The ionization structure of the Ring Nebula. II - Ultraviolet observations

1982 ◽  
Vol 253 ◽  
pp. 167 ◽  
Author(s):  
T. Barker
Keyword(s):  
Ionization Structure ◽  
Ring Nebula ◽  
Ultraviolet Observations

scholarly journals The Three-Dimensional Ionization Structure and Evolution of NGC 6720, The Ring Nebula

2007 ◽  
Vol 134 (4) ◽  
pp. 1679-1692 ◽  
Author(s):  
C. R. O'Dell ◽  
F. Sabbadin ◽  
W. J. Henney
Keyword(s):  
Three Dimensional ◽  
Ionization Structure ◽  
Ring Nebula

scholarly journals New advances in the field of planetary nebulae from ultraviolet observations

2011 ◽  
Vol 7 (S283) ◽  
pp. 45-52 ◽  
Author(s):  
Luciana Bianchi
Keyword(s):  
Planetary Nebulae ◽  
Ionic Species ◽  
Physical Parameters ◽  
Mass Relation ◽  
Chemical Enrichment ◽  
Intermediate Mass Stars ◽  
Ionization Structure ◽  
C And N ◽  
Ultraviolet Observations ◽  
Critical Constraints

AbstractThe ultraviolet (UV) domain, in particular shortwards of Lyα, provides unique information to unravel the physical parameters of Central Stars of Planetary Nebulae (CSPNe) and the paths for this elusive final stage of stellar evolution, thanks to a wealth of diagnostic transitions from ionic species not observable at other wavelengths. Intermediate mass stars are the major providers of important elements like C and N. Understanding how they shed most of their initial mass is critical for understanding the chemical enrichment of the ISM. Mass-loss diagnostic lines abound at UV wavelengths, and when the CSPN reaches the hottest Teff before turning on the WD-cooling sequence, and the wind fades, the last wind lines to disappear are found in the far-UV, as well as diagnostic lines for elements such as Ne. This domain also offers a host of H2 transitions, tracing the circum-stellar material expelled in previous phases. UV images and spectra of PNe add critical constraints to their ionization structure and to some abundances. Finally, the recent GALEX sky surveys in two UV bands afforded the first unbiased census of hot white dwarfs (WD) and post-AGB objects in the Milky Way, significantly expanding known catalogs and providing statistical constraints to the initial-final mass relation.

scholarly journals Imaging Spectrophotometry of the Ring Nebula

1993 ◽  
Vol 155 ◽  
pp. 194-194
Author(s):  
Nancy Jo Lame ◽  
Richard W. Pogge
Keyword(s):  
Emission Line ◽  
Ohio State University ◽  
State University ◽  
Ionization State ◽  
Ionization Structure ◽  
Ring Nebula ◽  
Fabry Perot ◽  
The Ohio State University ◽  
Line Imaging ◽  
Balmer Decrement

We present new results from a program of emission-line imaging spectrophotometry of planetary nebulae using the Ohio State University Imaging Fabry-Perot Spectrograph (IFPS). High-quality emission-line maps of the important diagnostic lines [NII]λλ5755,6583, [SII]λλ6717,6731, [OI]λ6300, [OIII]λ5007, Hα, and Hβ have been obtained. Maps of the ionization structure ([S II]/Hα, [N II]/Hα, [O III]/Hβ, and [O I]/[O III]), temperature in the N+ region, density in the S+ region, and Balmer decrement across the nebula are presented. These show considerable variation in ionization state, temperature and density. This detailed information will provide powerful constraints on photoionization models for the Ring Nebula.

scholarly journals On the Chemodynamics of NGC 6888

1991 ◽  
Vol 143 ◽  
pp. 422-422
Author(s):  
C. Esteban ◽  
J.M. Vilchez
Keyword(s):  
Major Axis ◽  
Chemical Abundances ◽  
Ionized Gas ◽  
Physical Conditions ◽  
Processed Material ◽  
Ionization Structure ◽  
Ring Nebula ◽  
Solar Abundances ◽  
H Ii Region ◽  
Emission System

