies of weak non-thermal radiation (Goal B); quiet sun science (Goal C), imaging of CME plasma (Goal D); observations coordinated with the trajectory of the Parker Solar Probe (Goal E); and measuring CME magnetic fields (Goal F). Goal A will focus on detailed investigations of individual events seen in the MWA data, using the unsurpassed spectroscopic imaging ability of the MWA to address some key solar physics questions. Detailed observations of type II bursts, of which MWA has observed two, and type III bursts will be one focus. Goal B will address studies of the numerous short lived and narrow band emission features, significantly weaker than those seen by most other instruments revealed by the MWA. These emission features do not resemble any known types of solar bursts, but are possible radio signatures of the “nanoflares' which have long been suspected to play a role in coronal heating. A large database of these events is needed to be able explore this possibility and to reliably estimate their contribution to coronal heating. These observations will contribute to this database. Goal C will focus on characterizing the Sun’s background thermal emissions, their short and long term variability and look for evidence of a scattering disc around the Sun. Goal D makes use of our high dynamic range capability to directly image the gyrosynchrotron emission from the CME plasma. Goal E proposes opportunistic observations during the perihelion of PSP. Finally, Goal F will explore the use of Faraday rotation of linearly polarised light from background radio source due CME plasma to build a 3D model for the CME magnetic field. |
100 |
G0009 | Trott, Cathryn | (continuation) Epoch of Reionisation (details)
Abstract: Detection of the signal of spatial fluctuations in the 21cm brightness temperature in the early Universe will open the door to exploration of this crucial era. The signal structure and evolution encode key astrophysical and cosmological information, which will allow an understanding of the first sources of ionising photons, the growth of structure, and the physical conditions in the intergalactic medium. With the recent announcement of the detection of the globally-averaged 21cm signal from the Cosmic Dawn (Bowman et al. 2018), the field of observational 21cm radio astronomy can begin to place physical limits on this period, but deeper understanding will require characterisation of the spatially-variant signal, as probed by low frequency interferometers such as the MWA and LOFAR. The Phase 2 Compact configuration, with its two redundant hexagonal sub-arrays, is specifically designed to provide the precision calibration and large-scale sensitivity required to execute this challenging experiment. With recent progress in the EoR collaboration to improve calibration through employing redundant calibration, obtaining extended configuration data to improve the sky model, forming a diffuse sky model for calibration, and assessing and classifying ionospheric activity, the EoR project requests September-December compact configuration observations of its two primary observing fields, and drift scans between the two fields, across the redshift range z = 6 – 17 (including ultralow observations of the Cosmic Dawn). These data will be processed with the improved calibration framework, and combined with existing high-quality data for competitive limits. |
720 |
G0021 | Bhat, Ramesh | (continuation) Tracking interstellar space weather toward timing-array millisecond pulsars (details)
Abstract:The LIGO detection of milli-Hertz gravitational wave (GW) signals from black-hole merger events, and its due recognition by the award of 2017 Nobel Prize, has further reinforced the important role of Pulsar Timing Array (PTA) experiments in extending the spectrum of gravitational-wave astronomy. PTAs exploit the clock-like stability of fast-spinning millisecond pulsars (MSPs) to make a direct de- tection of ultra-low frequency (nano-Hertz) gravitational waves, and this is a key science driver for the SKA and its pathfinders. The science enabled by PTAs is highly complementary to that possible with LIGO/VIRGO detectors, as PTAs are most sensitive to GW signals produced by supermassive black- hole mergers. PTA efforts over the past years suggest that interstellar propagation effects on pulsar signals, if not accurately measured and corrected for in timing measurements, may ultimately limit the detection sensitivity of PTAs. Interstellar medium (ISM) effects are much stronger at lower radio fre- quencies and therefore the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays. Here we propose to continue regular observations of three promising PTA pulsars that we have already demonstrated to be suitable for detailed studies using the MWA. The primary goals include characterising the nature of the turbulent ISM through high-quality scintillation and dis- persion studies, including the investigation of chromatic (frequency-dependent) dispersion measures (DMs) and high-precision DM determinations that are now possible with the MWA. Success of these efforts will define the breadth and scope of a more ambitious program in the future, when the MWA will be equipped with a better pulsar monitoring capability, thus bringing a new scientific niche for the MWA, and eventually for the SKA-low. |
12.5 (VCS) |
G0034 | Bhat, Ramesh | (continuation) Shadowing and Triggering on ASKAP FRB campaigns (details)
Abstract:Fast Radio Bursts (FRBs) is a rapidly emerging frontier of radio astronomy. Since their early discoveries by Lorimer et al. (2007) and Thornton et al. (2013), there have been a number of sig- nificant developments, including an explosion in their tally with the CHIME/FRB project coming online. Measurements of their scattering, scintillation, polarisation and Faraday rotation properties are becoming routine, and theoretical efforts to understand their origin continues. As observational evidence continues to mount in support of their extragalactic origin, the world-wide competitive race is on, with a suite of new generation instruments geared up to find them in large numbers, and ef- forts are in earnest to localise them. With its large field of view of ∼30 deg2 and interferometric advantages, ASKAP has proven to be a uniquely capable instrument for detecting them, as well as localising them on sky with arcsecond (or better) precision. The MWA’s co-location at the MRO site enables unique opportunities for undertaking efficient co-observing and triggering obseravtions. Our shadowing campaign last year has placed the most stringent constraints on low-frequency emission of FRBs and their spectral indices. For the 2019B semester, we propose to undertake a combination of shadowing and triggering strategies that will help maximise the FRB science with the MWA. Si- multaneous ASKAP+MWA detection of even a single FRB would mean a huge science payoff and will yield the first unambiguous constraints on the spectral and scattering properties of FRBs, besides putting an end to the long-unresolved puzzle relating to the lack of FRB emission at low frequencies. A detection within the MWA band (<300 MHz) will also help exclude certain classes of progenitor models that involve dense plasma surrounding FRB hosts, and confirm their cosmological distances. |
360 (+10 VCS) |
G0052 | Chauhan, Jaiverdhan | (continuation) Monitoring of X-ray binary transient outbursts with the MWA (details)
Abstract: We propose pointed observations with the MWA of any nearby, bright (at GHz frequencies) out- bursting X-ray binary (XRB) during the 2019–B observing semester. The low-frequency regime of radio jets in XRBs is still not fully explored, especially at frequencies < 500 MHz. XRBs can produce steep-spectrum, relativistically-moving transient jets near the peak of the outburst, when the source undergoes a transition from the hard to the soft X-ray spectral state. Transient jets can be observed in the low-frequency regime. We aim to study transient jets using MWA observations to constrain the radio spectrum in the low-frequency band. Simultaneous high-cadence monitoring of transient jets at low and high frequencies will provide observational measurements that can help to determine the low frequency emission geometry and thereby help in constraining various theoretical jet models. To this end, we aim to provide high-cadence low-frequency radio light curves of XRBs over the hard-to-soft X-ray spectral state transition. The MWA observations are important because MWA is providing a unique additional window into the sources that are typically extremely well covered across the electromagnetic spectrum, and provides a worthwhile addition to ongoing global campaigns, while providing new information about the jet geometry, magnetic field and other physical properties of jets. |
7 |
G0055 | Anderson, Gemma | (continuation) Rapid-response MWA observations of Swift and Fermi gamma-ray bursts (details)
Abstract:We request the use of the MWA rapid-response mode to perform triggered standard correlator and VCS observations of Swift and Fermi gamma-ray bursts (GRBs) during the 2019B semester. The prompt and early-time radio emission associated with GRBs is still a poorly explored regime, particularly at MHz frequencies. Short-duration GRBs (SGRBs), one of the two main classes of GRBs, are a hot topic in astronomy as they are linked with the compact binary coalescence of binary neutron stars (BNS), or a neutron star (NS) - black hole (BH) binary. BNS mergers are the main classes of gravitational wave events known to have electromagnetic counterparts (Abbott et al. 2017). Several theories predict such mergers should produce prompt, coherent emission (such as fast radio bursts, FRBs; Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014) the detection of which would allow us to distinguish between different binary merger models and scenarios. It is also possible that low-frequency pulsed radio emission could be generated by long-duration GRBs (LGRB; the other main GRB class resulting from stellar collapse; Usov & Katz, 2000). As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with GRBs may not arrive for seconds up to several minutes following the initial burst alerts at MWA frequencies. Given that the MWA rapid-response mode can automatically repoint the telescope within 14 seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. An additional advantage of the MWA is its large field-of-view, making it possible to follow-up Fermi detected GRB events, which have poor position constraints (order of ~10 deg). Such rapid-response MWA observations have the sensitivities necessary to rule out some GRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low. |
4 (+1 VCS) |
G0056 | Anderson, Gemma | (continuation) Catching the low frequency radio component of stellar X-ray superflares (details)
Abstract:We request the use of the new MWA rapid-response mode to perform triggered observations of X-ray/gamma-ray flaring magnetically active stars detected with the Swift Burst Alert Telescope and the Monitor of All-sky X-ray Image (MAXI) instrument during the 2019B observing semester. Flare stars, such as rapidly rotating M dwarfs (dMe) and tidally-locked RS Canum Venaticorum binaries (RS CVn), are known to produce coherent, highly-circularly polarised flares at low radio frequencies (<5 GHz), particularly in the MHz range (Spangler et al. 1974a). These low frequency flares are indicative of unusual emission mechanisms such as electron-cyclotron masers or plasma radiation (Dulk 1985). The MWA has already proven to be a sensitive instrument for low frequency flare star studies through the detection of flares at 154 MHz from UV Ceti in Stokes V maps, which are thermal noise (rather than confusion noise) limited. These flares were likely generated via the electron-cyclotron maser mechanism (Lynch et al. 2017). dMe and RS CVn also experience extreme flaring events via incoherent emission mechanisms, producing synchrotron X-ray/gamma-ray “superflares” that are bright enough to trigger high-energy satellites such as Swift. Rapid-response radio observations performed with the Arcminute Microkelvin Imager (AMI) at high (15 GHz) radio frequencies have demonstrated that such superflares are accompanied by giant radio gyrosynchrotron flares peaking within a few minutes of the high-energy trigger (Fender et al. 2015). However, it is unknown whether X-ray/gamma-ray superflares can also be temporally coincident with low-frequency (coherent) radio bursts. By using the MWA rapid-response mode to trigger on Swift- and MAXI-detected high-energy superflares, we can investigate whether the same magnetic event that produces these bright, incoherent X-ray/gamma-ray superflares could also trigger the emission mechanisms responsible for bright, coherent low-frequency radio flares, providing a more unified understanding of the plasma physics in these stellar systems. |
9 |
G0057 | Bhat, Ramesh | (continuation) The Southern-Sky MWA Rapid Two-metre (SMART) Pulsar Survey (details)
Abstract:Over the past decades, pulsars have firmly established themselves as nature’s premier laboratories for uncovering new vistas in extreme physics. With applications ranging from probing the state of ultra- dense matter to testing gravity in the strong-field regime, and from probing complex plasma physics in the relativistic regime to the search for ultra-low frequency gravitational waves, they enable us to push the frontiers of physics and astrophysics. This enviable accomplishment is the direct result of multiple large sky surveys of the past five decades, which not only led to a steady increase in the known pul- sar population, but also proven invariably rewarding by facilitating discoveries of exotic objects such as millisecond pulsars and those in relativistic binary orbits. Every major leap in radio astronomy in- strumentation or technology tends to trigger a large pulsar survey; the advent of Phase 2 MWA and the well-matured voltage-capture capability presents another unique opportunity. Motivated by this we have commenced an all-sky pulsar survey: the Southern-sky MWA Rapid Two-metre (SMART) pulsar sur- vey, which will surpass all previous and ongoing surveys in survey speed, owing to the development of novel strategies and survey methodologies. In 2018B we have undertaken the first phase of the survey, covering 20% of the sky in the VCS mode, spanning the LST range from 21 hr to 3 hr. In 2019B we request a similar allocation to extend the survey to 2-8 hr LST range. Our goal is to survey the entire sky visible to the MWA in a uniform and systematic manner. With a survey speed of ∼600 deg2 hr−1 , the entire sky can be completed in less than 100 hours, to reach a limiting sensitivity (10σ) of ∼3 mJy in pulsar flux density (at 150 MHz). Based on our initial pulsar census and refined simulation studies, we expect to discover more than 200 pulsars including ∼ 20 millisecond pulsars by the completion of the survey. Alongside its numerous scientific benefits, the SMART pulsar survey will also serve as an important reference survey for SKA-Low, which is slated to be the most efficient pulsar finding machine in the coming decades. |
17.5 (VCS) |
D0011 | Kaplan, David | (continuation) Searching for Prompt Emission from Binary Neutron Star Mergers (details)
Abstract: We propose a triggered search for prompt emission from up to three binary neutron stars discovered through gravitational waves with the LIGO/Virgo detectors. A detection of such emission would immediately yield enormous insight into the physics of the explosion, the cosmic baryon distribution, and other topics, and would open up a new avenue for multi-messenger exploitation of these amazing events. |
3 |
Croft, Steve | (continuation) MWA Followup of Neutrino Transient Candidates (details)
Abstract:We request MWA follow-up of neutrino transient candidates detected by the ANTARES/KM3NeT and IceCube telescopes during 2019-B. These observations would be disruptive target of opportunity observations. Around 30% of triggers are expected to be visible immediately from the MWA site (Adrian-Martinez et al. 2015). We expect to follow up three or four triggers during the semester. We request 30 min of prompt follow-up of each trigger, followed by a second epoch 1 – 2 weeks later (matched in LST range) for comparison. These will allow the strongest limits to date on prompt radio emission from neutrino transients and may aid in localization of these new astrophysical probes. |
4 |
Semester 2019-A, Ph II Extended
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0002 | Oberoi, Divya; Lonsdale, Colin; Cairns, Iver | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun (details)
Abstract:A hundred hours of observing time for solar observations is requested during the 2019-A observing semester. These data will be used to address science objectives for solar burst science (Goal A); studies of weak non-thermal radiation (Goal B); quiet sun science (Goal C), imaging of CME plasma (Goal D); observations coordinated with the trajectory of the Parker Solar Probe (Goal E); and measuring CME magnetic fields (Goal F). Goal A will focus on detailed investigations of individual events seen in the MWA data, using the unsurpassed spectroscopic imaging ability of the MWA to address some key solar physics questions. Detailed observations of type II bursts, of which MWA has observed two, and type III bursts will be one focus. Goal B will address studies of the numerous short lived and narrow band emission features, significantly weaker than those seen by most other instruments revealed by the MWA. These emission features do not resemble any known types of solar bursts, but are possible radio signatures of the “nanoflares' which have long been suspected to play a role in coronal heating. A large database of these events is needed to be able explore this possibility and to reliably estimate their contribution to coronal heating. These observations will contribute to this database. Goal C will focus on characterizing the Sun’s background thermal emissions, their short and long term variability and look for evidence of a scattering disc around the Sun. Goal D makes use of our high dynamic range capability to directly image the gyrosynchrotron emission from the CME plasma. Goal E proposes opportunistic observations during the perihelion of PSP. Finally, Goal F will explore the use of Faraday rotation of linearly polarised light from background radio source due CME plasma to build a 3D model for the CME magnetic field. |
100 |
G0008 | Hurley-Walker, Natasha | (continuation) GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey (details)
Abstract:We have examined the data taken for the GaLactic and Extragalactic All-sky MWA eXtended (GLEAM-X) survey and determined which nights cannot be processed due to highly active ionospheric weather. This proposal requests re-observations of these nights in order to complete our sky coverage. The aim of GLEAM-X is to create a legacy dataset for innovative low-frequency science which will serve many astronomers over coming years. This proposal covers an RA range of ~4 to 21h, with the expectation of observing the other half of the sky in 2020. A deeper all-sky survey at higher resolution will enable a legion of science capabilities, whilst maintaining advantages over LOFAR including larger field-of-view (and survey speed), wider frequency coverage, and better sensitivity to extended emission. We propose to cover the GLEAM frequency range of 72—231 MHz and use repeated drift scans over 20,000 deg2 this semester, and a further overlapping 20,000 deg2 in 2019-B. We will continue the successful snapshot imaging and image-plane combination strategy of GLEAM, and ionospheric triage methods we have developed for GLEAM-X. The GLEAM extragalactic sky catalogue improves the prospects for good ionospheric calibration in this new regime, as well as trivialising absolute flux density calibration. Extrapolating from GLEAM, GLEAM-X will have lower noise, higher surface brightness sensitivity, and possess the critical wide bandwidth that sets it apart from complementary surveys such as TGSS. These properties will enable a wide range of science, such as:
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190 |
G0015 | Kitaeff, Slava | (continuation) Radio Recombination Spectral Lines toward Galactic Centre and NGC6334 (details)
