Stellar magnetic fields from four Stokes parameter observations

TL;DR

This paper demonstrates that magnetic Doppler imaging using all four Stokes parameters reveals complex stellar magnetic fields, showing a strong dipolar component in the star HD 24712, with implications for understanding magnetic field evolution in intermediate and high-mass stars.

Contribution

It presents the first detailed magnetic Doppler imaging of HD 24712 using four Stokes parameters, revealing a predominantly dipolar magnetic field structure.

Findings

HD 24712 has a strong dipolar magnetic field.

Magnetic fields in HD 24712 show weak small-scale contributions.

Supports the hypothesis that old Ap stars have mainly dipolar fields.

Abstract

Magnetic Doppler imaging from four Stokes parameter observations has uncovered a new level of complexity of stellar magnetic fields previously not known. This new information is of interest to the evolution and structure of magnetic fields of intermediate and high-mass stars. Recently, we performed magnetic Doppler imaging study of the chemically peculiar star HD 24712 using phase-resolved spectropolarimetric observations of line-profiles in all four Stokes parameters. The observations were obtained with the HARPSpol instrument on the 3.6-m ESO telescope. Our analysis shows that the magnetic field of HD 24712 has very strong dipolar component with weak small-scale contributions. The finding of dipole-like field for HD 24712 gives evidence for the hypothesis that old Ap stars have predominantly dipolar magnetic fields. We plan on performing magnetic Doppler imaging from four Stokes parameter observations for other Ap/Bp stars as well, which will help us understand the nature of magnetic fields in these stars.