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

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        Author
        Sahai, Raghvendra
        Vlemmings, W.H.T.
        Gledhill, Timothy
        Sanchez Contreras, Carmen
        Lagadec, Eric
        Nyman, L.A.
        Quintana-Lacaci, G.
        Attention
        2299/17630
        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 Atacama Large Millimeter/submillimeter Array. We find (i) two very high-speed knotty, jet-like molecular outflows; (ii) a central high-density (>few x106 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 x10-4 Ms yr−1 in the past ∼455 years. 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 Ms) of very large (∼millimeter-sized) grains. The measured expansion ages of the above structural components imply that the torus (age∼160 years) and the younger high-velocity outflow (age∼110 years) 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.
        Publication date
        2017-01-20
        Published in
        The Astrophysical Journal
        Published version
        https://doi.org/10.3847/2041-8213/835/1/l13
        Other links
        http://hdl.handle.net/2299/17630
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