Proper motions of H2 O masers in the water fountain source IRAS 19190+1102.
DAY F.M., PIHLSTROM Y.M., CLAUSSEN M.J. and SAHAI R.
Abstract (from CDS):
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 ∼280 mas in position and are expanding outward at an angular rate of 2.35 mas/yr^. We detect maser emission at velocities between -53.3 km.s–1 and +78.0 km/s, 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 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 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.