Dust in the neutral globules of the Helix nebula, NGC 7293*

Meaburn, J.; Walsh, J. R.; Clegg, R. E. S.; Walton, N. A.; Taylor, D.; Berry, D. S.

doi:10.1093/mnras/255.2.177

Cited by 74 publications

(75 citation statements)

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“…First, the line temperatures were corrected for beam dilution based on the nebular size estimated from the optical image, assuming a Gaussian source distribution coupled to a Gaussian beam (see Table 2). However, molecular material in PNe is believed to exist in dense clumps of gas and dust, not spread uniformly throughout the nebula (see, e.g., Huggins et al 1992;Meaburn et al 1992;Huggins & Mauron 2002;Meixner et al 2005). Thus, the column densities derived from these calculations apply to these knots of material, not the entirety of the PN.…”

Section: Discussionmentioning

confidence: 99%

“…Perhaps even more striking is the identification of C 60 in several PNe with low central star temperatures (Cami et al 2010;García-Hernández et al 2010Otsuka et al 2013). The presence of long-lived molecular material is believed to arise from shielding by high-density clumps (Howe et al 1994), as seen in images of the Helix and the Ring (e.g., Meaburn et al 1992;Speck et al 2003;Meixner et al 2005).…”

Section: Introductionmentioning

confidence: 99%

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New Detections of HNC in Planetary Nebulae: Evolution of the [Hcn]/[Hnc] Ratio

Schmidt

Ziurys

2017

ApJ

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

New Detections of HNC in Planetary Nebulae: Evolution of the [Hcn]/[Hnc] Ratio

Schmidt

Ziurys

2017

ApJ

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“…More recently, it has been realized that many astrophysical outflows are also multiphase with cool condensed material embedded in a hotter and more dilute ambient medium. These systems include: planetary nebulae (e.g., Meaburn et al 1992), stellar winds (e.g., Bouret et al 2005), and quasar flows (e.g., Das et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Heating by Acoustic Waves of Multiphase Media

Chelouche

2009

ApJ

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We study the emission and dissipation of acoustic waves from cool dense clouds in pressure equilibrium with a hot, volume-filling dilute gas component. In our model, the clouds are exposed to a source of ionizing radiation whose flux level varies with time, forcing the clouds to pulsate. We estimate the rate at which acoustic energy is radiated away by an ensemble of clouds and the rate at which it is absorbed by, and dissipated in, the hot dilute phase. We show that acoustic energy can be a substantial heating source of the hot gas phase when the mass in the cool component is a substantial fraction of the total gas mass. We investigate the applicability of our results to the multiphase media of several astrophysical systems, including quasar outflows and cooling flows. We find that acoustic heating could have a substantial effect on the thermal properties of the hot phase in those systems.

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“…Therefore we examine the suggestion that the cometary tail heads are overrun by a transonic or supersonic stream of photoionized gas (Meaburn et al 1992(Meaburn et al , 1998O'Dell 2000;Meaburn et al 2005). We compare results with the knot dynamics observed by Meaburn et al (1998) and show these are reasonably well reproduced.…”

Section: Introductionmentioning

confidence: 89%

The tails in the Helix Nebula NGC 7293

Dyson¹,

Pittard²,

Meaburn

et al. 2006

A&A

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Aims. We have examined a stream-source model for the production of the cometary tails observed in the Helix Nebula NGC 7293 in which a transonic or moderately supersonic stream of ionized gas overruns a source of ionized gas. We have compared the velocity structures calculated with the available observational data. We have also investigated the suggestion that faint striations visible in the nebular gas are the decaying tails of now destroyed cometary globules. Methods. We have selected relevant results from extensive hydrodynamic calculations made with the COBRA code. Results. The velocities calculated are in good agreement with the observational data on tail velocities and are consistent with observations of the nebular structure. The results also are indicative of a stellar atmosphere origin for the cometary globules. Tail remnants persist for timescales long enough for their identification with striations to be plausible.

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Dust in the neutral globules of the Helix nebula, NGC 7293*

Cited by 74 publications

References 0 publications

New Detections of HNC in Planetary Nebulae: Evolution of the [Hcn]/[Hnc] Ratio

New Detections of HNC in Planetary Nebulae: Evolution of the [Hcn]/[Hnc] Ratio

Heating by Acoustic Waves of Multiphase Media

The tails in the Helix Nebula NGC 7293

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