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 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 The Real-Time Evolution of Sakurai's Star (V4334 Sgr) and other (V)LTP Objects

2006 ◽  
Vol 2 (S234) ◽  
pp. 75
Author(s):  
P.A.M. van Hoof ◽  
M. Bryce ◽  
A. Evans ◽  
S.P.S. Eyres ◽  
M. Hajduk ◽  
...  
Keyword(s):  
Real Time ◽  
Time Evolution ◽  
The Real

Design and Application of Aeolian Vibration Monitoring System for Overhead Transmission Line

2012 ◽  
Vol 239-240 ◽  
pp. 456-461
Author(s):  
Bu Sheng Tong ◽  
Yu Xiang Lv ◽  
Bei Ge Yang ◽  
Hui Xue ◽  
Shan Zhi
Keyword(s):  
Transmission Line ◽  
Real Time ◽  
Monitoring System ◽  
Theoretical Models ◽  
Correction Method ◽  
Fatigue Tests ◽  
Least Square ◽  
Vibration Monitoring ◽  
The Real ◽  
Aeolian Vibration

Aim at the shortage of traditional Aeolian vibration fatigue tests and theoretical models for transmission line, the Aeolian vibration monitoring system of transmission line based on the ZigBee wireless network was designed. The system transfer real-time field data of meteorological factors, tension of conductor and acceleration of monitoring nodes to background computer. The line vibration curve integrated directly from the acceleration sensor recorded data will present a serious problem of baseline drift. Therefore, based on least-square theory, a new baseline correction method is proposed to eliminate effect on drifts, and then obtain distortion less vibration curve of transmission line by twice integrations. The system running results show that track fitted with monitoring data is in good agreement with the real recorded trajectory. The system can satisfy the needs of the real time monitoring on transmission line site and be well applied to the calculation of conductor fatigue damage.

scholarly journals The Real-Time Evolution of V4334 Sgr

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 79 ◽  
Author(s):  
Peter van Hoof ◽  
Stefan Kimeswenger ◽  
Griet Van de Steene ◽  
Adam Avison ◽  
Albert Zijlstra ◽  
...  
Keyword(s):  
Real Time ◽  
Time Evolution ◽  
Planetary Nebula ◽  
Spectral Features ◽  
The Real ◽  
Thermal Pulse ◽  
Early Stages ◽  
Observational Record

V4334 Sgr (Sakurai’s object) is an enigmatic evolved star that underwent a very late thermal pulse a few years before its discovery in 1996. It ejected a new hydrogen-deficient nebula in the process. The source has been observed continuously since, at many wavelengths ranging from the optical to the radio regime. In this paper we evaluate these data and discuss the evolution of this object. We reach the conclusion that we have seen no evidence for photoionization of the nebula yet and that the spectral features we see are caused either by shocks or by dust. These shocks are an integral part of the hydrodynamic shaping that is now producing a new bipolar nebula inside the old planetary nebula (PN), implying that we have a detailed observational record of the very early stages of the shaping of a bipolar nebula.

scholarly journals Distances of the Central Stars and their Position in the HR Diagram

1983 ◽  
Vol 103 ◽  
pp. 391-409 ◽  
Author(s):  
S.R. Pottasch
Keyword(s):  
Galactic Center ◽  
Planetary Nebulae ◽  
Central Star ◽  
Magellanic Clouds ◽  
Constant Mass ◽  
Theoretical Predictions ◽  
Statistical Distance ◽  
Central Stars ◽  
Hr Diagram

Determination of the distances to individual planetary nebulae are discussed. Especially those methods which are independent of assumed nebular properties (mass, absolute flux, etc.) are assembled and discussed. In this way, reasonable approximations to the distance can be obtained for about 50 planetary nebulae. The accuracy of the distances is tested by comparing nebular properties derived from these distances with the properties of nebulae at the galactic center or in the Magellanic clouds. A comparison is also made with the statistical distance determinations; the conclusion is that the assumption of constant mass often leads to an overestimate of the distance, while the assumption of constant Hβ flux leads to distances having individual uncertainties of up to a factor of 3.The central star temperature determination is summarized. Individual central stars are placed on the HR diagram and compared with theoretical predictions. Deductions concerning the evolution which can be made from the observations are discussed.

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.

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 Tracking the Real-Time Evolution of a Writing Event: Second Language Writers at Different Proficiency Levels

2018 ◽  
Vol 68 (2) ◽  
pp. 469-506 ◽  
Author(s):  
Gabriela Adela Gánem-Gutiérrez ◽  
Alexander Gilmore
Keyword(s):  
Second Language ◽  
Real Time ◽  
Time Evolution ◽  
The Real ◽  
Proficiency Levels
Sign in / Sign up

Export Citation Format

Share Document