Proper Motions of H2O Masers in the Water Fountain Source IRAS 19190+1102

TL;DR

This study uses VLBA observations to analyze water masers in IRAS 19190+1102, revealing bipolar outflows, expansion dynamics, and potential new lobe formation in a water fountain pre-planetary nebula.

Contribution

First detailed VLBA measurement of water maser motions in IRAS 19190+1102, demonstrating bipolar outflows and dynamic evolution in a water fountain nebula.

Findings

Outflow velocity of 99.8 km/s

Dynamical age of about 59 years

Detection of potential new lobe formation

Abstract

We report on the results of two epochs of Very Long Baseline Array (VLBA) observations of the 22 GHz water masers toward IRAS 19190+1102. The water maser emission from this object shows two main arc-shaped formations perpendicular to their NE-SW separation axis. The arcs are separated by ~280 mas in position, and are expanding outwards at an angular rate of 2.35 mas/yr. We detect maser emission at velocities between -53.3 km/s to +78.0 km/s and there is a distinct velocity pattern where the NE masers are blueshifted and the SW masers are redshifted. The outflow has a three-dimensional outflow velocity of 99.8 km/s and a dynamical age of about 59 yr. A group of blueshifted masers not located along the arcs shows a change in velocity of more than 35 km/s between epochs, and may be indicative of the formation of a new lobe. These observations show that IRAS 19190+1102 is a member of the class of "water fountain"' pre-planetary nebulae displaying bipolar structure