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.

submitted to ApJ

References in corpus (3)

• Thermonuclear (type-I) X-ray bursts observed by the Rossi X-ray Timing Explorer
• Nucleosynthesis in Type I X-ray Bursts
• Low Mach number modeling of Type I X-ray burst deflagrations

Cited by in corpus (5)

• Neutron star mass and radius measurements from atmospheric model fits to X-ray burst cooling tail spectra
• Thermonuclear Bursts with Short Recurrence Times from Neutron Stars Explained by Opacity-Driven Convection
• Detection of burning ashes from thermonuclear X-ray bursts
• Model Atmospheres for X-ray Bursting Neutron Stars
• X-ray burst ignition location on the surface of accreting X-ray pulsars: Can bursts preferentially ignite at the hotspot?