# Physics

I recently completed a PhD under the supervision of Dr Andrew Melatos in the Astrophysics group at the University of Melbourne. My main research interests are neutron stars, magnetars, and gravitational waves.

### Gravitational waves from pulsar glitches

In a pulsar glitch, a sudden increase in frequency (spin up of the crust) is observed followed by a longer recovery period where the crust and interior fluid relax via viscous interactions. Differential rotation between crust and core generates Ekman pumping throughout the interior.

Ekman pumping is the process by which a liquid interior spin-up to match a differentially rotating crust. Compressibility and buoyancy act to decrease the penetration of the spin-up flow throughout the interior. These movies of cylindrical spin-up show extent to which different regions of the interior are spun-up by Ekman pumping for different values of compressibility and buoyancy.

Nonaxisymmetric interior flow inside a pulsar following a glitch produces a gravitational wave signal, which depends on these properties of the neutron star interior. Future gravitational wave observations will provide information about the nature of bulk nuclear matter under conditions that cannot be replicated in experiments on Earth.

For more details, see our paper on arXiv or ADS.

### Gravitational wave searches with higher criticism

We proposed a new method to enhance searches for periodic gravitational wave sources, such as rotating elliptical neutron stars, using a modified form of higher criticism, a statistical technique introduced by Donoho and Jin (2004). Compared to a direct search aiming to identify a single, bright source, higher criticism is designed to detect the presence of a collection of weak sources, none of which are strong enough to be reliably estimated or detected individually.

We applied higher criticism to simulated F-statistic and C-statistic values for a targeted search for a periodic source in a binary system. One advantage of higher criticism is its robustness to uncertainty in the source parameters. Under optimal conditions (i.e. binary orbit known exactly), higher criticism provided a 6% sensitivity increase, however this increased to > 30% for an unknown, phase-wandering source.

For more details, see our paper on arXiv or ADS.

### Publications

- Bennett & Melatos, 2014,
*Stochastic Microhertz Gravitational Radiation from Stellar Convection*, ApJ, 792 arXiv ADS - Lasky, Bennett & Melatos, 2013,
*Stochastic gravitational wave background from hydrodynamic turbulence in differentially rotating neutron stars*, PhysRevD, 87 arXiv ADS - Bennett, Melatos, Delaigle & Hall, 2013,
*Reanalysis of F-statistic gravitational-wave searches with the higher criticism statistic*, ApJ, 766 arXiv ADS - Abadie et al, 2011,
*Search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar*, PhysRevD, 83 arXiv ADS - Bennett, van Eysden & Melatos, 2010,
*Continuous-wave gravitational radiation from pulsar glitch recovery*, MNRAS, 409 arXiv ADS