scholarly journals Echelle Spectra of a Large Sample of Planetary Nebula Nuclei

1989 ◽  
Vol 131 ◽  
pp. 316-316
Author(s):  
James K. McCarthy
Keyword(s):  
High Resolution ◽  
Absorption Line ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
The Sun ◽  
Line Profiles ◽  
Large Sample ◽  
Central Stars

We have undertaken at Palomar Observatory to obtain high resolution spectra of a large sample of planetary nebula nuclei (PNN) in order to systematically investigate their spectral morphologies and then to derive temperatures and surface gravities by comparing absorption line profiles to model atmospheres. We have taken as our sample all those central stars of planetary nebulae within 1.3 kpc of the sun according to the distance determinations of Daub (Ap, J., 260, 612, 1982); of the 94 objects in this unbiased sample, 64 are in the sky visible from Palomar and 33 have central stars bright enough to be observed at a resolution of 5 000 with an “echellette” spectrograph on the 5-m Hale telescope, leaving 7 PNN (11% of the northern sample of 64 PNN) which are too faint to be observed at present.

scholarly journals Unified Model Atmosphere Studies of Central Stars of Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 82-82
Author(s):  
R. Gabler ◽  
A. Gabler ◽  
R. H. Méndez ◽  
R. P. Kudritzki
Keyword(s):  
High Resolution ◽  
Absorption Line ◽  
Spectroscopic Analysis ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Unified Model ◽  
Parallel Model ◽  
Line Profiles ◽  
Atmospheric Parameters ◽  
Central Stars

A first step in the accurate quantitative spectroscopic analysis of central stars of PN has been based on fitting the results of NLTE, hydrostatic, plane-parallel model atmosphere calculations to the observed H and He absorption-line profiles in high-resolution spectra of bright central stars (Méndez et al. 1988, A&A 190, 113 and subsequent papers). Such analyses have provided very useful determinations of the basic atmospheric parameters: Teff, log g and He abundance.

scholarly journals Spectroscopic Distances to Central Stars of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 168-168 ◽  
Author(s):  
R. H. Méndez ◽  
R. P. Kudritzki ◽  
A. Herrero ◽  
D. Husfeld ◽  
H. G. Groth
Keyword(s):  
Absorption Line ◽  
Planetary Nebulae ◽  
Interstellar Extinction ◽  
Model Atmosphere ◽  
Line Profiles ◽  
Available Information ◽  
Central Stars

We present spectroscopic distances for 22 central stars of planetary nebulae. These distances have been determined using information provided by our non-LTE model atmosphere analyses of the stellar H and He absorption line profiles. In this way, no assumptions about nebular properties are necessary.Our spectroscopic distances turn out to be larger than many other frequently cited values. We show that our distances are not in contradiction with the available information about the interstellar extinction, and we describe additional evidence supporting them.

scholarly journals Helium Rich Subdwarf O Stars and Central Stars of Planetary Nebulae

1985 ◽  
Vol 87 ◽  
pp. 322-343
Author(s):  
R.H. Méndez ◽  
C.H. Miguel ◽  
U. Heber ◽  
R.P. Kudritzki
Keyword(s):  
Absorption Line ◽  
Planetary Nebulae ◽  
Model Atmosphere ◽  
Evolutionary Status ◽  
Line Formation ◽  
Line Profiles ◽  
Plane Parallel ◽  
Computational Work ◽  
Work First ◽  
Central Stars

In this review we will discuss the hottest subluminous H-deficient stars, namely those with Teff > 30000 K. In the absence of reliable distance determinations for hot subluminous stars, the best way to discuss their properties and evolutionary status is to find their positions on the log g - log Teff diagram. In the last few years, after extensive computational work, first in Kiel and more recently also in Munich, it has become possible to obtain log g and Teff, together with the surface He abundance, directly by fitting the observed H and He absorption line profiles with theoretical profiles obtained from non-LTE model atmospheres and associated line formation codes. The non-LTE models are plane-parallel, in hydrostatic and radiative equilibrium, and the atmosphere is assumed to consist of H and He only. A recent paper by Groth et al. (1985) gives most of the references on the application of this non-LTE model atmosphere approach to the study of all kinds of hot subluminous stars.

scholarly journals The Weak Emission Line Stars

2003 ◽  
Vol 209 ◽  
pp. 235-236
Author(s):  
Jeffrey Fogel ◽  
Orsola De Marco ◽  
George Jacoby
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Emission Lines ◽  
Type I ◽  
Evolutionary Sequence ◽  
Lower Mass ◽  
Stellar Temperatures ◽  
Central Stars

In this paper, we study the evolution of the weak emission line central stars of planetary nebula (WELS), which are similar to the H-deficient Wolf-Rayet central stars except for systematically weaker emission lines. Our attempts at finding an evolutionary sequence for the WELS similar to what was established for Wolf-Rayet central stars, were unsuccessful. No correlation was found between any of the analysed quantities: emission and absorption line fluxes or stellar and nebular parameters from the literature. It does appear, however, that WELS have intermediate stellar temperatures (30–80 kK), and do not reside in the middle of Type I planetary nebulae, possibly indicating lower mass precursors.

scholarly journals Planetary Nebula Evolution Traced by Distance-Independent Parameters

1993 ◽  
Vol 155 ◽  
pp. 480-480
Author(s):  
C.Y. Zhang ◽  
S. Kwok
Keyword(s):  
Physical Properties ◽  
Mass Distribution ◽  
Planetary Nebula ◽  
Strong Support ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolution Model ◽  
The Core ◽  
Independent Parameters ◽  
Central Stars