Abstract:This proposal is a request to re-observe G0015 with a modified strategy using the improved MWA Phase II. After a number of unsuccessful attempts to detect radio recombination lines (RRLs) in G0015 data we’ve concluded that most of the data can not be used due to incorrect gains setup for most of the tiles during observing (See Part C for details). Successful detection of molecular lines and some recombination lines by Tremblay, C. et al. (2017, 2018a, 2018b) motivates us to re-observe Galactic Centre and observe NGC6334. We would also like take advantage of better capabilities of MWA Phase II and re-observe Galactic Centre and NGC6334 at the central frequency of 154.24 MHz, and observe both sources at 215.68 MHz, where the lines have been previously detected in greater optical depths. These observations can be taken and simultaneously processed for the search of molecular lines, although the processing requirements between molecules and recombination lines are somewhat different. See the proposal submitted by Chenoa Tremblay. As by-product, continuum images will have to be created. Deep integrated continuum images of the Galactic Centre and NGC6334 can also be developed to explore other scientific goals. |
40 |
G0018 | Tremblay, Chenoa | (continuation) Molecular Lines in the Galactic Centre (details)
Abstract:This proposal is a follow-up to our previous project which found two molecules in four objects around the Galactic Plane (Tremblay et. al., 2017) and molecules and recombination lines observed around the Orion Molecular Cloud Complex (Tremblay et al., 2018a, 2018b). By re-observing the Galactic Centre with the extended array we hope to confirm the results through associated transitions and search a greater frequency range than previous observations. Previous successful observations of the Galactic Centre were at 99--129MHz. Observing at 70-100MHz and 140-170MHz and using the wide field-of-view of the MWA we can continue to survey the Galactic Plane. By utilising the extended array, we will decrease the beam size which subsequently reduce the effects of beam dilution by 53% when the ratio of solid angles is calculated. This makes us increasingly sensitive to emission from more distant fields, like the Galactic Centre. These observations can be taken and simultaneously processed for the search of carbon recombination lines, although the processing requirements between molecules and recombination lines may be unique. See the proposal submitted by Slava Kitaeff for a separate recombination line project. Even though the search for spectral signatures requires the removal of the continuum, full continuum images are created a part of the developed spectral line pipeline. The long integration continuum image can provide better detail than other surveys around the Galactic Centre and so other science goals can be explored as well. For this data we will be utilising and modifying the already developed pipeline for calibrating, imaging, image combination and continuum subtraction strategies with the new long baselines. |
20 |
G0021 | Bhat, Ramesh | (continuation) Tracking interstellar space weather toward timing-array millisecond pulsars (details)
Abstract:The LIGO detection of milli-Hertz gravitational wave (GW) signals from black-hole merger events, and its due recognition by the award of 2017 Nobel Prize, has further reinforced the important role of Pulsar Timing Array (PTA) experiments in extending the spectrum of GW astronomy. PTAs ex- ploit the clock-like stability of fast-spinning millisecond pulsars (MSPs) to make a direct detection of ultra-low frequency (nano-Hertz) gravitational waves, and this is a key science driver for the SKA and its pathfinders. The science enabled by PTAs is highly complementary to that possible with LIGO/VIRGO detectors, as PTAs are most sensitive to GW signals from supermassive black-hole mergers. PTA efforts over the past few years suggest that interstellar propagation effects on pulsar signals, if not accurately measured and corrected for in timing measurements, may ultimately limit the detection sensitivity of PTAs. Interstellar medium (ISM) effects are much stronger at lower radio frequencies and therefore the MWA presents an exciting and unique opportunity to calibrate interstel- lar propagation delays. Here we propose further observations of three promising PTA pulsars that are proven suitable for detailed studies using the MWA, and exploratory observations of two additional ones. The main goal is to characterise the nature of the turbulent ISM through high-quality scintilla- tion and dispersion studies including the investigation of chromatic (frequency-dependent) dispersion measures (DMs). Success of these efforts will define the breadth and scope of a more ambitious pro- gram in the future, and will bring a new science niche for the MWA and SKA-low. |
8 (VCS) |
G0034 | Bhat, Ramesh | (continuation) Shadowing and Triggering on ASKAP FRB campaigns (details)
Abstract:Fast Radio Bursts (FRBs) is a rapidly emerging frontier of radio astronomy. Since their discovery by Lorimer et al. (2007) and Thornton et al. (2013), there has been a six-fold increase in the number of FRB detections, and measurements have been made of their scattering, scintillation, polarisation and Faraday rotation properties, thereby firmly establishing their astrophysical nature. As observational evidence continues to mount in support of their extragalactic origin, the world-wide competitive race is also ramping up, with a suite of new and existing instruments gearing up to find them in large num- bers, and efforts are in earnest to localise them. With its large field of view of ∼30 deg2 , ASKAP has proven to be a uniquely capable instrument for detecting FRBs in large numbers, as vividly demon- strated by the > 26 FRB detections by the CRAFT project in the past couple of years. The MWA’s co-location at the MRO site enables unique opportunities for undertaking efficient co-observing and triggering. Our shadowing campaign has already placed stringent constraints on low-frequency emis- sion of FRBs and their spectral indices. Simultaneous ASKAP+MWA detection of even a single FRB would mean a huge science payoff and will yield the first unambiguous constraints on the spectral and scattering properties of FRBs, besides putting an end to the long-unresolved puzzle relating to the lack of FRB emission at low frequencies. A detection within the MWA band (<300 MHz) will also help exclude certain classes of progenitor models that involve dense plasma surrounding FRB hosts, and confirm their cosmological distances. |
10 (+5 VCS) |
G0047 | Seymour, Nick | (continuation) The MWA Interestingly Deep Astrophysical (MIDAS) Survey (details)
Abstract:The long baselines of MWA Phase 2 present an exciting opportunity to probe deeper than has been possible in GLEAM and a factor of 4 deeper than is planned in GLEAM-X (the long baseline all-sky successor to GLEAM). MIDAS targets six well-studied extra-galactic fields and integrates down close to the natural confusion limit. These deeper surveys, covering a total of 3,000deg2 at higher resolution, will enable a legion of science covering galaxy evolution, clusters and the cosmic web, whilst maintaining the advantages the MWA has over LOFAR (including larger field- of-view, wider frequency coverage and better sensitivity to extended emission). In this proposal we will target the remaining two extra-galactic fields visible: GAMA15 and SPT/XXL fields. The other four fields were observed in 2018A, three at night and one, GAMA23, during the day. Our day time observations were very successful; hence we propose that our final two fields also be observed during the day in 2019A. As before these observations will cover the original GLEAM frequency range of 72-231 MHz. The GAMA15 field, ~60deg2, is a wide area multi-frequency survey with photometry across the UV to far-IR regime, providing estimates of star formation rate, stellar mass and environment. The SPT/XXL survey field, ~50deg2, has a complementary swath of multi-wavelength data. We will utilise calibration, imaging, and image combination strategies developed using pilot observations to be obtained in 2017B with the new long baselines and boot strap off GLEAM in a similar fashion to GLEAM-X. MIDAS will enable a wide range of science, such as:
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20 |
G0049 | Shan, Chenxi | (continuation) MWA Observations of Nearby Low-Luminosity QSO Sample (details)
Abstract:With the development of new radio telescopes reaching the fainter radio sky, star-forming galaxies and radio-quiet AGNs (Active Galactic Nuclei) have an expected, surprising emergence at the radio domain. The main players of the radio sky have a changing landscape. It has come to the realisation that there is a continuum of galaxy properties in radio bands, from pure star-forming galaxies with radio power dominated by star-forming processes, to the radio-loud objects powered with the central AGN, and a composite of the prior two kinds in between. We propose to use a nearby low-luminosity Quasi-Stellar Objects (LLQSOs) sample with the extended configuration of the MWA phase II to probe the changing landscape. The sample, which is well-studied via spatially resolved mapping by various instruments across many wavelength bands, is an ideal playground for probing the various radio populations, as the sample contains radio-loud AGNs, radio-quiet AGNs, star-forming galaxies, and composite galaxies. The observing targets are selected by performing a positional cross-match of the nearby LLQSO sample with the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) extragalactic catalogue searching for their low-frequency radio counterparts. As a follow up of our 2018-B pilot observations, we propose to observe another 6 targets for our sample in 2019-A. |
30 |
G0052 | Chauhan, Jaiverdhan | (continuation) Monitoring of X-ray binary transient outbursts with the MWA (details)
Abstract:We propose pointed observations with the MWA of any nearby, bright (at GHz frequencies) out- bursting X-ray binary (XRB) during the 2019–A observing semester. The low-frequency regime of radio jets in XRBs is still not fully explored, especially at frequencies <500 MHz. XRBs can produce two different types of radio jets over the course of a single outburst. Optically thick, flat-spectrum, compact steady jets are observed during the hard X-ray spectral state, whereas steep-spectrum, relativistically-moving transient jets are detected near the peak of the outburst, when the source undergoes a transition from the hard to the soft X-ray spectral state. Both types of jets can be observed in the low-frequency regime. We aim to study both types of radio jets using MWA obser- vations to constrain the radio spectrum in the low-frequency band. The main aim for the compact jets is to detect the possible low-frequency turn-over. The turn-over frequency, along with the spec- tral slope below the turn-over frequency will put observational constraints on the electron energy distribution and the magnetic field strength. Simultaneous high-cadence monitoring of transient jets at low and high frequencies will provide observational measurements essential for constraining the low-frequency emission geometry and thereby constrain various theoretical jet models. To this end, we aim to provide high-quality low-frequency radio light curves of XRBs covering a few epochs in the hard state, and denser sampling over the hard-to-soft state transition. |
20 |
G0053 | Hodgson, Torrance | (continuation) Searching for the Synchrotron Cosmic Web (details)
Abstract:This proposal seeks to use the new capabilities of the Murchison Widefield Array (MWA) phase II to augment the existing phase I data in the search for evidence of the synchrotron cosmic web. Previous searches using just phase I or phase II data in isolation have not been successful in detecting the cosmic web. The phase I configuration had a plenitude of short baselines that made it well suited to detect extended emission like the cosmic web, but deep observations were confusion limited after just a few hours of integration (Vernstrom et al. 2017). The phase II extended configuration increased the resolution and greatly reduced the confusion limit, but at the expense of the shorter baselines. We propose to combine phase I and II deep field data and jointly image, in an attempt to maximise the strengths of each array. To do this, we propose to make use of existing deep observations by the Epoch of Reionisation (EoR) group, and augment this data with new phase II observations. Detection of the synchrotron web would provide definitive support for our current models of cosmic evolution, as well as providing indirect evidence for magnetic fields on the very largest of cosmic scales. A null result, on the other hand, allows us to place even stronger constraints on these unknown parameters. |
94 (limited by visibility) |
G0055 | Anderson, Gemma | (continuation) Rapid-response MWA observations of Swift and Fermi gamma-ray bursts (details)
Abstract:We request the use of the new MWA rapid-response mode to perform triggered correlated and VCS observations of Swift and Fermi gamma-ray bursts (GRBs) during the 2019A semester. The prompt and early-time radio emission associated with GRBs is still a poorly explored regime, particularly at MHz frequencies. Short-duration GRBs (SGRBs), one of the two main classes of GRBs, are currently a hot topic in astronomy as they are linked with the compact binary coalescence of binary neutron stars (BNSs), or a neutron star (NS) - black hole (BH) binary. BNSs mergers are the main classes of gravitational wave events known to have electromagnetic counterparts (Abbott et al. 2017). Several theories predict such mergers should produce prompt, coherent emission (such as fast radio bursts, FRBs; Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014) the detection of which would allow us to distinguish between different binary merger models and scenarios. It is also possible that low-frequency pulsed radio emission could be generated by long-duration GRBs (LGRB; the other main GRB class resulting from stellar collapse; Usov & Katz, 2000). As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with GRBs may not arrive for seconds up to several minutes following the initial alerts at MWA frequencies. Given that the MWA rapid-response mode can automatically repoint the telescope within 16 seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. An additional advantage of the MWA is its large field-of-view, making it possible to follow-up Fermi detected GRB events, which have poor position constraints (order of ~10 deg). Such rapid-response MWA observations have the sensitivities necessary to rule out some GRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low. |
10 (+1 VCS) |
G0056 | Anderson, Gemma | (continuation) Catching the low frequency radio component of stellar X-ray superflares (details)
Abstract:We request the use of the new MWA rapid-response mode to perform triggered observations of X-ray/gamma-ray flaring magnetically active stars detected with the Swift Burst Alert Telescope and the Monitor of All-sky X-ray Image (MAXI) instrument during the 2019A observing semester. Flare stars, such as rapidly rotating M dwarfs (dMe) and tidally-locked RS Canum Venaticorum binaries (RS CVn), are known to produce coherent, highly-circularly polarised flares at low radio frequencies (<5 GHz), particularly in the MHz range (Spangler et al. 1974a). These low frequency flares are indicative of unusual emission mechanisms such as electron-cyclotron masers or plasma radiation (Dulk 1985). The MWA has already proven to be a sensitive instrument for low frequency flare star studies through the detection of flares at 154 MHz from UV Ceti in Stokes V maps, which are thermal noise (rather than confusion noise) limited. These flares were likely generated via the electron-cyclotron maser mechanism (Lynch et al. 2017). dMe and RS CVn also experience extreme flaring events via incoherent emission mechanisms, producing synchrotron X-ray/gamma-ray “superflares” that are bright enough to trigger high-energy satellites such as Swift. Rapid-response radio observations performed with the Arcminute Microkelvin Imager (AMI) at high (15 GHz) radio frequencies have demonstrated that such superflares are accompanied by giant radio gyrosynchrotron flares peaking within a few minutes of the high-energy trigger (Fender et al. 2015). However, it is unknown whether X-ray/gamma-ray superflares can also be temporally coincident with low-frequency (coherent) radio bursts. By using the MWA rapid-response mode to trigger on Swift and MAXI detected high-energy superflares, we can investigate whether the same magnetic event that produces these bright, incoherent X-ray/gamma-ray superflares could also trigger the emission mechanisms responsible for bright, coherent low-frequency radio flares, providing a more unified understanding of the plasma physics in these stellar systems. |
9 |
D0011 | Kaplan, David | (continuation) Searching for Prompt Emission from Binary Neutron Star Mergers (details)
Abstract:We propose a triggered search for prompt emission from a binary neutron star discovered through gravitational waves with the LIGO/Virgo detectors. A detection of such emission would immediately yield enormous insight into the physics of the explosion, the cosmic baryon distribution, and other topics, and would open up a new avenue for multi-messenger exploitation of these amazing events. |
6 |
Croft, Steve | (continuation) MWA Followup of Neutrino Transient Candidates (details)
Abstract:We request MWA followup of neutrino transient candidates detected by the ANTARES/KM3NeT and IceCube telescopes during 2019A. These observations would be disruptive target of opportunity observations. Around 30% of triggers are expected to be visible immediately from the MWA site (Adrian-Martinez et al. 2015). We expect to follow up three or four triggers during the semester. We request 30 min of prompt followup of each trigger, followed by a second epoch 1 – 2 weeks later for comparison. These will allow the strongest limits to date on prompt radio emission from neutrino transients and may aid in localization of these new astrophysical probes. |
4 | |
Weniger, Christoph | Axion dark matter searches with the Murchison Widefield Array (details)
Abstract:Astrophysical observations of galaxies and galaxy clusters, and cosmological observations of the temperature fluctuations of the cosmic microwave background provide strong evidence for the existence of dark matter (DM) in the Universe. One of the oldest and theoretically best motivated DM candidates are QCD axions, ultralight particle that solves the strong CP problem of the Standard Model of particle physics. For masses in the μeV range, these particles also naturally explain the observed amount of cold DM. Substantial experimental efforts are underway to search for these particles in laboratory experiments. Here, we propose to leverage on the fact that DM axions can resonantly convert into photons when traversing the strong magnetic field in the magnetosphere of neutron stars (NS). The observable signal is a narrow spectral line, with frequency that depends on the (unknown) axion mass. Detailed calculations show that slowly-spinning NSs lead to the most efficient conversion. An optimal target for axion searches is hence the large population of dead NSs, which can be inferred from population synthesis arguments. We propose here to use the unique capabilities of the Murchison Widefield Array to search for narrow spectral lines from the Galactic center (GC) region in the 80 – 300 MHz frequency range. The proposed searches are complementary to similar proposed work with the Green Bank, Effelsberg, and Sardinia radio telescopes. A discovery of an axion line would be a major breakthrough, but even null results will provide the strongest limits on the axion photon coupling and will significantly deepen our understanding of DM in the Universe. |
4 | |
Zic, Andrew | Space weather monitoring of Proxima Centauri (details)
