Simulations of X-ray Bursts

Flame spreading in X-ray bursts

We are using Castro to model the flame spreading across the surface of the neutron star. Our simulations resolve the burning front and the Rossby length (the scale where the Coriolis force and lateral spreading balance), allowing us to model the development and propagation of realistic flames moving through the neutron star atmosphere. Realistic nuclear reaction networks and conductivities are used.

Our goal of these studies is to learn how fast these flames can acceleration, understand any multidimensional effects that might help explain burst oscillations, and to explore the nucleosynthesis.

time series of XRB flame propagation

A time-series of a pure He flame moving across the surface of a neutron star, from Eiden et al. 2020.

volume renderings of the 3D flame view from above showing abar and nuclear energy generation

Volume renderings viewed from above of the 3D flame spreading simulation showing mean-molecular weight and nuclear energy generation rate, from Zingale et al. 2023.

Our results are described in the following papers:

Convection in X-ray bursts

We are modeling mixed H/He X-ray bursts with our low Mach number hydrodynamics code Maestro. The nucleosynthesis is described by a 10-nuclei network that approximates hot-CNO, 3-alpha, and rp-process breakout. These simulations are done in a plane-parallel geometry, with a 6 cm resolution. These calculations follow on from our initial pure He simulations. Our goal is to understand how a multi-dimensional treatment of the convection alters the nucleosynthesis.

Our results are described in the following papers:

Here's a model of the three-dimensional convection: