Evolutionary versus dynamical time scales for the evolution of the central stars of planetary nebulae

1990 ◽  
Vol 351 ◽  
pp. 230 ◽  
Author(s):  
J. K. McCarthy ◽  
J. R. Mould ◽  
R. H. Mendez ◽  
R. P. Kudritzki ◽  
D. Husfeld ◽  
...  
Keyword(s):  
Time Scales ◽  
Planetary Nebulae ◽  
Dynamical Time ◽  
Central Stars

scholarly journals Central Stars of Young Planetary Nebulae - A New Class of Variables

2003 ◽  
Vol 209 ◽  
pp. 237-238 ◽  
Author(s):  
G. Handler
Keyword(s):  
Mass Loss ◽  
Radial Velocity ◽  
Time Scales ◽  
Variable Star ◽  
Planetary Nebulae ◽  
Stellar Mass ◽  
New Class ◽  
Stellar Pulsation ◽  
Stellar Pulsations ◽  
Central Stars

A new class of variable star is proposed. These are variable central stars of young Planetary Nebulae exhibiting roughly sinusoidal (semi)regular photometric and/or radial velocity variations with time scales of several hours. Fourteen of these objects have been identified. Their temperatures are between 25000 and 50000 K and most show hydrogen-rich spectra. The most likely reason for the variability is stellar pulsation. Another possibility would be variable stellar mass loss, but in that case the mechansism causing it must be different from that operating in massive O stars. We speculate that it actually is the stellar pulsations which cause mass loss mdulations.

scholarly journals A Molecular Line Survey of CRL 2688 at 1 mm and 3 mm Wavelengths

2012 ◽  
Vol 8 (S292) ◽  
pp. 68-68
Author(s):  
Yong Zhang ◽  
Sun Kwok ◽  
Jun-ichi Nakashima ◽  
Dinh-V Trung
Keyword(s):  
Time Scales ◽  
Active Sites ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Interstellar Space ◽  
Molecular Line ◽  
Chemical Enrichment ◽  
Evolved Stars ◽  
The Galaxy ◽  
Dynamical Time

AbstractIt is well established that circumstellar envelopes (CSEs) around evolved stars are active sites of molecular synthesis, and CSEs are one of the major sources of chemical enrichment in the interstellar space. The investigation of molecular compositions in CSEs is essential to understand the chemical evolution of the Galaxy. In order to study circumstellar chemistry in different environments, we have been systematically performing molecular line surveys of a sample of evolved stars from asymptotic giant branch (AGB) stars, proto-planetary nebulae (PPNs), to planetary nebulae (PNs). The dynamical time scales in different evolutionary stages can impose a time limit on the reaction time scales. Here we report our results for CRL 2688.

scholarly journals The Central Stars of He 2–131 and He 2–138: Photometric Variations

1993 ◽  
Vol 155 ◽  
pp. 486-486
Author(s):  
R. G. Hutton ◽  
R. H. Méndez
Keyword(s):  
Mass Loss ◽  
Radial Velocity ◽  
Time Scales ◽  
Effective Temperature ◽  
Planetary Nebulae ◽  
Convincing Evidence ◽  
Stellar Winds ◽  
Line Profiles ◽  
Short Term ◽  
Central Stars

The central stars of the planetary nebulae He 2–131 and He 2–138 show variations in their visual magnitudes, with amplitudes of about 0.1 mag. and time scales of a few hours. This behavior appears to be very similar to that exhibited by the central stars of IC 418 and IC 4593. These four central stars have several other characteristics in common: a relatively low effective temperature, between 27000 and 40000 K; clear spectroscopic evidences of mass loss, both in the ultraviolet (IUE) and visible spectral regions; and short-term spectroscopic variability, in the form of radial velocity variations and/or of substantial changes in emission and P-Cygni-type line profiles. None of these central stars has shown convincing evidence of binarity; we attribute their behavior to variations in the stellar winds.

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 Dynamical time scales of friction dynamics in active microrheology of a model glass

Soft Matter ◽  
2021 ◽  
Author(s):  
Ata Madanchi ◽  
Ji Woong Yu ◽  
Mohamad Reza Rahimi Tabar ◽  
Won Bo Lee ◽  
S. E. E. Rahbari
Keyword(s):  
Time Scales ◽  
Supercooled Liquids ◽  
Model Glass ◽  
Heterogeneous Structures ◽  
Dynamical Time ◽  
Friction Dynamics

Owing to the local/heterogeneous structures in supercooled liquids, after several decades of research, it is now clear that supercooled liquids are structurally different from their conventional liquid counterparts. Accordingly, an...

scholarly journals The long-period binary central stars of the planetary nebulae NGC 1514 and LoTr 5

2017 ◽  
Vol 600 ◽  
pp. L9 ◽  
Author(s):  
D. Jones ◽  
H. Van Winckel ◽  
A. Aller ◽  
K. Exter ◽  
O. De Marco
Keyword(s):  
Planetary Nebulae ◽  
Long Period ◽  
Central Stars

scholarly journals Analysis of chemical abundances in planetary nebulae with [WC] central stars

2013 ◽  
Vol 558 ◽  
pp. A122 ◽  
Author(s):  
Jorge García-Rojas ◽  
Miriam Peña ◽  
Christophe Morisset ◽  
Gloria Delgado-Inglada ◽  
Adal Mesa-Delgado ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Chemical Abundances ◽  
Central Stars

scholarly journals Imaging the elusive H-poor gas in planetary nebulae with large abundance discrepancy factors

2016 ◽  
Vol 12 (S323) ◽  
pp. 65-69 ◽  
Author(s):  
Jorge García-Rojas ◽  
Romano L. M. Corradi ◽  
Henri M. J. Boffin ◽  
Hektor Monteiro ◽  
David Jones ◽  
...  
Keyword(s):  
Planetary Nebulae ◽  
Tunable Filter ◽  
Close Binary ◽  
Chemical Abundances ◽  
Dual Nature ◽  
Gas Phases ◽  
Binary Evolution ◽  
The Universe ◽  
Central Stars

AbstractThe discrepancy between abundances computed using optical recombination lines (ORLs) and collisionally excited lines (CELs) is a major, unresolved problem with significant implications for the determination of chemical abundances throughout the Universe. In planetary nebulae (PNe), the most common explanation for the discrepancy is that two different gas phases coexist: a hot component with standard metallicity, and a much colder plasma enhanced in heavy elements. This dual nature is not predicted by mass loss theories, and direct observational support for it is still weak. In this work, we present our recent findings that demonstrate that the largest abundance discrepancies are associated with close binary central stars. OSIRIS-GTC tunable filter imaging of the faint O ii ORLs and MUSE-VLT deep 2D spectrophotometry confirm that O ii ORL emission is more centrally concentrated than that of [Oiii] CELs and, therefore, that the abundance discrepancy may be closely linked to binary evolution.

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