A New Look at Carbon Abundances in Planetary Nebulae. II. BB 1, NGC 650, NGC 1535, NGC 2440, and NGC 7027

1996 ◽  
Vol 473 (1) ◽  
pp. 304-309 ◽  
Author(s):  
K. B. Kwitter ◽  
R. B. C. Henry
Keyword(s):  
Planetary Nebulae ◽  
Ngc 7027 ◽  
New Look

Abundance Anomalies in the X‐Ray Spectra of Planetary Nebulae NGC 7027 and BD +30o3639

2003 ◽  
Vol 589 (1) ◽  
pp. 439-443 ◽  
Author(s):  
Holly L. Maness ◽  
Saeqa D. Vrtilek ◽  
Joel H. Kastner ◽  
Noam Soker
Keyword(s):  
Planetary Nebulae ◽  
X Ray ◽  
Ngc 7027 ◽  
Abundance Anomalies

scholarly journals Photoionization modeling of the Galactic planetary nebulae Abell 39 and NGC 7027

2011 ◽  
Vol 7 (S283) ◽  
pp. 340-341 ◽  
Author(s):  
Ashkbiz Danehkar ◽  
David J. Frew ◽  
Quentin A. Parker ◽  
Orsola De Marco
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Ngc 7027

AbstractWe estimate distances to the spherical planetary nebula Abell 39 and the bipolar planetary nebula NGC 7027 by interpolating from a wide grid of photoionization models using the 3-D code, MOCASSIN. We find preliminary distances of 1.5 kpc and 0.9 kpc respectively, with uncertainties of about 30%.

scholarly journals Radio Spectroscopy of Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 127-128
Author(s):  
Eric J. Chaisson
Keyword(s):  
Stark Effect ◽  
Principal Quantum Number ◽  
Planetary Nebulae ◽  
Radio Continuum ◽  
Radio Lines ◽  
Ion Temperature ◽  
Radio Recombination Line ◽  
Ngc 7027 ◽  
Optical Line ◽  
Ion Impact

The H110α radio recombination line has been observed toward the planetary nebulae NGC 7027, IC 418, and NGC 6543 in order to ascertain the physical characteristics of the bulk nebular gas. The observations of NGC 7027 confirm the earlier findings of Chaisson and Malkan (Ap.J., 210, 108, 1976) and Churchwell, Terzian and Walmsley (A&A, 48, 331, 1976) who reported evidence for a substantial increase in linewidth with principal quantum number. Attributed to electron-ion impact broadening (Stark Effect), the observations imply an electron density Ne ≃ 50,000/cm3. The LTE-derived electron-ion temperature Te ≃ 18,000°K agrees reasonably well with most radio-line analyses, as well as with previous analyses of the radio continuum, of forbidden optical line ratios, and of optical recombination lines and their associated continuum. IC418's HllOa line is also wider than radio lines observed at higher frequencies, suggesting a Stark Effect consistent with Ne < 20,000/cm3; NGC 6543 shows no appreciable line broadening, providing an upper limit to the density Ne < 10,000/cm3. The LTE-derived Te values for IC 418 and NGC 6543 are approximately 14,000 and 7000°K, reasonably consistent with those found by other techniques. On the basis of this and other recent studies, I suggest that the bulkemission in the Hnα recombination lines observed to date, 77 < n < 111, can be explained by a simple model of optically thin planetary nebular gas largely homogeneous in temperature and in density, and only slightly removed from LTE.

scholarly journals Planetary Nebulae with Massive Nuclei

1983 ◽  
Vol 103 ◽  
pp. 230-230
Author(s):  
R. Tylenda
Keyword(s):  
Thermal Structure ◽  
Planetary Nebulae ◽  
General Rule ◽  
Central Star ◽  
Time Dependent ◽  
Equilibrium Conditions ◽  
Ngc 7027 ◽  
Different Temperatures ◽  
Far From Equilibrium ◽  
Central Stars

Massive central stars (M > 1 Mo) of planetary nebulae burn nuclear fuel on a time scale of hundreds or tens of years which is shorter than the recombination time in a typical planetary nebula. Consequently the ionization and thermal structure of a nebula with such a nucleus is expected to be far from equilibrium conditions. The greatest chance of observing such a nebula is when the central star cools down to the white dwarf region. Time-dependent photoionization models suggest the following non-equilibrium effects to be expected at this stage. Firstly, the nebula shows a double shell structure, i.e. a bright, inner ring is surrounded by a faint, extended halo best seen in the HI lines and infrared lines from low-ionization species, such as (Ne II) 12.8 μ. Secondly, the low-excitation emission ((O II), (Ne II), (S III)) is enhanced relative to the high-excitation ((O III), (Ne III), (S III)). Thirdly, different modifications of the Zanstra method result in significantly different temperatures for the central star with a general rule that THI > THeII > THeII/HI The He II Zanstra method gives the most reliable result. Fourthly, the electron temperature derived from the (O III) lines is appreciably higher than that obtained from the (N II) lines. It is suggested that NGC 7027 and NGC 2440 possess massive central stars and that the above time-dependent effects are currently observed in these nebulae.

