From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448

Abstract

[abridged] The class of water fountain nebulae is thought to represent the stage of the earliest onset of collimated bipolar outflows during the post-Asymptotic Giant Branch phase. They thus play a crucial role in the study of the formation of bipolar Planetary Nebulae (PNe). To date, 14 water fountain nebulae have been identified. The identification of more sources in this unique stage of stellar evolution will enable us to study the origin of bipolar PNe morphologies in more detail. We present the results of seven sources observed with the JVLA that were identified as water fountain candidates in an Effelsberg 100m telescope survey of 74 AGB and early post-AGB stars. We find that our sample of water fountain candidates displays strong variability in their 22 GHz H2O maser spectra. The JVLA observations show an extended bipolar H2O maser outflow for one source, the OH/IR star IRAS 18455+0448. This source was previously classified as a 'dying' OH/IR star based on the exponential decrease of its 1612 MHz OH maser and the lack of H2O masers. We therefore also re-observed the 1612, 1665, and 1667 MHz OH masers. We confirm that the 1612 MHz masers have not reappeared and find that the 1665/1667 MHz masers have decreased in strength by several orders of magnitude during the last decade. The OH/IR star IRAS 18455+0448 is confirmed to be a new addition to the class of water fountain nebulae. Its kinematic age is approximately 70 yr, but could be lower, depending on the distance and inclination. Previous observations indicate, with significant uncertainty, that IRAS 18455+0448 has a surprisingly low mass compared to available estimates for other water fountain nebulae. The available historical OH maser observations make IRAS 18455+0448 unique for the study of water fountain nebulae and the launch of post-AGB bipolar outflows...

8 pages, 5 figures, accepted for publication in A&A (revised minor typos)

References in corpus (6)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• A magnetically collimated jet from an evolved star
• Isolated vs. Common Envelope Dynamos in Planetary Nebula Progenitors
• VLA observations of the "water fountain" IRAS 16552-3050
• Stellar molecular jets traced by maser emission
• First detection of CO lines in a water fountain star

Cited by in corpus (6)

• First detection of surface magnetic fields in Post-AGB stars : the cases of U Monocerotis and R Scuti
• Observational identification of a sample of likely recent Common-Envelope Events
• The first "water fountain" collimated outflow in a planetary nebula
• VLBI observations of the G25.65+1.05 water maser superburst
• Do Water Fountain Jets Really Indicate the Onset of the Morphological Metamorphosis of Circumstellar Envelopes?
• An infrared study of Galactic OH/IR stars. III. Variability properties of the Arecibo sample