Open AccessMERLIN polarimetry of the OH masers in IRAS 20406+2953
Author(s) -
Bains I.,
Richards A. M. S.,
Gledhill T. M.,
Yates J. A.
Publication year - 2004
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2004.08209.x
Subject(s) - physics , astrophysics , maser , zeeman effect , faraday effect , magnetic field , polarization (electrochemistry) , circumstellar envelope , asymptotic giant branch , position angle , astronomy , stars , galaxy , chemistry , quantum mechanics
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.