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A magnetically collimated jet from the evolved star W43A

Published online by Cambridge University Press:  15 December 2006

W. H. T. Vlemmings ,
P. J. Diamond  and
H. Imai
W. H. T. Vlemmings
Affiliation:
Jodrell Bank Observatory, Univ. of Manchester, Macclesfield, Cheshire SK11 9DL, U.K. email: wouter@jb.man.ac.uk
P. J. Diamond
Affiliation:
Jodrell Bank Observatory, Univ. of Manchester, Macclesfield, Cheshire SK11 9DL, U.K. email: wouter@jb.man.ac.uk
H. Imai
Affiliation:
Department of Physics, Faculty of Science, Kagoshima University, Kagoshima 890-0065, Japan
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Abstract

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We present the first direct measurements of the magnetic field strength and direction in a collimated jet from an evolved star on its way to become a planetary nebula. Very Long Baseline Array (VLBA) observations of the linear and circular polarization of the H$_2$O masers in the collimated jet of W43A reveal a strong toroidal magnetic field, indicating that the jet is magnetically collimated. The magnetic field strength in the jet extrapolated back to the stellar surface yields a surface field of several Gauss, consistent with the measurements of maser polarization in a large sample of evolved stars. The origin of the magnetic field is yet unknown, although the jet precession might point to the existence of a heavy planet or stellar companion. This is the first direct observational evidence for magnetic collimation in the jets, that likely plays an important role in shaping planetary nebulae.

Keywords

magnetic fieldsmasersstars: AGB and post-AGB
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 2 , Symposium S234: Planetary Nebulae in our Galaxy and Beyond , April 2006 , pp. 267 - 270
Copyright
© 2006 International Astronomical Union