Modelling the molecular Zeeman-effect in M-dwarfs: methods and first results
Abstract
Aims: We present first quantitative results of the surface magnetic field measurements in selected M-dwarfs based on detailed spectra synthesis conducted simultaneously in atomic and molecular lines of the FeH Wing-Ford F4 Δ - X4 Δ transitions.
Methods: A modified version of the Molecular Zeeman Library (MZL) was used to compute Landé g-factors for FeH lines in different Hund's cases. Magnetic spectra synthesis was performed with the Synmast code.
Results: We show that the implementation of different Hund's case for FeH states depending on their quantum numbers allows us to achieve a good fit to the majority of lines in a sunspot spectrum in an automatic regime. Strong magnetic fields are confirmed via the modelling of atomic and FeH lines for three M-dwarfs YZ CMi, EV Lac, and AD Leo, but their mean intensities are found to be systematically lower than previously reported. A much weaker field (1.7-2 kG against 2.7 kG) is required to fit FeH lines in the spectra of GJ 1224.
Conclusions: Our method allows us to measure average magnetic fields in very low-mass stars from polarized radiative transfer. The obtained results indicate that the fields reported in earlier works were probably overestimated by about 15-30%. Higher quality observations are needed for more definite results.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2010
- DOI:
- 10.1051/0004-6361/201015229
- arXiv:
- arXiv:1008.2512
- Bibcode:
- 2010A&A...523A..37S
- Keywords:
-
- stars: atmospheres;
- stars: low-mass;
- stars: magnetic field;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted by A&