High Velocity Precessing Jets from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations

Abstract

We report the results of multi-epoch VLBA observations of the 22.2GHz water maser emission associated with the "water fountain" IRAS 18286-0959. We suggest that this object is the second example of a highly collimated bipolar precessing outflow traced by water maser emission, the other is W43A. The detected water emission peaks are distributed over a velocity range from -50km/s to 150km/s. The spatial distribution of over 70% of the identified maser features is found to be highly collimated along a spiral jet (jet 1) extended southeast to northwest, the remaining features appear to trace another spiral jet (jet 2) with a different orientation. The two jets form a "double-helix" pattern which lies across ~200 milliarcseconds. The maser distribution is reasonably fit by a model consisting of two bipolar precessing jets. The 3D velocities of jet 1 and jet 2 are derived to be 138km/s and 99km/s, respectively. The precession period of jet 1 is about 56 years. For jet 2, three possible models are tested and they give different values for the kinematic parameters. We propose that the appearance of two jets is the result of a single driving source with significant proper motion.

84 pages, 16 figures, accepted for publication in ApJ

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• The first "water fountain" collimated outflow in a planetary nebula
• Multipolar Planetary Nebulae: Not as Geometrically Diversified as Thought
• Annual Parallax Distance and Secular Motion of the Water Fountain Source IRAS 18286-0959
• CO Structure of the 21 Micron Source IRAS 22272+5435: A Sign of a Jet Launch?
• The spatiokinematical structure of H_2O and OH masers in the "water fountain" source IRAS 18460-0151
• Rapidly-evolving episodic outflow in IRAS 18113-2503: clues to the ejection mechanism of the fastest water fountain
• Determining mass accretion and jet mass-loss rates in post-asymptotic giant branch binary systems
• From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448
• Maser and Infrared Studies of Oxygen-Rich Late/Post-AGB Stars and Water Fountains: Development of a New Identification Method
• Sensitive CO and 13CO survey of water fountain stars. Detections towards IRAS 18460-0151 and IRAS 18596+0315
• Interferometric confirmation of "water fountain" candidates
• Jet parameters for a diverse sample of jet-launching post-AGB binaries
• Submillimeter H2O masers in water-fountain nebulae
• FLASHING: New high-velocity H${}_2$O masers in IRAS 18286$-$0959
• Do Water Fountain Jets Really Indicate the Onset of the Morphological Metamorphosis of Circumstellar Envelopes?
• Wide Field CO Mapping in the Region of IRAS 19312+1950
• Radio Stars and Their Lives in the Galaxy
• Deep into the Water Fountains: The case of IRAS 18043-2116
• Maser emission during post-AGB evolution
• A search for water maser emission from brown dwarfs and low-luminosity young stellar objects