Photospheric Hanle diagnostic of weak magnetic dipoles in stars

TL;DR

This paper introduces a novel spectropolarimetric technique utilizing the Hanle effect to detect and measure extremely weak stellar magnetic dipoles by analyzing linear polarization in specific spectral lines.

Contribution

It proposes a new diagnostic method based on Hanle-sensitive lines for weak stellar magnetic fields, expanding the capabilities of magnetic field measurements in stars.

Findings

Predicted polarization amplitudes are detectable with current instruments.

The technique can measure some of the weakest stellar magnetic fields.

A new application of the Hanle effect in stellar magnetometry is demonstrated.

Abstract

Diagnostic techniques for stellar magnetic fields based upon spectropolarimetry. We propose and explore a new technique based upon the linear polarization emitted in Hanle-sensitive lines in disk-integrated stars where a dipolar magnetic field breaks the rotational symmetry of the resonance scattering polarization. A star with a simple dipolar field and a 1-0 spectral line are used to compute polarization amplitudes and angles.Predicted amplitudes are low but within reach of present instruments. A new application of the Hanle effect is proposed and analyzed, a tool that allows measuring of some of the weakest stellar magnetic fields.