Abstract:Stellar flares and coronal mass ejections (CMEs) play an important role in the habitability of their planetary companions. M-dwarf stars are particularly interesting in this regard, as they are known to flare more frequently and powerfully than the Sun. At the same time, a large number of these stars are likely to host planets within their habitable zones. While stellar flares have been observed ubiquitously across the electromagnetic spectrum, observational identification and characterisation of space weather events such as CMEs around other stars is lacking. These space weather events are expected to cause effects such as magnetospheric compression and atmospheric stripping of planetary companions, degrading their habitability. One promising method to detect and characterise stellar CMEs is to detect low-frequency Type II bursts, associated with radio emission from the CME shock front. Analysis of these bursts from the Sun have enabled characterisation of the CME shock-front propagation speed, the density profile of the corona and interplanetary medium, and the mass and energy of the ejected material. Therefore, the detection and characterisation of Type II bursts from other stars may lead to rich insights into the activity of these stars, and its impact on the habitability of their planetary companions. We propose 54 hours of observations targeting the closest star to the Sun, Proxima Centauri. This star is a well-known active flare star, but its low-frequency emission remains observationally unconstrained. This program will enable us to understand the low-frequency emission of this star, and may allow us to make the first detection of a Type II burst from another star beyond the Sun. This will permit a more detailed characterisation of the impact of Proxima Centauri’s activity on various stellar parameters, as well as the habitability of any planetary companions such as Proxima Centauri b. |
54 | |
Bernardi, Gianni | Searching for the radio bridge in the A3395 and A3391 cluster pair (details)
Abstract:Detecting radio emission from gas bridges in between galaxy clusters before major mergers has the potential of unveiling so far underlooked pre-processing of gas matter and magnetic fields in large scale structures. We propose here to use the MWA observe the gas bridge in the A3391—A3395 interacting pair of galaxy clusters, whose emission has already been detected in the X-ray band and through the Sunyaev-Zeldovich effect. Through simulations, we predict that the radio emission from the bridge will be at the 10-20 mJy level, on scales of 10-20’ in ~150-200 MHz frequency range - mostly powered by weak shocks in the interaction regions of the two structures - in presence of ~0.1-0.2 μG magnetic fields. Such expectations are within the capabilities of a 4 hour long MWA observation. The proposed observations will shed light into acceleration mechanism in the outer regions of galaxy clusters which are important in the pre-processing of gas matter and magnetic fields well before more classic major mergers takes place. |
4.5 | |
Zhu, Zhenghao | Probing the synchrotron emission from virial shock surrounding Coma cluster (details)
Abstract:Galaxy clusters, located at the nodes of cosmic web, are thought to be grown by the infalling mass from surrounding environment. This process are expected to produce virial shocks and deposit a certain fraction of infalling energy into magnetic fields and electrons, latter of which would be accelerated into high relativistic speed. During this process, both γ-ray from inverse Compton emission and synchrotron emission in radio frequency are expected. Recently, Keshet et al. (2017) has found a preliminary evidence of the virial shock outside Coma cluster in γ-ray, but the very existence is still not confirmed, which makes the cluster virial shock remain a theory. With high sensitivity of MWA phase II, it is likely that a clear detection of radio emission from virial shock for the first time can be made by observing Coma cluster. Thus, we propose a deep pointed observation to Coma cluster across full MWA Phase II band 72-231 MHz, for a total observation time of 10 hours to investigate the virial shock. The high-quality radio images and spectral information would help us to confirm the existence of virial shock. Using this signal, we can also give constrains to the magnetic fields of the intergalactic medium (IGM) and trace the possible warm-hot IGM around. Besides, a detailed study of such diffuse structure could also help implement the task of removing the complicated foreground of the 21 cm signal from the era of reionization. |
10 | |
Krishnan, Vivek Venkatraman | Orbital Dynamics and the Radio Beam of PSR J1141-6545 (details)
Abstract:We propose timing observations of the relativistic pulsar - white-dwarf binary, PSR J1141−6545. This unique system offers access to a wide range of physics, from relativistic phenomena through pulsar emission mechanism studies, to the structure and distribution of interstellar plasma along our line-of-sight. Our recent analysis of data obtained over almost 2 decades suggests that the pulsar’s 1.4 GHz beam will precess away from our line-of-sight in the next 3-5 years. This provides a unique opportunity to perform regular observations of the pulsar across a wide range of frequencies, which might provide constraints on the latitudinal radius to frequency mapping of the pulsar beam. Our analysis of the 1.4 GHz data also revealed significant phase-resolved, secular Rotation Measure variations. The proposed observations of this pulsar at low frequencies will help resolve if these variations are magnetospheric, due to the intra-binary medium or to interstellar scattering, and result in reliable estimates of the pulsar’s geometry from the Position Angle sweep of its linear polarisation. |
6 (VCS) | |
Gong, Hongyu | Measuring Scattering Properties of Pulsars with Intermediate Dispersion at Low Frequency (details)
Abstract:Pulsars experience a profile broadening when their emissions traverse through turbulent interstellar medium (ISM). This multi-path propagation effect can be quantified by the scattering time scale τ which is strongly dependent on frequency (τ ∝ ν −α ), while the index α represents intrinsic properties of the ISM in depth. In literature, the scattering time scale indices are predicted by models to be α = 4 or 4.4, while showing large discrepancy in observational results. This is mainly caused by the local ISM complications through the pulsar signal transmission, however, could also be biased by observations taken in different frequencies at different time, and with dissimilar telescopes. Recently, using three pulsars, Kirsten et al. (2018) has proved that we are able to estimate τ with single epoch, multi-band MWA observations. Hence we are proposing a single 1.5- hours MWA VCS observation on a line-of-sight toward PSR J1820-0427, distributing the 24×128MHz channels into two different centre frequencies. Using this data set, we will be able to estimate τ at two MWA frequency bands and calculate α for at least six pulsars covered in this field. Results from this project could be used to accurately characterize the turbulence of the ISM and develop the Galactic electron density model. This project will also demonstrate that MWA is capable to measure scattering spectra indices for a large sample of pulsars with high efficiency. |
1.5 (VCS) | |
Morgan, John | An Interplanetary Scintillation Survey with the extended Phase II MWA (details)
Abstract:During the first half of 2016 we conducted IPS observations for approximately 1 hour daily using Director’s time. Just two of these observations have been used to write a series of papers [1-5], and work is ongoing to reduce a larger fraction these data. Here we propose to conduct a similar number of observations during 2019-A. With one hour of observing per day we can cover all solar elongations where we can make optimum IPS measurements. By using the Phase II extended MWA, we expect to approximately double our sensitivity. In our Guaranteed Time proposal we requested 1 hour per day. This is sufficient to cover all pointings relative to the Sun where we can make ‘optimum IPS measurements’. We have used this time to schedule 6✕10-minute observations per day at approximately 30° elongation from the Sun at Position Angles 60, 90, 120, 240, 270 and 300 (degrees relative to ecliptic North). Position angles further North than this are not accessible at this time of year. However a further 30 minutes per day would allow us to supplement these with Position Angles 150, 180 and 210, giving coverage of the areas of the sky affected by the polar solar wind. This wind is less dense and therefore produces weaker scintillation, however measurements made here will increase our astrophysical survey area and will be just as interesting from a Space Weather point of view. Additionally, the original call for proposals envisaged the semester finishing on 1 Jul. We would like to extend our observation campaign to the end of the semester which will give us considerably more sky coverage. Therefore we request:
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150 + 113.5 | |
Bhat, Ramesh | MWA Follow-up of a FAST Pulsar Candidate (details)
Abstract:The Five-hundred metre Aperture Spherical radio Telescope (FAST) in China is fast gearing up for science. With a sensitivity that surpasses all currently operational facilities, this largest single-dish telescope ever built will push the boundaries of parameter space in many areas of science including pulsar searches. Ongoing early science efforts have already led to a number of new pulsar discover- ies, underscoring the exciting scientific promise of this new facility. Here we propose to undertake low-frequency follow-up of a curious pulsar candidate that is potentially detectable with the MWA. The candidate is seemingly bright, with an estimated flux density of ∼4-5 mJy, albeit prominent only within the lower 100 MHz of the 300-800 MHz wide-band system that was used to make the de- tection. The indicated dispersion measure (DM) is highly anomalous for the line of sight and the observed degree of scattering is significantly lower than expected for such a DM. The candidate pul- sar is potentially detectable in a dedicated 1.5 hr observation with the MWA over a 200-230 MHz band. If confirmed, this pulsar will be an extremely interesting object to probe one of the strangely anomalous lines of sight in terms of both the degree of scattering and the dispersion measure. This will also serve as an excellent demonstration of the MWAs potential to undertake fruitful follow-ups of new pulsar discoveries and candidates to come from the FAST, which may open up promising avenues for synergetic science in the areas of pulsars using the two facilities. |
1.5 (VCS) | |
Deshpande, Avinash | Coordinated MWA-GBD Search for Radio Pulses from the Geminga Pulsar (details)
Abstract:Despite numerous deep searches over the past 20+ years, the radio pulses from the famous Geminga pulsar (the nearest and brightest gamma-ray pulsar) have remained so far illusive, in the midst of some claims of their detections and many reporting non-detections. The apparent radio-quiet nature of this famous gamma-ray pulsar presents a yet-unsolved puzzle, if not a mystery. The claimed detections, all at the low radio frequencies (~35-110 MHz), are essentially either of low significance (e.g., Malov et al. 2015) or of extremely rare ultra- bright pulses (at 34 MHz; see Maan 2015) with significant spread in the associated dispersion measures. A sensitive search for both periodic and occasional bright pulses done in coordinated manner from at least two distinct locations and simultaneously across a wide range of frequencies appears essential to improve chances of possible conclusive radio detection. With this view, we propose to conduct a coordinated search for radio pulses from the Geminga pulsar using the MWA in its wide-band mode and the Gauribidanur Decametre- wave Radio Telescope (GEETEE) observing in a narrow band around 35 MHz, both recording the data in voltage-capture mode. We request for four 45-min sessions (on 3 separate days) with the MWA to conduct the proposed search using 3 sessions, and one session to observe a control pulsar in the same observing mode. Success of the proposed observations will also pave way for an attractive coordinated mode between the MWA and the GEETEE, offering advantages in both, namely, wider spectral range and finer localization of direction. |
3 (VCS) | |
Kaur, Dilpreet | Looking for dispersion measure variations over the orbital phase of MSP J2241-5236 (details)
Abstract:Removal of dispersive smearing at lower observing frequencies requires phase coherent de-dispersed data. The newly augmented pulsar beamforming pipeline which re-constructs the data at much higher time resolution (∼ 1 μs) enables us to perform high time resolution studies of millisecond pulsars (MSPs). Using this we have made successful detections of a MSP J2241 − 5236 down to 80 MHz. This pulsar is rapidly emerging as a highly promising target for pulsar timing array experiments (PTA). The pulsar is in a 3.5 hour circular orbit with a low mass (0.012 M ) white dwarf companion. The timing studies from MeerKAT observations showed some systematic offset in pulse arrival times (TOAs), related to the binary parameters of this pulsar. These drifts in the TOAs could be due to minute variations in DM introduced by the companion’s stellar winds. The high-quality detections of this MSP with the MWA has enhanced the sensitivity of the telescope, to measure minute DM variations of the order of ∼ 10−4 pc cm−3 in our line of sight. Such subtle DM change is hard to recognize at any other timing frequencies with single observation. Taking advantage of the MWA’s large frequency leverage and the achievable timing precision, we propose the observations of full orbital period of this interesting target to investigate any contribution by the companion in the measured DM. |
3 (VCS) |
Semester 2018-B, Ph II Compact
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0002 | Oberoi, Divya; Lonsdale, Colin; Cairns, Iver | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 100 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 4 |
G0005 | Murphy, Tara | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 600 (commensal with G0009) |
G0009 | Trott, Cath | (continuation) Epoch of Reionisation | 600 |
G0021 | Bhat, Ramesh | (continuation) Tracking interstellar space weather toward timing-array millisecond pulsars | 7 |
G0034 | Bhat, Ramesh | (continuation) Shadowing and Triggering on ASKAP FRB campaigns | Up to 366 (triggered) |
G0038 | Meyers, Bradley | (continuation) Contemporaneous observations of the intermittent pulsar J1107-5907 with the MWA and UTMOST | Up to 4 (triggered) |
G0047 | Seymour, Nick | (continuation) GAMA23 Overwhelming Deep Survey | 60 |
G0049 | Shan, Chenxi | MWA Observations of Nearby Low-Luminosity QSOs: Pilot Study (toggle details)
Authors: Chenxi Shan (Shanghai Jiao Tong University (SJTU)) Abstract: With the development of new radio telescopes reaching the fainter radio sky, star-forming galaxies and radio-quiet AGNs (Active Galactic Nuclei) have an expected, surprising emergence at the radio domain. The main players of the radio sky have a changing landscape. It has realized that there is a continuum of galaxy properties in radio bands, from pure star-forming galaxies with radio power dominated by star-forming processes, to the radio-loud objects powered with the central AGN, and a composite of the prior two kinds in between. We proposed to use a sample of well-studied nearby low-luminosity Quasi-Stellar Objects (QSOs) with spatially resolved mapping via various instruments across many wavelength bands to probe their radio properties with the MWA. We performed a positional cross-match of a nearby QSO sample with the GaLactic and Extragalactic All-sky MWA Survey (GLEAM) extragalactic catalog searching for their low-frequency radio counterparts. Three targets, a radio-loud AGN, a radio-quiet AGN, and a star-forming galaxy, were selected for a pilot study of the effect of AGN feedback and the interplay between star formation and nucleus activity with the nearby QSOs. |
8 |
G0050 | Hu, Dan | An MWA Probe of Galaxy Groups in the Low-Frequency Radio Sky (toggle details)
Authors: Dan Hu (Shanghai Jiao Tong University (SJTU)), Melanie Johnston-Hollitt (Curtin University),Haiguang Xu (SJTU), Weitian Li (SJTU), Stefan Duchesne (Curtin University) Abstract: Diffuse radio structures (radio halos, mini-halos, and radio relics), which have been detected in > 100 galaxy clusters, are seldom reported in galaxy groups, tending to be found in higher mass cluster systems. However, recently diffuse emission has been reported in both low mass clusters using the MWA (e.g., Dwarakanath et al. 2018; Johnston-Hollitt et al. 2018), demonstrating the feasibility of less massive cluster systems to support diffuse emission. Consequently, understanding the distribution of diffuse radio emission as a function of mass is an important outstanding issue in cluster physics, and will provide valuable information to constrain cosmological models, and study the associated cluster physics (e.g., merger process, AGN feedback, magnetic fields). Additionally, understanding the true number counts for such sources will be vital to model and remove this component of the contaminating foreground important for detecting the EoR signal. We propose to carry out deep pointed observations of six galaxy groups across full MWA Phase II band 72-231 MHz, observed a 1 hour per frequency band, per source for a total of 24 hours. We will use the acquired high-quality radio images and spectral index maps derived across the band to characterize the spatial distributions of the diffuse radio emission components. Together with the existing high-quality Chandra, XMM-Newton, and SDSS data available, we will be able to describe the origin and evolution of diffuse radio structures in galaxy groups and distinguish between the roles of merger and AGN activity. |
30 |
G0051 | Hodgson, Torrance | Ultrasteep Spectrum Source Abell 2877 HT (toggle details)
Authors: Torrance Hodgson (Curtin University), Melanie Johnston-Hollitt (Curtin University) Abstract: We propose to re-observe an ultrasteep radio source (α = −3.4) provisionally labelled Abell 2877 HT. This source was previously imaged in GLEAM but due to the poor resolution of MWA Phase I, we have not been able to discern the morphology of this source. Abell 2877 HT has no obvious optical counterpart, and both cross referencing with other radio survey data, as well as a follow up observation with the Australia Telescope Compact Array in 2018, have failed to detect the source. We attribute this absence in other radio data due to observing frequencies that are too high and/or poor sampling and suppression of short baselines. We therefore propose to re-observe this source with MWA phase II which we expect will greatly improve the resolution, and allow us to discern between a number of competing explanations for this emission. |
5 |
G0052 | Chauhan, Jaiverdhan | Monitoring of X-ray binary transient outbursts with the MWA (toggle details)
Authors: Jaiverdhan Chauhan (ICRAR-Curtin), Dr. Gemma Anderson (ICRAR-Curtin), A/Prof. James Miller-Jones (ICRAR-Curtin), Dr. Paul Hancock (ICRAR-Curtin) Prof. David Kaplan (UWM), Dr. Marcin Sokolowski (ICRAR-Curtin), Abstract: We propose pointed observations with the MWA of any nearby bright (& 50 mJy) outbursting X-ray binary (XRB) during the 2018-B observing semester. The low-frequency behavior of radio jets in XRBs is still poorly understood, especially at frequencies < 1 GHz. XRBs can produce two different types of radio jets, optically thick, flat-spectrum, compact steady jets and steep-spectrum, relativistically-moving transient jets, over the course of a single outburst. Both types of jets can be bright in the low-frequency regime. We aim to study both types of radio jets using MWA observations to constrain the radio spectrum in the low-frequency band. Previous LOFAR observations have shown that the standard van der Laan model of expanding spheres of plasma does not provide a good description of the low-frequency behaviour of X-ray binary jets, so we seek additional observations to ascertain their low-frequency behaviour and thereby constrain jet models. To the end, we aim to provide high-quality low-frequency radio light curves of XRBs covering a few epochs in the hard state, and denser sampling over the hard-to-soft state transition. |
Up to 7 (triggered) |
G0053 | Hodgson, Torrance | Searching for the Synchrotron Cosmic Web (toggle details)
