PoS(8thEVN)044 Spatio-kinematics and distance of H 2 O masers in the pre-planetary nebula IRAS 19134+2131 Hiroshi Imai * Department of Physics, Faculty of Science, Kagoshima University, Japan E-mail: hiroimai@sci.kagoshima-u.ac.jp Raghvendra Sahai Jet Propulsion Laboratory, USA E-mail: raghvendra.sahai@jpl.nasa.gov Mark Morris Department of Physics and Astronomy, University of California Los Angeles, USA E-mail: morris@astro.ucla.edu Using the VLBA we have observed at six epochs H 2 O maser emission in the pre-planetary nebula IRAS 19134+2131 (I19134), in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100 km s -1 . The spatio-kinematical structure of the H 2 O masers indicates the existence of a fast, collimated (precessing) flow with an expansion velocity of ∼90 km s -1 and a dynamical age of only ∼40 years. Such a “water fountain” source is a signature of the recent operation of a stellar jet, that may be responsible for the final shape of the planetary nebula into which I19134 is expected to evolve. Because the positions of all detected maser features have been measured with respect to the extragalactic reference source J1925+2106 over one year, we analyzed maser feature motions that consist of an annual parallax, a secular motion following the Galactic rotation and the intrinsic motions by the flow. We obtained an annual parallax distance to I19134, D = 8.0 +0.9 -0.7 kpc and estimated the location of I19134 in the Galaxy, (R, θ , z)=(7.4 +0.4 -0.3 kpc, 62 ◦ ± 5 ◦ ,0.65 +0.07 -0.06 kpc). From a mean motion of the blue- shifted and red-shifted clusters of maser features, we estimated the 3-D secular motion of I19134, ( V R , V θ , V z )=(6 +53 -46 , 123 +20 -28 , -11 +39 -48 ) [km s -1 ]. We discuss the origin of I19134 on the basis of its kinematics in the Galaxy. The 8th European VLBI Network Symposium September 26-29, 2006 Toru´ n, Poland * Speaker. c  Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. http://pos.sissa.it/