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.

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 Structure and Evolution of Planetary Nebula Haloes

2003 ◽  
Vol 209 ◽  
pp. 439-446 ◽  
Author(s):  
Matthias Steffen ◽  
Detlef Schönberner
Keyword(s):  
Mass Loss ◽  
Numerical Simulations ◽  
Stellar Evolution ◽  
Planetary Nebula ◽  
Previous History ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Time Dependent ◽  
Density Structure ◽  
History Of

The density structure of the extended haloes of Planetary Nebulae (PN) is generally believed to reflect the previous history of heavy mass loss during the final stages of stellar evolution on the asymptotic giant-branch (AGB). In this review, we discuss different interpretations of the observed PN halo structures in the light of recent numerical simulations combining detailed AGB and post-AGB stellar evolution calculations with time-dependent hydrodynamical wind models.

scholarly journals 12. The Nuclei of Planetary Nebulae as Progenitors of White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 77-78
Author(s):  
C. R. O'Dell
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
Rapid Change ◽  
Planetary Nebulae ◽  
Review Article ◽  
The Past ◽  
The Subject ◽  
Central Stars

Stellar evolution is characterized by fast and slow phases. Usually the periods of rapid change are difficult to follow observationally; but, this does not seem to be the case when passing through the planetary nebula stage. Because of their high intrinsic luminosities and easy identification, it is possible to identify and study these objects and their central stars rather completely. It is quite relevant to discuss these objects at a symposium on white dwarfs since the central stars may be in the immediate progenitor stage before white dwarfs. The actual picture of the evolution of the nuclei has changed rather little in the past few years and is the subject of an earlier review article (O'Dell, 1968) to which the reader is referred.

scholarly journals Spectral analysis of the hybrid PG 1159-type central stars of the planetary nebulae Abell 43 and NGC 7094

2019 ◽  
Vol 489 (1) ◽  
pp. 1054-1071 ◽  
Author(s):  
L Löbling ◽  
T Rauch ◽  
M M Miller Bertolami ◽  
H Todt ◽  
F Friederich ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Stellar Evolution ◽  
Surface Composition ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Thermodynamical Equilibrium ◽  
Non Local ◽  
Rich Material ◽  
Stellar Masses ◽  
Central Stars

Abstract Stellar post asymptotic giant branch (post-AGB) evolution can be completely altered by a final thermal pulse (FTP) which may occur when the star is still leaving the AGB (AFTP), at the departure from the AGB at still constant luminosity (late TP, LTP) or after the entry to the white-dwarf cooling sequence (very late TP, VLTP). Then convection mixes the He-rich material with the H-rich envelope. According to stellar evolution models the result is a star with a surface composition of $\mathrm{H}\approx \, 20$ per cent by mass (AFTP), ≈ 1 per cent (LTP), or (almost) no H (VLTP). Since FTP stars exhibit intershell material at their surface, spectral analyses establish constraints for AGB nucleosynthesis and stellar evolution. We performed a spectral analysis of the so-called hybrid PG 1159-type central stars (CS) of the planetary nebulae Abell 43 and NGC 7094 by means of non-local thermodynamical equilibrium models. We confirm the previously determined effective temperatures of $\mbox{$T_\mathrm{eff}$}\, = 115\, 000\pm 5\, 000 \, \mathrm{K}$ and determine surface gravities of $\log\,(g\,/\,(\mathrm{cm}\,\mathrm{s}^{-2} )) = 5.6\pm 0.1$ for both. From a comparison with AFTP evolutionary tracks, we derive stellar masses of $0.57^{+0.07}_{-0.04}$ M⊙ and determine the abundances of H, He, and metals up to Xe. Both CS are likely AFTP stars with a surface H mass fraction of 0.25 ± 0.03 and 0.15 ± 0.03, respectively, and an Fe deficiency indicating subsolar initial metallicities. The light metals show typical PG 1159-type abundances and the elemental composition is in good agreement with predictions from AFTP evolutionary models. However, the expansion ages do not agree with evolution time-scales expected from the AFTP scenario and alternatives should be explored.

