Issue |
A&A
Volume 634, February 2020
|
|
---|---|---|
Article Number | L10 | |
Number of page(s) | 5 | |
Section | Letters to the Editor | |
DOI | https://doi.org/10.1051/0004-6361/201937301 | |
Published online | 10 February 2020 |
Letter to the Editor
Discovery of a Sirius-like binary system with a very strongly magnetic white dwarf
Binarity among magnetic white dwarfs
1
Armagh Observatory and Planetarium, College Hill, Armagh BT61 9DG, Northern Ireland, UK
e-mail: John.Landstreet@Armagh.ac.uk, Stefano.Bagnulo@Armagh.ac.uk
2
University of Western Ontario, Department of Physics & Astronomy, London, ON N6A 3K7, Canada
Received:
11
December
2019
Accepted:
19
January
2020
Non-interacting binary systems containing a magnetic white dwarf and a main-sequence star are considered extremely rare, perhaps non-existent. In the course of a search of magnetic fields in high-mass white dwarfs we have discovered a Sirius-like wide binary system composed of a main-sequence G0 star and an M ∼ 1.1 M⊙ white dwarf with a huge (hundreds of MG) magnetic field. This star, WDS J03038+0608B, shows a circular polarisation amplitude of 5% in the continuum, with no evidence of variability on a 1 d timescale, little or no linear polarisation in the blue part of the spectrum, and about 2% linear polarisation in the red part of the optical spectrum. A search in the literature reveals the existence of four more binary systems that include a magnetic white dwarf and a non-degenerate companion; three such systems passed unremarked in previous studies. We estimate that up to a few percent of magnetic white dwarfs may be found to occur in wide binary pairs. However, at least four of the five known binary systems with a magnetic white dwarf are too widely separated to be expected to evolve into systems experiencing Roche-lobe overflow, and cannot be considered as progenitors of magnetic cataclysmic variable (AM Her and DQ Her) systems.
Key words: stars: magnetic field / white dwarfs / binaries: visual / stars: individual: WD0301+059
© ESO 2020
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