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arXiv · 1205.6517

Laterally Propagating Detonations in Thin Helium Layers on Accreting White Dwarfs

Dean M. Townsley·Kevin Moore·Lars Bildsten
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Abstract

Theoretical work has shown that intermediate mass (0.01Msun 0.8Msun) WDs, these helium shells can be dense enough (5x10^5 g/cc) that the convectively burning region runs away on a timescale comparable to the sound travel time across the shell; raising the possibility for an explosive outcome. The nature of the explosion (i.e. deflagration or detonation) remains ambiguous. In the case of detonation, this causes a laterally propagating front whose properties in these geometrically thin and low density shells we begin to study here. Our calculations show that the radial expansion time of <0.1 s leads to incomplete helium burning, in agreement with recent work by Sim and collaborators, but that the nuclear energy released is still adequate to realize a self-sustaining detonation propagating laterally at slower than the Chapman-Jouguet speed. Our simulations resolve the subsonic region behind the front and are consistent with a direct computation of the reaction structure from the shock strength. The ashes are typically He rich, and consist of predominantly Ti-44, Cr-48, along with a small amount of Fe-52, with very little Ni-56 and with significant Ca-40 in carbon-enriched layers. If this helium detonation results in a Type Ia Supernova, its spectral signatures would appear for the first few days after explosion. (abridged)

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Dean M. Townsley, Kevin Moore, Lars Bildsten. 2012-05-29. Laterally Propagating Detonations in Thin Helium Layers on Accreting White Dwarfs. https://doi.org/10.1088/0004-637x/755/1/4

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