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 A Search for Cool Companions of Planetary Nebula Nuclei

1989 ◽  
Vol 131 ◽  
pp. 312-312
Author(s):  
A. F. Bentley
Keyword(s):  
Planetary Nebula ◽  
Main Sequence ◽  
Large Fraction ◽  
Planetary Nebulae ◽  
Observational Methods ◽  
Late Type ◽  
Main Sequence Stars ◽  
Multiple Star ◽  
Central Stars

At present only a small number of planetary nebulae are known to possess binary nuclei. Since approximately 2/3 of main sequence stars are members of binary or multiple star systems, one might expect a large fraction of PN central stars to have gravitationally bound companions. Additionally, late-type stars are more numerous, and due to their low luminosities would be difficult to detect by visual observational methods at distances where PN are typically found (≧ 1 kpc). (Only 5 known PN are thought to be nearer than 0.5 kpc). It is thus possible, and in our view probable, that a significant number of PN nuclei possess cool companions, hitherto undetected.

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.

scholarly journals 35. Stellar Constitution

1985 ◽  
Vol 19 (1) ◽  
pp. 479-502
Author(s):  
A. N. Cox ◽  
D. Sugimoto ◽  
P. H. Bodenheimer ◽  
C. S. Chiosi ◽  
D. J. Faulkner ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
Massive Stars ◽  
Structure Stability ◽  
Current Interest ◽  
Late Type ◽  
Dwarf Stars ◽  
Entire Field ◽  
Stellar Formation ◽  
Central Stars

This report of Commission 35, as in past reports, consists of some details of only a few selected topics. This is necessary because a survey of the entire field of stellar formation, structure, stability, evolution, pulsation, and explosions for the three year period from mid-1981 to mid-1984 would be excessively long. Our topics here, in order from the most massive stellar classes to the least are: Massive Stars (R.M. Humphreys), Rotation in Late Type Stars (W. Benz), Helioseismology (J. Christensen-Dalsgaard), Planetary Nebula Central Stars (E.M. Sion), Pulsations in Hot Degenerate Dwarf Stars (A.N. Cox and S.D. Kawaler), and White Dwarfs (V. Weidemann). There is some overlap in the reviewing of these last three reports because the topics are very closely related. Concentration in this dying stage of stellar evolution seems appropriate because of the great current interest in these matters.

scholarly journals Stellar wind models of central stars of planetary nebulae

2020 ◽  
Vol 635 ◽  
pp. A173 ◽  
Author(s):  
J. Krtička ◽  
J. Kubát ◽  
I. Krtičková
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebula ◽  
Loss Rate ◽  
Mass Loss Rate ◽  
Planetary Nebulae ◽  
Terminal Velocity ◽  
Asymptotic Giant Branch ◽  
Central Stars ◽  
Loss Rates

Context. Fast line-driven stellar winds play an important role in the evolution of planetary nebulae, even though they are relatively weak. Aims. We provide global (unified) hot star wind models of central stars of planetary nebulae. The models predict wind structure including the mass-loss rates, terminal velocities, and emergent fluxes from basic stellar parameters. Methods. We applied our wind code for parameters corresponding to evolutionary stages between the asymptotic giant branch and white dwarf phases for a star with a final mass of 0.569 M⊙. We study the influence of metallicity and wind inhomogeneities (clumping) on the wind properties. Results. Line-driven winds appear very early after the star leaves the asymptotic giant branch (at the latest for Teff ≈ 10 kK) and fade away at the white dwarf cooling track (below Teff = 105 kK). Their mass-loss rate mostly scales with the stellar luminosity and, consequently, the mass-loss rate only varies slightly during the transition from the red to the blue part of the Hertzsprung–Russell diagram. There are the following two exceptions to the monotonic behavior: a bistability jump at around 20 kK, where the mass-loss rate decreases by a factor of a few (during evolution) due to a change in iron ionization, and an additional maximum at about Teff = 40−50 kK. On the other hand, the terminal velocity increases from about a few hundreds of km s−1 to a few thousands of km s−1 during the transition as a result of stellar radius decrease. The wind terminal velocity also significantly increases at the bistability jump. Derived wind parameters reasonably agree with observations. The effect of clumping is stronger at the hot side of the bistability jump than at the cool side. Conclusions. Derived fits to wind parameters can be used in evolutionary models and in studies of planetary nebula formation. A predicted bistability jump in mass-loss rates can cause the appearance of an additional shell of planetary nebula.

scholarly journals Pulsations in the Nucleus of Planetary Nebula IC 418?

