http://arxiv.org/abs/1910.08582
Understanding the origin of the magnetic fields in white dwarfs (WDs) has been a puzzle for decades. A scenario that has gained considerable attention in the past years assumes that such magnetic fields are generated through a dynamo process during common-envelope evolution. We performed binary population models using an up-to-date version of the BSE code to confront the predictions of this model with observational results. We found that the hypothesis that the WD magnetic field is generated during common-envelope evolution cannot explain the observed distribution of WD magnetic fields in polars and pre-polars. The model also fails in explaining the dominance of low-temperature WDs in pre-polars. Finally, the model predicts that nearly all cataclysmic variables and ~80-90 per cent of close detached WD+M-dwarf binaries should be magnetic, which is in dramatic disagreement with the observations. Therefore, either the common-envelope dynamo scenario should be substantially revised or an alternative process is generating the strong WD magnetic fields in close WD binaries.
D. Belloni and M. Schreiber
Tue, 22 Oct 19
74/91
Comments: submitted to MNRAS Letter, comments are welcome
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