Making use of the results from recent infrared and radio surveys of planetary nebulae, we have selected 431 nebulae to form a sample where a number of distance-independent parameters (e.g., Tb, Td, I60μm and IRE) can be constructed. In addition, we also made use of other distance-independent parameters ne and T∗ where recent measurements are available. We have investigated the relationships among these parameters in the context of a coupled evolution model of the nebula and the central star. We find that most of the observed data in fact lie within the area covered by the model tracks, therefore lending strong support to the correctness of the model. Most interestingly, we find that the evolutionary tracks for nebulae with central stars of different core masses can be separated in a Tb-T∗ plane. This implies that the core masses and ages of the central stars can be determined completely independent of distance assumptions. The core masses and ages have been obtained for 302 central stars with previously determined central-star temperatures. We find that the mass distribution of the central stars strongly peaks at 0.6 M⊙, with 66% of the sample having masses <0.64 MM⊙. The luminosities of the central stars are then derived from their positions in the HR diagram according to their core masses and central star temperatures. If this method of mass (and luminosity) determination turns out to be accurate, we can bypass the extremely unreliable estimates for distances, and will be able to derive other physical properties of planetary nebulae.

The Electron Temperature of the Planetary Nebula IC 418

1969 ◽  
Vol 1 (5) ◽  
pp. 216-217
Author(s):  
A. E. Le Marne ◽  
P. A. Shaver
Keyword(s):  
High Resolution ◽  
Electron Temperature ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Pencil Beam ◽  
Radio Observatory ◽  
A Current

In a current programme at the Molonglo Radio Observatory using the high-resolution pencil beam of the instrument (∼3′ arc) an attempt is being made to extend the measured spectra of known planetary nebulae down to 408 MHz. Of 23 such planetaries already investigated, 14 have been detected. The main results will be given elsewhere; here it is proposed to discuss in detail only the well-known planetary nebula IC 418.

scholarly journals Non-LTE Model Atmosphere Analysis of Central Stars

1983 ◽  
Vol 103 ◽  
pp. 343-357 ◽  
Author(s):  
R.H. Méndez ◽  
R. P. Kudritzki ◽  
K. P. Simon
Keyword(s):  
Absorption Line ◽  
Model Atmosphere ◽  
Helium Abundance ◽  
Line Profiles ◽  
Atmospheric Parameters ◽  
Central Stars

This review will be concentrated on the determination of the main atmospheric parameters (Teff, log g, helium abundance) of PN nuclei, and of other subluminous objects, by fitting the observed absorption line profiles with theoretical profiles obtained from non-LTE model atmosphere calculations.

scholarly journals Structure of selected Planetary Nebulae surrounding WR-type central stars

1997 ◽  
Vol 180 ◽  
pp. 230-230
Author(s):  
S.K. Górny ◽  
K. Gȩsicki ◽  
A. Acker
Keyword(s):  
Velocity Field ◽  
Planetary Nebula ◽  
Radial Direction ◽  
Planetary Nebulae ◽  
Late Type ◽  
Computer Codes ◽  
Central Stars

The main aim of this work was to confirm that expansion of planetary nebulae surrounding Wolf-Rayet type central stars is characterized by turbulent motions or strong variations of velocity in the radial direction relative to the nucleus. Such properties have already been found in Ml-25, M3-15 and Pel-1 by Gesicki & Acker (1995). We have analyzed the photoionization structure and velocity field of the NGC 40 - a planetary nebula with late type ([WC 8]) Wolf-Rayet nucleus. The spectra of Hα and [NII] lines have been obtained with the 1.5m telescope at the Observatoire de Haute-Provence. The spectrograph Aurelie with dispersion of 5Å/mm and a 3″ circular entrance was used. The method and the details of the applied computer codes are published in Gesicki et al. (1996).

scholarly journals De-Centered Central Stars of Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 541-542 ◽  
Author(s):  
Aubrie McLean ◽  
Martín A. Guerrero ◽  
Robert A. Gruendl ◽  
You-Hua Chu
Keyword(s):  
Binary System ◽  
Mass Loss ◽  
Planetary Nebulae ◽  
Central Star ◽  
Large Sample ◽  
Preliminary Results ◽  
Wide Range ◽  
Central Stars

The origin of the wide range of morphologies observed in planetary nebulae (PNe) is not well established. The influence of a binary companion of the central star can naturally explain this variety of morphologies, but very few PNe have known binary central stars. The evolution of the binary system with mass loss may result in the displacement of the central star from the nebular center. The large sample of PNe observed by HST is being used to search for de-centered central stars. Preliminary results indicate that the occurrence of de-centered central stars is widespread among all morphological types of PNe.

scholarly journals A High Resolution Far-UV Spectral Atlas of CSPNs and Hot White Dwarfs

1993 ◽  
Vol 155 ◽  
pp. 91-91
Author(s):  
R.W. Tweedy
Keyword(s):  
High Resolution ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolutionary Sequence ◽  
Spectroscopic Analyses ◽  
Spectroscopic Information ◽  
The University ◽  
Phd Thesis ◽  
Central Stars

A high-resolution IUE spectral atlas of central stars of planetary nebulae and hot white dwarfs has been produced (part of Tweedy, 1991, PhD thesis from the University of Leicester, UK), and examples from it are shown here. It has been sorted into an approximate evolutionary sequence, based on published spectroscopic analyses, from the cool 28,000K young central star He 2–138, through the hot objects like NGC 7293 and NGC 246 at 90,000K and 130,000K respectively, down to 40,000K DA white dwarfs like GD 2, which is the chosen cutoff for this selection. Copies of a revised version of this atlas, which will include more recent spectroscopic information and also white dwarfs down to 35,000K – to include the Si III object GD 394 – will be sent to anyone who requests one.

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