A1 Refereed original research article in a scientific journal
Circular polarimetry of suspect wind-accreting magnetic pre-polars
Authors: Hakala Pasi, Parsons Steven G., Marsh Thomas R., Gansicke Boris T., Ramsay Gavin, Schwope Axel, Hermes J. J.
Publisher: OXFORD UNIV PRESS
Publication year: 2022
Journal: Monthly Notices of the Royal Astronomical Society
Journal acronym: MON NOT R ASTRON SOC
Volume: 513
Issue: 3
First page : 3858
Last page: 3870
Number of pages: 13
ISSN: 0035-8711
eISSN: 1365-2966
DOI: https://doi.org/10.1093/mnras/stac1111
Web address : https://academic.oup.com/mnras/article/513/3/3858/6573877
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/175454828
We present results from a circular polarimetric survey of candidate detached magnetic white dwarf - M dwarf binaries obtained using the Nordic Optical Telescope, La Palma. We obtained phase resolved spectropolarimetry and imaging polarimetry of seven systems, five of which show clearly variable circular polarisation. The data indicate that these targets have white dwarfs with magnetic field strengths >80 MG. Our study reveals that cyclotron emission can dominate the optical luminosity at wavelengths corresponding to the cyclotron emission harmonics, even in systems where the white dwarfs are only wind-accreting. This implies that a very significant fraction of the stellar wind of the companion star is captured by the magnetic white dwarf reducing the magnetic braking in pre-cataclysmic variables (CVs). Furthermore, the polarimetric confirmation of several detached, wind-accreting magnetic systems provides observational constraints on the models of magnetic CV evolution and white dwarf magnetic field generation. We also find that the white dwarf magnetic field configuration in at least two of these systems appears to be very complex.
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