Pulsars are fabulous tools for probing the interstellar medium (ISM) of our Galaxy. Their radiation appears pulsed to observers; it is spatially coherent and highly polarised – an ideal combination that enables these beamed radio signals to carry imprints of the ionised, turbulent and magneto-ionic properties of the media through which they propagate before arriving at radio telescopes. At the low radio frequencies (i.e. longer wavelengths) in which the Murchison Widefield Array (MWA) operates, these propagation effects are also hugely magnified as a result of the strong dependencies with the observing frequency. This makes pulsars unique probes of ISM structure of at micro- to milli-arcsecond scales that are inaccessible by other observational means. ISM effects lead to delays, distortions and modulations of pulsar signals, resulting in substantial sources of ‘noise’ in timing datasets, which must be accurately modelled in science applications such as pulsar timing arrays (PTAs).
PTAs are Galactic-scale gravitational-wave detectors consisting of a celestial distribution of the most stable millisecond-period pulsars that are timed regularly over many years. It is our primary method for advancing nanohertz-frequency gravitational-wave astronomy, opening a new window for probing the Universe. It allows us to study the supermassive binary black-hole populations and the physics of the early Universe. This is a key science driver for the Square Kilometre Array (SKA) project. Recent evidence supporting an all-sky gravitational-wave background signature in multiple PTA datasets is regarded as one of the most significant discoveries in modern physics. In order to advance this new field further, and increase the detection sensitivity of current and future PTAs, low-frequency data sets are essential, as they will allow us to mitigate or account for the timing ‘noise’ resulting from ISM effects. The Murchison Widefield Array (MWA) is especially promising for this, as the sole low-frequency capable facility in the southern hemisphere and as the official Australian precursor for SKA-Low, the low-frequency component of SKA Observatory (SKAO).
Aim
This project will take advantage of the new and advanced capabilities of the upgraded MWA (Phase III) to establish a pulsar monitoring program at low radio frequencies, sampling hundreds of pulsar sight lines at regular cadence. It will develop state-of-the-art processing pipelines, to facilitate a careful assessment of interstellar delays and propagation effects in datasets. It will also develop and explore new techniques to exploit the voltage beam data products obtainable using the upgraded MWA, for novel applications such as ‘cyclic spectroscopy’ that can yield improved interstellar corrections in PTA datasets, and potentially even a holographic reconstruction of the ISM at very small (sub-au) physical scales. This will lead to new insights into the micro-structure and physics of the ISM, alongside providing measurements and datasets that are of great value for PTA noise modelling and science.
Objectives
(1) Undertake early science projects using the new beamformer capability developed for the upgraded (Phase III) MWA, to showcase high-fidelity pulsar measurements that are now attainable in observations of bright millisecond pulsars.
(2) Set up and establish a pulsar monitoring programme, sampling many pulsar sight lines at regular cadence, and develop the processing and analysis pipelines for routine data processing.
(3) Systematic analysis of new data sets for detailed characterisation of the ISM, eventually leading to a tomographic view of the local ISM that is highly relevant for the majority of PTA pulsars.
Significance
Gearing up the MWA as a premier pulsar monitoring facility in the southern hemisphere will be a game changer for low-frequency pulsar astronomy in the southern hemisphere. It will also facilitate wide-ranging high-time resolution science that rely on regular monitoring. The MWA has already demonstrated its potential for making high precision measurements of ISM properties in millisecond pulsar observations. Datasets from a high-cadence monitoring project will have a great legacy value for the global PTA efforts, and will become a treasure trove for ISM science, especially for probing the ISM physics at small physical scales that are inaccessible by any other types of observations.
Ideal Candidate
The candidate should have a sound background in physics and astrophysics, and a strong inclination for developing or exploring novel signal processing techniques, and to develop/implement analysis pipelines that will run on high-performance supercomputers. A background in radio astronomy with some research experience is an additional advantage. Familiarity with high performance computing and signal processing in radio astronomy is desirable. Additionally, the applicants should meet the eligibility criteria for entry into a PhD program at Curtin University.
This project is open to International and Domestic applicants.
Scholarship
If you are identified as the preferred candidate for this project, you may be considered for an RTP scholarship.
Enquires and How to Apply
For enquires about this opportunity contact Dr Ramesh Bhat at Ramesh.Bhat@curtin.edu.au
To formally apply submit an Expression of Interest to Dr Ramesh Bhat during the Central Scholarship round (July 1st – July 31st 2026)