Zeeman split lines in CP stars: a discovery of low-contrast fields in slow rotators?

TL;DR

This paper demonstrates that high-resolution Zeeman line observations can reveal detailed magnetic field geometries in CP stars, uncovering unexpectedly homogeneous fields in slow rotators, challenging previous multipolar models.

Contribution

It introduces a method to constrain stellar magnetic field geometry using differential Zeeman line measurements, revealing homogeneous fields in slow rotators.

Findings

Homogeneous magnetic fields found in slow rotator CP stars.

Zeeman line analysis constrains magnetic field distribution.

Results challenge low-order multipolar field models.

Abstract

We show that high-resolution observations of resolved Zeeman split lines can be used to obtain new constraints on the stellar magnetic field geometry. In particular, the contrast of the field strength distribution over the stellar surface can be deduced from the differential measurement of the second moment of the pi and sigma Zeeman components. Our analysis of the triplet lines in slowly rotating cool magnetic CP stars uncovers a surprisingly homogeneous field structure, inconsistent with any low-order multipolar geometry.