Authors: Torrance Hodgson (Curtin University), Melanie Johnston-Hollitt (Curtin University), and Ben McKinley (Curtin University) Abstract: This proposal seeks to use the new capabilities of the Murchison Widefield Array (MWA) phase II to search for evidence of the synchrotron cosmic web. In particular, the extended baselines reduce the confusion limit that was encountered in previous searches using the MWA (Vernstrom et al. 2017), allowing us to probe for fainter diffuse emission. This, in addition to the other features of the MWA such as its wide field of view and sensitivity to extended angular features on the sky, make it an ideal apparatus for this search. We propose three deep field observations: two observations that trace out the expected filamentary structure of the Horologium Reticulum supercluster; and one of a cluster pair previously identified in X-ray ob- servations as being linked by a filament (Planck Collaboration et al. 2013). Detection of the synchrotron web would provide definitive support for our current models of cosmic evolution, as well as providing indirect evidence for magnetic fields on the very largest of cosmic scales. A null result, on the other hand, allows us to place even stronger constraints on these unknown parameters. |
40 |
G0054 | Beardsley, Adam | m-mode Observations with the MWA (toggle details)
Authors: Dr. A. P. Beardsley (ASU), Prof. J. D. Bowman (ASU), Prof. D. C. Jacobs (ASU), Prof. C. M. Trott (Curtin), Prof. R. B. Wayth (Curtin), M. Kriele (Curtin), Dr. J. L. B. Line (Curtin), Dr. C. R. Lynch (Curtin) Abstract: We propose to conduct pilot observations to deploy the m-mode analysis strategy on MWA data with the intent of filling a gap in the Global Sky Model, which is commonly used as a diffuse foreground model for Epoch of Reionization measurements. Current EoR power spectrum experiments are limited by the large dynamic range required to overcome foregrounds to reach the faint redshifted 21cm signal. Understanding how these instruments couple with the large scale diffuse structure residing in the Milky Way and other nearby radio sources is crucial to make an EoR detection. We will utilize the flexibility of MWA tiles by only using a single dipole per tile in two 25 hour drift scans, and leverage the surface brightness sensitivity of the compact Phase-II configuration. These features of the MWA will help us to simplify the m-mode analysis technique and capture the large scale structure in the low frequency southern sky. |
50 |
G0055 | Anderson, Gemma | Rapid-response MWA observations of Swift and Fermi gamma-ray bursts (toggle details)
Authors: Dr Gemma Anderson (ICRAR-Curtin), Dr Paul Hancock (ICRAR-Curtin), Dr Antonia Rowlinson (U. Amsterdam/ASTRON), Dr Andrew Williams (ICRAR-Curtin), A/Prof David Kaplan (U. Wisconsin, Milwaukee), A/Prof Tara Murphy (U. Sydney), Prof. Steven Tingay (ICRAR-Curtin), Dr Keith Bannister (CSIRO), Dr Martin Bell (UTS), and A/Prof. James Miller-Jones (ICRAR-Curtin) Abstract: "We request the use of the new MWA rapid-response mode to perform triggered observations of Swift and Fermi gamma-ray bursts (GRBs) during the 2018B observing semester. The prompt and early-time radio emission associated with GRBs is still a poorly explored regime, particularly at MHz frequencies. Short-duration GRBs (SGRBs), one of the two main classes of GRBs, are currently a hot topic in astronomy as they are linked with the compact binary coalescence of binary neutron stars (BNSs), or a neutron star (NS) - black hole (BH) binary. BNSs mergers are the main classes of gravitational wave events known to have electromagnetic counterparts (Abbott et al. 2017). Several theories predict such mergers should produce prompt, coherent emission (such as fast radio bursts, FRBs; Totani, 2013; Falcke & Rezzolla, 2014; Zhang, 2014) the detection of which would allow us to distinguish between different binary merger models and scenarios. It is also possible that low-frequency pulsed radio emission could be generated by long-duration GRBs (LGRB; the other main GRB class resulting from stellar collapse; Usov & Katz, 2000). As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with GRBs may not arrive for seconds up to several minutes following the initial alerts at MWA frequencies. Given that the MWA rapid-response mode can automatically repoint the telescope within 10 seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. An additional advantage of the MWA is its large field-of-view, making it possible to follow-up Fermi detected GRB events, which have poor position constraints on the order of ~10 deg. Such rapid-response MWA observations have the sensitivities necessary to rule out some GRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low. |
Up to 12 (triggered) |
G0056 | Anderson, Gemma | Catching the low frequency radio component of stellar X-ray superflares (toggle details)
Authors: Dr. Gemma Anderson (Curtin), Dr. Christene Lynch (Curtin/ASTRO3D), Dr. Paul Hancock (Curtin), Mr. Andrew Zic (U. Sydney), Dr. Tara Murphy (U. Sydney), Dr. David Kaplan (UW-Milwaukee), Dr. Emil Lenc (CSIRO), and A/Prof. James Miller-Jones (ICRAR-Curtin) Abstract: We request the use of the new MWA rapid-response mode to perform triggered observations of X-ray/gamma-ray flaring magnetically active stars detected with the Swift Burst Alert Telescope and the Monitor of All-sky X-ray Image (MAXI) instrument during the 2018B observing semester. Flare stars, such as rapidly rotating M dwarfs (dMe) and tidally-locked RS Canum Venaticorum binaries (RS CVn), are known to produce coherent, highly-circularly polarised flares at low radio frequencies (<5 GHz), particularly in the MHz range (Spangler et al. 1974a). These low frequency flares are indicative of unusual emission mechanisms such as electron-cyclotron masers or plasma radiation (Dulk 1985). The MWA has already proven to be a sensitive instrument for low frequency flare star studies through the detection of flares at 154 MHz from UV Ceti in Stokes V maps, which are thermal noise (rather than confusion noise) limited. These flares were likely generated via the electron-cyclotron maser mechanism (Lynch et al. 2017). dMe and RS CVn also experience extreme flaring events via incoherent emission mechanisms, producing synchrotron X-ray/gamma-ray “superflares” that are bright enough to trigger high-energy satellites such as Swift. Rapid-response radio observations performed with the Arcminute Microkelvin Imager (AMI) at high (15 GHz) radio frequencies have demonstrated that such superflares are accompanied by giant radio gyrosynchrotron flares peaking within a few minutes of the high-energy trigger (Fender et al. 2015). However, it is unknown whether X-ray/gamma-ray superflares can also be temporally coincident with low-frequency (coherent) radio bursts. By using the MWA rapid-response mode to trigger on Swift and MAXI detected high-energy superflares, we can investigate whether the same magnetic event that produces these bright, incoherent X-ray/gamma-ray superflares could also trigger the emission mechanisms responsible for bright, coherent low-frequency radio flares, providing a more unified understanding of the plasma physics in these stellar systems. |
Up to 9 (triggered) |
G0057 | Bhat, Ramesh | The Southern-sky MWA Rapid Two-metre (SMART) pulsar survey (toggle details)
Authors: N. D. R. Bhat (Curtin; PI), N. A. Swainston (Curtin), S. E. Tremblay (Curtin), J. W. T. Hessels (ASTRON), G. Hobbs (CASS), W. van Straten (AUT), D. Kaplan (UWM), S. M. Ord (CASS), R. M. Shannon (Swinburne) Abstract: Over the past decades, pulsars have firmly established themselves as nature's premier laboratories for uncovering new vistas in extreme physics. With applications ranging from probing the state of ultra-dense matter to testing gravity in the strong-field regime, and from probing complex plasma physics in the relativistic regime to the search for ultra-low frequency gravitational waves, they enable us to push the frontiers of physics and astrophysics. This enviable accomplishment is the direct result of multiple large sky surveys of the past five decades, which not only led to a steady increase in the known pulsar population, but also proven invariably rewarding by facilitating discoveries of exotic objects such as millisecond pulsars and those in relativistic binary orbits. Every major leap in radio astronomy instrumentation or technology tends to trigger a large pulsar survey; the advent of Phase 2 MWA and the well-matured voltage-capture capability now brings another unique opportunity. We propose to conduct an all-sky survey, the {\bf S}outhern-sky {\bf M}W{\bf A} {\bf R}apid {\bf T}wo-metre (SMART) pulsar survey, which will surpass all previous and ongoing surveys in survey speed, owing to the development of novel strategies and survey methodologies. Our goal is to survey the entire sky visible to the MWA in a uniform systematic manner. With a survey speed of $\sim$600 \sqdeghr, the entire sky can be completed in less than 100 hours, to reach a limiting sensitivity (10$\sigma$) of $\sim$3 mJy in pulsar flux density (at 150 MHz). Based on our initial pulsar census and simulation studies, we expect to discover more than 100 pulsars. Alongside its numerous scientific benefits, this SMART survey will also serve as an important demonstrator survey for SKA-Low, which is expected to be the most efficient pulsar finding machine in the coming decades. |
17 |
Webster, Rachel | MWA Beam Measurement (toggle details)
Authors: Prof Rachel Webster (Melbourne); Dr Jack Line (Melbourne), Dr Ben McKinley (Curtin), A/Prof Randall Wayth (Curtin) Abstract: "In order to measure the signal from the spatial fluctuation in the 21cm EoR signal, the shape of the beam needs to be understood to better than 1dB over the entire visible sky. Currently, a ‘full embedded element’ (FFE) model is used for in the EoR pipelines. However the pilot experiment (Line+ 2018, submitted) established that there are individual differences in the tile beams at a level that may be an issue for EoR experiments. Therefore we plan to conduct a second experiment to obtain more data, collected commensally during EoR observing, to achieve the following scientific goals:
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600 (commensal with G0009) | |
Kaplan, David | Searching for Prompt Emission from Binary Neutron Star Mergers (toggle details)
Authors: David Kaplan (UWM); Gemma Anderson (Curtin); Keith Bannister (CSIRO); Ian Brown (UWM); Dougal Dobie (Sydney); Bryan Gaensler (Toronto); Paul Hancock (Curtin); Emil Lenc (CSIRO); Christene Lynch (Curtin); Tara Murphy (University of Sydney); Andrew Williams (Curtin) Abstract: We propose a triggered search for prompt emission from a binary neutron star discovered through gravitational waves with the LIGO/Virgo detectors. A detection of such emission would immediately yield enormous insight into the physics of the explosion, the cosmic baryon distribution, and other topics, and would open up a new avenue for multi-messenger exploitation of these amazing events. |
Up to 1 (triggered) | |
Sobey, Charlotte | Targeted pulsar search towards a candidate identified in POGS (POlarization from the GLEAM Survey) (toggle details)
Authors: C. Sobey (Curtin University, CSIRO), C. Riseley (CSIRO), N. D. R. Bhat (Curtin University,CAASTRO), D. Kaur (Curtin University (CAASTRO), S. J. McSweeney(Curtin University, CAASTRO), B. W. Meyers (Curtin University,CSIRO,CAASTRO), S. M. Ord (CSIRO), S. E. Tremblay (Curtin University, CAASTRO), M. Xue(Curtin University, CAASTRO) Abstract: We propose to conduct a pulsar search towards GLEAM J134038–340234 – the first pulsar candidate identified using POGS (POlarization from the GLEAM Survey; MWA imaging data). The source has properties consistent with that of a pulsar, including a steep spectral index and a high degree of linear polarisation. Only a handful of pulsars have been discovered using imaging data, including the first isolated millisecond pulsar and the first pulsar located in a globular cluster. Using existing sky survey images to identify pulsar candidates presents an efficient method for discovering new, and potentially unusual, pulsars, especially using low-frequency instruments like the MWA. |
1 | |
Croft, Steve | MWA Followup of Neutrino Transient Candidates (toggle details)
Authors: Steve Croft (UC Berkeley); David Kaplan (UWM); Clancy James (Curtin); Damien Dornic (Marseille); Marcos Santander (Alabama); Tara Murphy (University of Sydney); Andrew Williams (Curtin); and the MWA Transients collaboration Abstract: We request MWA followup of neutrino transient candidates detected by the ANTARES/KM3NeT and IceCube telescopes during 2018B. These observations would be disruptive target of opportunity observations. Around 30% of triggers are expected to be visible immediately from the MWA site (Adrian-Martinez et al. 2015). We expect to follow up three or four triggers during the semester. We request 30 min of prompt followup of each trigger, followed by a second epoch 1 – 2 weeks later for comparison. These will allow the strongest limits to date on prompt radio emission from neutrino transients and may aid in localization of these new astrophysical probes. |
Up to 4 (triggered) |
Semester 2018-A, Ph II Extended
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
D0009 | Anderson, Gemma | (continuation) Rapid-response MWA observations of Swift and Fermi gamma-ray bursts | 13 |
G0001 | Bell, Martin | (continuation) The MWA Transients Survey (MWATS) | 720 (commensal w/ G0008) |
G0002 | Oberoi, Divya | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 150 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 9 |
G0008 | Hurley-Walker, Natasha | (continuation) GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey | 672 (commensal with G0001) |
G0017 | McKinley, Benjamin | (continuation) Measuring the global sky temperature (including the EoR) with the Moon | 152 |
G0018 | Tremblay, Chenoa | (continuation) Molecular Transitions in Vela and Orion | 36 |
G0021 | Bhat, Ramesh | (continuation) Tracking interstellar space weather toward timing-array millisecond pulsars | 12 |
G0024 | Xue, Mengyao | (continuation) Filling the gap of existing MWA-VCS archival data | 3 |
G0024 | Meyers, Bradley | (continuation) RRATs and intermittent pulsars at low frequencies | 20 |
G0024 | Sobey, Charlotte | Studying the evolution of polarised emission from pulsars at low-frequencies
(toggle details)
Authors: C. Sobey (ICRAR, CSIRO), S. Johnston (CSIRO), M. Xue (ICRAR, CAASTRO), N.D.R. Bhat (ICRAR, CAASTRO), S.E. Tremblay (ICRAR, CAASTRO), S.J. McSweeney (ICRAR, CAASTRO), B.W. Meyers (ICRAR, CSIRO, CAASTRO), S.M. Ord (CSIRO) Abstract: We propose to observe several polarised pulsars at three centre frequencies between 105 and 230 MHz using the MWA. We will study the properties and evolution of the pulse profiles at low frequencies, with complementary information already available from the Parkes telescope at higher frequencies. This will provide further insights into the radio emission mechanism behaviour from pulsar magnetospheres with extremely high magnetic field strengths (~10^12 G), which is currently not well understood. |
5.5 |
G0034 | Bhat, Ramesh | (continuation) Shadowing and Triggering on ASKAP FRB campaigns | 360 |
G0035 | Lynch, Christene | (continuation) MWA targeted campaign of nearby, flaring M dwarf stars | 85 |
G0036 | Allison, James | (continuation) HIghZ: A blind 21-cm line survey for high-redshift radio galaxies | 50 |
G0041 | Staveley-Smith, Lister | (continuation) MAGE-X: A Deep Survey of the Magellanic System | 80 |
G0045 | Duchesne, Stefan William | An MWA Phase II follow-up of MWA-detected diffuse, non-thermal galaxy cluster emission
(toggle details)
Authors: S. W. Duchesne (Victoria U. of Wellington & Peripety Scientific Ltd.), Dr. M. Johnston-Hollitt (CEO, Peripety Scientific Ltd.), Dr. Q. Zheng (Victoria U. of Wellington & Peripety Scientific Ltd.), Dr. G. Bernardi (IRA-INAF & Rhodes University), S.R. Keel (Victoria U. of Wellington & Peripety Scientific Ltd.) Abstract: After performing surveys on non-biased samples of galaxy clusters we have compiled a new catalogue of diffuse, non-thermal radio sources associated with galaxy clusters (haloes and relics) with the Galactic and Extragalactic All-sky MWA survey and the Epoch of Reionization 0-hour field. These catalogues are hindered by the low resolution of the Phase I MWA and follow-up observations with the extended configuration MWA Phase II are required to confirm the nature of the emission. We propose 8 target fields comprised of a number of clusters to be observed in 5 frequencies for moderate integration times in the extended configuration. These observations will allow the confirmation of the objects as well as a description of their spectral energy distributions, further confirming their nature. Confirming these haloes and relics will allow them to be added to the currently small (<70 of each) global samples of such emission, allowing better insight into the dynamical nature of clusters leading to constraints on cosmological parameters, indirectly probing the evolution of cosmic magnetism. |
15 |
G0046 | Bernardi, Gianni | An unbiased census of radio halos in mass-selected, low redshift galaxy clusters: the low frequency view
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Authors: G. Bernardi (IRA-INAF & Rhodes University) Abstract: The presence of Mpc-scale diffuse synchrotron emission (radio halos) in galaxy clusters is currently explained through the turbulent (re)acceleration of particles following cluster mergers. Although this scenario has received increasing observational support, its key predictions can only be tested through observations of statistically significant cluster samples. Such a sample was recently observed with KAT-7 (Bernardi et al. 2016). We propose to observe the KAT-7 sample with the MWA in order to characterize its low frequency radio properties and provide the first stringent test of the turbulent (re)acceleration model in mass-selected, low-redshift clusters. |
47 |
G0048 | Venturi, Tiziana | The Universe’s largest scale structures: MWA observations of the Shapley Concentration
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Authors: T. Venturi (IRA-INAF) Abstract: The Shapley Concentration is a galaxy supercluster (few tens of degrees) in the Local Universe (z < 0.048) which is currently undergoing cluster mergers and group accretion. It is a diversified environment, with cluster complexes in advanced evolutionary stage, groups of clusters in the very early stages of merger, fairly massive clusters with ongoing accretion activity, and smaller groups located in filaments. These features makes it an ideal place to observe the signatures of the formation of large-scale structures in the Universe. We propose to observe the Shapley Concentration at 150 and 216 MHz in order to detect diffuse synchrotron emission on Mpc scales and, therefore, directly probing its large-scale dynamical and mass assembly processes. |
9 |
Lynch, Christine | Catching the low frequency radio component of stellar X-ray superflares
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Authors: Dr. C. Lynch (U. Sydney, CAASTRO), Dr. G. Anderson (Curtin), Dr. T. Murphy (U. Sydney, CAASTRO), Dr. D. Kaplan (UW-Milwaukee), Dr. K. Bannister (CSIRO), Dr. A. Williams (Curtin), A. Zic (U. Sydney, CAASTRO) Abstract: We propose a Directors Discretionary Time project to test the capabilities of the MWA to provide efficient radio follow up to extreme X-ray stellar flares that trigger the Swift Burst Alert Telescope (BAT). Flaring activity is a common characteristic of magnetically active stars. These events produce emission throughout the electromagnetic spectrum, implying a range of physical processes, yet the details connecting energetics at different wavelengths are still unclear. Fender et al. (2015) discovered GHz radio emission associated with a X-ray superflare detected by Swift-BAT, with radio activity lasting up to 48 hours after the initial event. Whether low-frequency radio emission is associated with X-ray superflares is unknown. The purpose of the proposed observations is to determine whether the magnetic events that lead to these X-ray superflares also result in bright low-frequency radio bursts. By doing this we can characterize the physical processes that occur during the most extreme stellar flare events. |
2 |
Semester 2017-B, Ph II Extended
ID | PI | Title | Time awarded (hours) |
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G0001 | Bell, Martin | (continuation) The Murchison Widefield Array Transients Survey | 152 (commensal w/ G0008) |
