| Issue |
A&A
Volume 696, April 2025
|
|
|---|---|---|
| Article Number | L17 | |
| Number of page(s) | 6 | |
| Section | Letters to the Editor | |
| DOI | https://doi.org/10.1051/0004-6361/202554395 | |
| Published online | 25 April 2025 | |
Letter to the Editor
Extremely asymmetric bipolar magnetic field of the Bp star HD 57372⋆
Department of Physics and Astronomy, Uppsala University, Box 516 75120 Uppsala, Sweden
⋆⋆ Corresponding author: oleg.kochukhov@physics.uu.se
Received:
6
March
2025
Accepted:
8
April
2025
Fossil magnetic fields of early-type stars are typically characterised by symmetric or slightly distorted oblique dipolar surface geometries. Contrary to this trend, the late-B magnetic chemically peculiar star HD 57372 exhibits an unusually large rotational variation of its mean magnetic field modulus, suggesting a highly atypical field configuration. We present a Zeeman Doppler imaging analysis of HD 57372 that reveals an exceptionally asymmetric bipolar magnetic topology, which is rarely observed in early-type stars. According to our magnetic field maps, reconstructed from the intensity and circular polarisation profiles of Fe, Cr, and Ti lines, approximately 66% of the stellar surface is covered by a diffuse, outward directed radial field, with local field strength reaching 11.6 kG. The remaining 34% hosts a highly concentrated inward directed field with a strong horizontal component and a peak strength of 17.8 kG. These unusual surface magnetic field characteristics make HD 57372 a notable object for testing fossil-field theories and interpreting phase-resolved spectropolarimetric observations of early-type stars.
Key words: polarization / stars: chemically peculiar / stars: early-type / stars: magnetic field / stars: individual: HD 57372
© The Authors 2025
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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