Effects of Tangential Velocity in the Reactive Relativistic Riemann Problem
Abstract
Type I Xray bursts are thermonuclear burning events that occur on the surfaces of accreting neutron stars. Burning begins in a localized spot in the star’s ocean layer before propagating across the entire surface as a deflagration. On the scale of the entire star, the burning front can be thought of as discontinuity. To model this, we investigated the reactive Riemann problem for relativistic deflagrations and detonations and developed a numerical solver. Unlike for the Newtonian Riemann problem, where only the velocity perpendicular to the interface is relevant, in the relativistic case the tangential velocity becomes coupled through the Lorentz factor and can alter the waves present in the solution. We investigated whether a fast tangential velocity may be able to cause a deflagration wave to transition to a detonation. We found that such a transition is possible, but only for tangential velocities that are a significant fraction of the speed of light or for systems already on the verge of transitioning. Consequently, it is highly unlikely that this transition would occur for a burning front in a neutron star ocean without significant contributions from additional multidimensional effects.
 Publication:

The Astrophysical Journal
 Pub Date:
 October 2019
 DOI:
 10.3847/15384357/ab40ab
 arXiv:
 arXiv:1806.07301
 Bibcode:
 2019ApJ...884..110H
 Keywords:

 stars: neutron;
 Xrays: binaries;
 Xrays: bursts;
 Astrophysics  High Energy Astrophysical Phenomena;
 Physics  Fluid Dynamics
 EPrint:
 16 pages, 10 figures, Accepted for publication in ApJ