2004A&A...420..265I

Using the Very Large Array (VLA) and the Very Long Baseline Array (VLBA), we have observed water maser emission in the proto-planetary nebula candidate IRAS 19134+2131, in which the water maser spectrum has two groups of emission features separated in radial velocity by ∼100km/s. The blue-shifted and red-shifted clusters of maser features are clearly separated spatially by ∼150mas, indicative of a fast collimated flow. However, not all of the maser features are aligned along the axis of the flow, as is seen in the similar high-velocity water maser source, W43A. Comparing the VLA and VLBA maps of the water maser source, we find 4 maser features that were active for 2 years. Using only VLBA data, we identified proper motions for 8 maser features. The full 3D outflow velocity is estimated to be ∼130km/s, indicating that the dynamical age of the flow is only ∼50yr. On the basis of the relative positions with respect to the nearby extragalactic reference source, J1925+2106, we also obtain a secular motion of IRAS 19134+2131 of µ_l=-4.6±0.7mas/yr along the Galactic plane toward the Galactic centre. This indicates a ``far distance" (≥16kpc) for IRAS 19134+2131 if the Galactic rotation curve remains flat at 220km/s.