Pulsars—rapidly spinning neutron stars that beam radio waves like cosmic lighthouses—are notoriously difficult to time with precision because their pulses change shape and timing in unpredictable ways. This project builds a new mathematical framework to track those changes. Current timing methods treat each pulse as a simple tick, but pulsars often glitch, switch between emission modes, or suffer from timing noise that blurs their signals. The team will use simulation-based inference and hierarchical recycling to connect millions of individual pulses across long time spans, correcting for these distortions. They will analyse archival data from the MeerKAT telescope in South Africa, Jodrell Bank Observatory, and Tasmania’s Mt Pleasant Radio Observatory. If successful, the work will sharpen the sensitivity of pulsar timing arrays—networks of pulsars used as a galactic-scale detector for low-frequency gravitational waves. That could enable the first detection of the stochastic gravitational-wave background, a faint rumble from merging supermassive black holes across the universe. The method will also reveal new details about neutron star interiors, including superfluidity and the behaviour of matter at extreme densities. This is fundamental science: it will not change daily life directly, but it lays the groundwork for the Square Kilometre Array, which will discover thousands more pulsars and open a new window on gravity and matter.
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Since their discovery, observations of the lighthouse-like rotating neutron stars known as pulsars have produced deep insights into fundamental physics, from superfluidity and the nature of matter at supranuclear densities to the most precise tests of strong gravity. Furthermore, by carefully timing an array of pulsars, international teams now stand on the precipice of making the first detection of the stochastic gravitational-wave background and opening up the low-frequency gravitational-wave spectrum. This proposal aims to build and apply a new hierarchical profile-domain timing framework with game-changing potential to better time and learn about pulsars that exhibit correlated changes in their timing and shape properties. We will innovate with state-of-the-art Simulation-based Inference to speed up inference by orders of magnitude and apply hierarchical recycling to enable us to phase-connect millions of pulsations. Our methodology will allow us to improve precision timing for pulsar timing arrays by modelling frequency and polarisation evolution and studying the white noise known as jitter. We will also study pulsar astrophysics, such as glitches, mode-nulling/switching, and timing noise, seeking to deliver new insights about the nature of neutron stars and their environments. Together with international project partners, we will study archival data from the MeerKAT Thousand Pulsar Array data set, the STFC-supported Jodrell Bank Observatory (JBO), Mt Pleasant Radio Observatory (MPRO) in Tasmania, and others. In the long term, this work will build the foundation for our group to contribute to analysing data from the forthcoming Square Kilometre Array (SKA), which will revolutionise the radio view of pulsars. Its unprecedented sensitivity and large field of view will enable an order of magnitude increase in the number of known pulsars and regular high-fidelity timing of a large swath of the population. Our project will succeed because we bring together domain-specific knowledge, a history of innovation across astrophysics, leadership experience, technical experts to overcome existing computational challenges, project partners with access and expertise on pertinent data, a passionate and involved supervisory team, and a supportive environment to foster the necessary creativity. Our project is important as we will develop a new approach to pulsar timing with game-changing potential to improve the resolution of pulsar timing arrays, generate new insights into neutron star astrophysics, and pave the way to grow Royal Holloway's new astronomy group and contribute to SKA science.
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