scholarly journals Full polarization VLBA maps of a proto-planetary nebula

2007 ◽  
Vol 3 (S242) ◽  
pp. 324-325
Author(s):  
Kim McAlpine ◽  
A.J. Kemball ◽  
J. L. Jonas
Keyword(s):  
Stellar Evolution ◽  
Planetary Nebula ◽  
Morphological Evolution ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Spherically Symmetric ◽  
Agb Stars ◽  
Vlbi Observations ◽  
Two Phases ◽  
Insight Into

AbstractThe morphological evolution of stars from the asymptotic giant branch (AGB) to the planetary nebula (PN) phases presents an intriguing problem in stellar research. Planetary nebulae show bright-rims, well-defined shell-like structures and a large proportion of them are axisymmetric. In contrast their progenitor AGB stars are largely spherically symmetric (Sahai, 2004). Studies of proto-planetary nebulae, which are objects in transition between these two phases of stellar evolution, offer insight into the mechanisms which are responsible for the onset of axisymmetry. This poster presents the first polarization VLBI observations of the 1612 MHz OH maser emission from the proto-planetary nebula candidate OH O.9+1.3. The morphology, kinematics and polarization properties of these masers are discussed.

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 New models for the rapid evolution of the central star of the Stingray Nebula

2021 ◽  
Author(s):  
T M Lawlor
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Planetary Nebula ◽  
Rapid Evolution ◽  
Central Star ◽  
Asymptotic Giant Branch ◽  
Initial Mass ◽  
Thermal Pulse ◽  
The Past ◽  
New Models

Abstract We present stellar evolution calculations from the Asymptotic Giant Branch (AGB) to the Planetary Nebula (PN) phase for models of initial mass 1.2 M⊙ and 2.0 M⊙ that experience a Late Thermal Pulse (LTP), a helium shell flash that occurs following the AGB and causes a rapid looping evolution between the AGB and PN phase. We use these models to make comparisons to the central star of the Stingray Nebula, V839 Ara (SAO 244567). The central star has been observed to be rapidly evolving (heating) over the last 50 to 60 years and rapidly dimming over the past 20–30 years. It has been reported to belong to the youngest known planetary nebula, now rapidly fading in brightness. In this paper we show that the observed timescales, sudden dimming, and increasing Log(g), can all be explained by LTP models of a specific variety. We provide a possible explanation for the nebular ionization, the 1980’s sudden mass loss episode, the sudden decline in mass loss, and the nebular recombination and fading.

scholarly journals Surface magnetic activity of the fast-rotating G5 giant IN Comae, central star of the faint planetary nebula LoTr 5

2019 ◽  
Vol 624 ◽  
pp. A83 ◽  
Author(s):  
Zs. Kővári ◽  
K. G. Strassmeier ◽  
K. Oláh ◽  
L. Kriskovics ◽  
K. Vida ◽  
...  
Keyword(s):  
Time Series ◽  
Differential Rotation ◽  
Planetary Nebula ◽  
Spectral Synthesis ◽  
Binary Star ◽  
Rotation Period ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Stellar Surface ◽  
Average Lifetime

Context. On the asymptotic giant branch, low to intermediate mass stars blow away their outer envelopes, forming planetary nebulae. Dynamic interaction between the planetary nebula and its central progenitor is poorly understood. The interaction is even more complex when the central object is a binary star with a magnetically active component, as is the case for the target in this paper. Aims. We aim to quantify the stellar surface activity of the cool binary component of IN Com and aim to explain its origin. In general, we need a better understanding of how central binary stars in planetary nebulae evolve and how this evolution could develop such magnetically active stars as IN Com. Methods. We present a time series of 13 consecutive Doppler images covering six months in 2017 that we used to measure the surface differential rotation with a cross-correlation method. Hitherto unpublished high-precision photometric data from 1989 to 2017 are presented. We applied Fourier-transformation-based frequency analysis to both photometry and spectra. Very high resolution (R ≈ 200 000) spectra were used to update IN Com’s astrophysical parameters by means of spectral synthesis. Results. Our time-series Doppler images show cool and warm spots coexisting with an average surface temperature contrast of −1000 K and +300 K with respect to the effective temperature. Approximately 8% of the stellar surface is covered with cool spots and ∼3% with warm spots. A consistent cool polar spot is seen in all images. The average lifetime of the cool spots is not much more than a few stellar rotations (one month), while the warm spots appear to live longer (three months) and are mostly confined to high latitudes. We found anti-solar surface differential rotation with a shear coefficient of α = −0.026 ± 0.005 suggesting an equatorial rotation period of 5.973 ± 0.008 d. We reconfirm the 5.9 day rotation period of the cool star from photometry, radial velocities, and Hα line-profile variations. A long-term V-brightness variation with a likely period of 7.2 yr is also found. It appears in phase with the orbital radial velocity of the binary system in the sense that it is brightest at highest velocity and faintest at lowest velocity, that is, at the two phases of quadrature. We redetermine [Ba/Fe], [Y/Fe], and [Sr/Fe] ratios and confirm the overabundance of these s-process elements in the atmosphere of IN Com.

