Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 2003
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003aas...20314005g&link_type=abstract
American Astronomical Society Meeting 203, #140.05; Bulletin of the American Astronomical Society, Vol. 36, p.586
Astronomy and Astrophysics
Astronomy
Scientific paper
We model a thermonuclear explosion of a carbon-oxygen white dwarf (WD) using a three-dimensional (3D) hydrodynamic model based on reactive Euler equations coupled with a simplified four-equation kinetic scheme. Our previous 3D numerical simulations of the deflagration stage of the explosion have shown that the deflagration leaves large amounts of unburned carbon and oxygen near the center of the star. This disagrees with observations and suggests that the deflagration may trigger a detonation. We study this possibility by igniting a detonation at 1.5-1.6 s after the beginning of the deflagration phase. By that time, the turbulent combustion and convective flows produce a very inhomogeneous mixture of burned and unburned materials that extends from the center to about 0.5-0.8 of the radius of the expanding WD. The detonation is ignited near the WD center and propagates through the layers of unburned material with the velocity about 12,000 km/s, which is comparable to the expansion velocities induced in outer layers of the WD by the subsonic burning. The detonation releases additional energy, burns all carbon and oxygen in central parts of the WD to iron-group elements, produces intermediate-mass elements in low-density outer layers, and leaves a layer of unburned material near the WD surface. The resulting explosion parameters are in agreement with observations.
This work was supported in part by the NASA ATP program (NRA-02-OSS-01-ATP) and by the Naval Research Laboratory (NRL) through the Office of Naval Research. Computing facilities were provided by the DOD HPCMP program.
Gamezo Vadim N.
Khokhlov Alexei M.
Oran Elaine S.
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