Neutron Stars and Pulsar Timing
Stars with that have masses greater than about 8 times that of our Sun will end their lives in core-collapse supernovae. One of the potential remnants of these explosions is a neutron star, incredibly dense and compact objects host to extremely strong magnetic and gravitational fields. Some spinning neutron stars have be observed to emit beams of electromagnetic radiation from along their magnetic poles which we observe as periodic flashes of light. These neutron stars are referred to as pulsars
By precisely measuring the arrival time of these light pulses we can learn a swath of information about the properties of pulsars, attempt to detect gravitational waves originating from supermassive black holes, and undertake the some of the most precise tests of General Relativity.
Some pulsars have been observed to undergo sudden spin-up events, resulting in deviations in their measured pulse arrival times. These "glitches" in the pulsar spin are thought to arise either from a star-quake in the neutron star crust, or from coupling between the crust and superfluid interior of the star. Measurements of these glitches allow us to probe how matter behaves at the ultra-high densities that exist inside neutron stars.
In order to understand the global, population-level properties of pulsars, we must observe large samples of them. This is where the 'Parkes Young Pulsar Array' (P574) project comes in. By monitoring 270 pulsars over many years (some even back to the 1990s!), we have been able to learn a swathe of information about how their spin evolves with time, and even use them as tools to study the ionised gas that permeates the Galaxy. I am also involved in the 'Thousand Pulsar Array' project that operates on the MeerKAT telescope.
Magnetars
Magnetars are a class of slowly rotating neutron stars which posses the most powerful magnetic fields in the known universe. Many of these objects have been observed to emit extremely energetic x-ray and gamma-ray bursts. Of the 24 known magentars (see: the McGill magnetar catalogue), we have only ever observed 5 that emit pulsed radio emission similar to pulsars. These "radio loud" magnetars display large variations in their brightness and rotational stability over times, in addition to emitting remarkable millisecond-in-width spikes in their single-pulses.
Four such radio-loud magnetars are actively the careful watch of the Parkes Magnetar Monitoring Programme (P885). By studiously tracking their rotational and emissive properties, this project has uncovered several new and surprising behaviours in these extreme objects. This includes rare propagation effects in their magnetic fields, and sudden suppression of their radio emission.
Galactic Fast Radio Burst Analogues
Fast radio bursts (or "FRBs" for short) are brief, millisecond-duration flashes of radio waves that have been detected from distant galaxies. Despite first being identified in 2007, exactly how and where FRBs are produced remains a cosmic mystery. However, recent advances in the 2020s suggest that a significant fraction of FRBs are caused by magnetic explosions around magnetars. Several repeating sourcs of FRBs have also displayed some unusual behaviours that could indicate their progenitor objects reside in orbit around a star of some kind.
Determining exactly how FRBs are produced, and what sort of objects/systems they come from is challenging. The distances to them makes imaging the individual objects that cause FRBs extremely difficult, even those that come from nearby galaxies. However, there are several objects within our own Galaxy that we can use as proxies to better understand the astrophysics of FRBs. These include radio-emitting magnetars, for which one has been seen to emit extremely luminous radio bursts similar to geneuine FRBs, and pulsars that orbit main-sequence stars.