scholarly journals ISO-SWS observations of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 145-150
Author(s):  
D.A. Beintema
Keyword(s):  
Solid State ◽  
Short Wavelength ◽  
Planetary Nebulae ◽  
Spectral Lines ◽  
Ngc 7027 ◽  
First Results

First results of the ISO1 Short-Wavelength Spectrometer on three bright planetary nebulae NGC 6543, NGC 7027 and NGC 6302 provide a wealth of information on solid-state features and spectral lines. Spectra from 2.4 to 45 μm are presented, at a reduced resolution of about 600.

scholarly journals The Central Stars of the Planetary Nebulae NGC 7027 and NGC 6543

1997 ◽  
pp. 134-134
Author(s):  
P. A. M. van Hoof ◽  
D. A. Beintema ◽  
F. Lahuis ◽  
S. R. Pottasch
Keyword(s):  
Planetary Nebulae ◽  
Ngc 7027 ◽  
Central Stars

scholarly journals Rings and arcs around evolved stars – II. The Carbon Star AFGL 3068 and the Planetary Nebulae NGC 6543, NGC 7009, and NGC 7027

2020 ◽  
Vol 495 (2) ◽  
pp. 2234-2246 ◽  
Author(s):  
M A Guerrero ◽  
G Ramos-Larios ◽  
J A Toalá ◽  
B Balick ◽  
L Sabin
Keyword(s):  
Proper Motion ◽  
Planetary Nebulae ◽  
Carbon Star ◽  
Agb Stars ◽  
Spiral Pattern ◽  
High Quality ◽  
Hydrodynamic Simulations ◽  
Evolved Stars ◽  
Ngc 7027 ◽  
Regular Patterns

ABSTRACT We present a detailed comparative study of the arcs and fragmented ring-like features in the haloes of the planetary nebulae (PNe) NGC 6543, NGC 7009, and NGC 7027 and the spiral pattern around the carbon star AFGL 3068 using high-quality multi-epoch HST images. This comparison allows us to investigate the connection and possible evolution between the regular patterns surrounding AGB stars and the irregular concentric patterns around PNe. The radial proper motion of these features, ≃15 km s−1, are found to be consistent with the AGB wind and their linear sizes and interlapse times (500–1900 yr) also agree with those found around AGB stars, suggesting a common origin. We find evidence using radiative-hydrodynamic simulations that regular patterns produced at the end of the AGB phase become highly distorted by their interactions with the expanding PN and the anisotropic illumination and ionization patterns caused by shadow instabilities. These processes will disrupt the regular (mostly spiral) patterns around AGB stars, plausibly becoming the arcs and fragmented rings observed in the haloes of PNe.

scholarly journals Structure

1968 ◽  
Vol 34 ◽  
pp. 456-462 ◽  
Author(s):  
R. Minkowski
Keyword(s):  
Near Infrared ◽  
Planetary Nebulae ◽  
Seyfert Galaxy ◽  
Seyfert Galaxies ◽  
Brightness Distribution ◽  
Line Intensities ◽  
Near Ultraviolet ◽  
Ngc 7027 ◽  
Expansion Pattern ◽  
Ngc 1068

My first task is to give summaries of the sessions on observations of the spectra of planetary nebulae and on the spectra of the central stars.About the spectra of planetary nebulae there is little more to say than that the observations of line intensities in the range from the near ultraviolet to the near infrared have made impressive progress. Most important is the extension of the observations into the infrared which has led to the discovery by Gillet, Low and Stein of unexpectedly high intensities in the continuous spectrum of NGC 7027 between 4μ and 14μ (75 to 22 THz). In this respect NGC 7027 and the Seyfert galaxy NGC 1068 resemble each other. Similarity of the compositions of the emission-line spectra of these two objects has been noted long ago; some lines of low ionization – [O II], [S II] –, however, are stronger in the Seyfert galaxies. The physical significance of the similarity of the infrared continua is not clear at this time, but I see no reason to reject the classification of NGC 7027 as a planetary nebula. It has a very irregular brightness distribution with much structure, but an outline which is roughly elliptical and the usual expansion pattern with a velocity of expansion of 21 km/sec.

scholarly journals The central stars of the Planetary Nebulae NGC 7027 and NGC 6543

1997 ◽  
Vol 180 ◽  
pp. 134-134
Author(s):  
P.A.M. Van Hoof ◽  
D. A. Beintema ◽  
F. Lahuis ◽  
S. R. Pottasch
Keyword(s):  
Infrared Spectra ◽  
Short Wavelength ◽  
Planetary Nebulae ◽  
Space Observatory ◽  
Infrared Space Observatory ◽  
Ngc 7027 ◽  
Photo Ionization ◽  
Central Stars

Infrared spectra of NGC 7027 and NGC 6543 ranging from 2.4 μm to 45 μm were obtained with the Short Wavelength Spectrometer on board the Infrared Space Observatory. A first analysis of these spectra, with the aid of photo-ionization models, is presented in Beintema et al. (1996).

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