Journal
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
Volume 427, Issue 1, Pages 190-203Publisher
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2012.21993.x
Keywords
hydrodynamics; supernovae: general; white dwarfs
Categories
Funding
- NSF AST [0905801]
- Office of Science of the US Department of Energy [DE-AC02-05CH11231]
- NSF
- David and Lucile Packard Foundation
- Thomas and Alison Schneider Chair in Physics
- NASA [PF1-120088, NAS8-03060]
- Deutsche Forschungsgemeinschaft [RO-3399/4-1, RO-3399/4-2]
- Direct For Mathematical & Physical Scien [905801] Funding Source: National Science Foundation
- Division Of Astronomical Sciences [905801] Funding Source: National Science Foundation
- Division Of Astronomical Sciences
- Direct For Mathematical & Physical Scien [1206097] Funding Source: National Science Foundation
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The merger of two white dwarfs (WDs) creates a differentially rotating remnant which is unstable to magnetohydrodynamic instabilities. These instabilities can lead to viscous evolution on a time-scale short compared to the thermal evolution of the remnant. We present multidimensional hydrodynamic simulations of the evolution of WD merger remnants under the action of an alpha-viscosity. We initialize our calculations using the output of eight WD merger simulations from Dan et al., which span a range of mass ratios and total masses. We generically find that the merger remnants evolve towards spherical states on time-scales of hours, even though a significant fraction of the mass is initially rotationally supported. The viscous evolution unbinds only a very small amount of mass (less than or similar to 10(-5)M(circle dot)). Viscous heating causes some of the systems we study with He WD secondaries to reach conditions of nearly-dynamical burning. It is thus possible that the post-merger viscous phase triggers detonation of the He envelope in some WD mergers, potentially producing a Type Ia supernova via a double-detonation scenario. Our calculations provide the proper initial conditions for studying the long-term thermal evolution of WD merger remnants. This is important for understanding WD mergers as progenitors of Type Ia supernovae, neutron stars, R Coronae Borealis stars and other phenomena.
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