scholarly journals A Method of Determination of the Temperature of Nuclei of the Planetary Nebulae

1968 ◽  
Vol 34 ◽  
pp. 330-331
Author(s):  
G.S. Khromov
Keyword(s):  
Heavy Ions ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Independent Method ◽  
Heavy Elements ◽  
Color Temperature ◽  
High Excitation ◽  
Method Of Determination

I would like to make a few comments on the problem of the determination of the temperatures of nuclei of planetary nebulae.It can be shown that in a high-excitation planetary nebula two independent Strömgren zones of heavy elements can be found. The first is a He III zone; the second corresponds to a zone of the luminescence of Ne V forbidden lines and originates due to combined absorption by the heavy ions Ne IV, O V and N V. If so, a relatively independent method of the determination of the color temperature of nuclei can be suggested.

scholarly journals Models of Planetary Nebulae: Generalisation of the Multiple Winds Model

1989 ◽  
Vol 131 ◽  
pp. 411-424 ◽  
Author(s):  
F. D. Kahn
Keyword(s):  
Planetary Nebula ◽  
High Speed ◽  
Planetary Nebulae ◽  
Central Star ◽  
Theoretical Description ◽  
Basic Theory ◽  
Spectral Lines ◽  
High Excitation ◽  
General Shape ◽  
Fast Wind

According to the multiple winds model a planetary nebula forms as the result of the interaction of a fast wind from the central star with the superwind that had previously been emitted by the progenitor star. The basic theory which deals with the spherically symmetrical case is briefly summarised. Various improvements are then considered in turn. A better history is clearly needed of the way that the central star becomes hotter, it is unrealistic to make the assumption that the superwind is spherically symmetrical, and finally there are likely to be important instabilities at some of the interfaces in the PN, notably that between the shocked superwind and the HII layer. These changes in the theoretical description produce a better understanding of the conditions in the outer parts of a PN and of the nature of its general shape, and they should lead to an explanation for the occurrence of high speed motions, and of highly ionized species and high excitation spectral lines.

scholarly journals Spectroscopy of Extragalactic Planetary Nebulae in the Ultraviolet

1983 ◽  
Vol 103 ◽  
pp. 545-545
Author(s):  
T.R. Gull ◽  
S.P. Maran ◽  
T.P. Stecher ◽  
L. H. Aller
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Magellanic Clouds ◽  
Emission Lines ◽  
High Excitation ◽  
Long Wavelength ◽  
International Ultraviolet Explorer ◽  
Interstellar Media ◽  
Progenitor Stars ◽  
Stellar Envelopes

Three high-excitation planetary nebulae in the Magellanic Clouds were successfully observed with the International Ultraviolet Explorer. Emission lines as well as nebular and stellar continua were detected. Fluxes in the lines 1550 C IV, 1640 He II, 1663 O III, and 1909 C III were measured in spectra of LMC P40, SMC N2, and SMC N5 obtained with the IUE short wavelength spectrograph; 2422 Ne IV was measured in P40 with the long wavelength spectrograph. The data were analyzed together with groundbased observations by Aller in order to derive ionization models and the nebular abundances of He, C, N, O, S, Ar. The C abundances are as large as those typically found in galactic planetaries, although the interstellar media of the Clouds are notably deficient in C. Thus, the C was synthesized in the progenitor stars and presumably was lifted to the stellar envelopes by convection prior to the ejection of the nebulae. Other planetary nebulae in the Clouds, as well as the planetary nebula in the Fornax galaxy, may be observable with IUE.

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 Magnetic fields around AGB stars and Planetary Nebulae

2013 ◽  
Vol 9 (S302) ◽  
pp. 389-397 ◽  
Author(s):  
W. H. T. Vlemmings
Keyword(s):  
Magnetic Fields ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Heavy Elements ◽  
Current Evidence ◽  
Circumstellar Envelope ◽  
Agb Stars ◽  
Significant Progress ◽  
Natural Explanation ◽  
Shaping Process

AbstractStars with a mass up to a few solar masses are one of the main contributors to the enrichment of the interstellar medium in dust and heavy elements. However, while significant progress has been made, the process of the mass-loss responsible for this enrichment is still not exactly known and forces beyond radiation pressure might be required. Often, the mass lost in the last phases of the stars life will become a spectacular planetary nebula. The shaping process of often strongly a-spherical PNe is equally elusive. Both binaries and magnetic fields have been suggested to be possible agents although a combination of both might also be a natural explanation.Here I review the current evidence for magnetic fields around AGB and post-AGB stars pre-Planetary Nebulae and PNe themselves. Magnetic fields appear to be ubiquitous in the envelopes of apparently single stars, challenging current ideas on its origin, although we have found that binary companions could easily be hidden from view. There are also strong indications of magnetically collimated outflows from post-AGB/pre-PNe objects supporting a significant role in shaping the circumstellar envelope.

