The “Water-Fountain Nebula” IRAS 16342−3814: [ITAL]Hubble Space Telescope[/ITAL]/Very Large Array Study of a Bipolar Protoplanetary Nebula

Sahai, Raghvendra; Hekkert, P. te Lintel; Morris, Mark; Zijlstra, A. A.; Likkel, L.

doi:10.1086/311955

Cited by 72 publications

(101 citation statements)

References 18 publications

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“…Figure 4 shows the SEDs. The black lines are the result of the selected Sahai et al (1999), (3) assuming an a max = 100.0 μm dust model, (4) assuming an a max = 10.0 μm dust model, (5) based on comparison of the intensity image.…”

Section: Dust Particlesmentioning

confidence: 99%

Dust shell model of the water fountain source IRAS 16342–3814

Murakawa

Izumiura²

2012

A&A

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Aims. We investigate the circumstellar dust shell of the water fountain source IRAS 16342-3814. Methods. We performed two-dimensional radiative transfer modeling of the dust shell, taking into account previously observed spectral energy distributions (SEDs) and our new J-band imaging and H-and K S -band imaging polarimetry obtained using the VLT/NACO instrument. Results. Previous observations expect an optically thick torus in the equatorial plane because of a striking bipolar appearance and a large viewing angle of 30−40 • . However, models with such a torus as well as a bipolar lobe and an AGB shell cannot fit the SED and the images simultaneously. We find that an additional optically and geometrically thick disk located inside a massive torus solves this problem. The masses of the disk and the torus are estimated to be 0.01 M at the a max = 100 μm dust and 1 M at a max = 10 μm dust, respectively. Conclusions. We discuss a possible formation scenario for the disk and torus based on a similar mechanism to the equatorial back flow. IRAS 16342-3814 is expected to undergo mass loss at a high rate. The radiation from the central star is shielded by the dust that was ejected in the subsequent mass loss event. As a result, the radiation pressure on dust particles cannot govern the motion of the particles anymore. The mass loss flow can be concentrated in the equatorial plane by help of an interaction, which might be the gravitational attraction by the companion, if it exists in IRAS 16342-3814. A fraction of the ejecta is captured in a circum-companion or circum-binary disk and the remains are escaping from the central star(s) and form the massive torus.

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Section: Dust Particlesmentioning

confidence: 99%

Dust shell model of the water fountain source IRAS 16342–3814

Murakawa

Izumiura²

2012

A&A

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“…The optical photometry of van der Veen et al cannot be fitted, and are also inconsistent with the HST image (Sahai et al 1999b): it is believed that these data represent a nearby field star. The infrared data also is not well fitted: the model predicts that the extinction towards the star (AV = 27 mag) is too low to hide the star beyond a few micron.…”

Section: The Disk Parameters Of Iras 16342−3814mentioning

confidence: 89%

“…The highly variable H2O masers occur in pairs at opposite velocity, at a number of discrete velocities (Likkel, Morris & Maddalena 1992). HST images show two asymmetric bipolar reflection lobes on either side of a dark lane which is identified as an edge-on equatorial disk or torus (Sahai et al 1999b). The forbidden stellar ve- locity argues that IRAS 16342−3814 belongs to a lowermass, old population.…”

Section: Iras 16342−3814mentioning

confidence: 99%

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Bipolar Outflows from OH/IR Stars

