We present proper motion measurements of circumstellar water masers obtained with the VLBA. The objects observed include S Persei, VX Sagittarii, U Herculis, VY Canis Majoris, NML Cygni, IK Tauri and RX Bootis. Results of the observations and modeling indicate that the water masers exist in a kinematically complex region of the circumstellar envelope, which is not well fit by the standard model of a uniformly expanding spherical wind. Attempts at fitting an ellipsoidal geometric distribution with a variety of kinematic models are presented. Estimates for the distances of the stars are also discussed. A change in position of the maser spots as a function of velocity has been measured. This effect may be used to place limits on accelerations in the masing gas.
|Original language||English (US)|
|Title of host publication||The Tenth Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun|
|Editors||R.A. Donahue, J.A. Bookbinder|
|State||Published - 1998|
|Name||Astronomical Society of the Pacific Conference Series|
- MASERS, EVOLVED STARS, CIRCUMSTELLAR SHELLS