Semester 2023A (CFP-2023-A) will run observations during the periodApril 1, 2023 to August 15, 2023(subject to availability of the array).
The array will be in thecompactconfiguration throughout 2023. TheData Lifecycle Policywill come into effect, and PIs are encouraged to make use of pre-correlationfringe stopping.
Compact configuration: This subset of the array includes 72 tiles arranged in two regular hexagonal configurations near the existing MWA core for improved EoR capabilities. More details of the MWA Phase II upgraded array can be found inWayth et al. (2018)The surveyed coordinates of the different array configurations can be found here (note the multiple pages within the spreadsheet): MWA Tile Coordinates.xlsx
Data Lifecycle Policy:The MWA’s capacity to observe is more greatly limited by the volume of data products, than available time on sky. As a result, there are no particular restrictions on the number of available semester hours for 2023A, and scheduling priority will be given to the proposals ranked highest by the Time Allocation Committee. Following all proposal submissions for this Call, the MWA Operations Team will calculate the expected amount of data that will be ingested to the MWA data archive in 2023A. If there is inadequate storage space in the archive to support the requested observations, the MWA Operations Team will work with the MWA Principal Scientist to identify observations for deletion and begin a consultation process with the Collaboration. For more information on the MWA Data Retention Policy and Procedure, clickhere.
Fringe stopping: A newly-implemented process of keeping the correlation pointing centre at a fixed RA/Dec, allowing the use of longer correlator integration times and lower frequency resolutions (depending on the science case), significantly reducing the volume of visibilities produced. Click through to read more details onfringe stopping, thecorrelator modes, and otherrelevant technical information.
Detecting Exoplanetary Magnetic Field from a Neptune size Exoplanet Around the Young Solar-like star, DS TucA
We propose to observe the radio emission from a close-in warm Neptune around an active solar-like star, DS TucA, that will inform us about the exoplanetary magnetic field via interactions of the stellar wind and coronal mass ejections with the exoplanetary magnetosphere. Our radio observations has three key outcomes that include 1) the search for a highly polarized coherent radio emission in the 70MHz band associated with the stellar wind interaction with the magnetosphere of DS TucAb; 2) the search for a highly polarized coherent radio emission in the 70MHz band associated with a transient coronal mass ejection event interacting with the magnetosphere of DS TucAb; 3) constraints on the properties of “elusive” CMEs resulted in such star-planet interaction and constraints on the exoplanetary magnetic field.
Rapid-response triggering on O4 gravitational wave events with the Murchison Widefield Array
We request the use of the Murchison Widefield Array rapid-response mode to perform VCS triggered observations of gravitational wave-detected binary neutron star (BNS) and neutron star-black hole (NSBH) mergers during the O4 observing run with LIGO-Virgo-Kagra (LVK). While the prompt and early-time radio emission associated with BNS mergers is an unexplored regime, leading theories suggest that fast radio bursts (FRBs) may be related to these events (Totani, 2013; Zhang, 2014). LVK will broadcast very early-time (~seconds) BNS and BHNS merger arterts on which we can trigger rapid-response VCS observations. However, such alerts will have no positional information. Not only are GW notoriously hard to localise, they are also in the local Universe (<190 Mpc), making it difficult to rely on latency afforded by dispersion delay. Luckily, MWA is positioned under one of the two highest sensitivity sky regions of LVK. By employing a subarray configuration that covers a large portion of this sky region, we have a 12% chance of detecting coherent radio emission from a BNS merger when triggering a VCS observation. The LVK is projected to detect up to 20 BNS mergers per month. We therefore request to trigger on up to 10 events during O4 (beginning May 2023) during 2023A, of which we estimate up to 2 will be an MWA-detectable GW-FRB event. For each real event we require >3 hrs VCS recording to target all emission models (2 events, total 6 hrs recorded VCS data). When not in use, we request that MWA operates in a “no capture” mode pointed at the LVK high sensitivity region using our recommended sub-array pointings. On receiving a GW trigger, we request to download the voltage buffer data and continue observing the event. With low (and potentially negative) latency VCS data, we can target all BNS merger FRB emission mechanisms.