G0002 | Oberoi, Divya; Cairns, Iver; Lonsdale, Colin | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 100 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 6 |
G0005 | Murphy, Tara | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 100 (commensal w/ G0009) |
G0008 | Hurley-Walker, Natasha | (continuation) GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey: Pilot observations | 152 (commensal with G0001) |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 190 |
G0017 | McKinley, Benjamin | (continuation) Using the Moon to detect the global EoR signal | 88 |
G0021 | Bhat, Ramesh | (continuation) Tracking interstellar space weather toward timing-array millisecond pulsars | 9 |
G0024 | McSweeney, Sam | Chasing the pulsar emission mechanism via the phenomenon of sub-pulse drifting
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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. |
3 |
G0024 | Zue, Mengyao | Filling the gap of existing MWA-VCS archival data II
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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 (cataloged) pulsars in these areas. This project will form part of the PhD program of Mengyao Xue. |
4.5 |
G0034 | Bhat, Ramesh | (continuation) Low frequency shadowing of the Parkes SUPERB survey | 336 |
G0034 | Bhat, Ramesh | Shadowing ASKAP FRB campaigns
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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. |
360 |
G0035 | Lynch, Christene | (continuation) MWA targeted campaign of nearby, flaring M dwarf stars | 51 |
G0036 | Allison, James | (continuation) HIghZ: A search for HI absorption in high-redshift radio galaxies | 27 |
G0038 | Meyers, Bradley | (continuation) Sporadic Pulsar Emission at Low Frequencies | 7.5 |
G0039 | Trott, Cathryn | LoBES: Long Baseline Epoch of Reionisation Survey
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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. |
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G0040 | Lynch, Christene | Follow up observations of UV Ceti to better constrain 154 MHz flares
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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. <\div> |
100 |
G0041 | Staveley-Smith, Lister | MAGE-X: A Deep Survey of the Magellanic System
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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. |
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G0042 | Murphy, Tara | Searching for pulsars in the image domain: pilot study
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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. |
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G0043 | Offringa, André | Deep imaging with the extended MWA: EoR foregrounds and source population analysis
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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. |
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G0044 | Zheng, Cathie | Deep Imaging of Two Selected EoR Fields: Preparing for SKA
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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. |
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Kaplan, David | A Search for Variable and Transient Sources in the Magellanic Cloud Fields with the MWA
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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. |
80 (commensal w/ G0008) |
Semester 2017-A, Ph II Compact
ID | PI | Title | Time awarded (hours) |
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G0001 | Bell, Martin | (continuation) The MWA Transients Survey (MWATS) | 80 (commensal with G0008) |
G0002 | Cairns, Iver; Oberoi, Divya | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 100 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 6 |
G0005 | Murphy, Tara | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 730 (commensal with G0009) |
G0008 | Hurley-Walker, Natasha | (continuation) GaLactic and Extragalactic All-Sky MWA-eXtended (GLEAM-X) survey: Pilot observations | 80 |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 730 |
G0021 | Bhat, Ramesh | (continuation) Tracking Interstellar Space Weather Toward Timing-Array Millisecond Pulsars | 7 |
G0034 | Bhat, Ramesh | Low Frequency Shadowing of the Parkes SUPERB Survey (toggle details)
Authors: Bhat, N. D. R.; Ord, S. M.; Tremblay, S. E.; Shannon, R. M.; van Straten, W.; Kaplan, D. L.; Macquart, J.-P.; Kirsten, F. Abstract: "The recent LIGO detection of milli-Hertz gravitational wave (GW) signals from black-hole merger events has further reinforced the important role of Pulsar timing array (PTA) experiments in the GW astronomy. PTAs exploit the clock-like stability of fast-spinning millisecond pulsars (MSPs) to make a direct detection of ultra-low frequency (nano-Hertz) gravitational waves, and this is a key science objective for the SKA. The science enabled by PTAs is highly complementary to that possible with LIGO-like detectors. PTA efforts of the past few years clearly suggest that interstellar propagation effects on pulsar signals may ultimately limit the detection sensitivity of PTAs if they are not accurately measured and corrected for in timing measurements. Interstellar medium (ISM) effects are much stronger at lower radio frequencies and therefore the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays. This will potentially lead to enhanced sensitivity and scientific impact of PTA projects. Since our demonstration early this year of our ability to form a coherent (tied-array) beam by re-processing the recorded VCS data (Bhat et al. 2016), we have successfully ported the full processing pipeline on to the Galaxy cluster of Pawsey and also demonstrated the value of high-sensitivity multi-band pulsar observations that are now possible with the MWA. Here we propose further observations of three most promising PTA pulsars that will be nightly objects in the 2017A period. The main science driver is to characterise the nature of the turbulent ISM through high-quality scintillation and dispersion studies including the investigation of chromatic (frequency-dependent) DMs. Success of these efforts will define the breadth and scope of a more ambitious program in the future, bringing in a new science niche for MWA and SKA-low." |
520 |
G0035 | Lynch, Christene | MWA targeted campaign of nearby, flaring M dwarf stars (toggle details)
Authors: Lynch, C.; Murphy, T.; Kaplan, D. L. Abstract: Flaring activity is a common characteristic of magnetically active stellar systems. Flare events produce emission throughout the electromagnetic spectrum, implying a range of physical processes. Early 100 - 200 MHz observations of M dwarf flare stars detected bright (>100 mJy) flares with occurrence rates between 0.06 - 0.8 flares per hour. These rates imply that observing 100 - 200 MHz flares from M dwarf stars is fairly easy with many detections expected for modern low-frequency telescopes. However, long observational campaigns using these modern telescopes have not reproduced these early detections. This could be because the rates are over estimated and contaminated by radio frequency interference. Recently Lynch et al. (submitted) detected four flares from UV Ceti at 154 MHz using the Murchison Widefield Array. The flares have flux densities between 10-65 mJy --- a factor of 100 fainter than most flares in the literature at these frequencies --- and are only detected in circular polarization. The flare rates for these newly detected flares are roughly consistent with earlier rates however the uncertainties are large. Building off this result we propose a 102 hour survey of the closet six M dwarf stars with observed magnetic activity traced in X-rays and 100 - 200 MHz emission. The rates measured from this survey would inform the duration required for future blind surveys for flares from M dwarf stars. |
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G0036 | Allison, James | HIghZ: A search for HI absorption in high-redshift radio galaxies (toggle details)
Authors: Allison, J.; Callingham, J.; Sadler, E.; Wayth, R.; Curran, S.; Mahoney, E. Abstract: We will use the unique low-frequency spectral capability of the MWA to carry out a pilot survey for neutral gas in the interstellar medium of the most distant (z>5) radio galaxies in the Universe. Through detection of the HI 21-cm line in absorption we aim to place stringent lower limits on the source redshift, confirming its location in the early Universe. Our sample makes use of the excellent wide-band spectral information available from the recently completed MWA GLEAM survey, from which we have selected a sample of ultra-steep peaked-spectrum radio sources that have a spectral turnover below 300 MHz. These sources should be ideal candidates for high-redshift compact radio galaxies since they have (a) spectral peaks that turnover below 1GHz and (b) very steep (alpha < -1.0) spectral indices that are consistent with the high density environments expected for radio galaxies in the early Universe. Using the MWA, we aim to verify this hypothesis through the detection of significant column densities of cold HI. This pathfinder project will provide important technical information that will inform future absorption surveys both with the MWA and, ultimately, the SKA-LOW telescope. |
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G0037 | Sadler, Elaine | A search for HI absorption in the z=5.2 radio galaxy TN 0924-2201 (toggle details)
Authors: Sadler, E.; Allison, J.; Curran, S.; Wayth, R. Abstract: "We request time to use the MWA in spectral-line mode to search for redshifted 21 cm HI absorption associated with the distant, gas-rich radio galaxy TN 0924-2201. This is a challenging project that breaks new ground in high-redshift HI studies and aims to pave the way for future blind HI absorption surveys with the extended MWA. TN 0924-2201 is the highest-redshift radio galaxy currently known, with a confirmed spectroscopic redshift of z=5.2 (van Breugel et al. 1999) and a continuum flux density of 550 mJy at 230 MHz. Klamer et al. (2005) detected CO 1-0 emission from this galaxy, and found that it contains a large (~1e11 solar mass) reservoir of molecular gas. The redshift of this galaxy places the 21cm HI line within the MWA band, and the brightness of the continuum source (coupled with the presence of molecular gas) makes this the most promising test case in which to search for 21cm HI absorption with the MWA. Detection of an HI line in this distant galaxy appears feasible, and if successful this would be a very high-profile result for MWA. It would also provide an important proof of concept for future large, HI-based searches for high-redshift radio galaxies with MWA and SKA1-low." |
20 |
G0038 | Meyers, Bradley | (continuation) Sporadically Emitting Pulsars at Low Frequencies | 6 |
Xue, Mengyao | Filling the gap of existing MWA-VCS archival data (toggle details)
Authors: Xue, M.; Bhat, R.; Tremblay, S.; Ord, S.; Sobey, C.; Kirsten, F. Abstract: Since July 2014, around 110 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. Except some short duration test data and calibration data, the total amount of the observation data which have a duration longer than 400 s is 84 hours. 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. But there are still some 'holes' in the sky that we do not have VCS archival data for 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 MWA-VCS data set. We will also census known (cataloged) pulsars in these areas. These observations would be performed between 170-200 MHz. This project will form part of the PhD program of Mengyao Xue. |
3 (partially commensal with G0038) | |
Hurley-Walker, Natasha | Applying SPAM to the extended MWA (toggle details)
Authors: Hurley-Walker, N.; Intema, H. Abstract: "The extended baselines of the MWA move the instrument into a more difficult calibration and imaging regime, where the more widely-separated antennas are more likely to view the sky through different ionospheric conditions, leading to differential refractive effects over the array. Current extrapolations by Trott, Jordan, and Hurley-Walker imply that the diffractive scale will remain larger than the longest baseline for ~50-70% of observations, but these are extrapolations only. Other instruments have performed observations with baselines longer than the diffractive scale, and used software techniques to mitigate the ionospheric distortions. One such survey is the Tata Institute of Fundamental Research Giant Metrewave Radio Telescope Sky Survey (TGSS) at 150 MHz. Intema et al. (2016) used the Source Peeling & Atmospheric Modeling (SPAM) software to produce a catalogue of over 600,000 sources from data that had previously been slow and difficult to process. This proposal is for a short series of observations to test the usage of the SPAM software on the extended MWA, and to find the optimal observing parameters for its use. If successful, this could assist other groups in effectively utilising the long baselines." |
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Semester 2016-B, Ph II Compact
ID | PI | Title | Time awarded (hours) |
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G0005 | Murphy, Tara | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 350 (commensal w/ G0009) |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 730 |
G0021 | Bhat, Ramesh | Tracking interstellar space weather toward timing-array millisecond pulsars (toggle details)
Authors: N. D. R. Bhat (Curtin), S. M. Ord (Curtin), S. E. Tremblay (Curtin), R. M. Shannon (Curtin/CASS), W. van Straten (Auckland), D. Kaplan (UWM), J.-P. Macquart (Curtin), F. Kirsten (Curtin) Abstract: Recent LIGO detection of milli-Hertz gravitational wave (GW) signals from a black-hole merger event has further reinforced the important role of Pulsar timing array (PTA) experiments in the GW astronomy. PTAs exploit the clock-like stability of fast-spinning millisecond pulsars (MSPs) to make a direct detection of ultra-low frequency (nano-Hertz) gravitational waves. The science enabled by PTAs is thus highly complementary to that possible by LIGO-like detectors. PTAs are also a key science objective for the SKA. PTA efforts over the past few years suggest that interstellar propaga- tion effects on pulsar signals may ultimately limit the detection sensitivity of PTAs unless they are accurately measured and corrected for in timing measurements. Interstellar medium (ISM) effects are much stronger at lower radio frequencies and therefore the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays. This will potentially lead to enhanced sensi- tivity and scientific impact of PTA projects. Since our first demonstration of ability to form a coherent (tied-array) beam by reprocessing the recorded VCS data (Bhat et al. 2016), we have successfully ported the full processing chain to the Galaxy cluster of Pawsey and demonstrated the value of high-sensitivity multi-band pulsar obser- vations that are now possible with the MWA. Here we propose further observations of two most promising PTA pulsars that will be nightly objects in the 2016B period. Our main science driver is to characterise the nature of the turbulent ISM through high-quality scintillation and dispersion studies including the investigation of chromatic (frequency-dependent) DMs. Success of these efforts will define the breadth and scope of a more ambitious program in the future, bringing in a new science niche for the MWA and SKA-low. |
3 (partially commensal with G0027) |
G0027 | Xue, Mengyao | Polarimetric Observation of Pulsars with Hexes (toggle details)
Authors: Mengyao Xue (Curtin), Ramesh Bhat (Curtin), Steven Tremblay (Curtin), Stephen Ord (Curtin/CSIRO), Charlotte Sobey (Curtin/CASS), Franz Kirsten (Curtin) Abstract: The MWA VCS pipeline is now reliably generating high time resolution observations of radio pulsars in all four Stokes parameters. Here, we are proposing to test the polarimetric response of and our ability to calibrate the new Hex array currently under construction. These ob- servation will provide data that will be used to study the pulsars themselves (including their emission mechanism and beam geometry), the interstellar medium and towards understanding the Galactic magnetic field. We are proposing a set of observations of three pulsars (J0034-0534, J0437-4715, and J2145-0750) at a wide range of hour angles to characterise the fidelity and sta- bility of the polarimetric solutions with the hexes. The observation would be performed between 170-200 MHz and 140-170 MHz respectively. This project will form part of the PhD program of Mengyao Xue. |
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G0029 | Meyers, Bradley | A Low Frequency Study of Rotating Radio Transients (toggle details)
Authors: B. Meyers (Curtin), S. Tremblay (Curtin), R. Bhat (Curtin), R. Shannon (Curtin/CASS) Abstract: Rotating radio transients (RRATs) are neutron stars whose radio emission is typically detectable as sporadic emission (as opposed to periodic emission). This RRAT study will observe two RRATs (J0614-03, J0545-03) which have low to moderate dispersion measures and should be detectable with the MWA. Nominally, both RRATs should be within a single pointing, due to the increased field-of-view provided by the compact hex-tile core. Given our first concrete detec- tion of the RRAT J2325-0530 with the recently implemented coherent beamformer, we expect that these sources will also be detectable. Observations below 300MHz of these RRATs have not been reported, thus the MWA provides an opportunity to perform the first low-frequency, high time resolution studies of these objects. |
2 |
G0030 | McSweeney, Sammy | Testing the expanded MWA with high sensitivity observations of 47 Tuc pulsars (toggle details)
Authors: S.J. McSweeney (Curtin, PI), N.D.R. Bhat (Curtin), S.E. Tremblay (Curtin), S. M. Ord (CASS) Abstract: Globular clusters are breeding grounds of binary millisecond pulsars, which provide perfect tools for a wide range of astrophysics. 47 Tuc, located in the far southern hemisphere has proven to be a real gold mine, with 24 pulsars already known. Its extreme southern latitude (at a declination of -72deg) makes it inaccessible to almost all telescopes except Parkes, which operate only at frequencies >700 MHz. In this proposal we seek 1.5 hr time to confirm our tantalising detections of two of 47 Tuc pulsars in MWA VCS data recorded last year. If confirmed, this will constitute the first low-frequency detection of 47 Tuc pulsar(s), and the very first detection of a pulsar in a globular cluster with the MWA. This will have important implications for targeted searches with the expanded MWA and SKA-low, besides the prospects of probing the cluster ISM via low-frequency MWA observations. |
1.5 |
G0031 | Paul, Sourabh | Detection of redshifted HI from the Epoch of Reionization using drift scans (toggle details)
Authors: Sourabh Paul, Akash Kumar Patwa, Shiv Sethi, K.S. Dwarakanath (RRI) Abstract: The detection of redshifted HI from the Epoch of Reionization (EoR) is one of the outstanding aims of modern day observational cosmology. Like many other radio in- terferometers, EoR research is one of the major science goals of MWA. We, at RRI have been involved in EoR research from past few years. We have successfully developed an independent pipeline to extract the delay power spectra from MWA tracking observation. We, simultane- ously have been progressing towards the set up of another pipeline to obtain the power spectra from drift scan observation. We seek, based on our existing endeavors, 30 hours of drift scan data from MWA observing time 2016B. Our aims are to attain both 2d & 1d power spectra, also to study various foreground removal and noise reduction strategies. The new ‘hex configuration’ of MWA would be a favorable feature for this effort, owing to many short spacing & redundant baselines, which are essential requirements for EoR science. |
30 |
G0032 | Croft, Steve | Breakthrough Listen on MWA Pilot Study (toggle details)
