scholarly journals From Planetary Nebulae to White Dwarfs: Constraints from the Asteroseismology of the Pulsating Planetary Nebula Central Star RXJ 2117+3412

2002 ◽  
Vol 185 ◽  
pp. 610-611
Author(s):  
P. Moskalik ◽  
G. Vauclair
Keyword(s):  
Planetary Nebula ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Central Star

AbstractWe summarize the results of an asteroseismological study of the pulsating planetary nebula central star RXJ 2117+3412.

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 The Remarkable Evolution of the Post-Agb Star FG SGE

1998 ◽  
Vol 11 (1) ◽  
pp. 363-363
Author(s):  
Johanna Jurcsik ◽  
Benjamin Montesinos
Keyword(s):  
Time Scales ◽  
Effective Temperature ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Evolutionary Models ◽  
Single Star ◽  
Line Intensities ◽  
Evolutionary Changes ◽  
Evolutionary Studies

FG Sagittae is one of the most important key objects of post-AGB stellar evolutionary studies. As a consequence of a final helium shell flash, this unique variable has shown real evolutionary changes on human time scales during this century. The observational history was reviewed in comparison with predictions from evolutionary models. The central star of the old planetary nebula (Hel-5) evolved from left to right in the HR diagram, going in just hundred years from the hot region of exciting sources of planetary nebulae to the cool red supergiant domain just before our eyes becoming a newly-born post-AGB star. The effective temperature of the star was around 50,000 K at the beginning of this century, and the last estimates in the late 1980s give 5,000-6,500 K. Recent spectroscopic observations obtained by Ingemar Lundström show definite changes in the nebular line intensities. This fact undoubtedly rules out the possibility that, instead of FG Sge, a hidden hot object would be the true central star of the nebula. Consequently, the observed evolutionary changes are connected with the evolution of a single star.

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 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.

scholarly journals Energy Distribution of Planetary Nebulae (UV to Radio)

1993 ◽  
Vol 155 ◽  
pp. 99-108
Author(s):  
C.Y. Zhang
Keyword(s):  
Energy Distribution ◽  
Planetary Nebula ◽  
Spectral Energy Distribution ◽  
Planetary Nebulae ◽  
Central Star ◽  
Spectral Energy ◽  
Significant Progress ◽  
Dust Shell ◽  
The Past ◽  
Entire Wavelength Range

The past decade has seen significant progress in our understanding of spectral energy distribution of planetary nebulae over the entire wavelength range from UV to radio. In this review we show the detailed breakdown of the energy budget for a planetary nebula as a system of the three components, i.e., the central star, the gaseous nebula and the dust shell. This picture of the energy distribution is further discussed in the context of planetary nebula evolution.

scholarly journals A Speculation into the Origin of Neutral Globules in Planetary Nebulae: Could the Helix’s Comets Really be Comets?

1995 ◽  
Vol 12 (2) ◽  
pp. 170-173
Author(s):  
Grant Gussie
Keyword(s):  
Solar System ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Oort Cloud ◽  
Asymptotic Giant Branch ◽  
Neutral Gas ◽  
Red Giant ◽  
The Masses

AbstractA novel explanation for the origin of the cometary globules within NGC 7293 (the ‘Helix’ planetary nebula) is examined, namely that these globules originate as massive cometary bodies at large astrocentric radii. The masses of such hypothetical cometary bodies would have to be several orders of magnitude larger than those of any such bodies observed in our solar system in order to supply the observed mass of neutral gas. It is, however, shown that comets at ‘outer Oort cloud’ distances are likely to survive past the red giant and asymptotic giant branch evolutionary phases of the central star, allowing them to survive until the formation of the planetary nebula. Some observational tests of this hypothesis are proposed.

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 On the triple-star origin of the planetary nebula Sh 2-71

2019 ◽  
Vol 489 (2) ◽  
pp. 2195-2203 ◽  
Author(s):  
David Jones ◽  
Ondřej Pejcha ◽  
Romano L M Corradi
Keyword(s):  
Mass Loss ◽  
Triple System ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
Radial Velocities ◽  
Proper Motions ◽  
Numerical Integrations ◽  
Open Questions ◽  
Triple Star

ABSTRACT Recent studies have indicated that triple-star systems may play a role in the formation of an appreciable number of planetary nebulae, however, only one triple central star is known to date (and that system is likely too wide to have had much influence on the evolution of its component stars). Here, we consider the possibility that Sh 2-71 was formed by a triple system that has since broken apart. We present the discovery of two regions of emission, seemingly aligned with the proposed tertiary orbit (i.e. in line with the axis formed by the two candidate central star systems previously considered in the literature). We also perform a few simple tests of the plausibility of the triple hypothesis based on the observed properties (coordinates, radial velocities, distances, and proper motions) of the stars observed close to the projected centre of the nebula, adding further support through numerical integrations of binary orbits responding to mass loss. Although a number of open questions remain, we conclude that Sh 2-71 is currently one of the best candidates for planetary nebula formation influenced by triple-star interactions.

scholarly journals The Continuum Emission from Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 226-226
Author(s):  
Sueli M. Viegas-Aldrovandi
Keyword(s):  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Central Star ◽  
The Other ◽  
Continuum Emission ◽  
Other Hand ◽  
The Continuum ◽  
Hr Diagram

The study of nebular continuum emission is important for several reasons (Pottasch 1984, Planetary Nebulae, Dordrecht: Reidel). First of all, it can provide information about the temperature and the density of the nebula, when the object is large enough, or when the central star is weak enough, so that the nebular continuum is easily observed without interference from the stellar continuum. On the other hand, for small planetary nebulae, both the central star and the nebula contribute to the observed continuum. In this latter case, in order to obtain the stellar continuum the theoretical nebular emission must be used. Thus, studies of the evolution of planetary nebula nuclei through the HR diagram rely on a good calculation of the theoretical nebular continuum.

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