Y & N
30 total (~6 saved)
Advancing the Southern-sky MWA Rapid Two-metre (SMART) survey to completion
This proposal seeks telescope time to advance the SMART survey and bring its data collection effort to completion. The SMART survey is an all-sky pulsar search project that exploits the large field-ofview and voltage-capture capabilities of the MWA for conducting sensitive searches for pulsars and fast transients in the sky south of +30 deg in declination in the 140-170 MHz band. It capitalises on the compact configuration of the array for enormous beamforming efficiency in tessellating large parts of the sky. The substantial computational cost of pulsar searching at low frequencies necessitates data processing to be approached in multiple passes. The on-going first-pass processing, where we essentially perform a shallow survey for long-period pulsars, has already yielded promising results, and has thus far resulted in the discoveries of 5 pulsars, including 3 new ones, an independent discovery, and a rediscovery of a previously incorrectly characterised pulsar – all from analysis and scrutiny of a small fraction (∼5-10%) of data processed to date. Papers reporting the first pulsar discoveries, as well as a subsystem description paper on beamforming, have been published, and the first two in the SMART survey series have just been accepted for publication. Furthermore, with our commissioning effort over the past year successfully attaining the milestone of full coherent-beam sensitivity for the new tied-array software beamformer, the system is now ready for the next major campaign of SMART observations. In 2023A, we propose to undertake another intense observing campaign to cover the last remaining swathe of the sky in the 16-21 LST range which will accrue 1.6 PB of data from 25 hr of VCS observations. Besides the numerous science payoffs to result from the processing and analysis of data over the next several years, the SMART survey data will also serve as a valuable legacy data set and as an important reference for future large surveys planned with the SKA-Low.
Timing and spectropolarimetric observations of a long-period radio transient
New long-period radio transients have recently been detected, and their existence challenges previous under-standing of pulsar and magnetar emission mechanisms. By monitoring the Galactic plane in near real-time with the Murchison Widefield Array, we detected a new long-period radio transient with a repeating timescale of∼21minutes. Follow-up with the MWA and other telescopes has illuminated its broadband spectral and polarisation behaviour, and enabled precise timing measurements. Here, we request further follow-up of this source with the MWA to better unravel its low-frequency dynamic spectrum, accumulate further timing and pulse measurements, and co-observe with MeerKAT to examine its broadband spectro-polarimetric behaviour.
Space weather monitoring using pulsars as probes
Space weather refers to the conditions of heliospheric plasma flows (the “solar wind”) and transient eruptions such as coronal mass ejections (CMEs) and solar energetic particle events. This flow of particles provides the link between the Sun and Space Weather events in the terrestrial environment, which have potentially critical societal impacts. Despite decades of study, it remains difficult to remotely sense coronal mass ejections, in particular their magnetic field orientation, which has a huge impact on their geo-effectiveness. Existing methods for measuring solar wind and CME properties have limitations, and in-situ measurements from space probes are expensive and limited in number. To address these challenges, we propose to measure the properties of the solar corona, wind, and CMEs over a range of solar altitudes through regular monitoring of pulsars at low solar elongations. This pathfinder study will be the first serious observations of pulsars with the MWA during the daytime, and hence the first use of MWA pulsar observations for space weather studies.
MWA Observations of the Sun
A hundred hours of observing time for solar observations is requested during the 2023-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) and observations coordinated with various spacecraft and the updated GMRT (Goals E and F). 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. Goal F proposes coordinated observations with the upgraded GMRT to verify unexpected presence of linear polarization in some active solar emissions observed using the MWA.
Commissioning the commensal FRB search pipeline using the MWAX real-time beamformer
In the last few years, the FRB field witnessed significant breakthroughs. The first interferometric localisations by the ASKAP CRAFT team enabled redshift measurements, which ultimately confirmed extra-galactic origin of FRBs. At lower frequencies, CHIME detected large sample of repeating and non-repeating FRBs at frequencies between 400 – 800 MHz, and many of these FRBs were observed down to400 MHz – only 100 MHz above the highest observing frequencies of the MWA. Moreover, at least one of the CHIME repeating FRBs (FRB 20180916B) was also detected by LOFAR at frequencies down to110 MHz (the first ever FRB detections below 300 MHz). The LOFAR observations, coordinated with the APERTIF radio telescope operating at GHz frequencies, showed that the low-frequency bursts were typically observed at different epochs than the high frequency signals. This provides further evidence to conduct independent searches for low-frequency FRBs, as the low-frequency signals may not be simultaneous with bursts at higher frequencies (see also Sokolowski et al., 2018).This proposal is a continuation of the 2022A proposal G0086 for science commissioning of the real-time FRB search pipeline using incoherent beams implemented in the new MWA correlator (MWAX).We will continue using selected pulsars which are known to be bright and/or to emit bright single pulses. So far, the real-time pipeline has been tested on a single coarse channel (bandwidth 1.28 MHz), and the progress is described in this proposal. In 2023A we will focus testing the pipeline on more than 1frequency channel (at least 2) as the first step towards performing the real-time searches using the full MWA observing bandwidth of 30.72 MHz. We will also try to confirm detection of pulsars with higher DM (≳10). Although the sensitivity to FRBs in the incoherent mode is reduced by about a factor of≈11,our estimations based on the current FRB rates at these frequencies show that it should be possible to detect at least several FRBs per year assuming continuous sky observations and full observing bandwidth of 30.72 MHz. However, even initial non-detections can firmly establish FRB rates at frequencies below300 MHz, which are currently highly uncertain.
