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Polarization properties of R Cas SiO masers

Published online by Cambridge University Press:  24 July 2012

K. A. Assaf
Affiliation:
University of Manchester, Oxford Road, Manchester, M13 9PL, UKemail: kam@jb.man.ac.uk
P. J. Diamond
Affiliation:
CSIRO Astronomy and Space Sciences, PO Box 76, Epping, NSW 1710, Australia email: philip.diamond@csiro.au
A. M. S. Richards
Affiliation:
University of Manchester, Oxford Road, Manchester, M13 9PL, UKemail: kam@jb.man.ac.uk
M. D. Gray
Affiliation:
University of Manchester, Oxford Road, Manchester, M13 9PL, UKemail: kam@jb.man.ac.uk
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Abstract

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Silicon monoxide maser emission has been detected in the circumstellar envelopes of many evolved stars. It is a good tracer of the wind dynamics within a few stellar radii of the central star. We investigated the polarization morphology in the circumstellar envelope of an AGB star, R Cas, by using the VLBA to map the linear and circular polarization of the v=1, J=1-0 SiO maser transition during 23 epochs over two stellar cycles. The average fractional circular polarization is a few percent. The average fractional linear polarization per epoch is 11–58%, but some isolated features exceed 100%, probably because the total intensity emission is smoother and more resolved-out. The maser electric polarization vector angle has a preferrential tendency to be either parallel or perpendicular to the radial direction to the star.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2012

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