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K.B. Marvel (American Astronomical Society)
I present maps of the water maser emission associated with the evolved star U Herculis. The masers are distributed in a roughly circular distribution with a diameter of about 150 mas, or 8.5 x 1014 cm. This is consistent with recent VLA mapping reported by Colomer et al. (1999). The masers have proper motions consistent with their line-of-sight velocity distribution. Simple kinematic models are applied to the data and show that the water maser proper motions are roughly consistent with radial outflow, although the full velocity range of the best-fit outflow is not well-sampled by the maser distribution. I present three-dimensional images of the synthesized data cubes formed by mapping the velocity axis to a dimensional axis through a best-fit kinematic model. This allows a more realistic visualization of the three-dimensional structure of the water masers associated with evolved stars. This research was performed with the NRAO-VLBA and the data were reduced and analyzed at NRAO-Socorro, the Owens Valley Radio Observatory and the American Astronomical Society.