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Session 79 - White Dwarf Stars.
Display session, Wednesday, January 15
White dwarf cosmochronology has for the past decade been used to provide independent age estimates for the local Galactic disk. One research group has, on the basis of the spindle form of the C--O phase diagram, argued that a large-scale redistribution of matter will occur such that after solidification the core will be more oxygen-rich and the mantle more carbon-rich than before solidification begins. These authors claim that the associated release of gravitational binding energy will provide a significant delay in the cooling timescale and hence increase by 10 to 20% the white dwarf cosmochronometric ages obtained by ignoring this proposed mixing process. This claim rests on the simple analytical argument that the C-rich material on the liquid side of the crystallization front will exhibit a Rayleigh-Taylor instabilty with the overlying C--O material, and that mixing will occur on a timescale which is short relative to the advance of the crystallization front. In this work, we explore this process by means of smoothed particle hydrodynamics simulations. We discuss the results of our simulations and the consequences for white dwarf cosmochronometric age estimates.
Program listing for Wednesday