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arXiv · 1010.1529

The formation of high-field magnetic white dwarfs from common envelopes

J. Nordhaus·S. Wellons·D. S. Spiegel·B. D. Metzger·E. G. Blackman
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Abstract

The origin of highly-magnetized white dwarfs has remained a mystery since their initial discovery. Recent observations indicate that the formation of high-field magnetic white dwarfs is intimately related to strong binary interactions during post-main-sequence phases of stellar evolution. If a low-mass companion, such as a planet, brown dwarf, or low-mass star is engulfed by a post-main-sequence giant, the hydrodynamic drag in the envelope of the giant leads to a reduction of the companion's orbit. Sufficiently low-mass companions in-spiral until they are shredded by the strong gravitational tides near the white dwarf core. Subsequent formation of a super-Eddington accretion disk from the disrupted companion inside a common envelope can dramatically amplify magnetic fields via a dynamo. Here, we show that these disk-generated fields are sufficiently strong to explain the observed range of magnetic field strengths for isolated, high-field magnetic white dwarfs. A higher-mass binary analogue may also contribute to the origin of magnetar fields.

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J. Nordhaus, S. Wellons, D. S. Spiegel, B. D. Metzger, E. G. Blackman. 2010-10-07. The formation of high-field magnetic white dwarfs from common envelopes. https://doi.org/10.1073/pnas.1015005108

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