scholarly journals The IAC morphological catalog of Northern Galactic Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 24-25 ◽  
Author(s):  
A. Manchado ◽  
M. A. Guerrero ◽  
L. Stanghellini ◽  
M. Serra-Ricart
Keyword(s):  
Magnetic Fields ◽  
Mass Loss ◽  
Stellar Evolution ◽  
Morphological Study ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Intermediate Mass ◽  
Evolutionary Scheme ◽  
Late Stages

Planetary Nebulae (PNs) are highly representative of the late stages of intermediate mass stellar evolution. However, there are still many unresolved questions in their evolutionary scheme. Mass loss processes during the Asymptotic Giant Branch (AGB) are not fully understood. Binarity, rotation and magnetic fields may play an important role in PNs formation. The morphological study of PNs will help us to address those questions, and therefore a meaningful homogeneous database is needed.

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 Molecular Evolution from AGB Stars to Planetary Nebulae

2011 ◽  
Vol 7 (S280) ◽  
pp. 203-215 ◽  
Author(s):  
Sun Kwok
Keyword(s):  
Chemical Synthesis ◽  
Stellar Evolution ◽  
Planetary Nebulae ◽  
Active Phase ◽  
Molecular Ions ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
The Galaxy ◽  
Short Time ◽  
Late Stages

AbstractThe late stages of stellar evolution from the Asymptotic Giant Branch (AGB) to planetary nebulae represent the most active phase of molecular synthesis in a star's life. Over 60 molecular species, including inorganics, organics, radicals, chains, rings, and molecular ions have been detected in the circumstellar envelopes of evolved stars. Most interestingly, complex organic compounds of aromatic and aliphatic structures are synthesized over very short time intervals after the end of the AGB. Also appeared during the post-AGB evolution are the unidentified 21 and 30 μm emission features, which are believed to originate from carbonaceous compounds.The circumstellar environment is an ideal laboratory for the testing of theories of chemical synthesis. The distinct spectral behavior among AGB stars, proto-planetary nebulae (PPN), and planetary nebulae (PN) and the short evolutionary time scales that separate these stages pose severe constraints on models. In this paper, we will present an observational summary of the chemical synthesis in the late stages of stellar evolution, discuss chemical and physical processes at work, and speculate on the possible effects these chemical products have on the Galaxy and the Solar System.

scholarly journals Late stages of stellar evolution: Numerical tests on AGB models

1997 ◽  
Vol 180 ◽  
pp. 354-354
Author(s):  
Valentina Luridiana
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Numerical Models ◽  
Intermediate Mass ◽  
Numerical Tests ◽  
Intermediate Mass Stars ◽  
Late Stages

We have calculated numerical models for intermediate mass stars, following the evolution from the MS to the AGB phase. The sequences have been obtained with the Göttingen hydrodynamical code. The Schwarzschild criterion for convection is used. Mass loss is modeled using the formula proposed by Blöcker:

scholarly journals The role of convection in AGB modeling

2006 ◽  
Vol 2 (S239) ◽  
pp. 258-265
Author(s):  
Paolo Ventura
Keyword(s):  
Mass Loss ◽  
Chemical Evolution ◽  
Cross Sections ◽  
Stellar Evolution ◽  
Asymptotic Giant Branch ◽  
Intermediate Mass ◽  
Convective Envelope ◽  
Evolutionary Phase ◽  
Physical And Chemical

AbstractThe modeling of the Asymptotic Giant Branch phase is made highly uncertain by some still unsolved issues related to the input macro-physics used to calculate the stellar evolution, namely mass loss, nuclear cross sections, overshooting and convective modeling. We show that in the massive intermediate mass models, which achieve at the bottom of their convective envelope temperatures sufficiently high to favour an advanced nucleosynthesis, the treatment of convection plays a major role in determining the physical and chemical evolution of the stellar models during this evolutionary phase.

