Volume 375, Number 1, August III 2001
|Page(s)||L1 - L4|
|Published online||15 August 2001|
Circular polarization of circumstellar water masers around S Per
Sterrewacht Leiden, Postbus 9513, 2300 RA Leiden, The Netherlands
2 Jodrell Bank Observatory, University of Manchester, Macclesfield, Cheshire, SK11 9DL, England, UK
3 Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands
Corresponding author: W. Vlemmings, email@example.com
Accepted: 22 June 2001
We present the first circular polarization measurements of circumstellar H2O masers. Previously the magnetic field in circumstellar envelopes has been estimated using polarization observations of SiO and OH masers. SiO masers are probes of the high temperature and density regime close to the central star. OH masers are found at much lower densities and temperatures, generally much further out in the circumstellar envelope. The detection of the circular polarization of the (616-523) rotational transition of the H2O maser could be attributed to Zeeman splitting due to the magnetic field in the intermediate temperature and density regime. The fields inferred here agree well with predicted values for a combination of the r-2 dependence of a solar-type magnetic field, and the coupling of the field to the high density masing regions. We also discuss the unexpected narrowing of the circular polarization spectrum.
Key words: masers / polarization / stars: circumstellar matter / stars: individual: S Per / stars: magnetic fields / stars: supergiants / techniques: interferometric
© ESO, 2001
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