First detection of CO lines in a water fountain star

Abstract

[Context] Water fountain stars are very young post-AGB stars with high velocity water maser jets. They are the best objects to study the onset of bipolar jets from evolved stars due to their young dynamical ages. [Methods] We use the Arizona Radio Observatory 10m telescope to observe the CO J=2-1 line and compare the line parameters with that of masers. [Results] We report the detection of 12CO and 13COJ=2-1 lines from IRAS 16342-3814. The inferred 12CO mass loss rate is an order of magnitude lower than the infrared and OH mass loss rates, indicating a very cold and thick O-rich circumstellar envelope around the star. We also find a 12CO expansion velocity of Vexp = 46 +- 1 km/s that is too high for an AGB wind and confirm the systemic velocity of 44 +- 1 km/s. In addition we measure a very low 12CO/13CO line ratio of 1.7. [Conclusions] The first detection of CO lines has provided a new way to investigate the water fountain stars. Given the high expansion velocity of the CO gas and its relation to maser velocities, we infer that the CO emission region is co-located with the OH mainline masers in the warm base of the optical bipolar lobes, while the high velocity OH1612MHz and H2O masers are located in the side walls and at the farthest ends of the bipolar lobes, respectively. Further observations are highly desired to understand the very low 12CO/13CO line ratio.

arXiv comment5 pages, 1 figure, accepted by A&A Letter

References in corpus (14)

• The Milky Way in Molecular Clouds: A New Complete CO Survey
• Stellar Models and Yields of Asymptotic Giant Branch Stars
• Bipolar outflows in OH/IR stars
• The interaction of planetary nebulae and their AGB progenitors with the interstellar medium
• Abundances in intermediate-mass AGB stars undergoing third dredge-up and hot-bottom burning
• The spatio-kinematical structure and distance of the pre-planetary nebula IRAS 19134+2131
• A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Pre-Planetary Nebula IRAS 22036+5306
• Polarimetric observations of OH masers in proto-planetary nebulae
• The massive expanding molecular torus in the planetary nebula NGC 6302
• CO Isotopes in Planetary Nebulae
• The mineralogy, geometry and mass-loss history of IRAS 16342-3814
• Stellar molecular jets traced by maser emission
• The chemistry of compact planetary nebulae
• A Spitzer Study of the Mass Loss Histories of Three Bipolar Pre-Planetary Nebulae

Cited by in corpus (14)

• ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-velocity bipolar jets and an Expanding Torus
• High Velocity Precessing Jets from the Water Fountain IRAS 18286-0959 Revealed by VLBA Observations
• 870 um observations of evolved stars with LABOCA
• CO Structure of the 21 Micron Source IRAS 22272+5435: A Sign of a Jet Launch?
• Rapidly-evolving episodic outflow in IRAS 18113-2503: clues to the ejection mechanism of the fastest water fountain
• From the ashes: JVLA observations of water fountain nebula candidates show the rebirth of IRAS 18455+0448
• Sensitive CO and 13CO survey of water fountain stars. Detections towards IRAS 18460-0151 and IRAS 18596+0315
• CO J=3-2 Emission from the "Water Fountain" Sources IRAS 16342-3814 and IRAS 18286-0959
• Extremely Strong ^{13}CO J=3-2 Line in the "Water Fountain" IRAS 16342-3814: Evidence for the Hot-Bottom Burning
• Observed relationship between CO2-1 and dust emission during post-AGB phase
• Dust shell model of the water fountain source IRAS 16342--3814
• A Fast bipolar H2 outflow from IRAS 16342-3814: an old star reliving its youth
• CO observations of water-maser post-AGB stars and detection of a high-velocity outflow in IRAS 15452-5459
• Early Science with the Large Millimetre Telescope: Molecules in the Extreme Outflow of a proto-Planetary Nebula