The Motion of Water Masers in the Pre-Planetary Nebula IRAS 16342-3814

TL;DR

This study uses VLBA observations to analyze water maser motions in the pre-planetary nebula IRAS 16342-3814, revealing high-velocity jets with bow shock structures and a short dynamical timescale of about 100 years.

Contribution

First high-resolution VLBA imaging of water masers in IRAS 16342-3814, showing bow shock structures and detailed 3D velocity measurements of the jet.

Findings

Water masers form bow shocks on either side of a collimated jet.

Water maser velocities are approximately 180 km/s, indicating a short dynamical timescale.

Evidence suggests possible jet precession, though not directly observed.

Abstract

We present high angular resolution observations, using the Very Long Baseline Array (VLBA) of the NRAO, of the high-velocity water masers toward the "water-fountain" pre-planetary nebula, IRAS 16342-3814. The detailed structure of the water masers appears to be that of bow shocks on either side of a highly collimated jet. The proper motions of the water masers are approximately equal to the radial velocities; the three-dimensional velocities are approximately +/-180 km/s, which leads to a very short dynamical time-scale of ~100 years. Although we do not find direct evidence for precession of the fast collimated jet, there may be indirect evidence for such precession.