2-dimensional Helium Detonations on the Surface of Neutron Stars

We present two-dimensional hydrodynamic simulations of helium detonations on the surfaces of neutron stars performed with the FLASH Code -- a multidimensional, adaptive hydrodynamics code developed at the Center for Astrophysical Thermonuclear Flashes at the University of Chicago. These calculations show the evolution of the detonation as it breaks through the atmosphere of the neutron star and propagates across the surface. The calculation shows a series of surface waves propagating behind the detonation, and the bouncing of the atmosphere as the detonation evolves. The sensitivity of the results to spatial resolution and initial conditions are explored. The event is followed as the detonation travels 2 km across the surface of the neutron star. The detonation velocity implies a timescale of a few milliseconds to propagate around the star. The relevance of such a model to observed X-ray bursts is discussed.