scholarly journals Is there a Connection Between Thermal Pulses and PNe Halos: An Approach to an Answer

1993 ◽  
Vol 155 ◽  
pp. 365-365
Author(s):  
Adam Frank ◽  
Bruce Balick ◽  
Will Van Der Veen
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Published Data ◽  
Agb Stars ◽  
Thermal Pulses

We wish to explore the hypothesis that the shells and halos of planetary nebulae are formed during the thermal pulsing of progenitor AGB stars. Using published data and model results we compare the AGB interpulse time ΔtT and the time between shell ejections ΔtD for a sample of PNe with halos. ΔtT is derived from the Paczynski relation using the PNe central star luminosity. ΔtD is calculated using the radii and velocity of PNe shells and halos.

scholarly journals Chemical Enrichment and Central Star Properties

1993 ◽  
Vol 155 ◽  
pp. 572-572
Author(s):  
C.Y. Zhang
Keyword(s):  
Planetary Nebulae ◽  
Central Star ◽  
Agb Stars ◽  
Physical Processes ◽  
Chemical Abundances ◽  
Core Mass ◽  
Chemical Enrichment ◽  
The Core ◽  
Stellar Temperature ◽  
Independent Parameters

We have selected a sample of planetary nebulae, for which the core masses are determined using distance-independent parameters (Zhang and Kwok 1992). The chemical abundances of He, N, O, and C are taken from the literature for them. Relationships of the ratios of He/H, N/O, and C/O with various stellar parameters of planetary nebulae (PN), such as the core mass, the mass of the core plus the ionized nebular gas, the stellar age and temperature, are examined. It is found that the N/O increases with increasing mass, while the C/O first increases and then decreases with the core mass. No strong correlation seems to exist between the He/H and the core mass. A correlation of the N/O and He/H with the stellar temperature exists. The current dredge-up theory for the progenitor AGB stars cannot satisfactorily account for these patterns of chemical enrichment in PN. Furthermore, the correlations of the N/O and He/H with the stellar age and temperature indicate that besides the dredge-ups in the RG and AGB stages, physical processes that happen in the planetary nebula stage may also play a role in forming the observed patterns of chemical enrichment in the planetary nebulae.

scholarly journals Thermal Pulses and Planetary Nebula Ejection

1993 ◽  
Vol 155 ◽  
pp. 291-298 ◽  
Author(s):  
P.R. Wood ◽  
E. Vassiliadis
Keyword(s):  
Mass Loss ◽  
Planetary Nebula ◽  
Planetary Nebulae ◽  
Stellar Surface ◽  
Agb Stars ◽  
Theoretical Evolution ◽  
Thermal Pulses

Thermal pulses in AGB stars cause large luminosity variations at the stellar surface. The role of these luminosity variations in the production of planetary nebulae is discussed. Results of theoretical evolution calculations which include mass loss modulated by thermal pulses are presented.

scholarly journals An imaging and spectroscopic survey of the Abell Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 287-287
Author(s):  
N. A. Walton ◽  
J. R. Walsh ◽  
G. Dudziak
Keyword(s):  
White Dwarf ◽  
Surface Brightness ◽  
Planetary Nebulae ◽  
Central Star ◽  
Large Size ◽  
Low Surface Brightness ◽  
Thermal Pulses ◽  
Central Stars

The Abell catalogue of planetary nebulae (PN) are distinguished by their large size, low surface brightness and generally faint central stars. They are thought to be old PN approaching the White Dwarf cooling track. A number have evidence for late thermal pulses (H-poor ejecta near the central star, e.g. A78) and binary central stars.

The real time evolution of post-AGB stars

2019 ◽  
Vol 15 (S357) ◽  
pp. 154-157
Author(s):  
Marcin Hajduk
Keyword(s):  
Real Time ◽  
Time Evolution ◽  
Planetary Nebulae ◽  
Theoretical Models ◽  
Central Star ◽  
Maximum Temperature ◽  
Additional Parameter ◽  
Agb Stars ◽  
The Real ◽  
Hr Diagram

AbstractEvolution of post-AGB stars is extremely fast. They cross the HR diagram vertically on a timescale of hundreds to some ten thousands of years to reach maximum temperature in their lifetime. This is reflected in an increasing excitation of planetary nebulae on a timescale of years and decades. Since evolutionary timescale of post-AGB stars is very sensitive to their mass, observed changes can be used to determine model dependent central star masses. If an additional parameter is determined (e.g. luminosity or dynamic age), the observed evolution of planetary nebulae can be utilized for observational verification of theoretical models.

scholarly journals Stellar yields and abundances: new directions from planetary nebulae

