Dr Aidan Hotan

Research interests

Neutron stars, in the form of radio pulsars and magnetars. Unlocking the secrets of the pulsar emission mechanism through high-resolution observations and using pulsars to test our understanding of fundamental physical theories.

The death of a massive star can leave behind an incredibly dense, compact object called a neutron star. These tiny stars hold 1.3 times the mass of the Sun but are only about 10 km in radius! Though extremely compact, neutron stars lie at the heart of many extremely interesting astronomical sources. They tend to be magnetised and rapidly spinning, which can lead to the release of large amounts of energy. Spinning neutron stars that produce directed beams of radiation are called pulsars. Their distinctive signal is similar to the regular flashing of a light-house beacon. The arrival times of pulsar pulses can reveal a wide range of information about the source. The highly regular nature of the signal from a pulsar can also be exploited to test theories of gravity and particle physics in other regions of the Milky Way galaxy!

Young pulsars are particularly bright and are sometimes associated with the gaseous remnants of the star from which they formed. Sometimes older pulsars are spun-up as they capture matter from a binary companion, leading to rotation periods of only a few milliseconds. These different kinds of pulsars provide pieces of a complicated puzzle that we are still a long way from solving. More recently, astronomers have discovered that neutron stars with extremely strong magnetic fields can produce energy through the decay of the magnetic field itself, unifying two classes of object (anomalous X-ray pulsars and soft gamma repeaters) that were once thought to be completely different. Since 2006, pulsed radio emissions from these so-called magnetars have opened up a new way to study yet another form of neutron star.

I study the radio signals from neutron stars with very high time resolution, using advanced electronic recording techniques. An investigation into the complicated structure and energy distribution of single pulses from the young Vela pulsar is currently underway, in collaboration with the University of Tasmania. I am also helping to analyse the structure and polarisation of pulses from a rare class of pulsar (known as a RRAT) that spends most of its time turned off. Future plans include the establishment of a magnetar monitoring experiment at the Ceduna radio telescope, to catch energetic and unpredictable outbursts from these new sources.