Multidimensional Modeling of Type I X-ray Bursts. II. Two-Dimensional Convection in a Mixed H/He Accretor

Abstract

Type I X-ray Bursts (XRBs) are thermonuclear explosions of accreted material on the surfaces of a neutron stars in low mass X-ray binaries. Prior to the ignition of a subsonic burning front, runaway burning at the base of the accreted layer drives convection that mixes fuel and heavy-element ashes. In this second paper in a series, we explore the behavior of this low Mach number convection in mixed hydrogen/helium layers on the surface of a neutron star using two-dimensional simulations with the Maestro code. Maestro takes advantage of the highly subsonic flow field by filtering dynamically unimportant sound waves while retaining local compressibility effects, such as those due to stratification and energy release from nuclear reactions. In these preliminary calculations, we find that the rp-process approximate network creates a convective region that is split into two layers. While this splitting appears artificial due to the approximations of the network regarding nuclear flow out of the breakout reaction 18Ne(a,p)21Na, these calculations hint at further simplifications and improvements of the burning treatment for use in subsequent calculations in three dimensions for a future paper.

arXiv commentsubmitted to ApJ

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Cited by in corpus (20)

• Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra
• Equation of state constraints for the cold dense matter inside neutron stars using the cooling tail method
• Nuclear Physics of the Outer Layers of Accreting Neutron Stars
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Angular momentum fluctuations in the convective helium shell of massive stars
• Detection of burning ashes from thermonuclear X-ray bursts
• MAESTROeX: A Massively Parallel Low Mach Number Astrophysical Solver
• Meeting the Challenges of Modeling Astrophysical Thermonuclear Explosions: Castro, Maestro, and the AMReX Astrophysics Suite
• Model Atmospheres for X-ray Bursting Neutron Stars
• Dynamics of Laterally Propagating Flames in X-ray Bursts. I. Burning Front Structure
• X-ray burst ignition location on the surface of accreting X-ray pulsars: Can bursts preferentially ignite at the hotspot?
• Dynamics of Laterally Propagating Flames in X-ray Bursts. II. Realistic Burning & Rotation
• The imprint of convection on Type I X-ray bursts: Pauses in photospheric radius expansion lightcurves
• Thermal convection in rotating spherical shells: temperature-dependent internal heat generation using the example of triple-$\alpha$ burning in neutron stars
• Toward Resolved Simulations of Burning Fronts in Thermonuclear X-ray Bursts
• Thermonuclear (Type Ia) Supernovae and Progenitor Evolution
• Hydrodynamical simulations of proton ingestion flashes in Type I X-ray Bursts
• Simulating Lateral H/He Flame Propagation in Type I X-ray Bursts
• The onset of low Prandtl number thermal convection in thin spherical shells
• Modelling low Mach number stellar hydrodynamics with MAESTROeX