Interferometric confirmation of "water fountain" candidates

Abstract

Water fountain stars (WFs) are evolved objects with water masers tracing high-velocity jets (up to several hundreds of km s${}^{-1}$). They could represent one of the first manifestations of collimated mass-loss in evolved objects and thus, be a key to understanding the shaping mechanisms of planetary nebulae. Only 13 objects had been confirmed so far as WFs with interferometer observations. We present new observations with the Australia Telescope Compact Array and archival observations with the Very Large Array of four objects that are considered to be WF candidates, mainly based on single-dish observations. We confirm IRAS 17291-2147 and IRAS 18596+0315 (OH 37.1-0.8) as bona fide members of the WF class, with high-velocity water maser emission consistent with tracing bipolar jets. We argue that IRAS 15544-5332 has been wrongly considered as a WF in previous works, since we see no evidence in our data nor in the literature that this object harbours high-velocity water maser emission. In the case of IRAS 19067+0811, we did not detect any water maser emission, so its confirmation as a WF is still pending. With the result of this work, there are 15 objects that can be considered confirmed WFs. We speculate that there is no significant physical difference between WFs and obscured post-AGB stars in general. The absence of high-velocity water maser emission in some obscured post-AGB stars could be attributed to a variability or orientation effect.

To be published in Monthly Notices of the Royal Astronomical Society. 13 pages, 10 figures, 7 tables. Updated version with several typos corrected

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Cited by in corpus (5)

• Observational identification of a sample of likely recent Common-Envelope Events
• Rapidly-evolving episodic outflow in IRAS 18113-2503: clues to the ejection mechanism of the fastest water fountain
• FLASHING: New high-velocity H${}_2$O masers in IRAS 18286$-$0959
• An infrared study of Galactic OH/IR stars. III. Variability properties of the Arecibo sample
• Searching for nascent planetary nebulae: OHPNe candidates in the SPLASH survey