SIMBAD references

2007ApJ...656.1150S - Astrophys. J., 656, 1150-1166 (2007/February-3)

Adaptive optics imaging of IRAS 18276-1431: a bipolar preplanetary nebula with circumstellar ``Searchlight beams'' and ``Arcs''.


Abstract (from CDS):

We present high angular resolution images of the post-AGB nebula IRAS 18276-1431 (also known as OH 17.7-2.0) obtained with the Keck II adaptive optics (AO) system in its natural guide star (NGS) mode in the Kp, Lp, and Msnear-infrared bands. We also present supporting optical F606W and F814W HST images as well as interferometric observations of the 12CO J=1-0, ^ 13^CO J=1-0, and 2.6 mm continuum emission with OVRO. The envelope of IRAS 18276-1431 displays a clear bipolar morphology in our optical and NIR images with two lobes separated by a dark waist and surrounded by a faint 4.5''x3.4'' halo. Our Kp-band image reveals two pairs of radial ``searchlight beams'' emerging from the nebula center and several intersecting, arclike features. From our CO data we derive a mass of M>0.38D/3 kpc2 M and an expansion velocity Vexp=17 km/s for the molecular envelope. The density in the halo follows a radial power law ∝/r3, which is consistent with a mass-loss rate increasing with time. Analysis of the NIR colors indicates the presence of a compact central source of ∼300-500 K dust illuminating the nebula in addition to the central star. Modeling of the thermal IR suggests a two-shell structure in the dust envelope: (1) an outer shell with inner and outer radius Rin∼1.6x1016 and Rout≳1.25x1017 cm, dust temperature Tdust∼105-50 K, and a mean mass-loss rate of M{dot}~10–3 M/yr; and (2) an inner shell with Rin∼6.3x1014 cm, Tdust∼500-105 K, and M{dot}∼3x10–5 M/yr. An additional population of big dust grains (radius a≳0.4 mm) with Tdust=150-20 K and mass Mdust=(0.16-1.6)x10–3D/3 kpc2 Mcan account for the observed submillimeter and millimeter flux excess. The mass of the envelope enclosed within Rout=1.25x1017 cm derived from SED modeling is ∼1D/3 kpc2 M.

Abstract Copyright:

Journal keyword(s): Stars: Circumstellar Matter - Infrared: Stars - Instrumentation: Adaptive Optics - ISM: Jets and Outflows - ISM: Planetary Nebulae: General - Stars: AGB and Post-AGB - Stars: Imaging - Stars: Mass Loss

Simbad objects: 17

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