The viscous evolution of white dwarf merger remnants
2012 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 427, no 1, 190-203 p.Article in journal (Refereed) Published
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.
Place, publisher, year, edition, pages
2012. Vol. 427, no 1, 190-203 p.
hydrodynamics, supernovae: general, white dwarfs
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-84772DOI: 10.1111/j.1365-2966.2012.21993.xISI: 000310675400016OAI: oai:DiVA.org:su-84772DiVA: diva2:582063