Starfire: Simulating Thermonuclear Ignition Neutron Stars

Supervisory team:
Prof. Diego Altamirano and Dr. João Mendonça

What happens when nuclear fire races across the surface of a neutron star? This project uses numerical simulations to study how thermonuclear X-ray bursts ignite and spread, linking computational models with observations. You will develop transferable coding skills while exploring extreme astrophysics, with applications extending to stellar explosions and exoplanet atmospheres.

Type I X-ray bursts—also known as thermonuclear bursts—occur on the surfaces of neutron stars in low‑mass X‑ray binary systems. As gas from a companion star accretes onto the neutron star, it spreads across the surface and forms a layer of fresh material. Under the star’s immense gravity, this layer becomes compressed and heated until it reaches the critical temperature and density required for thermonuclear ignition.

At that point, nuclear fusion of hydrogen begins, rapidly converting hydrogen into helium and later to heavier elements. The resulting runaway nuclear burning releases an enormous amount of energy in the form of X‑rays—an a burst lasting only seconds to minutes, yet radiating more energy than the Sun emits in a week. These bursts provide a unique observational window into the extreme physical conditions found on neutron star surfaces.

In this project, you will develop and run numerical simulations to model how the burning front spreads across the neutron star once ignition occurs. The results will be compared with observational data and theoretical predictions to refine our understanding of thermonuclear processes in compact stars.

Beyond neutron stars, you will also explore how the computational tools and methods developed here can be applied to other astrophysical and planetary contexts—such as flame propagation in other stellar environments and atmospheric dynamics on exoplanets.

You will join the High‑Energy Astrophysics Group at the University of Southampton and collaborate with leading researchers worldwide. We are looking for a candidate who enjoys programming and has strong coding skills, with enthusiasm for using computational methods to tackle challenging astrophysical problems.

You must have a UK 2:1 honours degree, or its international equivalent.

Essential skills:

• strong, well‑developed programming and coding skills
• enthusiasm for using computational methods to address challenging problems
• ability to solve complex problems and tackle demanding computational tasks

Desirable skills:

• experience applying computational techniques to astrophysical problems
• an interest in astrophysics and computational research
• experience with scientific computing, modelling, or simulation

We offer a range of funding opportunities for both UK and international students. Horizon Europe fee waivers automatically cover the difference between overseas and UK fees for qualifying students.

Competition‑based Presidential Bursaries from the University cover the difference between overseas and UK fees for top‑ranked applicants.

Competition‑based studentships offered by our schools typically cover UK‑level tuition fees and a stipend for living costs for top‑ranked applicants.

Funding will be awarded on a rolling basis, so apply early for the best opportunity to be considered.

For more information, please visit our postgraduate research funding pages.

If you have a general question, email our Doctoral College (doctoral co).

For an initial conversation, email Professor Diego Altamirano ().