Improved Methods for the Measurement and Analysis of Stellar Magnetic Fields
Abstract
The paper presents several improved methods for the measurement of magnetic fields on cool stars which take into account simple radiative transfer effects and the exact Zeeman patterns. Using these methods, high-resolution, low-noise data can be fitted with theoretical line profiles to determine the mean magnetic field strength in stellar active regions and a model-dependent fraction of the stellar surface (filling factor) covered by these regions. Random errors in the derived field strength and filling factor are parameterized in terms of signal-to-noise ratio, wavelength, spectral resolution, stellar rotation rate, and the magnetic parameters themselves. Weak line blends, if left uncorrected, can have significant systematic effects on the derived magnetic parameters, and thus several methods are developed to compensate partially for them. The magnetic parameters determined by previous methods likely have systematic errors because of such line blends and because of line saturation effects. Other sources of systematic error are explored in detail. These sources of error currently make it difficult to determine the magnetic parameters of individual stars to better than about + or - 20 percent.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- January 1988
- DOI:
- 10.1086/165907
- Bibcode:
- 1988ApJ...324..441S
- Keywords:
-
- Cool Stars;
- Field Strength;
- Magnetic Measurement;
- Radiative Transfer;
- Stellar Magnetic Fields;
- Late Stars;
- Random Errors;
- Stellar Activity;
- Zeeman Effect;
- Astrophysics;
- STARS: LATE-TYPE;
- STARS: MAGNETIC