Poster abstract details

Some of water vapor maser sources are associated with post-AGB stars such as planetary and pre-planetary nebulae and "water fountain" sources. They provide a great opportunity to directly determine distances to these objects via trigonometric parallax measurement; leading us to directly determine their physical parameters and to understand the properties of the central stellar objects. At the same time, their secular motions should tell us their orbits in the Milky Way; leading us to estimate the origins and masses of their progenitor stars. Here we show the results of trigonometric parallax measurenets towards K3-35, IRAS 19312+1950, and IRAS 18286-0959; they are a planetary nebula, a pre-planetary nebula, and a water fountain source, respectively.