The ``water-fountain nebula'' IRAS 16342-3814: Hubble Space Telescope/Very Large Array study of a bipolar protoplanetary nebula.
SAHAI R., TE LINTEL HEKKERT P., MORRIS M., ZIJLSTRA A. and LIKKEL L.
Abstract (from CDS):
We present Hubble Space Telescope (HST) Wide-Field and Planetary Camera 2 images and VLA OH maser emission-line maps of the cold infrared object IRAS 16342-3814, believed to be a protoplanetary nebula. The HST images show an asymmetrical bipolar nebula, with the lobes separated by a dark equatorial waist. The two bright lobes and the dark waist are simply interpreted as bubble-like reflection nebulae illuminated by starlight escaping through polar holes in a dense, flattened, optically thick cocoon of dust, which completely obscures the central star. A faint halo can be seen surrounding each of the lobes. The bubbles are likely to have been created by a fast outflow (evidenced by H2O emission) plowing into a surrounding dense, more slowly expanding, circumstellar envelope of the progenitor asymptotic giant-branch (AGB) star (evidenced by the halo). The IRAS fluxes indicate a circumstellar mass of about 0.7 M☉(D/2 kpc) and an AGB mass-loss rate of about 10–4M☉.yr–1 (Vexp/15 km.s–1)(D/2 kpc)2 (assuming a gas-to-dust ratio of 200). OH features with the largest redshifted and blueshifted velocities are concentrated around the bright eastern and western polar lobes, respectively, whereas intermediate-velocity features generally occur at low latitudes, in the dark waist region. We critically examine evidence for the post-AGB classification of IRAS 16342-3814.
Stars: Circumstellar Matter - ISM: Planetary Nebulae: General - Stars: AGB and Post-AGB - Stars: Mass Loss