The Magnetic Field of the Active Planet-hosting M Dwarf AU Mic
Abstract
AU Mic is a young, very active M dwarf star with a debris disk and at least one transiting Neptune-size planet. Here we present a detailed analysis of the magnetic field of AU Mic based on previously unpublished high-resolution optical and near-infrared spectropolarimetric observations. We report a systematic detection of circular and linear polarization signatures in the stellar photospheric lines. Tentative Zeeman Doppler imaging modeling of the former data suggests a nonaxisymmetric global field with a surface-averaged strength of about 90 G. At the same time, linear polarization observations indicate the presence of a much stronger ≈2 kG axisymmetric dipolar field, which contributes no circular polarization signal due to the equator-on orientation of AU Mic. A separate Zeeman broadening and intensification analysis allowed us to determine a mean field modulus of 2.3 and 2.1 kG from the Y- and K-band atomic lines, respectively. These magnetic field measurements are essential for understanding environmental conditions within the AU Mic planetary system.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2020
- DOI:
- 10.3847/1538-4357/abb2a2
- arXiv:
- arXiv:2008.10668
- Bibcode:
- 2020ApJ...902...43K
- Keywords:
-
- Stellar activity;
- Stellar magnetic fields;
- M dwarf stars;
- 1580;
- 1610;
- 982;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - Earth and Planetary Astrophysics
- E-Print:
- 13 pages, 8 figures