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D. A. Boboltz, K. J. Johnston, A. L. Fey, R. A. Gaume, R. P. Olling, N. Zacharias (USNO)
We report on an effort to image the SiO maser emission associated with asymptotic giant branch (AGB) stars as part of an ongoing preparatory science program to select sources for possible observation by NASA's SIM PlanetQuest mission. Thus far the v=1 and v=2, J=1-0 SiO masers toward 37 AGB stars have been observed using the VLA in the A-configuration. Analysis of the resulting images shows that we are able to resolve SiO maser shells as small as 10 mas across. For many of these stars, our maps represent the first images of the circumstellar envelope at a distance of just a few stellar radii. We discuss the implications of the maser spot maps with regards to the determination of maser shell size, structure, asymmetry, and kinematics. Comparisons are made to higher resolution VLBA images of the SiO masers for a few stars in which results are available.
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Bulletin of the American Astronomical Society, 37 #2
© 2005. The American Astronomical Soceity.