1995 ◽  
Vol 155 ◽  
pp. 443-444
Author(s):  
E. Kuczawska ◽  
S. Zola
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
New Class ◽  
Photometric Observations ◽  
Theoretical Results ◽  
Central Stars

AbstractIC 418 belongs to the group of about a dozen planetary nebulae with central stars that show irregular spectroscopic and photometric variations. Recent theoretical results provide arguments that this group may constitute a new class of pulsators. We present new photometric observations of the nucleus of IC 418 showing variations with a timescale of about 1/4 day. We discuss two possible explanations of the observed phenomena: pulsational instability and an unstable wind.

scholarly journals Wind inhomogeneities in [Wc] central stars of planetary nebulae

2003 ◽  
Vol 212 ◽  
pp. 192-193
Author(s):  
Yves Grosdidier ◽  
Anthony F.J. Moffat ◽  
Agnès Acker
Keyword(s):  
Emission Line ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Spectroscopic Evidence ◽  
Poster Paper ◽  
Central Stars ◽  
Present Poster

In the present poster paper, we summarize the observational spectroscopic evidence for wind clumping originating in some [WC8-10] and [WO4] central stars of planetary nebulae. Specifically, we concentrate on the C iii λ5696 and C iv λλ5801/12 emission-line variability observed for well-known planetary nebula nuclei.

scholarly journals Close Binaries and the Abundance Discrepancy Problem in Planetary Nebulae

Galaxies ◽  
2018 ◽  
Vol 6 (4) ◽  
pp. 110
Author(s):  
R. Wesson ◽  
D. Jones ◽  
J. García-Rojas ◽  
H. Boffin ◽  
R. Corradi
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Close Binaries ◽  
Problem Analysis ◽  
Recombination Line ◽  
Central Stars ◽  
Recent Establishment

Motivated by the recent establishment of a connection between central star binarity and extreme abundance discrepancies in planetary nebulae, we have carried out a spectroscopic survey targeting planetary nebula with binary central stars and previously unmeasured recombination line abundances. We have discovered seven new extreme abundance discrepancies, confirming that binarity is key to understanding the abundance discrepancy problem. Analysis of all 15 objects with a binary central star and a measured abundance discrepancy suggests a cut-off period of about 1.15 days, below which extreme abundance discrepancies are found.

scholarly journals The Photographic Observations of Some Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 41-41
Author(s):  
Xiangliang Hao
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Processing Method ◽  
Primary Research ◽  
Temperature Changes ◽  
Long Period ◽  
The Earth ◽  
Long Time ◽  
Central Stars

The first planetary nebula was discovered by Messier in 1794. But for some reasons it has not been studied detail for a long time, especially for the central star Of planetary nebula. The primary research for these objects showed that the lifetime of a planetary nebula is about 5 104 years, but in this period the luminosity of central star varies from 63 L⊙ to nearly 3.5 104L⊙ and then decrease to 100 L⊙; its temperature changes from 3.4 104 to 105K and then begins to decrease (Seaton 1966). The radius of central stars also have fast varies in planetary nebula phase. For these reasons we consider that in the planetary nebula phase the activities of central star is very drastic and the result of these activities must cause some variation at the surface of central star witch may be detected on the earth, especially for the surface light variations. Some observers have been trying to find the luminosity variations in central stars. But until now no one has made systematical survey for these. Since the different authors used different instruments amd different processing methods at different places which may be caused a lot of uncertainty in the photometry of planetary nebulae and central stars. So it is hard to decide whether the differences between the authors or the essential variations of the objects is responsible of the observing differences. Therefore, we have selected over fifty planetary nebulae to observe for a long period at Beijing Observatory using the same instrument and the same processing method. From these observations we may determine the light variations and the brightness of the planetary nebulae and central stars more correctly.

scholarly journals THE CHANDRA PLANETARY NEBULA SURVEY (ChanPlaNS). III. X-RAY EMISSION FROM THE CENTRAL STARS OF PLANETARY NEBULAE

2015 ◽  
Vol 800 (1) ◽  
pp. 8 ◽  
Author(s):  
R. Montez Jr. ◽  
J. H. Kastner ◽  
B. Balick ◽  
E. Behar ◽  
E. Blackman ◽  
...  
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
X Ray ◽  
Central Stars

scholarly journals Proto-Planetary Nebulae

2003 ◽  
Vol 209 ◽  
pp. 113-120 ◽  
Author(s):  
Bruce J. Hrivnak
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Central Stars

The study of proto-planetary nebulae (PPNs) leads to a better understanding of both the preceding asymptotic giant branch and the succeeding planetary nebula phases of stellar evolution. Recent results are reviewed, emphasizing the properties of the central stars and the shape and chemistry of the nebulae. The study of PPNs is seen to be important in its own right.

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