Detection of Strong Magnetic Fields on M Dwarfs

摘要: We have detected Zeeman splitting of the Fe I line (geff = 2.5) at 8468.40 A in very active M4.5 Ve stars Gliese 729 and 873 (EV Lac). High-resolution (R 120,000), low-noise (~0.5%) spectra show clear Zeeman-shifted σ components from which we infer field strengths 2-4 kG, independent uncertainties model atmospheres. Similar observations a sequence (M0 V-M5 V) low-activity M dwarfs demonstrate that wing are not due to ubiquitous TiO lines vicinity. This strongly suggests discrepancies shape magnetically sensitive iron magnetic fields rather than differences photospheric temperature. By fitting ratio inactive profiles with simple one-component models, estimate 50 ± 13% photosphere EV Lac is covered by 3.8 0.5 kG fields, while 2.6 0.3 fields. confirms earlier reports large on dwarf flare stars. see evidence for distribution strength, spatially across surface and/or depth. The twofold increase strength relative G K predicted flux tube equilibrium arguments, but 1 difference measured these two may also grow activity as filling factor approaches unity.