Proper motion of water masers associated with IRAS 21391+5802: Bipolar Outflow and an AU-scale Dusty Circumstellar Shell

We present VLBA observations of water maser emission associated with the star forming region IRAS 21391+5802, which is embedded in a bright rimmed cometary globule in IC1396. The angular resolution of the maps is ∼ 0.8 mas, corresponding to a spatial resolution of ∼0.6 AU, at an estimated distance of 750 pc. Proper motions are derived for 10 maser features identified consistently over three epochs, which were separated by intervals of about one month. The Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 National Astronomy and Ionosphere Center, Cornell University, Department of Astronomy, Ithaca, NY 14853