ALMA Observations of the Water Fountain Pre-Planetary Nebula IRAS 16342-3814: High-velocity bipolar jets and an Expanding Torus

Abstract

We have mapped 12CO J=3-2 and other molecular lines from the "water-fountain" bipolar pre-planetary nebula (PPN) IRAS 16342-3814 with ~0."35 resolution using ALMA. We find (i) two very high-speed knotty, jet-like molecular outflows, (ii) a central high-density (> few x 10^6 cm^{-3}), expanding torus of diameter 1300 AU, and (iii) the circumstellar envelope of the progenitor AGB, generated by a sudden, very large increase in the mass-loss rate to >3.5 x 10^{-4} Msun/yr in the past ~455 yr. Strong continuum emission at 0.89 mm from a central source (690 mJy), if due to thermally-emitting dust, implies a substantial mass (0.017 Msun) of very large (~mm-sized) grains. The measured expansion ages of the above structural components imply that the torus (age~160 yr) and the younger high-velocity outflow (age~110 yr) were formed soon after the sharp increase in the AGB mass-loss rate. Assuming a binary model for the jets in IRAS 16342, the high momentum rate for the dominant jet-outflow in IRAS 16342 implies a high minimum accretion rate, ruling out standard Bondi-Hoyle-Lyttleton wind accretion and wind Roche lobe overflow (RLOF) models with white-dwarf or main-sequence companions. Most likely, enhanced RLOF from the primary or accretion modes operating within common envelope evolution are needed.

Accepted or Publication in Astrophysical Journal (Letters) 16 DEC, 2016 5 figures

References in corpus (5)

• A Massive Bipolar Outflow and a Dusty Torus with Large Grains in the Pre-Planetary Nebula IRAS 22036+5306
• Astrophysical Explosions Driven by a Rotating, Magnetized, Gravitating Sphere
• The Motion of Water Masers in the Pre-Planetary Nebula IRAS 16342-3814
• ALMA view of the circumstellar environment of the post-common-envelope-evolution binary system HD101584
• First detection of CO lines in a water fountain star

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