Astrophys. J., 835, L13-L13 (2017/January-3)
ALMA observations of the water fountain pre-planetary nebula IRAS 16342-3814: high-velocity bipolar jets and an expanding torus.
SAHAI R., VLEMMINGS W.H.T., GLEDHILL T., SANCHEZ CONTRERAS C., LAGADEC E., NYMAN L.-A. and QUINTANA-LACACI G.
Abstract (from CDS):
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×106 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 3.5×10–4M☉ 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 M☉) 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.
© 2017. The American Astronomical Society. All rights reserved.
circumstellar matter - stars: AGB and post-AGB - stars: mass-loss - stars: winds, outflows - techniques: interferometric - techniques: interferometric
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