PROPER MOTIONS OF H2O MASERS IN THE WATER FOUNTAIN SOURCE IRAS 19190+1102

We report on the results of two epochs of Very Long Baseline Array observations of the 22 GHz water masers toward IRAS 19190+1102. The water maser emission from this object shows two main arc-shaped formations perpendicular to their NE-SW separation axis. The arcs are separated by similar to 280 mas in position and are expanding outward at an angular rate of 2.35 mas yr(-1). We detect maser emission at velocities between -53.3 km s(-1) and +78.0 km s(-1), and there is a distinct velocity pattern where the NE masers are blueshifted and the SW masers are redshifted. The outflow has a three-dimensional outflow velocity of 99.8 km s(-1) and a dynamical age of about 59 yr. A group of blueshifted masers not located along the arcs shows a change in velocity of more than 25 km s(-1) between epochs, and may be indicative of the formation of a new lobe. These observations show that IRAS 19190+1102 is a member of the class of "water fountain" pre-planetary nebulae displaying bipolar structure.