• Postdoc in the Department of Physics & Astronomy at Stony Brook University, NY.
  • Completed PhD entitled ‘Multiscale modelling of neutron star oceans’ in the Gravity Group of the Department of Mathematics at the University of Southampton 2014-2018.
  • I research type I X-ray bursts and convection in massive stars before they supernova by building computational simulations.
  • Fellow of the Software Sustainability Institute 2017.
  • I did my undergraduate and masters at Churchill College, University of Cambridge 2010-2014: Natural Sciences, MA MSci.
  • Experience coding in python, C++, fortran, CUDA, OpenMP, MPI, Java, Matlab.
  • In my free time, I like to bake (& eat) lots of cake, listen to music and do taekwondo.
  • I drink a lot of coffee.

Research

Convection in the cores of massive stars

When massive stars (i.e. stars with masses greater than 8 solar masses) reach the ends of their lives, they explode as a core-collapse supernova. Prior to this, the structure of the star is very complex, with many distinct layers. The exact structure and composition of these layers is very important to the late-time evolution of the star and the subsequent supernova. Due to their complexity, the extreme conditions involved and the stars’ shear size, modelling these systems is incredibly challenging. In order to properly capture the mixing between layers, 3d modelling is required, but this is very expensive computationally. To make this problem tractable, new numerical methods are therefore required. The MAESTROeX code uses the low Mach number approximation to filter out sound waves. In my work, I will be using this code to investigate the effects of rotation in convective cores.

Type I X-ray bursts

For my PhD thesis, I considered type I X-ray bursts. This is something which I am continuing to work on at Stony Brook.

Type I X-ray bursts are thermonuclear explosions which occur on the surface of accreting neutron stars. It is believed that the burning begins in a localised spot in the ocean of the star before spreading across the entire surface. Burning begins in a localised spot in the star’s ocean layer before spreading across the entire surface. By gaining a better understanding of X-ray bursts, tighter limits can be determined for other neutron star properties such as the mass, radius, spin frequency and magnetic field. The ocean environment is very extreme, involving much higher pressure, temperature and magnetic field strength compared to the conditions typically found in terrestrial systems. In my work, I am particularly interested in looking at the effects of the strong gravitational field, modelling the ocean using general relativistic hydrodynamics.

Modelling bursts

The physics of bursts covers a wide range of scales, which introduces a number of challenges when modelling them. We use the multiscale approach to couple together multiple physical models in order to best capture the physics across these various scales. On the smallest scales, the physics is dominated by turbulent burning. The speed of propagation of the burning front is much slower than the acoustic speed, making it difficult to model this with conventional numerical schemes. We therefore instead use the low Mach number approximation, which we have derived and implemented for the relativistic fluid equations based on the existing approach deveoped for the Newtonian case. On larger scales, the burning front can be thought of as a discontinuity. To model this, we investigate the reactive Riemann problem for relativistic deflagrations and detonations and develop a numerical solver. The large scale propagation of the burning front is believed to be dominated by the Coriolis force. To capture this behaviour, we have derived and implemented a model for the relativistic form of the shallow water equations.

My current work involves building hybrid scheme to combine the best features of these approximations, extending existing adaptive mesh refinement techniques to include different physical models at different scales.