scholarly journals High-resolution spectroscopic study of the planetary nebula Abell 78

1999 ◽  
Vol 193 ◽  
pp. 374-375
Author(s):  
Selene Medina ◽  
Miriam Peña
Keyword(s):  
Chemical Composition ◽  
High Resolution ◽  
Spectroscopic Study ◽  
Spectral Resolution ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Heavy Elements ◽  
Physical Parameters ◽  
Processed Material

High resolution optical spectra of the planetary nebula Abell 78 were gathered, covering the wavelength ranges 3500–6600 Å and 3358–7361 Å, with a spectral resolution of ∼0.1 Å. Two different regions of Abell 78 are analyzed: the strongest knot near the central star which is thought to be a mass-loaded wind from the central star, and the outer, hydrogen-rich envelope. Physical parameters and chemical composition of both regions are estimated. The inner knot appears to be cooler and denser than the hydrogen-rich envelope. The chemical composition of the inner knot shows that there is almost no hydrogen near the central star and the emission is dominated by helium and processed material which has been dredged-up from the inner layers of the star. The outer, hydrogen-rich envelope appears to be deficient in heavy elements, mainly in oxygen, compared to the average abundances that are found among galactic planetary nebulae.

scholarly journals The Electron Temperature in the He++ Regions in Planetary Nebulae

1978 ◽  
Vol 76 ◽  
pp. 164-165
Author(s):  
R. Tylenda
Keyword(s):  
Electron Temperature ◽  
Observational Data ◽  
Planetary Nebulae ◽  
Method Of Determination ◽  
Effective Temperatures ◽  
Central Stars

A method of determination of the electron temperature in the He++ regions in planetary nebulae from observed intensities of [NeV] λ3426 and [NeIV] λ4714–25 relative to HeII λ4686 is presented. It has been used for 22 planetary nebulae for which the observational data have been taken from Kaler's Catalogue (Ap. J. Suppl., 31, 517). The electron temperatures in the He++ regions range from 15,000°K to 30,000°K for most of the studied planetaries and are usually significantly higher than the temperatures determined from [01II] lines which refer to the He++ regions. A correlation between the electron temperatures and effective temperatures of central stars has been found; the planetaries with hotter nuclei have slightly higher electron temperatures in the He++ regions. Finally, intensities of ultraviolet lines of [NeV] λ2975 and [NeIV] λ2424 have been predicted for the studied nebulae.

scholarly journals IRAS 21282+5050: A Transitional Planetary Nebula

1989 ◽  
Vol 106 ◽  
pp. 233-233
Author(s):  
L. Likkel ◽  
M. Morris ◽  
A. Omont ◽  
T. Forveille
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Far Infrared ◽  
Color Temperature ◽  
Evolved Stars ◽  
Almost All

IRAS 21282+5050 is very compact planetary nebula with a substantial molecular shell. It is carbon-rich and exhibits infrared features attributed to PAH molecules. It has a far infrared color temperature higher than almost all other planetary nebulae, with IRAS flux ratios similar to low color temperature evolved stars. We present VLA images of IRAS 21282 at wavelengths of 2 and 6 cm (with FWHM beamsizes of 0.5” and 0.9”, respectively).

scholarly journals Luminosity functions of Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 413-413
Author(s):  
Marcelle Tremblay ◽  
Sun Kwok
Keyword(s):  
Mass Distribution ◽  
Planetary Nebula ◽  
Luminosity Function ◽  
Planetary Nebulae ◽  
Core Mass ◽  
The Core ◽  
Luminosity Functions

Planetary nebulae have recently been shown to be useful as standard candles (Ciardullo et al. 1989, ApJ, 339, 53; Jacoby 1989, ApJ, 339, 39). Distances to many galaxies have been determined by fitting a planetary nebula luminosity function (PNLF) to observations of the OIII 5007å line of PNe. Here, the effect of the core mass distribution on the determination of the luminosity function is investigated and a technique for interpolating between model evolutionary tracks is discussed.

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