Authors: Steve Croft (UC Berkeley), Dr. Andrew Siemion (UC Berkeley), Prof. David Kaplan (UWMilwaukee), Dr. Steven Tremblay (Curtin) Abstract: We propose a pilot study, using the Voltage Capture System, for Breakthrough Listen on the MWA. Breakthrough Listen (BL) is a major new project that aims to dramatically improve the coverage of parameter space in the search for intelligent life beyond Earth. BL has already deployed hardware and software to the Green Bank Telescope, and will bring a similar program with the Parkes Telescope online in the second half of 2016. The low frequency sky is however currently very poorly explored. The superb capabilities of the MWA (large field of view, low frequency of operation, and location in a very radio quiet site) provide a unique opportunity for a pilot study to obtain voltage data for a SETI (Search For Extraterrestrial Intelligence) study of the Galactic Plane. We propose commensal observations, piggybacking on the proposed pulsar search of Tremblay et al. Using existing VCS software, combined with the pipeline developed for Breakthrough Listen at GBT and Parkes, we will perform a blind search for candidate signals from extraterrestrial intelligence. Although the chances of a detection are not large, particularly for a pilot study such as that proposed here, the Breakthrough Listen team plan to perform extensive testing and analysis on the data obtained which should be useful for other users of the MWA VCS. We will make the secondary SETI data products and associated documentation available as a resource to the community via the Breakthrough Listen online archive. |
2 (commensal with G0033) |
G0033 | Tremblay, Steve | A pilot ‘blind’ pulsar search at low frequencies using the compact MWA (toggle details)
Authors: Steve Tremblay (Curtin, PI), N. D. R. Bhat (Curtin), Nick Swainston (Curtin), Charlotte Sobey (Curtin), David Kaplan (UWM) Abstract: The voltage capture system (VCS) has been running for roughly a year and a half now. In that time it has generated four publications to date (more in preparation) and detected over three dozen known pulsars. However, due to the combination of a large field of view and a large tile separation of the MWA’s design, we have not been to able to undertake a pulsar survey, as this has been overly computationally expensive. The new, compact configuration changes this and we propose to perform a small pilot survey of a single field that is well populated with pulsars to lay the foundation for a larger future survey. |
2 |
G0034 | Hancock, Paul | A pilot study using the MWA-Hex configurations to search for fast radio transients. (toggle details)
Authors: Dr. Paul Hancock (Curtin), Dr. Randall Wayth (Curtin), Ms. Xiang Zhang (Curtin/Purple Mountain Observatory), Prof. David Kaplan (UWM), A. Prof Tara Murphy (Sydney University), Dr Emil Lenc (Sydney University), A. Prof Jonathan Pober (Brown University), Dr. John Morgan (Curtin University), Dr. Rajan Chhetri (Curtin University) Abstract: We propose a pilot study to test the feasibility to use the MWA-Hex configuration to search for radio transients. Projects are already making use of data from the MWA-128T to search for many transient events. Data from G0001 (MWATS) is being used to search for pulsars based on their scintillating behavior (Bell et al., 2016). Project G0026 is searching for intrinsic emission associated with fireballs. Project G0005 has used data from EoR observations to search for fast radio bursts and conduct a blind survey for radio transients (see Rowlinson et al., 2016). These areas of research are still of great interest, and we would like to be able to continue these programs into 2017A, however the feasibility of the MWA-Hex configuration for these projects has not yet been demonstrated. We are asking for 20h of observations to demonstrate the feasibility of the MWA-Hex configuration for fast radio transient detection. |
14 |
G0035 | Chhetri, Rajan | High time resolution observations of the Interplanetary Scintillation of compact sources in MWA images (toggle details)
Authors: Rajan Chhetri, Research Associate, (Curtin University), John Morgan, Research Fellow, (Curtin Univer- sity), Steven Tremblay, Postdoctoral Researcher, (Curtin University), Jean-Pierre Macquart, Senior Re- search Fellow, (Curtin University), Jonathan Pober, Asst. Professor, (Brown University), Paul Hancock, Early Career Research Fellow, (Curtin University) Abstract: A pilot study made with day time observations with the Murchison Widefield Array (MWA) has clearly demonstrated the feasibility using interplanetary scintillation (IPS) to identify compact components (∼ 0.1 arcsec) in MWA data. Subsequently, regular daytime observations have been made with the MWA since December 2015 to obtain an even coverage of the sky with the intention of producing a catalogue of scintil- lating, compact sources using Director’s discretionary time. Analysis of these data is ongoing. Preliminary results from this analysis have affirmed the validity of the IPS technique from the pilot study. These studies made with correlator integration time of 0.5 seconds have suggested that a finer time resolution is necessary to fully resolve and characterise the IPS in very compact sources. Proof of concept work to image with only short baselines in the pilot data to simulate the MWA config- uration in 2016-B was done by J. Morgan and has shown the possibility of using the MWA configuration in Hexagonal mode to identify IPS. Regular observations in October - December period will allow us to obtain an even sky coverage for our overall project. Hence, we request time to make 6 minute observations (+ 1 minute calibration scan of the sun) twice weekly in the Voltage Capture System (VCS) mode to identify and characterise IPS due to compact com- ponents in the MWA data. |
3.27 |
Semester 2016-A, Ph I
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0001 | Bell, Martin | (continuation) The MWA Transient Survey (MWATS) | 30 |
G0002 | Cairns, Iver | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 100 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 9 |
G0005 | Rowlinson, Antonia | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 350 (commensal w/ G0009) |
G0008 | Seymour, Nicholas | (continuation) A Galactic and Extragalactic All-Sky MWA Survey at 300 MHz | 210 |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 350 |
G0021 | Bhat, Ramesh | Tracking interstellar space weather toward timing-array millisecond pulsars (toggle details)
Authors: N. D. R. Bhat (Curtin), S. M. Ord (Curtin), S. E. Tremblay (Curtin), R. M. Shannon (Curtin/CASS), W. van Straten (Swinburne), D. Kaplan (UWM), J.-P. Macquart (Curtin), F. Kirsten (Curtin) Abstract: Pulsar timing array (PTA) experiments exploit the clock-like stability of fast-spinning millisecond pulsars for direct detection of low-frequency (nano-Hertz) gravitational waves (GWs). Detection of GWs is an eagerly pursued goal of modern astronomy and a key objective of the Square Kilometre Array (SKA). There is now increasing realisation that interstellar propagation effects on pulsar sig- nals may ultimately limit the detection sensitivity of PTAs unless they are accurately measured and corrected for in timing measurements. The influence of the interstellar medium is much higher at low radio frequencies; therefore the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays and thereby significantly enhance the sensitivity and scientific impact of the Parkes pulsar timing array (PPTA) project. Significant improvements have been made to enhance pulsar observing capabilities of the MWA. Our development of a tied-array beam processing pipeline for VCS-recorded data yields an order of magnitude improvement in sensitivity for pulsar observations with the MWA, opening up new science avenues, as well demonstrated through our recent work on high-resolution dynamic spectral studies of the timing-array millisecond pulsar PSR J0437−4715. The full processing pipeline including stan- dard pulsar software packages are now successfully tested on the Galaxy cluster of Pawsey. We will take advantage of these improved capabilities to build on our pilot project and propose to make regular observations of the four best PTA pulsars in the semester 2016A. Our main scientific goals are characterising the nature of the turbulent ISM through high-quality scintillation studies as well as making high-precision DM measurements which we will compare with Parkes measurements to look for any evidence of chromatic (frequency-dependent) DMs. Success of this project will define the breadth and scope of a much more ambitious program in the future, bringing in a new science niche for the MWA and SKA-low. |
12.5 (partially commensal with G0024, G0028) |
G0024 | Tremblay, Steven | Searching for FRBs and RRATs in MWA Pulsar Observations (toggle details)
Authors: Dr. S.E. Tremblay (Curtin), Dr. C.M. Trott (Curtin), Prof. S.J. Tingay (Curtin), Dr. N.D.R. That (Curtin), Dr. S.M. Ord (Curtin), Dr. J.-P. Macquart (Curtin) Abstract: Fast Radio Bursts (FRBs) are millisecond-duration events whose dispersion measures exceed the con- tribution of the Milky Way’s ISM by factors of > 5, placing them prima facie at cosmological distances. The origin of FRBs is presently a topic of intense speculation and poorly constrained by observational facts. The localisation of such an event would provide a breakthrough in this field. The MWA has the potential to make a decisive contribution by furnishing the first interferometric localisation of an event, and the first detection outside the 1.2-1.5 GHz band. This is facilitated by the uniquely large field of view presented to each MWA tile, in conjunction with its ability to combine tiles for sub-arcminute localisation. In this proposal we seek commensal observing time to detect and, for the first time, localise FRBs, thereby confirming their cosmological origins and opening a new field of astrophysics and cosmology. While most FRBs to date have been discovered well off the Galactic plane, we would be remiss not to search these data for FRBs. All these observations will be analysed similar to our previously approved program (G0024). A continued MWA observing campaign searching for FRBs will compliment LOFARs similar Northern Hemisphere search for these events at low radio frequencies. Low frequency detections, or or more stringent limits, from either of these telescopes will provide spectral constraints on these events which have only been detected at 1.4 GHz so far. Additionally, since our analysis pipeline improvements have removed the lower limit on our DM search, we are now automatically performing a search for Rotating Radio Transients (RRATs) as well. |
24 (partially commensal with G0021, G0028) |
G0025 | Seymour, Nicholas | Detection of HI Absorption toward a z~5.3 Radio-loud QSO (toggle details)
Authors: Dr. Nick Seymour (ICRAR/Curtin), Dr. Randall Wayth (ICRAR/Curtin), Dr. Thomas Franzen (ICRAR/Curtin), Dr. Minh Huynh (ICRAR/UWA) Abstract: Searching for and detecting HI absorption is a powerful technique to measure the neutral HI gas abundance within powerful radio sources or in intervening sources along the line of site. The sensitivity of this technique is independent of redshift as a given optical depth causes a fractional decrease in the spectrum. Hence only a bright radio source is required at the appropriate redshift. Traditionally this technique is limited to low redshifts (below z=1) due to the frequency coverage of the most sensitive radio telescopes (0.7-1.4GHz). However, the MWA presents the opportunity to conduct such an experiment in the early Universe (z>3.5) at frequencies below 315MHz. For technical and scientific considerations our best candidate, which we propose here, is the very bright quasar 7C 1023+2558 at z=5.28. We request a 4hour pilot observation of this unique galaxy in the early Universe to search for internal and intervening HI absorption |
4.5 |
G0026 | Hancock, Paul | A search for intrinsic radio emission from Fireballs with the MWA (toggle details)
Authors: Dr. Paul Hancock (Curtin), Dr. Randall Wayth (Curtin), Ms. Xiang Zhang (Curtin/Purple Mountain Observatory), Prof. David Kaplan (UWM), Prof. Steven Tingay (Curtin) Abstract: We propose to use the MWA to search for radio emission from bright meteors (fireballs). Radio emission coincident with fireballs has been observed and studied for some time, however it has always been under- stood that the radio emission is a result of reflected terrestrial radio sources. Recently the Long Wavelength Array (LWA), reported a detection of radio emission from fireballs (Obenberger et al., 2014) using the Pro- totype All-Sky Imager (PASI). The remarkable aspect of this detection is that the authors claim that the observed emission cannot be simply reflected RFI, and that there must be intrinsic emission associated with these fireball events. Five of the radio transients detected by PASI were coincident with known fireball events, thanks to an overlap between the field of view of the PASI and nearby fireball monitoring cameras. The PASI actually detected some 44 bright radio transients, however the overlap with the optical cameras meant that only 5 could be positively identified with optical events. Though the MWA has a snapshot field of view that is only ~1/5th of that of the LWA all-sky camera, the MWA is able to form higher cadence (0.5s vs 5s) images at higher resolution (2” vs 4.4deg), and with a much broader frequency coverage (30MHz vs 75kHz). If the MWA is able to observe a fireball then it will be able to provide unprecedented detail on the nature of the radio emission, and determine if there is an intrinsic, non-thermal, component to these events. Recently two wide-angle optical cameras have been installed near the MWA as part of the Desert Fireball Network (DFN, Bland et al., 2012). The DFN cameras provide an all night, every night, monitoring of the optical sky, with the aim of detecting bright fireballs. In combination with the MWA these cameras will provide a continuous multi-wavelength view of the sky, allowing for the study of both bright and faint fireball events. This project will: 1) Observe radio emission from fireballs with the MWA, 2) determine whether the radio emission is intrinsic to the fireball or simply reflected RFI, and 3) determine the transient foreground due to atmospheric events such as meteors. |
14 |
G0027 | Ord, Steve | Polarimetric Tied-Array Observations of Pulsars (toggle details)
Authors: Mengyao Xue (Curtin), Stephen Ord (Curtin/CSIRO), Ramesh Bhat (Curtin), Steven Tremblay (Curtin), Ryan Shannon (Curtin/CSIRO) Abstract: The MWA VCS pipeline is now reliably generating high time resolution observations of radio pulsars. We are proposing to expand this capability into the realm of polarimetric, calibrated tied array beam formation. These technologies will enable pointed polarimetric observations of known pulsars to study the pulsars themselves, the interstellar medium and the ionosphere. We are proposing a set of observations of three pulsars at at wide range of hour angles to characterise the fidelity and stability of the polarimetric solutions. This would be performed across the whole MWA band in picket-fence mode, which distributes the 24x1.28 MHz channels of the MWA receiver across the MWA observing band, thereby providing an excellent study of the wide bandwidth evolution of pulsar radio emission. These observations will form part of the PhD program of Menygao Xue. |
6 |
G0028 | Shannon, Ryan | Simultaneous wide-band observations of pulsars with MWA and Parkes (toggle details)
Authors: Dr. Ryan Shannon (Curtin/CSIRO), Dr. Ramesh Bhat (Curtin), Dr. George Hobbs (CSIRO), Dr. Steve Ord (CSIRO), Dr. Steven Tremblay (Curtin) Abstract: While pulsars are well known to emit over a wide range of frequencies, the total bandwidth over which the emission is correlated and the pulse-to-pulse variability of this bandwidth are poorly understood. Given this uncertainty, it is unsurprising that the effects of this variability on precision pulsar timing are unknown. We therefore propose to answer three questions about the broadband nature of pulsar emission: 1) Over what bandwidths are individual pulses correlated? 2) Does this bandwidth vary across the pulsar population? 3) How does this bandwidth affect pulsar timing? To answer these questions, we propose to study 5 bright pulsars that span the neutron star popula- tion, exhibit a diverse range of pulsar phenomenology. We request 5 hours of simultaneous Parkes- Murchinson Widefield Array observations to conduct simultaneous multi-frequency single-pulse obser- vations jointly with the MWA These measurements will be used to construct better empirical models for pulsar emission, test theoretical predictions, and assess the effects of broadband variability on pulsar timing measurements. |
5 (partially commensal with G0021, G0024) |
G0029 | Tremblay, Steven | A Pilot Study of Intermittent and Sporadically Emitting Pulsars at Low Frequencies (toggle details)
Authors: Dr. S.E. Tremblay (Curtin/CAASTRO), Mr. B. Meyers (Curtin), Dr. N.D.R. That (Curtin), Dr. F. Kirsten (Curtin), Dr. S. Ord (Curtin), Dr. R. Shannon (Curtin/CASS), Dr. J.-P. Macquart (Curtin) Abstract: This pilot study will observe a collection of pulsars which are known to exhibit high pulse-to-pulse vari- ability. The observations of nulling pulsars (B1133+16 and B2045-16), RRATs (J0941-39, J1226-3223, J1653-2330), intermittent pulsars (B1931+24, J1832+0029), and giant pulse emitters (J1824-2452A, J1823-3021A) will guide us in developing a full observing program of these fascinating sources. Up until now observations of these objects were restricted to frequencies above 300 MHz. The MWA opens the door to perform low-frequency studies of these objects which is essential to understand possible similarities and the underlying physical mechanism behind pulse-to-pulse variability. In this pilot project we aim at first detecting each of the above objects which is greatly supported by the coherent beamforming capabilities developed recently. After first detection and characterisation of each target (e.g. pulse profile, brightness, nulling fraction) we will design a future large-scale program to pinpoint the linkages between these species of pulsars and which will shed light on the fundamentals of the pulsar emission mechanism. |
8 |
Semester 2015-A, Ph I
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0001 | Bell, Martin | (continuation) The MWA long-term radio sky monitor | 60 |
G0002 | Oberoi, Divya | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 100 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 16 |
G0005 | Hancock, Paul & Feng, Lu | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 175 (commensal w/ G0009) |
G0008 | Staveley-Smith, Lister | (continuation) A Galactic and Extragalactic All-Sky MWA Survey | 280 |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 175 |
G0010 | Ewall-Wice, Aaron | (continuation) Constraining X-ray and Dark Matter heating before the Epoch of Reionization (EoR): Further exploration of systematics in calibration with the MWA | 30 |
G0016 | Murphy, Tara | (continuation) Search for circularly polarised emission from the youngest exoplanets | 40 |
G0017 | McKinley, Benjamin | Using the Moon to detect the global EoR signal (toggle details)
Authors: Dr. Benjamin McKinley (U. Melbourne), Dr. Randall Wayth (Curtin), Prof. Rachel Webster (U. Melbourne), Prof. Frank Briggs (ANU), Prof. Judd Bowman (ASU), Dr. Gianni Bernardi (SKA SA), Dr. Natasha Hurley-Walker (Curtin), Dr. Emil Lenc (U. Sydney), Mr. Jack Line (U. Melbourne), Dr. Andre Offringa (Astron), Dr. Bart Pindor (U. Melbourne), Dr. Pietro Procopio (U. Melbourne), Prof. Steven Tingay (Curtin), Dr. Cathryn Trott (Curtin) Abstract: We propose to measure the global redshifted 21-cm signal from the epoch of reionisation using the MWA and a novel technique involving observations of the Moon. The global signal and how it evolves as a function of redshift, can provide information on when reionisation of the Universe occurred, how long it took, and what types of ionising sources were responsible. Currently, only loose limits on the reionisation history exist from single dipole experiments, which face challenging systematic errors, such as frequency-dependent receiver noise contamination. The use of an interferometer would overcome many of the problems associated with the singe dipole experiments, however, interferometers are insensitive to a spatially-invariant global average, such as the global EoR signal. Lunar occultation imprints a spatial structure on the global signal, which allows it to be detected with an interferometer such as the MWA, using the brightness temperature of the Moon as a reference. The fact that the Moon moves relative to the background sky can also be exploited to reduce the effects of side lobe confusion and imaging artefacts through uv differencing of identical observations on different days. With 160 hours of observing time (including ‘on Moon’ and ‘off Moon’ observations, as well as calibration scans) we can expect sub-Kelvin sensitivity to the occulted Moon signal, which contains the global EoR signal, across the frequency range of 80-200 MHz. This will allow us to place the best limits yet on the global signal at certain frequencies. It will also enable us to measure the Galactic global signal and learn more about the thermal properties of the Moon. Perhaps most importantly, it will allow us to develop the techniques and tools required to make a robust detection in the future with more observing time and possibly an enhanced MWA. |