scholarly journals Catalogue of the central stars of planetary nebulae

2020 ◽  
Vol 640 ◽  
pp. A10
Author(s):  
W. A. Weidmann ◽  
M. B. Mari ◽  
E. O. Schmidt ◽  
G. Gaspar ◽  
M. M. Miller Bertolami ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
Late Stage ◽  
Planetary Nebulae ◽  
Surface Gravity ◽  
Physical Parameters ◽  
Evolutionary Models ◽  
Pertinent Information ◽  
Central Stars ◽  
Statistical Improvement ◽  
Magnitude Estimates

Planetary nebulae represent a potential late stage of stellar evolution, however, their central stars (CSPNe) are relatively faint and, therefore, pertinent information is available for merely < 20% of the Galactic sample. Consequently, the literature was surveyed to construct a new catalogue of 620 CSPNe featuring important spectral classifications and information. The catalogue supersedes the existing iteration by 25% and includes physical parameters such as luminosity, surface gravity, temperature, magnitude estimates, and references for published spectra. The marked statistical improvement enabled the following pertinent conclusions to be determined: the H-rich/H-poor ratio is 2:1, there is a deficiency of CSPNe with types [WC 5-6], and nearly 80% of binary central stars belong to the H-rich group. The last finding suggests that evolutionary scenarios leading to the formation of binary central stars interfere with the conditions required for the formation of H-poor CSPN. Approximately 50% of the sample with derived values of log L⋆, log Teff, and log g, exhibit masses and ages consistent with single stellar evolutionary models. The implication is that single stars are indeed able to form planetary nebulae. Moreover, it is shown that H-poor CSPNe are formed by higher mass progenitors. The catalogue is available through the Vizier database.

scholarly journals WORKPLANS: Workshop on Planetary Nebula Observations

Galaxies ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 23 ◽  
Author(s):  
Isabel Aleman ◽  
Jeronimo Bernard-Salas ◽  
Joel H. Kastner ◽  
Toshiya Ueta ◽  
Eva Villaver
Keyword(s):  
Observational Data ◽  
Planetary Nebula ◽  
Dust Emission ◽  
Planetary Nebulae ◽  
Research Field ◽  
Theoretical Modeling ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Open Questions ◽  
Giant Branch Stars

This workshop is the second of the WORKPLANS series, which we started in 2016. The main goal of WORKPLANS is to build up a network of planetary nebulae (PNe) experts to address the main open questions in the field of PNe research. The specific aims of the WORKPLANS workshop series are (i) to discuss and prioritize the most important topics to be investigated by the PN community in the following years; (ii) to establish a network of excellent researchers with complementary expertise; (iii) to formulate ambitious observing proposals for the most advanced telescopes and instrumentation presently available (ALMA, SOFIA, VLT, GTC, HST, etc.), addressing those topics; and (iv) to develop strategies for major proposals to future observatories (JWST, ELT, SPICA, Athena, etc.). To achieve these goals, WORKPLANS II brought together experts in all key sub-areas of the PNe research field, namely: analysis and interpretation of PNe observational data; theoretical modeling of gas and dust emission; evolution from Asymptotic Giant Branch stars (PNe progenitors) to PNe; and the instrumentation and technical characteristics of the relevant observatories.

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