Hydrodynamic Simulations of X-ray Bursts Winds

Neutron stars (NSs) in low-mass X-ray binaries accrete hydrogen and helium from a companion star. This accreted matter can ignite on the NS surface in a thermonuclear explosion, resulting in a bright X-ray flash known as a Type I X-ray burst. Such bursts provide crucial insights into the properties of NSs and the accretion process. About 20% of bursts are photospheric radius expansion bursts, in which the peak luminosity exceeds the Eddington limit and radiation forces drive an optically thick wind. We are carrying out time-dependent simulations of burst winds. Our calculations, which currently use the MESA stellar evolution code, will eventually be integrated with the general relativistic radiation-hydrodynamic code Athena++. These will be the first simulations of burst winds in full general relativity and provide realistic synthetic spectra that can be directly compared to observations and help better constrain important NS parameters.