We present preliminary results on an extensive spectroscopical study of the WR Ring nebula NGC 6888. The observations combine high spatial (1.5 arcsec/pixel) and spectral resolution (30 to 50 km s–1) covering most of the optical range - λλ 3600 to 6800 å- at 3 different slit positions along the major axis of the nebula. The spectra of the central parts give an emission system with three different velocities: a) VLSR=-64 km s–1, b) VLSR=+18 km s–1, and c) VLSR=+78 km s–1. Assuming that NGC 6888 is in fact an expanding bubble of gas, as demonstrated by Marston and Meaburn (1988), we can identify components a) and c) as those moving towards us and receeding parts of the shell, while b) could be related to the ambient interstellar ionized gas outside the bubble. We have isolated the spectrum for each component in order to analyse the ionization structure and excitation mechanism, as well as to derive their physical conditions and chemical abundances. The use of diagnostic diagrams indicates that the nebula is basically photoionized, without any significant contribution of shock excitation in the zones studied. The ambient interstellar component shows a spectrum typical of an H II region with nearly solar abundances. In the case of the bubble components, their spectra produce [N II]/Hα line ratios which are outside the H II region box, and entering the extended planetary nebulae locus, suggesting a contribution of ejected nitrogen in the bubble. This fact is evident from the abundance analysis we have performed, finding that, with respect to the values quoted for the ambient gas, the O/H is deficient by a factor 4, N/H is 2.5 times higher, and helium is enhanced by a factor 2. These quoted values clearly indicate that a substantial fraction of the gas in the bubble is processed material ejected from the central massive star.

scholarly journals The Ionization Structure of NGC 6720 and NGC 7009

1983 ◽  
Vol 103 ◽  
pp. 522-522
Author(s):  
T. Barker
Keyword(s):  
Spectral Range ◽  
Central Star ◽  
Resonance Fluorescence ◽  
Recombination Line ◽  
Line Intensities ◽  
Ionization Structure ◽  
Ring Nebula ◽  
Central Stars ◽  
Good Agreement ◽  
Made In

Measurements of line intensities over a spectral range generally as great as 1300 Å to 11,000 Å have been made in four positions in the Ring Nebula and eight positions in NGC 7009. Ionic abudances determined from optical and UV lines are in good agreement, except that the C2+ abundance inferred from the optical 4267 Å recombination line is as much as 10 times higher than that measured from the 1906, 1909 Å CIII) lines. In both nebulae, this discrepancy is greatest nearest the central star. At the present time the most attractive explanation seems to be that the 4267 Å line is affected by resonance fluorescence due to light from central stars of planetaries.

scholarly journals The Filamentary Structure of the Ring Nebula

1978 ◽  
Vol 76 ◽  
pp. 289-289
Author(s):  
L.E. Goad
Keyword(s):  
Narrow Band ◽  
Emission Lines ◽  
Low Density ◽  
High Excitation ◽  
Filamentary Structure ◽  
Interference Filters ◽  
Stellar Radiation ◽  
Ionization Structure ◽  
Ring Nebula ◽  
Structure Calculations

Image-tube photographs taken through narrow-band interference filters have been used to obtain monochromatic surface brightnesses of the Ring Nebula (NGC 6720) in the strongest emission lines of H I, He I, He II, [N II], [O I], [O II], [O III], and [S II]. These data have been used to analyze the spatial distribution of the various ionized species within the nebula. The bulk of the observed emission is shown to arise from a network of neutral filaments whose inner surfaces are ionized by the incident stellar radiation. The filamentary network is embedded in a low-density, high-temperature medium which is the source of most of the observed high-excitation lines. The ionization structure of several prominent filaments is examined in detail and comparisons are made to recent ionization structure calculations.

Ultraviolet Observations of the Powering Source of the Supergiant Shell in IC 2574

2000 ◽  
Vol 120 (4) ◽  
pp. 1794-1800 ◽  
Author(s):  
Susan G. Stewart ◽  
Fabian Walter
Keyword(s):  
Ultraviolet Observations
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