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Title: Multidimensional modeling of type I X-ray bursts. II. Two-dimensional convection in a mixed H/He accretor

Type I X-ray bursts are thermonuclear explosions of accreted material on the surface of 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 paper, the second 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 {sup 18}Ne(α, p){sup 21}Na, these calculations hint at further simplifications and improvements of the burning treatment for use in subsequent calculations in three dimensions for a future paper.
Authors:
 [1] ;  [2] ; ; ;  [3]
  1. Department of Astronomy and Astrophysics, The University of California Santa Cruz, Santa Cruz, CA 95064 (United States)
  2. Department of Physics and Astronomy, Stony Brook University, Stony Brook, NY 11794-3800 (United States)
  3. Center for Computational Sciences and Engineering, Lawrence Berkeley National Laboratory, Berkeley, CA 94720 (United States)
Publication Date:
OSTI Identifier:
22356611
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 788; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ALPHA REACTIONS; COMPRESSIBILITY; COSMOLOGY; HELIUM; HYDRODYNAMICS; MANY-DIMENSIONAL CALCULATIONS; NEON 18; NEUTRON STARS; NEUTRONS; NUCLEAR REACTIONS; PROTON-EMISSION DECAY; SIMULATION; SODIUM 21; SOUND WAVES; SUBSONIC FLOW; SURFACES; THERMONUCLEAR EXPLOSIONS; X RADIATION