160 |
G0018 | Tremblay, Chenoa | Detecting Molecular Lines with the MWA (toggle details)
Authors: Chenoa D. Tremblay, Andrew J.Walsh, Slava Kitaeff, Steven Tremblay, Natasha Hurley-Walker Abstract: Sprectal line data has been used to explore our Galaxy since the 1800s, when scientists first classified stars. However, the chemistry within our Galaxy is virtually unexplored in the region of 100-300MHz. Instruments like the Robert C. Byrd Green Bank Telescope has been used to publish data on recombination lines at 80-100MHz, but no one has published to date any data on complex molecules in this frequency range. The MWA offers a chance to explore the constant chemical reactions that happen each second within our Galaxy and discover what information may be hiding in this frequency range. The current 10kHz spectral resolution may be well-suited for discovery of broad molecular lines. In this proposal we would like to map the Orion region in January or February over the full frequency range of the MWA in order hunt for molecular lines. Additionally we would like an hour of VCS time, also in Orion, to process through a polyphase filter bank (PFB) to assess the MWA's performance at higher spectral resolution. |
11 |
G0019 | Lonsdale, Colin | Investigation of non-closing digital effects in the MWA correlator (toggle details)
Authors: Colin Lonsdale, Leo Benkevitch, Roger Cappallo, Phil Erickson, Lynn Matthews, Divya Oberoi, John Morgan, Steven Tremblay Abstract: We request Voltage Capture System (VCS) data on the Sun in order to explore the parameter space of digital Van Vleck corrections along two axes. These two axes are (1) the effective number of bits being toggled in the post fine PFB data streams entering the cross multipliers, and (2) the strength of the correlation on a given baseline. The primary goal is to develop a quantitative understanding of the magnitude of the necessary Van Vleck corrections across the typical range of MWA operational conditions, and thereby devise methods of applying the corrections. Such corrections are a necessary but perhaps not sufficient step toward achieving the full potential of the MWA in high dynamic range imaging of strong sources. The necessary data can be gathered within 1 hour, but to insure against unanticipated problems, we request a second hour, to be gathered after the first set of data has been thoroughly inspected. |
2 |
G0020 | Lonsdale, Colin | Characterizing the ionosphere over the MWA under a variety of conditions (toggle details)
Authors: Colin Lonsdale, Roger Cappallo, Phil Erickson, Lynn Matthews, Divya Oberoi, John Morgan, Emil Lenc Abstract: We request imaging observations across a comprehensive range of local times and levels of geomagnetic activity in order to gather information on the nature, severity and duty cycles of different ionospheric conditions and phenomena at the MWA site. The ionospheric information derived from the imagery will take the form of refractive displacements of source positions, and where feasible measurements of ionospheric Faraday rotation (FR), as a function of time and position. This investigation is primarily driven by the short term need to characterize ionospheric FR as the primary contaminant to the weaker FR effects expected from the heliosphere caused by coronal mass ejections (CMEs). Secondary goals of the work are to provide information on ionospheric effects for use in other MWA science investigations for which it is desirable to remove or avoid the worst of those effects, and to study the ionospheric effects themselves, to which the MWA has unique sensitivity due to the inherent precision of interferometric phase measurements in terms of ionospheric electron density gradients. |
20 |
G0021 | Bhat, Ramesh | Low-frequency investigations of the Parkes pulsar timing array millisecond pulsars (toggle details)
Authors: N. D. R. Bhat (Curtin), S. M. Ord (Curtin), S. E. Tremblay (Curtin), S. J. Tingay (Curtin), M. Bailes (Swinburne), D. Kaplan (UW), van Straten (Swinburne); R. Shannon (CASS) Abstract: Pulsar timing array (PTA) experiments exploit the clock-like stability of fast-spinning millisecond pulsars for the prospective direct detection of low-frequency (nano-Hertz) gravitational waves (GWs). Detection of GWs is an eagerly pursued goal of modern astronomy and will mark a major breakthrough. There is now increasing realisation that the interstellar propagation effects on pulsar signals may ultimately limit the detection sensitivity of PTAs unless they are accurately measured and corrected in timing measurements. The influence of the interstellar medium is much higher at low radio frequencies; therefore the MWA presents an exciting and unique opportunity to calibrate interstellar propagation delays and thereby significantly enhance the sensitivity and scientific impact of the Parkes pulsar timing array (PPTA) project. The MWA’s potential in this arena is vividly demonstrated by our recent work on scintillation and profile studies of the millisecond pulsar (MSP) PSR J0437-4715, using data recorded during the VCS commissioning phase. With the full bandwidth recording now possible with the VCS, and the ability to form coherent (phased-array) beam, it is now possible to exploit the full potential of the MWA forpulsar science. We propose observations of PPTA pulsars for multiple science goals; we will (i) demonstrate the MWA’s unique capability for high-precision dispersion measure (DM) determinations and profile evolution studies, by exploiting its flexibility to distribute the 30.72 MHz of available bandwidth to span the full 80-300 MHz range; (ii) conduct three-weekly monitoring of PSR J0437-4715 for scintillation and DM variability; and (iii) perform a low-frequency census of millisecond pulsars. The success of this pilot project will define the breadth and scope of a more ambitious, larger-scale program in the future, bringing in a new science niche for the MWA and SKA-low. |
12 |
G0022 | Ord, Stephen | Pursuing the Fast with the First: Pulsar Surveys with the first Operational SKA Pathfinders (toggle details)
Authors: Dr. Ord (Curtin), Dr. Bhat (Curtin), Dr. Tremblay (Curtin), Dr. Hessels(ASTRON), Dr. Kaplan (UWM), Prof. Tingay (Curtin), Mr. McSweeney (Curtin) Abstract: Discovering new pulsars is one of two main science drivers for SKA Phase 1 because it will enable "Strong Field Tests of Gravity". The MWA provides an opportunity to develop the techniques required to achieve this goal, and it will discover dozens of pulsars along the way. We intend to use the observations taken for the MSP census observations of Bhat et al to begin a survey for pulsars and radio transients with the MWA. We will develop novel processing and analysis pipelines with these data and the presence of known millisecond pulsars in every field will confirm the validity of our survey methods. As an extension to this commensal program we also intend a targeted search of the globular cluster 47-Tucanae (47-Tuc). 47-Tuc contains 23 known millisecond pulsars, the first 11 of which were discovered at 50 and 70cm (Manchester et al 1990). The cluster is at a declination of -72 degrees, therefore the MWA is the only low frequency instrument able to observe it. This an ideal test observation for the MWA pulsar survey pipeline: it is at a known DM so the number of DM trials is reduced, all the radio pulsars have been found within 1.2 arcmin of the centre, so a single tied array beam will encompass the cluster region of interest. The pulsars are distant, but intrinsically luminous and scintillation increases their measured intensity by a factor of ten. The brightest of the 47-Tuc pulsars (J, C and E) should be easily observable, and even if no new pulsars are discovered these observations will provide details of the observability of the 47-Tuc pulsars at SKA-Low observing frequencies. |
12 |
G0023 | Tingay, Steven | Shadowing the Kepler K2 mission with the MWA and SkyMapper (toggle details)
Authors: Steven Tingay(Curtin), Randall Wayth (Curtin University), Paul Hancock (Curtin University), Christian Wolf (ANU), Fang Yuan(ANU), Brad Tucker (UC Berkeley), Christopher Onken (ANU), Brian Schmidt (ANU), Andre Offringa (ASTRON) Abstract: We propose MWA observations coordinated with observations by SkyMapper and the Kepler K2 mission, to monitor radio variables and transients and to correlate variability and transient behavior between radio and optical wavelengths. This opportunity is based on Kepler’s schedule, which will continuously observe Fields 4 and 5 of its K2 mission in a broad optical band (420-‐900 nm), 24hrs/day, from 7 Feb 2015 to 24 April 2015 (Field 4: centred at 03:56:18.2; +18:39:38) and from 26 April 2015 to 11 July 2015 (Field 5: centred at 08:40:37.8; +16:49:47) with a field radius of ~8 degrees and a small pixel filling factor. The Kepler K2 mission provides a unique opportunity for Australia’s premier widefield optical and radio telescopes (SkyMapper and the MWA) to undertake coordinated radio/optical searches for transient and variable phenomena over wide fields. Rapid publication of the MWA results will provide a large-‐scale database of variability information for thousands of radio sources in each of the Kepler K2 fields, to be utilized by the PIs of dozens of science projects that form the Kepler K2 target list. This will be a unique resource for Kepler K2 science, that can only be produced by the MWA. |
15 |
G0024 | Tremblay, Steven | Pursuing the Fast with the First: FRBs and the First Operational SKA Pathfinders (toggle details)
Authors: Dr. S.E. Tremblay (Curtin), Prof. S.J. Tingay (Curtin), Dr. S.M. Ord (Curtin), Dr. N.D.R. Bhat (Curtin), Dr. C.M. Trott (Curtin) Abstract: Fast Radio Bursts (FRBs) are a recently discovered new population of highly dispersed radio transients (Thornton et al. 2013). The dispersion of FRBs cannot be accounted for by the ISM within our own Galaxy, with excesses of 15 to 35 times the expected DM_MilkyWay reported. The MWA been predicted to have a unique ability to detect and localise these exciting and still unexplained phenomena (Trott et al. 2013A) due to the large field of view of each tile, and the ability to combine tiles for localization. In this proposal we seek time for an observational program to detect and, for the first time, localise FRBs, thereby confirming their cosmological origins and opening a new field of astrophysics and cosmology. 12 hours of this proposal are commensal with other proposals for observing known pulsars. While most FRBs to date have been discovered well off the galactic plane, we’d be remiss not to search these data for FRBs. The remaining non-commensal observations will be performed at higher galactic latitudes and analysed similar to our pilot program we’ve performed under Director’s discretionary time. A supported MWA observing campaign searching for FRBs will strongly compliment LOFARs similar Northern Hemisphere search for these events at low radio frequencies. Low frequency detections, or limits, from either of these telescopes will provide spectral constraints on these events which have only been detected at ~1.4 GHz so far. |
40 |
OA002 | Maan, Yogesh | Using the MWA for Confirmatory Detection, Localization and Study of the Lowest Dispersion Measure Pulsar (toggle details)
Authors: Dr. Yogesh Maan (NCRA-TIFR), Dr. N.D. Ramesh Bhat (Curtin) Abstract: Recently, a pulsar with a period of 785 ms has been discovered at a very low frequency (34 MHz), using the Gauribidanur radio telescope. The dispersion measure of the pulsar is just 1.55 pc cm.3, i.e., lowest among those of the known radio pulsars. Given that the Gauribidanur telescopefs beam is quite wide (0.5. in RA and 35. in Dec.), the declination of the pulsar could be anywhere between ~50deg and ~13deg. Further, this source might be one of those pulsars for which, only their wider, low frequency radio emission beams could be seen from earth. Hence, any effort to re-detect the pulsar as well as to localize its position needs to use a telescope which can facilitate observations in the above mentioned large declination range at a frequency as close to the detection frequency (34 MHz) as possible. The MWA is the only telescope which can be used to observe such a large declination range in the southern sky hemisphere, at frequencies below and around 100 MHz. To make a confirmatory detection of the pulsar and to localize its sky position, we propose to use the MWA in the voltage capture system (VCS) observing mode to carry out tracked observations of the field likely to contain the pulsar. To cover the aforementioned declination range, we will make two pointings of 1 hour each, separated by 15. in declination. A potential detection using these observations would help in revealing a member of the local population of pulsars, as well as enable further study of the pulsar at 100 MHz and other suitable radio frequencies. |
2 |
Semester 2014-B, Ph I
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0001 | Bell, Martin | (continuation) The MWA long-term radio sky monitor | 60 |
G0002 | Oberoi, Divya | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 70 |
G0003 | Hancock, Paul | (continuation) Exploiting the MWA field of view to study scintillation and the structure of turbulence in the Milky Way | 10.2 |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 22 |
G0005 | Hancock, Paul & Feng, Lu | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 880 (commensal w/ G0009) |
G0008 | Staveley-Smith, Lister | (continuation) A Galactic and Extragalactic All-Sky MWA Survey | 280 |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 880 |
G0010 | Ewall-Wice, Aaron | (continuation) Constraining X-ray and Dark Matter heating before the Epoch of Reionization (EoR): Further exploration of systematics in calibration with the MWA | 24 |
G0015 | Kitaeff, Slava | Spectral Line Observation toward Galactic Centre and NGC6334 (toggle details)
Authors: Prof. Slava Kitaeff (ICRAR/UWA), Dr. Anish Roshi (NRAO), Prof. John Dickey (U. Tasmania), Dr. Divya Oberoi (MIT/Haystack), Prof Lister Staveley-‐Smith (ICRAR/UWA), Dr. Andrew Walsh (ICRAR/Curtin), Krystal Cook (UWA, student), Dr. Maria Cunningham (UNSW), Dr. A. R. Offringa (ANU), Dr. Paul Jones(UNSW) Abstract: We propose to observe radio recombination line (RRLs) toward the star-forming complex NGC6334 and Galactic Centre with the MWA. The primary goal of the project is to detect the narrow spectral lines (less than 30 km/sec). We will develop a technique for accurate bandpass calibration that is critical for detection of weak spectral lines as the bandshape changes with pointing. We will also attempt to search for the molecular lines. |
10 |
G0016 | Murphy, Tara | A search for circularly polarised emission from exoplanets and ultracool dwarfs (toggle details)
Authors: Dr. Tara Murphy (U. Sydney/CAASTRO), Dr. David Kaplan (UWMilwaukee), Dr. Martin Bell (CASS), Dr. Ramesh Bhat (Curtin/CAASTRO), Dr. Megan DeCesar (UW-Milwaukee), Dr. Paul Hancock (Curtin/CAASTRO), Dr. Emil Lenc (U. Sydney/CAASTRO), Cleo Loi (U. Sydney/CAASTRO), Dr. Andre Offringa (ANU/CAASTRO), Dr. Randall Wayth (Curtin/CAASTRO), Dr. Peter Williams (Harvard CfA)Abstract: Magnetised extrasolar planets are expected to emit strongly at radio wavelengths, in the same way as magnetised planets in our own solar system. Emission is expected at low radio frequencies tied to the electron gyrofrequency. However, previous searches have all been negative. Any detection would directly constrain the magnetic field strength and geometry. In contrast, a number of ultracool dwarfs show steady and transient radio emission at cm wavelengths which is again directly related to the magnetic field geometry. Understanding the prevalence and properties of such emission will help explain the enhanced activity of ultra-cool dwarfs compared to other classes of stars. |
40 |
Semester 2014-A, Ph I
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0001 | Bell, Martin | (continuation) The MWA long-term radio sky monitor | 40 + 20 comm. |
G0002 | Oberoi, Divya | (continuation) MWA Observations of Solar Radio Bursts and the Quiet Sun | 30 |
G0003 | Hancock, Paul | (continuation) Exploiting the MWA field of view to study scintillation and the structure of turbulence in the Milky Way | 4.6 + 5 comm. |
G0004 | Kaplan, David | (continuation) Monitoring the Galaxy with the MWA | 16.5 |
G0005 | Kudryavtseva, Nadia | (continuation) Search for Variable and Transient Sources in the EOR Fields with the MWA | 350 (commensal w/ G0009) |
D0001 | Rowell, Gavin | (continuation) Technical investigation of H.E.S.S. and MWA linkages for transient source studies | 10 |
G0008 | Staveley-Smith, Lister | (continuation) A Galactic and Extragalactic All-Sky MWA Survey | 140 |
G0009 | Webster, Rachel | (continuation) Epoch of Reionisation | 350 |
G0011 | Johnston-Hollitt, Melanie |
Testing Predictions for Diffuse Radio Emission in Massive Galaxy Clusters (toggle details) Authors: Dr. Melanie Johnston-Hollitt, Dr. Gianfranco Brunetti, Dr. Rossella Cassano, Siamak Dehghan, Prof. Daniele Dallacasa, Dr. Luke Hindson, Dr. Natasha Hurley-Walker, Dr. Ruta Kale, Rowan Miller, Sara Shakouri, Dr. Tiziana Venturi, Dr. Cathie Zheng Abstract: We propose to undertake a point and track study of 25 massive (M > 4x10^14 solar masses) galaxy clusters with declinations between 0 and -65 degrees drawn from the Planck SZ Cluster Catalogue. This sample will be matched to the resolution of the MWA and thus limited to z less than 0.13 and will be used to search for as yet undetected radio halos and relics using the MWAfs unique instrumental niche for low frequency observations in the Southern Hemisphere. With such a mass-selected sample in hand, we will be able to undertake an unbiased examination of radio halo and relic generation in galaxy clusters including correlation of halos and relics to dynamical state and undertake the first widespread search for the predicted population of ultra-steep spectrum radio halos expected to be only detectable below 300 MHz. |
42 |
G0012 | Johnston-Hollitt, Melanie |
The Horologium-Reticulum Supercluster as a cosmic laboratory to investigate the role of environment on the radio source population (toggle details) Authors: Dr. Melanie Johnston-Hollitt, Siamak Dehghan, Dr Luke Hindson, Dr Natasha Hurley-Walker, Dr Emil Lenc, Rowan Miller, Sara Shakouri, Dr. Cathie Zheng Abstract: We propose to use the MWA to map the 180 square degree area of the Horologium-Reticulum supercluster (HRS) down to the confusion limit at 95, 155 and 215 MHz. Combined with our existing extensive spectroscopic data and 1.4 GHz imaging, this will provide an unprecedented opportunity to examine the low frequency radio source population as a function of environment from filaments and groups to rich clusters. As a secondary science goal we will examine the rotation measure across this field from known regions of diffuse polarized emission in the northern clusters. We are particularly fortunate in these observations as the HRS is suitable away from the Galactic plane close to the known MWA polarization calibrator, PMN J0351-2744, allowing excellent polarization characterization of the field. |
12 |
OA001 | Kale, Ruta |
