A<i>Hubble Space Telescope</i>Snapshot Survey of Proto–Planetary Nebula Candidates: Two Types of Axisymmetric Reflection Nebulosities

Ueta, Toshiya; Meixner, M.; Bobrowsky, M.

doi:10.1086/308208

Cited by 209 publications

(414 citation statements)

References 86 publications

(78 reference statements)

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“…2Dust is a radiative transfer code for axisymmetric systems. While the mass loss is spherically symmetric for most of the AGB phase, the highly evolved AGB stars as well as their post-AGB successors exhibit bipolar geometries (e.g., Ueta et al 2000;Meixner et al 2002). The dust around post-AGB stars is also similar to AGB star circumstellar dust.…”

Section: The Model Gridmentioning

confidence: 99%

The mass-loss return from evolved stars to the Large Magellanic Cloud

Srinivasan

Sargent

Meixner

2011

A&A

110

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Context. Outflows from asymptotic giant branch (AGB) and red supergiant (RSG) stars inject dust into the interstellar medium. The total rate of dust return provides an important constraint to galactic chemical evolution models. However, this requires detailed radiative transfer (RT) modeling of individual stars, which becomes impractical for large data sets. An alternative approach is to select the best-fit spectral energy distribution (SED) from a grid of dust shell models, allowing for a faster determination of the luminosities and mass-loss rates for entire samples. Aims. We have developed the Grid of RSG and AGB ModelS (GRAMS) to measure the mass-loss return from evolved stars. The models span the range of stellar, dust shell and grain properties relevant to evolved stars. The GRAMS model database will be made available to the scientific community. In this paper we present the carbon-rich AGB model grid and compare our results with photometry and spectra of Large Magellanic Cloud (LMC) carbon stars from the SAGE (Surveying the Agents of Galaxy Evolution) and SAGE-Spec programs. Methods. We generate models for spherically symmetric dust shells using the 2Dust code, with hydrostatic models for the central stars. The model photospheres have effective temperatures between 2600 and 4000 K and luminosities from ∼2000 L to ∼40 000 L . Assuming a constant expansion velocity, we explore five values of the inner radius R in of the dust shell (1.5, 3, 4.5, 7 and 12 R star ). We fix the outer radius at 1000 R in . Based on the results from our previous study, we use amorphous carbon dust mixed with 10% silicon carbide by mass. The grain size distribution follows a power-law and an exponential falloff at large sizes. The models span twenty-six values of 11.3 μm optical depth, ranging from 0.001 to 4. For each model, 2Dust calculates the output SED from 0.2 to 200 μm. Results. Over 12 000 models have dust temperatures below 1800 K. For these, we derive synthetic photometry in optical, nearinfrared and mid-infrared filters for comparison with available data. We find good agreement with magnitudes and colors observed for LMC carbon-rich and extreme AGB star candidates from the SAGE survey, as well as spectroscopically confirmed carbon stars from the SAGE-Spec study. Our models reproduce the IRAC colors of most of the extreme AGB star candidates, consistent with the expectation that a majority of these enshrouded stars have carbon-rich dust. Finally, we fit the SEDs of some well-studied carbon stars and compare the resulting luminosities and mass-loss rates with those from previous studies.

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Section: The Model Gridmentioning

confidence: 99%

The mass-loss return from evolved stars to the Large Magellanic Cloud

Srinivasan

Sargent

Meixner

2011

A&A

110

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“…When imaged, post asymptotic giant branch (AGB) stars often display a highly nonspherical structure (Ueta et al 2000). The cause for this asphericity and at which point in the post main sequence evolution the deviations from a spherical wind start has been, and still is, a matter of debate.…”

Section: Introductionmentioning

confidence: 99%

The color dependent morphology of the post-AGB star HD 161796

Min

Jeffers

Cánovas

et al. 2013

A&A

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Context. Many protoplanetary nebulae show strong asymmetries in their surrounding shells, pointing to asymmetries during the mass loss phase. Questions concerning the origin and the onset of deviations from spherical symmetry are important for our understanding of the evolution of these objects. Here we focus on the circumstellar shell of the post-AGB star HD 161796. Aims. We aim to detect signatures of an aspherical outflow, and to derive its properties. Methods. We used the imaging polarimeter the Extreme Polarimeter (ExPo), a visitor instrument at the William Herschel Telescope, to accurately image the dust shell surrounding HD 161796 in various wavelength filters. Imaging polarimetry allows us to separate the faint, polarized, light that comes from circumstellar material from the bright, unpolarized, light from the central star.Results. The shell around HD 161796 is highly aspherical. A clear signature of an equatorial density enhancement can be seen. This structure is optically thick at short wavelengths and changes its appearance to optically thin at longer wavelengths. In the classification of the two different appearances of planetary nebulae from HST images it changes from being classified as DUst-Prominent Longitudinally-EXtended (DUPLEX) at short wavelengths to star-obvious low-level-elongated (SOLE) at longer wavelengths. This strengthens the interpretation that these two appearances are manifestations of the same physical structure. Furthermore, we find that the central star is hotter than often assumed and the relatively high observed reddening is a consequence of circumstellar rather than interstellar extinction.

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“…Imaging surveys in broad-band optical and the near-IR of post-AGB objects over more than a decade have been key to progress in understanding the earliest phase of PN evolution (e.g., Ueta, et al 2000, Siodmiak et al 2008. The distribution of morphological types in these studies contrasts somewhat with surveys of Galactic PNe in that pre-PN samples tend to show a higher fraction of bi-polar types.…”

Section: Morphology In Planetary Nebulaementioning

confidence: 99%

Shape, structure, and morphology in planetary nebulae

Shaw¹

2011

Proc. IAU

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Abstract.A revival over the past two decades in planetary nebula (PN) morphological studies springs from a combination of factors, including the advent of wide-area, high dynamic range detectors; the growing archives of high resolution images from the X-ray to the sub-mm; and the advent of sophisticated models of the co-evolution of PNe and their central stars. Yet the story of PN formation from their immediate precursors, the AGB stars, is not yet fully written. PN morphology continues to inspire, provide context for physical interpretation, and serve as an ultimate standard of comparison for many investigations in this area of astrophysics. After a brief review of the remarkable successes of PN morphology, I summarize how this tool has been employed over the last half-decade to advance our understanding of PNe.

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AHubble Space TelescopeSnapshot Survey of Proto–Planetary Nebula Candidates: Two Types of Axisymmetric Reflection Nebulosities

Cited by 209 publications

References 86 publications

The mass-loss return from evolved stars to the Large Magellanic Cloud

The mass-loss return from evolved stars to the Large Magellanic Cloud

The color dependent morphology of the post-AGB star HD 161796

Shape, structure, and morphology in planetary nebulae

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