Dynamics of Laterally Propagating Flames in X-ray Bursts. II. Realistic Burning & Rotation

TL;DR

This study uses realistic physics in hydrodynamics simulations to analyze how neutron star rotation and thermal structure influence the behavior of flames in X-ray bursts, revealing conditions for steady burning and propagation.

Contribution

It introduces more realistic reaction rates, thermal conductivities, and rotation effects into simulations of flame propagation in X-ray bursts, improving upon previous approximations.

Findings

Lower rotation rates hinder flame ignition.

Higher rotation rates enhance nuclear burning and steady propagation.

Elevated crustal temperatures accelerate flame movement.

Abstract

We continue to investigate two-dimensional laterally propagating flames in type I X-ray bursts using fully compressible hydrodynamics simulations. In the current study we relax previous approximations where we artificially boosted the flames. We now use more physically realistic reaction rates, thermal conductivities, and rotation rates, exploring the effects of neutron star rotation rate and thermal structure on the flame. We find that at lower rotation rates the flame becomes harder to ignite, whereas at higher rotation rates the nuclear burning is enhanced by increased confinement from the Coriolis force and the flame propagates steadily. At higher crustal temperatures, the flame moves more quickly and accelerates as it propagates through the atmosphere. If the temperature is too high, instead of a flame propagating across the surface the entire atmosphere burns steadily. All of the software used for these simulations is freely available.