2016 ◽  
Vol 12 (S323) ◽  
pp. 86-94
Author(s):  
Maria Lugaro ◽  
Amanda I. Karakas ◽  
Marco Pignatari ◽  
Carolyn L. Doherty
Keyword(s):  
Noble Gas ◽  
Planetary Nebulae ◽  
Central Star ◽  
High Energy ◽  
Type I ◽  
Agb Stars ◽  
Capture Process ◽  
New Directions ◽  
Energy Environment ◽  
Central Stars

AbstractPlanetary nebulae retain the signature of the nucleosynthesis and mixing events that occurred during the previous AGB phase. Observational signatures complement observations of AGB and post-AGB stars and their binary companions. The abundances of the elements heavier than iron such as Kr and Xe in planetary nebulae can be used to complement abundances of Sr/Y/Zr and Ba/La/Ce in AGB stars, respectively, to determine the operation of theslowneutron-capture process (thesprocess) in AGB stars. Additionally, observations of the Rb abundance in Type I planetary nebulae may allow us to infer the initial mass of the central star. Several noble gas components present in meteoritic stardust silicon carbide (SiC) grains are associated with implantation into the dust grains in the high-energy environment connected to the fast winds from the central stars during the planetary nebulae phase.

scholarly journals Magnetic fields during the evolution towards planetary nebulae

2011 ◽  
Vol 7 (S283) ◽  
pp. 176-179 ◽  
Author(s):  
Wouter Vlemmings
Keyword(s):  
Magnetic Fields ◽  
Energy Budget ◽  
Magnetic Energy ◽  
Planetary Nebulae ◽  
Central Star ◽  
Agb Stars ◽  
Evolved Stars ◽  
Short Summary ◽  
New Instruments

AbstractMagnetic fields appear ubiquitous throughout the envelopes of evolved stars. However, their origin and role in the formation of planetary nebulae is still unclear. As observations of magnetic fields are complicated and time consuming, the observed samples of AGB and post-AGB stars and planetary nebulae are still small. Still, magnetic energy seems to dominate the energy budget out to a distance of several tens of AU from the central star and the field morphology often appears to be well ordered. A short summary is given of the current observations and the potential of new instruments such as ALMA is discussed.

scholarly journals Interstellar Reddening Towards S188, Hw4 and We1–6

1993 ◽  
Vol 155 ◽  
pp. 178-178
Author(s):  
W. Saurer
Keyword(s):  
Planetary Nebula ◽  
Star Clusters ◽  
Planetary Nebulae ◽  
Central Star ◽  
Line Of Sight ◽  
Published Data ◽  
Nearby Stars ◽  
Ubv Photometry ◽  
Distance Relation

Photoelectric UBV photometry of stars was carried out in the angular vicinity (radius = 15′) of 3 planetary nebulae. An extinction distance relation was constructed for the line of sight towards each planetary nebula. This relation was verified by published data on nearby stars and star clusters. The distances derived are 850 ± 300 pc for PK 128 −04 1 (S 188, Simeis 22), 400 ± 200 pc for PK 149 −09 1 (HW 4), and (less reliable) 800 pc ± 400 pc for PK 224 +01 1 (We 1–6). For the central star of PK 224 +01 1 our observations gave V = 15.76 ± 0.03 mag, (B–V) = −0.08 ± 0.03 mag and (U–B) = −0.87 ± 0.03 mag.

scholarly journals From the Tip of the AGB Towards a Planetary: A Hydrodynamical Simulation

2000 ◽  
Vol 177 ◽  
pp. 469-477
Author(s):  
D. Schönberner ◽  
M. Steffen ◽  
J. Stahlberg ◽  
K. Kifonidis ◽  
T. Blöcker
Keyword(s):  
Mass Loss ◽  
Dynamical Evolution ◽  
Central Star ◽  
Rapid Decline ◽  
Agb Stars ◽  
Natural Consequence ◽  
Hydrodynamical Simulation ◽  
Exploratory Investigation ◽  
Fast Wind ◽  
Thermal Pulses

We present a first exploratory investigation of the dynamical evolution of a dusty stellar wind envelope along the upper AGB and its transformation into a planetary nebula. We find the existence of AGB stars with detached shells to be a natural consequence of the mass-loss variations during a thermal pulse. It is also demonstrated that due to the large dynamical effects caused by the ionizing radiation field and the fast wind of the central star, it is impossible to deduce the AGB mass loss history from the planetary's density and velocity distribution. The structure of the halo, however, is still determined by the AGB mass loss history. The rapid decline of mass loss expected in the aftermath of thermal pulses leads to extended shells of low densities and explains halos with sharp boundaries.

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.

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