Zijlstra

2001

Post-Agb Objects as a Phase of Stellar Evolution

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We investigate the development of bipolar outflows during the early post-AGB evolution. A sample of ten OH/IR stars with irregular OH spectra and unusually large expansion velocities is observed at high angular resolution. The sample includes bipolar nebulae (e.g. OH231.8+4.2), bright post-AGB stars (HD 101584) and reflection nebulae (e.g. Roberts 22). The IRAS colour-colour diagram separates the sample into different types of objects. One group may contain the immediate progenitors to the (few) extreme bipolar planetary nebulae. Two objects show colours and chemistry very similar to the planetary nebulae with late IR-[WC] stars. One object is a confirmed close binary.A model is presented consisting of an outer AGB wind which is swept up by a faster post-AGB wind, with either the AGB or Post-AGB wind being non-spherically symetric. The interface of the two winds is shown to exhibit a linear relation between velocity and distance from the star, giving the impression of an accelerating outflow. The OH data confirms the predicted linear velocity gradients, and also reveals toruslike, uniformly expanding components.All sources are discussed in detail using optical/HST images where available. ISO data for Roberts 22 reveal a chemical dichotomy, with both crystalline silicates and PAHs features being present. IRAS 16342−3814 shows a dense torus with mass 0.1 M ⊙ and density of 10 8 cm −3 ; HST data shows four point-like sources located symmetrically around the nebula, near the outer edge of the dense torus.Lifetimes for the bipolar OH/IR stars are shown to be in excess of 10 4 yr, longer than normal post-AGB timescales. This suggests that the toruses or disks are nearstationary. We suggest that accretion from such a disk slows down the post-AGB evolution. Such a process could explain the link between the long-lived bipolar nebular geometry and the retarded star.

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“…Likkel et al (1992) proposed that the OH masers of W43A are located in a biconical outflow surrounding the H 2 O maser jet at lower latitudes. Likewise, Sahai et al (1999) suggest that the OH masers of the water-fountain source IRAS 16342-3814 are located at intermediate systemic latitudes, where the outflow velocity is much lower than along the polar axis. So far, no systematic studies have been performed to explain the morphology of the OH masers in water-fountains.…”

Section: Introductionmentioning

confidence: 92%

The kinematics and magnetic fields in water-fountain sources based on OH maser observations

Amiri

Vlemmings

Langevelde

2011

A&A

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Context. water-fountain sources are a class of post-AGB objects that exhibit bipolar jet-like structures traced by H 2 O maser emission. The circumstellar envelopes of these objects show deviations from spherical symmetry. While the H 2 O masers originate in a collimated outflow in the polar region, the OH masers may be distributed in the equatorial region or a biconical outflow in the circumstellar shell. Magnetic fields could play an important role in collimating the jet and shaping the circumstellar envelope of these objects. Aims. The aim of this project is to understand the morphology of the OH masers in three water-fountain sources, for which we obtained high-resolution interferometric data. We compare the observational parameters of the spectral profile and spatial distribution with our models in order to constrain the morphology and velocity fields of the OH maser shell. We would also like to understand the role of the magnetic field in shaping the circumstellar envelope of these stars. Methods. We observed the OH masers of three water-fountain sources (OH 12.8-0.9, OH 37.1-0.8, and W43A) in full polarization spectral line mode using the UK Multi-Element Radio Linked Interferometer Network. Additionally, we performed reconstruction models of OH maser shells distributed uniformly in equatorial or biconical outflows and compared them with the OH maser observations.Results. The OH masers of W43A seem to be located in the equatorial region of the circumstellar shell, while for OH 12.8-0.9 the masers are likely distributed in a biconical outflow. We measured magnetic fields of ∼360 μG and ∼29 μG on average for OH 37.1-0.8 and OH 12.8-0.9, respectively. The measured field strengths show that a large-scale magnetic field is present in the circumstellar environment of these stars. Conclusions. Our observations show that the OH maser region of the three water-fountain sources studied in this work show signs of aspherical expansion. Reconstruction of the OH maser distribution of these objects show both biconical and equatorial distributions. Magnetic fields likely play an important role in shaping the OH maser region of water-fountain sources.

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The “Water-Fountain Nebula” IRAS 16342−3814: [ITAL]Hubble Space Telescope[/ITAL]/Very Large Array Study of a Bipolar Protoplanetary Nebula

Cited by 72 publications

References 18 publications

Dust shell model of the water fountain source IRAS 16342–3814

Dust shell model of the water fountain source IRAS 16342–3814

Bipolar Outflows from OH/IR Stars

The kinematics and magnetic fields in water-fountain sources based on OH maser observations

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