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Paper: Rotation and Strong Magnetism of White Dwarfs
Volume: 493, 19th European Workshop on White Dwarfs
Page: 71
Authors: Kissin, Y.; Thompson, C.
Abstract: We study the co-evolution of rotation and magnetism during the post-main sequence expansion of 1 and 5 M stars. The magnetic field is sourced by a dynamo operating near the core-envelope boundary, which is driven by the downward pumping of angular momentum though the envelope. In stars with strong and magnetized main-sequence winds, this angular momentum must be supplied by a binary planetary or stellar companion. Magnetic helicity is advected into the growing core as the magnetic field enforces solid-body rotation there, corresponding to a dipolar magnetic field ∼ 106–107 G in the white dwarf (WD) remnant. We estimate the residual spin that results from a shutoff of the dynamo, combined with decoupling of core and envelope, during the last stages of the AGB. Only a thin magnetized layer is left behind in a massive WD: the ohmic transport time is typically less than a Gyr, suggesting that the incidence of strong magnetism in massive WDs will be observed to decrease with age.
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