Magnetic field observations of low-mass stars

TL;DR

This paper reviews recent direct magnetic field measurements in low-mass M dwarf stars, highlighting the prevalence of strong magnetic fields across the spectral range and discussing insights from Zeeman Doppler imaging.

Contribution

It compiles and summarizes recent observational data on magnetic fields in M dwarfs, emphasizing the detection of strong fields and the potential of polarized light analysis for understanding magnetic generation.

Findings

Strong magnetic fields are present in all M dwarfs of spectral type M6 and later.

Zeeman Doppler imaging reveals weaker but informative magnetic fields.

Magnetic fields of kilo-Gauss strength are common across the M spectral range.

Abstract

Direct measurements of magnetic fields in low-mass stars of spectral class M have become available during the last years. This contribution summarizes the data available on direct magnetic measurements in M dwarfs from Zeeman analysis in integrated and polarized light. Strong magnetic fields at kilo-Gauss strength are found throughout the whole M spectral range, and so far all field M dwarfs of spectral type M6 and later show strong magnetic fields. Zeeman Doppler images from polarized light find weaker fields, which may carry important information on magnetic field generation in partially and fully convective stars.