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Astron. Astrophys. 319, 589-592 (1997)

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The origin of strong magnetic fields in circumstellar SiO masers

T.W. Hartquist 1 and J.E. Dyson 2, 3

1 Max-Planck-Institut für extraterrestrische Physik, D-85740 Garching, Germany
2 Department of Physics and Astronomy, The University of Leeds, Leeds LS2 9JT, UK
3 Department of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK

Received 27 November 1995 / Accepted 20 August 1996


We suggest that the Parker instability, acting in the regions where shocks form in response to stellar pulsations, gives rise to the fragments in which SiO masers exist in the atmospheres of evolved stars. The production of maser fragments in this manner is compatible with the Alfvén speeds in them greatly exceeding their kinematic and thermal speeds. The magnetic structure in an evolved star's envelope probably results in momentum transfer to gas from grains subject to radiation pressure being widely distributed even to regions where grains have not yet formed; the consequences for mass loss of the magnetic redistribution of momentum transfer require exploration.

Key words: stars: AGB; post AGB – stars: magnetic fields – stars: mass loss

Send offprint requests to: J.E. Dyson

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© European Southern Observatory (ESO) 1997

Online publication: July 3, 1998