Synchrotron emission on cluster and supercluster scales: the Shapley supercluster (toggle details) Authors: R. Kale, S. Bardelli, G. Brunetti, R. Cassano, D. Dallacasa, K. S. Dwarakanath, S. Giacintucci, M. Johnston-Hollitt, M. Rossetti, T. Venturi Abstract: The inter-galactic medium (IGM) that permeates the space between individual galaxies through-out the large-scale structure of the Universe beyond the most massive clusters remains elusive. With 0.1-1 μG magnetic fields and electrons accelerated at the shocks due to infalling matter, the cosmic web is expected to be a source of synchrotron emission on scales of a few Mpc forming a ‘synchrotron web’. The unprecedented surface brightness sensitivity and short baseline uv-coverage of the Murchison Widefield Array in combination with the TIFR GMRT Sky Survey provides a unique opportunity to probe the synchrotron web. We propose MWA observations of the Shapley supercluster (SSC) region. SSC consists of several merging clusters and galaxy groups forming a filamentary structure located at a mean redshift of 0.048. It is a unique candidate to find diffuse emission on cluster and supercluster scales. A wealth of information on SSC is available in this collaboration at frequency bands ranging from X-rays to low radio frequencies. The compact and extended radio galaxies, background radio sources and a radio halo in the SSC region are well known at several radio frequencies in the range 240 MHz - 5 GHz. The proposed observations with the MWA will be the first to explore radio emission on supercluster scales and lead to pathbreaking discoveries at low radio frequencies. |
3 |
Semester 2013-B, Ph I
ID | PI | Title | Time awarded (hours) |
---|---|---|---|
G0001 | Bell, Martin |
The MWA long-term radio sky monitor (toggle details) Authors: Dr. Martin Bell (Sydney/CAASTRO), Dr. Tara Murphy (Sydney/CAASTRO), Prof. David Kaplan (UW‐Milwaukee), Dr. Nadia Kudryavtseva (Curtin), Lu Feng (MIT), Dr. Randall Wayth (Curtin), Dr. Paul Hancock (Sydney/CAASTRO), Prof. Bryan Gaensler (Sydney/CAASTRO), Dr. Natasha Hurley‐Walker (Curtin), Dr. Keith Bannister (CSIRO/CAASTRO), Dr. Steve Croft (UC Berkeley), Dr. Cath Trott (Curtin), Dr. J-P Marquart (Curtin), Dr. Davide Burlon (Sydney/CAASTRO) and the MWA transients collaboration. Abstract: We propose a wide-field, long-term survey to search for, and monitor, low frequency transient and variable radio sources in the southern sky. This survey would target relatively long duration transient and variable activity (> one month) over almost the entire southern hemisphere. We request 60 hours of night time observing with a cadence of one observation per month. Using drift scan observations of three different declination strips at 150 MHz only, we plan to gradually re-visit different overlapping regions of the sky over the observing semester. These regions will be searched with the Variables and Slow Transients (VAST) detection pipeline. The motivation for this survey is as follows: (i) To obtain temporal data on an extremely large and robust sample of low frequency sources to probe, explore and quantify both intrinsic and extrinsic variability. (ii) To search and find new classes of low frequency radio transients that previously remained undetected and obscured from multi-wavelength discovery. (iii) To place rigorous statistics on the occurrence of both transients and variables prior to the Australian SKA era. |
50 |
G0002 | Cairns, Iver | Unbiased Solar Observations for Burst, Calibration, and Quiet Sun Studies (toggle details)
Authors: Iver Cairns, Divya Oberoi, Tim Bastian, Leo Benkevitch, Judd Bowman, Alina Donea, Owen Giersch, Bernie Jackson, Gaetan Le Chat, Leon Golub, Justin Kasper, John Kennewell, Colin Lonsdale, Vasili Lobzin, Lynn Matthews, John Morgan, Janardhan Padmanabhan, Prasad Subramanian, R. Ramesh, John Raymond, Kathy Reeves, Alan Rogers, Steven Tingay, Steven Tremblay, Durgesh Tripathi, David Webb, Stephen White Abstract: Thirty hours of daytime observing is desired with an unbiased observing pattern over one solar rotation (1 specific hour per day for 30 consecutive days). Three sets of related science goals will be addressed: (A) Solar Radio Bursts, focusing on their imaging, polarization, and spectral properties and their correlation with solar activity like coronal mass ejections (CMEs) and flares, searching for radio “nanoflares” and investigating their role in coronal heating, and observations in conjunction with NuSTAR; (B) Calibration of MWA and solar phenomena via comparisons with the galactic background radiation and EDGES, Learmonth, and Culgoora observations; and (C) Quiet Sun science, including variability of the intrinsic flux and spectral index of background emission and comparing the observed solar scattering disk with expected scattering from density turbulence. A relatively long and unbiased observing pattern will allow us to explore the new phase space opened up by MWA free of any pre-conceived notions. |
30 |
G0003 | Hancock, Paul | Exploiting the MWA field of view to study scintillation and the structure of turbulence in the Milky Way (toggle details)
Authors: Dr. Paul Hancock (SIfA/CAASTRO Sydney University), Prof. David Kaplan (UWMilwaukee), Dr. James Miller-Jones (Curtin University), Dr. Martin Bell (SIfA/CAASTRO Sydney University), Prof. Bryan Gaensler (SIfA/CAASTRO Sydney University), Dr. Natasha Hurley-Walker (Curtin University), Dr. Jean Pierre Macquart (Curtin University), Dr John Morgan (Curtin University), Dr. Tara Murphy (SIfA/CAASTRO Sydney University), Dr. Randall Wayth (Curtin University), and the MWA transients collaboration. Abstract: We propose to use the MWA to carry out a search for low frequency, scintillation induced variability of extragalactic radio sources. At frequencies 300MHz the variability is likely to be dominated by (strong) refractive interstellar scintillation (RISS). The degree and timescale of variability of compact radio sources is related to variations in gas density along the line of sight, and as such can be used to probe the turbulent structure of the intervening gas. Probing many lines of sight through the Milky Way and Magellanic clouds therefore provides a measure of turbulence in the ISM. The work of Slee & Siegman (1988) used sources that sparsely covered the southern sky, and found a high incidence of variability which was in part attributed to scintillation. Their analysis also showed a weak increase in variability at low galactic latitudes. With a denser coverage of the Galactic plane it is possible to look for correlations in the RISS properties between closely spaced sources that could demonstrate the spatial structure of the ISM. By including fields outside of the Galactic plane we can also measure the correlation between the strength and incidence of scintillation with Galactic latitude. Such a project has not yet been carried out due to the large amount of observing time required to conduct a blind survey of extragalactic point sources, and then monitor a large population of them long enough to see monthly and yearly variations. With the large field of view of the MWA and the relatively short amount of time required to reach the confusion limit, this project is ideally suited to the MWA. |
21 |
G0004 | Kaplan, David | Monitoring the Galaxy with the MWA (toggle details)
Authors: Prof. David Kaplan (UWM); Dr. James Miller-Jones (Curtin); Dr. Megan DeCesar (UWM); Dr. Martin Bell (University of Sydney), Dr. Tara Murphy (Sydney), Dr. Randall Wayth (Curtin), Dr. Paul Hancock (Sydney), Prof. Bryan Gaensler (Sydney), Dr. Natasha Hurley-Walker (Curtin), Dr. Keith Bannister (CSIRO), Lu Feng (MIT), Dr. Nadia Kudryavtseva (Curtin), Dr. Peter Williams (Harvard/Smithsonion CfA), Dr. Cath Trott (Curtin) and the MWA Transients collaboration Abstract: We propose weekly MWA monitoring of the Galactic Plane, including the Galactic Center. We aim to monitor the periastron passage of the gas cloud G2 as it orbits Sgr A constrain the nature of the mysterious bursting source GCRT J1745-3009, and provide high-cadence radio light curves of X-ray binary outbursts. At the same time, the extremely wide field-of-view afforded by the MWA means that the specific targets listed below will be joined by many serendipitous targets spread throughout the Galaxy. Using the transients pipeline, we will also monitor other classes of radio transient, including magnetar giant outbursts, flare stars and active binaries. |
36 |
G0005 | Kudryavtseva, Nadia | Search for Variable and Transient Sources in the EOR Fields with the MWA (toggle details)
Authors: Dr. Nadia Kudryavtseva (Curtin), Lu Feng (MIT), Prof. David Kaplan (UW – Milwaukee), Dr. Martin Bell (Sydney, CAASTRO), Dr. Tara Murphy (Sydney), Dr. Daniel Mitchell (Melbourne, CAASTRO), Dr. Randall Wayth (Curtin, CAASTRO), Dr. Natasha HurleyWalker (Curtin), Dr. Steven Tingay (Curtin), Dr. Paul Hancock (Sydney, CAASTRO), Dr. Keith Bannister (CSIRO, CAASTRO), Prof. Bryan Gaensler (Sydney, CAASTRO), Dr. Jean-Pierre Macquart (Curtin), Dr. Cathryn Trott (Curtin, CAASTRO), Dr. Davide Burlon (Sydney), Dr. James Miller-Jones (Curtin), Dr. Roberto Soria (Curtin), Dr. John Morgan (Curtin), Dr. Hayley Bignall (Curtin), Dr. Rachel Webster (Melbourne), Prof. Jacqueline Hewitt (MIT), Prof. Edo Berger (Harvard), Dr. Peter Williams (Harvard) and the MWA transients collaboration. Abstract: 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 nonrepeating transient sources, such as merging black holes, and tidal disruption events are expected to emit at MWA frequencies. However, the low-frequency radio sky is not well explored. Observations with the MWA are extremely well-suited for blind transient surveys due to its large instantaneous field of view and high sensitivity. We propose a survey of transient and variable sources in the EOR (Epoch of Reionisation) fields. This is a commensal observation, sharing data with the EOR collaboration. This proposal targets transient events on time scales from 8 seconds to weeks and covers 1830 square degrees of the sky over 370 hours of observations. This will allow us to study the variable and transient nature of multiple types of sources. |
353 (commensal w/ G0009) |
G0006 | Offringa, Andre | Spectral details of extragalactic point sources (toggle details)
Authors:A. R. Offringa (ANU, CAASTRO), F. H. Briggs (ANU), L. Hindson (Wellington) Abstract: We intend to study the detailed spectra of extragalactic continuum radio sources with highest achievable level of calibration. The study will make use of the extensive MWA data sets taken in the course of fulfilling other high-priority MWA programs. The results will complement and enhance other key MWA projects by building confidence in our understanding of the instrument’s behaviour and reliability in the calibration. The project will result in low-frequency high-resolution spectral energy distributions (SEDs) for hundreds of extragalactic point-like sources. Using these SEDs, we will verify whether low-frequency source spectra are smooth. This is a key assumption that is required for extracting the redshifted 21-cm emission of the Epoch of Reionisation (EoR) from lowfrequency measurements, but one that has never been extensively tested. This project does not require additional observing time, as we will only use data sets already taken for the EoR project. |
154 (commensal w/ G0009) |
D0001 | Rowell, Gavin | Technical investigation of H.E.S.S. and MWA linkages for transient source studies (toggle details)
Authors: G. Rowell, S. Balenderan, F. Brun, P. Chadwick, W. Domainko, J. Hawkes, J. Hinton, L. McComb, P. O'Brien, D. Parsons, G. Puehlhofer, E. de Ona Wilhelmi, J-P. Lenain for the H.E.S.S. Collaboration Abstract: This proposal aims to explore the technical aspects of linking the H.E.S.S. and MWA telescopes in gamma-ray and radio studies of transient sources. We will investigate two aspects (1) MWA triggers for H.E.S.S. follow-up observations and (2) H.E.S.S. triggers for MWA follow-up or re-pointing. We request access to a sample of MWA trigger data from the 2013-B period in order to configure data pipelines to/from H.E.S.S. and to investigate transient alert filtering and follow-up policies. A companion proposal to support this activity has recently been submitted to H.E.S.S. |
N/A |
G0008 | Staveley-Smith, Lister | A Galactic and Extragalactic All-Sky MWA Survey (toggle details)
Authors: Prof Lister Staveley-Smith (ICRAR/UWA), Dr Natasha Hurley-Walker, Dr K. S. Dwarakanath (RRI), Prof Bryan Gaensler (U. Sydney), Dr D. Anish Roshi (NRAO), Dr Randall Wayth (ICRAR/Curtin), Dr Takuya Akahori (U. Sydney), Mr Craig Anderson (U.Sydney), Dr Edo Berger (CfA), Dr Gianni Bernardi (SKA-SA), Dr Judd Bowman (ASU), Dr Robert Braun (CSIRO), Dr Davide Burlon (U. Sydney), Mr Joe Callingham (U.Sydney), Dr Ettore Carretti (CSIRO), Dr Roland Crocker (ANU), Prof John Dickey (U. Tasmania), Dr Jamie Farnes (U. Sydney), Dr Sean Farrell (U.Sydney), Dr Ilana Feain (CSIRO), Dr Bi-Qing For (ICRAR/UWA), Ms Niloofar Gheissari (U. Sydney), Prof Anne Green (U. Sydney), Dr Lisa Harvey-Smith (CSIRO), Dr Luke Hindson (VUW), Dr Alex Hill (CSIRO), Dr Carole Jackson (CSIRO), Dr Daniel Jacobs (ASU), Dr Melanie Johnston-‐Hollitt (VUW), Ms Jane Kaczmarek (U. Sydney), Dr Slava Kitaeff (ICRAR/UWA), Dr Nadia Kudryavtseva (ICRAR/Curtin), Dr Emil Lenc (U. Sydney), Mr George Lijo (RRI), Dr Naomi McClure-‐Griffiths (U. Sydney), Mr Ben McKinley (ANU), Dr Daniel Mitchell (U.Melbourne), Dr Miguel Morales (U. Washington), Dr John Morgan (ICRAR/Curtin), Dr Paul Nulsen (Harvard/CfA), Dr Divya Oberoi (MIT/Haystack), Dr Andre Offringa (ANU), Dr Steven Ord (ICRAR/Curtin), Dr Shane O'Sullivan (U. Sydney), Dr Cormac Purcell (U. Sydney), Prof. Peter Quinn (ICRAR/UWA), Prof Elaine Sadler (U.Sydney), Dr. Lakshmi Saripalli (RRI), Dr Nick Seymour (CSIRO), Ms Sara Shakouri (VUW), Dr Pat Slane (CfA), Mr Raghav Srinivasa (VUW), Ms Kim Steele (ICRAR/Curtin), Dr Xiaohui Sun (U. Sydney), Dr Ravi Subrahmanyan (RRI), Prof Steven Tingay (ICRAR/Curtin), Dr. N. Udaya Shankar (RRI), Dr Andrew Walsh (ICRAR/Curtin), Dr. Peter Williams (CfA), Dr Alex Zauderer (CfA), Dr Cathie Zheng (VUW), Dr Maria Cunningham (UNSW), Dr George Heald (ASTRON), Dr Paul Jones (UNSW), Dr Ruta Kale (U.Bologna & INAF), Dr Gavin Rowell (U.Adelaide) Abstract: We propose a GaLactic and Extragalactic All-sky MWA (GLEAM) survey at the full range of MWA frequencies (80-230 MHz) in order to study phenomena ranging in scale from pulsar wind nebulae to the Cosmic Web. Commensurate with the low frequency and high surface brightness sensitivity of the MWA, our science aims are dominated by the study of non-thermal processes in diffuse objects. For example, detection of new giant radio galaxies will allow us to probe intergalactic pressure in a wider range of environments than currently available; stacking of emission from the cosmic web will allow us to better constrain the amplification of primordial magnetic fields; and a study of clusters will allow us to discriminate between viable cosmic ray acceleration processes in the largest virialised objects in the Universe. Studies of nearby galaxies will allow de-blending of the non-thermal and thermal components of radio emission, an examination of the non-thermal radio/FIR relation, and its dependence on spatial scale. Within our own Galaxy, the proposed frequency coverage will give excellent spectral coverage for rotation measure studies of the Galactic magnetic field and its threedimensional configuration. It will also be a valuable resource for the discovery of the Galaxy’s "missing" supernova remnants. The GLEAM survey will provide valuable knowledge on foreground subtraction techniques for the proposed EOR project, will provide an important sky template for the study of transient radio sources, and will provide a list of polarisation-selected pulsar candidates for further study. Furthermore, the GLEAM survey overlaps and complements the ongoing LOFAR MSSS survey, and will provide a valuable low-frequency reference for the ASKAP EMU survey. Finally, the science aims are related to at least two of the key SKA science goals, provide a low-risk, high-return range of science and will be a valuable all-sky legacy for the astronomy community. |
114 |
G0009 | Webster, Rachel | Epoch of Reionisation (toggle details)
Authors: Adam Beardsley (Washington), Dr Gianni Bernardi (CfA), Prof Judd Bowman (Arizona State), Prof Frank Briggs (ANU), Josh Dillon (MIT), Aaron Ewall-Wice (MIT), Lu Feng (MIT), Prof Steve Furlanetto (UCLA), Prof Bryan Gaensler (Sydney), Robert Goeke (MIT), Dr Lincoln Greenhill (CfA), Dr Bryna Hazelton, (Washington), Prof Lars Herquist (Harvard), Prof Jackie Hewitt (MIT), Dr Daniel Jacobs (Arizona State), Dr Emil Lenc (Sydney), Dr Al Levine (MIT), Dr Adrian Liu (UC Berkeley), Prof Avi Loeb (Harvard), Dr Colin Lonsdale (Haystack MIT), Ben McKinley(ANU), Dr Daniel Mitchell (Melbourne), Prof Miguel Morales (Washington), Dr Ed Morgan (MIT), Abraham Neben (MIT), Dr André Offringa (ANU), Sourabh Paul (RRI), Dr Bart Pindor (Melbourne), Dr Pietro Procopio (Melbourne), Dr Ron Remillard (MIT), Jenny Riding (Melbourne), Dr Shiv Sethi (RRI), Prof Udaya Shankar (RRI), Prof Ravi Subrahmanyan (RRI), Dr Ian Sullivan (Washington), Prof Max Tegmark (MIT), Prof Steven Tingay (Curtin), Dr Cath Trott (Curtin), Dr Randall Wayth (Curtin), Prof Rachel Webster (Melbourne), Dr Chris Williams (MIT), Prof Stuart Wyithe (Melbourne) Abstract: The Murchison Widefield Array is designed to measure the fluctuations in the 21cm emission from neutral hydrogen during the Epoch of Reionisation. The built telescope with 128 tiles has the sensitivity to detect the theoretical signal, with sufficient observing time. The real challenge will be to understand and remove the foreground signals from the galaxy and extragalactic sources. We have demonstrated a pipeline that successfully removes the foregrounds from a few hours of data obtained on the MWA 32-tile test array. This proposal requests 400 hours of observing time in semester 2013-B to (1) acquire an adequately sensitive dataset to probe and understand the limitations of the array design for foreground removal, (2) obtain the first dataset required to meet the estimated sensitivity requirements for a detection of the Epoch of Reionisation, (3) establish the optimal observing strategy for such a detection, and (4) explore the large N-small d design parameter space to advise the design of SKA-low as those options are being narrowed down over the next 12 months. We note that the MWA Statement of Collaboration specifies that priority will be given to the EoR and SHI collaborations during early science operations. |
353 |
G0010 | Ewall-Wice, Aaron |
Constraining Xray and Dark Matter heating Before the Epoch of Reionization (EoR): Preliminary Observations at Low Frequency with the MWA (toggle details) Authors:. Aaron Ewall-Wice (MIT), Pierre Christian (CfA), Abraham Neben (MIT), Josh Dillon (MIT), Jackie Hewitt (MIT), Andrei Mesinger (SNS), Avi Loeb (CfA), Frank Briggs (ANU), Max Tegmark (MIT) Abstract: The MWA 128T is designed to detect the power spectrum of 21cm fluctuations in the high redshift intergalactic medium (IGM) during the Epoch of Reionization (EoR). During the late stages of reionization (6< ~z < ~10), these fluctuations are dominated by the ionization structures sourced by the first generations of luminous galaxies. Prior to reionization, many models predict that the X-ray heating, from high mass X-ray binaries, miniquasars, and dark matter (DM) annihilation, raised the temperature of the IGM to bring it into emission against the Cosmic Microwave Background (CMB). At low redshift, when the gas is already heated, the 21cm brightness temperature is expected to depend little on the spin temperature, so power spectrum fluctuations are dominated by ionization. At higher redshifts, before the completion of heating, (z > ~10) large fluctuations in the spin temperature can increase the amplitude of the power spectrum above the MWA’s expected thermal noise. A detection or non-detection of these spin temperature fluctuations would constrain the thermal history of the IGM, complementing a low redshift power spectrum detection that would constrain the reionization history. Encoded in this thermal history is the abundance of early astrophysical sources of X-rays, as well as cosmological information such as the warm dark matter (WDM) particle mass and the cold dark matter (CMD) annihilation cross-section. Beyond the thermal noise, foreground removal, terrestrial radio-frequency interference (RFI; particularly the FM band), and ionosphere propagation effects are severe challenges at low frequencies. Also, the increased size of the field of view will likely present an additional calibration challenge. This proposal requests 24 hours of observing time in semester 2013-B to determine whether thermal sensitivity limited measurements within the EoR window are possible in the presence of low frequency systematics. |
16 |
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