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.
Oleg Kochukhov (Fri,) studied this question.
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