Planetary nebulae often express beautiful, multipolar, point symmetric shapes - while their progenitors are characterised as having
spherical layered structures. As stars exhaust their nuclear fuel and depart from the asymptotic giant branch, they launch powerful
jets that are believed to be responsible for creating the diverse shapes of PNe. Spectacular examples of collimated jets are those
traced by water masers, in objects named "water fountains" (with jet speeds and sizes on the order of 100 km/s and 1000 au
respectively). Water fountains are very rare due to their short timescales (on the order of 100 years) and as such the launching
mechanism of their collimated jets remains an unresolved puzzle.
In this talk, I introduce the VLBI maser astrometric results of IRAS 18113-2503, a water fountain with multiple bipolar bow shocks in
its high-velocity (150-300 km/s) collimated outflow. We find that the bow-shocks are formed by an evolved stellar system in
short-lived episodic outbursts in every ~10 years, and that the jets exhibit an exponential decrease in their velocity as a function
of distance from the central star. Using a simple model, we use the astrometric results to derive the physical properties of the jet,
its source and surroundings, and argue that the most reasonable driving mechanism is a binary system on a 10 au scale.
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