20 (+ engineering test time)
Rapid-response MWA observations of Swiftgamma-ray bursts
We request the use of the MWA rapid-response mode to perform triggered VCS observations of Swift detected short gamma-ray bursts (SGRBs) during the 2023A semester. The prompt and early-time radio emission associated with SGRBs is still a poorly explored regime, particularly at MHz frequencies. SGRBs are linked with binary neutron star (BNS) mergers and predicted to 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. As prompt radio emission becomes delayed with decreasing frequency due to dispersion, such signals associated with SGRBs 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 20 seconds of receiving an alert, MWA is uniquely capable of being on-target in time to observe the earliest prompt emission. The MWA VCS observation with its high temporal resolution is most suitable for searching for the prompt radio emission associated with SGRBs. We focus on Swift alerts, which, unlike Fermi alerts, provide ~arcsec localisations for GRBs. This enables us to localise the GRB to within a synthesised beam of MWA and coherently beamform the VCS data, which can maximize our sensitivity. Even with non-detection, such rapid-response MWA VCS observations have the sensitivities necessary to rule out some SGRB models, which will in-turn constrain different neutron star equation-of-state models. These experiments also directly test transient strategies for SKA-Low.
Survey at the Subaru HSC LAE fields
We propose 54 hours of MWA Observation at three different regions where the Subaru HSC surveyed Lyman alpha emitters (LAEs). The observing frequency range is 181.76-190.72 MHz and 202.24-221.44MHz. This radio signal corresponds to the redshifted 21 cm line at the cosmic reionization. The 21 cm line signal at the frequency originated from the neutral hydrogen atoms in the intergalactic medium (IGM). As the high-z galaxies are the candidate for ionizing sources of the IGM, the 21cm line signal correlates with the distribution of galaxies such as LAEs. The cross-correlation of the 21 cm line and galaxy is an important quantity to reveal the high-z galaxy evolution and the process of reionization. Subaru HSC surveyed COSMOS, DEEP23, and SXDS fields and found many LAEs at z=6.6 and 5.7. We attempt, therefore, the cross-correlation analysis between the 21 cm line observed with the MWA and the LAE distribution. As the total field of view is important to reduce the error of the cross-correlation, we proposed the MWA observation toward the 3 fields. By combining the 20 hours of data observed in 2017, the total data amount will be 74 hours. The data will be calibrated with the hyperdrive. The expected sensitivity should be low enough to constrain some cold and neutral IGM models once foregrounds such as Galactic synchrotron radiation are statistically removed.
MWA drift-scan observation at ultralow frequency
We propose 96 hours of MWA compact array drift scan observation covering the wide range of RA (21h to 5h) at the frequency range from 74.24 MHz to 103.68 MHz. The radio signal at the frequency range corresponds to the redshifted 21 cm line from the cosmic dawn where the first stars were formed. The 96 hours of observation data can achieve the sensitivity enough to detect the 21 cm power spectrum which is enhanced by excess radio background. The drift-scan observation fixed the beam toward the zenith allows us to use an accurate model of the MWA beam. The wide survey area reduces the cosmic variance. To use the gaussian process regression (GPR) based foreground removal method, we need to determine the model parameters using actual data. However, the result can be biased if there are a few samples. As we will have statistically independent realizations of foregrounds, we can improve the accuracy of GPR. We will attempt to improve the accuracy of calibration by fitting LST and frequency binned gain solution with a smooth function. The frequency range can suffer from RFI contamination, and therefore we fill the flagged visibility data by performing the gaussian process regression based inpainting. In this work, we attempt to improve the upper limits on the 21 cm power spectrum at z=15 and constrain models of the thermal history at high redshift.
Deep Imaging of Fields with MWA Compact Configuration
The exploration of the Epoch of Reionization (EoR) has been identified as a key scientific project for Phase I of the Square Kilometre Array (SKA1). To image the tomography of EoR structures, deep observations totalling 5000 hours will be conducted over five targeted areas of 20 square degrees using SKA1-Low. However, the tomographic imaging reconstruction for SKA1-low, as an interferometer at low frequencies, suffers from various systematic errors. The faint EoR signal is heavily obscured by bright foregrounds originating from our Galaxy and extragalactic sources. To achieve the desired detection sensitivity of ~1mK for future 1000-hour integration observations of each EoR field with SKA1-Low, pre-observations and pre-researches of a few selected fields with existing radio facilities over a wide waveband should be made in order to understand the ‘quietness’ and ‘cleanness’ of the candidate fields and their environmental effects, making predictions for large-scale structure observations In order to investigate the EoR foregrounds, we have observed several fields with the extended configuration of MWA II. In this proposal, we seek to observe two selected fields with the compact configuration of MWA to study large-scale structures, aiming at preparing for the upcoming SKA1 EoR observations.