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 Radio Supernovae as Direct Evidence of Stellar Evolution in Real Time

1998 ◽  
Vol 11 (1) ◽  
pp. 367-367
Author(s):  
S.D. Van Dyk ◽  
M.J. Montes ◽  
K.W. Weiler ◽  
R.A. Sramek ◽  
N. Panagia
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
Loss Rate ◽  
Direct Evidence ◽  
Mass Loss Rate ◽  
X Ray ◽  
Stringent Constraint ◽  
Clear Change ◽  
Late Stages ◽  
Circumstellar Environment

The radio emission from supernovae provides a direct probe of a supernova’s circumstellar environment, which presumably was established by mass-loss episodes in the late stages of the progenitor’s presupernova evolution. The observed synchrotron emission is generated by the SN shock interacting with the relatively high-density circumstellar medium which has been fully ionized and heated by the initial UV/X-ray flash. The study of radio supernovae therefore provides many clues to and constraints on stellar evolution. We will present the recent results on several cases, including SN 1980K, whose recent abrupt decline provides us with a stringent constraint on the progenitor’s initial mass; SN 1993J, for which the profile of the wind matter supports the picture of the progenitor’s evolution in an interacting binary system; and SN 1979C, where a clear change in presupernova mass-loss rate occurred about 104 years before explosion. Other examples, such as SNe 19941 and 1996cb, will also be discussed.

scholarly journals Miras, mass loss, and the origin of planetary nebulae

1981 ◽  
Vol 59 ◽  
pp. 353-356 ◽  
Author(s):  
L. A. Willson
Keyword(s):  
Mass Loss ◽  
Fundamental Mode ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Mira Variables ◽  
Moderate Mass

Mira variables are found at the tip of the asymptotic giant branch, with L≈3000-5000Lʘ and TeH3000K. (Feast 1981; Willson 1981a). They are fundamental mode pulsators (Willson 1979, 1981a). A typical Mira has P~350 days, R~200-300Rʘ, M~1-2Mʘ (Willson 1979; 1981a). From the atmospheric velocities of the Miras plus a fundamental mode period-massradius relation one finds present masses for the Miras which are not very different from their progenitor masses (Willson 1981a). This suggests that pre-Mira mass loss is moderate -- ≲20% of the mass is lost before pulsation starts. In fact one expects only moderate mass loss before the Mira stage;

scholarly journals Evolutionary Tracks for Central Stars of Planetary Nebulae

1989 ◽  
Vol 131 ◽  
pp. 463-472 ◽  
Author(s):  
Detlef Schönberner
Keyword(s):  
Mass Loss ◽  
White Dwarf ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Helium Burning ◽  
Hydrogen Burning ◽  
Stellar Envelope ◽  
Thermal Pulse ◽  
Pulse Cycle ◽  
Central Stars

Our understanding of the evolution of Central Stars of Planetary Nebulae (CPN) has made considerable progress during the last years. This was possible since consistent computations through the asymptotic giant branch (AGB), with thermal pulses and (in some cases) mass loss taken into account, became available (Schönberner, 1979, 1983; Kovetz and Harpaz, 1981; Harpaz and Kovetz, 1981; Iben, 1982, 1984; Wood and Faulkner, 1986). It turned out that the evolution depends very sensitively on the inital conditions on the AGB. More precisely, the evolution of an AGB remnant is a function of the phase of the thermal-pulse cycle during which this remnant was created on the tip of the AGB by the planetary-nebula (PN) formation process (Iben, 1984, 1987). This was first shown by Schönberner (1979), and then fully explored by Iben (1984). In short, two major modes of PAGB evolution to the white dwarf stage are possible, according to the two main phases of a thermally pulsing AGB star: the hydrogen-burning or helium-burning mode. If, for instance, the PN formation, i.e. the removal of the stellar envelope by mass loss, happens during a luminosity peak that follows a thermal pulse of the helium-burning shell, the remnant leaves the AGB while still burning helium as the main energy supplier (Härm and Schwarzschild, 1975). On the other hand, PN formation may also occur during the quiescent hydrogen-burning phase on the AGB, and the remnant continues then to burn mainly hydrogen on its way to becoming a white dwarf.

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