A kinematic determination of the structure of the double ring planetary nebula NGC 2392, the Eskimo

1990 ◽  
Vol 362 ◽  
pp. 226 ◽  
Author(s):  
C. R. O'dell ◽  
Larry D. Weiner ◽  
You-Hua Chu
Keyword(s):  
Planetary Nebula ◽  
Double Ring

Determination of Hydraulic Properties in Sloping Landscapes from Tension and Double-Ring Infiltrometers

2004 ◽  
Vol 3 (3) ◽  
pp. 964-970 ◽  
Author(s):  
Waduwawatte Bodhinayake ◽  
Bing Cheng Si ◽  
Kosuke Noborio
Keyword(s):  
Hydraulic Properties ◽  
Double Ring

Spectrum and chemical analysis of the double-ring planetary nebula IC 1297

1986 ◽  
Vol 311 ◽  
pp. 930 ◽  
Author(s):  
Lawrence H. Aller ◽  
Charles D. Keyes ◽  
Walter A. Feibelman
Keyword(s):  
Chemical Analysis ◽  
Planetary Nebula ◽  
Double Ring

Detection of the Angular Expansion Rate and Determination of the Distance of the Planetary Nebula NGC 6302

1993 ◽  
Vol 416 ◽  
pp. 620 ◽  
Author(s):  
Yolanda Gomez ◽  
Luis F. Rodriguez ◽  
James M. Moran
Keyword(s):  
Planetary Nebula ◽  
Expansion Rate ◽  
Angular Expansion

scholarly journals Determination of Hydraulic Properties in Sloping Landscapes from Tension and Double-Ring Infiltrometers

2004 ◽  
Vol 3 (3) ◽  
pp. 964-970 ◽  
Author(s):  
W. Bodhinayake ◽  
B. C. Si ◽  
K. Noborio
Keyword(s):  
Hydraulic Properties ◽  
Double Ring

scholarly journals Confronting expansion distances of planetary nebulae with Gaia DR2 measurements

2019 ◽  
Vol 625 ◽  
pp. A137 ◽  
Author(s):  
D. Schönberner ◽  
M. Steffen
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Precise Determination ◽  
Asymptotic Giant Branch ◽  
Correction Factors ◽  
Trigonometric Parallaxes ◽  
Formation And Evolution ◽  
Hydrodynamical Simulations ◽  
Good Agreement

Context. Individual distances to planetary nebulae are of the utmost relevance for our understanding of post-asymptotic giant-branch evolution because they allow a precise determination of stellar and nebular properties. Also, objects with individual distances serve as calibrators for the so-called statistical distances based on secondary nebular properties. Aims. With independently known distances, it is possible to check empirically our understanding of the formation and evolution of planetary nebulae as suggested by existing hydrodynamical simulations. Methods. We compared the expansion parallaxes that have recently been determined for a number of planetary nebulae with the trigonometric parallaxes provided by the Gaia Data Release 2. Results. Except for two out of 11 nebulae, we found good agreement between the expansion and the Gaia trigonometric parallaxes without any systematic trend with distance. Therefore, the Gaia measurements also prove that the correction factors necessary to convert proper motions of shocks into Doppler velocities cannot be ignored. Rather, the size of these correction factors and their evolution with time as predicted by 1D hydrodynamical models of planetary nebulae is basically validated. These correction factors are generally greater than unity and are different for the outer shell and the inner bright rim of a planetary nebula. The Gaia measurements also confirm earlier findings that spectroscopic methods often lead to an overestimation of the distance. They also show that even modelling of the entire system of star and nebula by means of sophisticated photoionisation modelling may not always provide reliable results. Conclusions. The Gaia measurements confirm the basic correctness of the present radiation-hydrodynamics models, which predict that both the shell and the rim of a planetary nebula are two independently expanding entities, created and driven by different physical processes, namely thermal pressure (shell) or wind interaction (rim), both of which vary differently with time.

scholarly journals Density Distribution and Chemical Abundances in NGC 7027

1978 ◽  
Vol 76 ◽  
pp. 357-358
Author(s):  
Andrea Preite-Martinez ◽  
Nino Panagiat
Keyword(s):  
Density Distribution ◽  
Planetary Nebula ◽  
Constant Density ◽  
Chemical Abundances ◽  
Line Intensities ◽  
Ngc 7027

The data available on permitted and forbidden line intensities of the planetary nebula NGC 7027 have been analyzed in terms of non-constant density models. The significance of the derived density distribution is discussed. Some implications to the determination of the chemical abundances are also discussed.

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