MERLIN polarimetry of the OH masers in IRAS 20406+2953
Abstract
We present the third in a series of results from our programme of the detection and measurement of magnetic fields in protoplanetary nebulae (PPN), using full-polarization MERLIN observations of OH masers. These are the first maps of the OH 1612- and 1667-MHz masing emission from IRAS 20406+2953. We have identified a Zeeman pair in the 1612-MHz data; this result heralds the second magnetic field strength measured in a PPN. We show that the field, of strength -3.1 mG, is sufficiently strong to be shaping the outflowing mass from the star. By considering the spatial distribution of the masers and the structure of the linear polarization data, we suggest a field configuration that is toroidal. The observed change in polarization position angle between the peak red- and blueshifted components of the maser features, if attributed to Faraday rotation within the circumstellar envelope, gives an electron density of ~1 cm-3. We show that this is sufficient to freeze the field into the outflowing wind.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- October 2004
- DOI:
- 10.1111/j.1365-2966.2004.08209.x
- Bibcode:
- 2004MNRAS.354..529B
- Keywords:
-
- masers;
- stars: AGB and post-AGB;
- circumstellar matter;
- stars: individual: IRAS 20406+2953;
- radio lines: stars