Trigonometric distance and maser kinematics of the fastest water fountain source

Gabor Orosz, Hiroshi Imai, Jose F. Gomez, J. Ricardo Rizzo, Olga Suarez, Ross A. Burns & Akiharu Nakagawa

Kagoshima University, Japan

Water fountains are evolved stars with collimated and high-velocity outflows traced by water masers. IRAS 18113-2503 is the water fountain with the fastest jets known and has the largest velocity dispersion of masers in each lobe. Here, we present its parallax distance (~10 kpc) and maser kinematics yielded by VLBI astrometry with the Japanese VERA network. We find maser proper motions of 6.2-8.5 mas/yr, corresponding to outflow velocities of 300-420 km/s. We discuss the morphology of the water fountain outflow, the stellar properties, evolution and motion in the Milky Way, and address the variability of the masers.

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