scholarly journals Theoretical abundances in Planetary Nebulae

1997 ◽  
Vol 180 ◽  
pp. 257-257
Author(s):  
Paola Marigo
Keyword(s):  
Chemical Composition ◽  
Mass Loss ◽  
Analytical Model ◽  
Planetary Nebulae ◽  
Stellar Winds ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Thermal Pulse ◽  
Intermediate Mass Stars

A semi-analytical model has been constructed to calculate the TP-AGB evolution of low-and intermediate-mass stars (Marigo et al. 1996), starting from the first thermal pulse until the complete ejection of the envelope by stellar winds. We estimate the changes in the chemical composition of the envelope due to different processes: (i) the intershell nucleosynthesis and convective dredge-up; (ii) envelope burning in the most massive AGB stars (M ≥ 3–4M⊙); (iii) mass loss by stellar winds.

scholarly journals Near–Infrared Imaging of Proto-Planetary Nebulae

1993 ◽  
Vol 155 ◽  
pp. 340-340 ◽  
Author(s):  
R.E.S. Clegg ◽  
N. A. Walton ◽  
M.J. Barlow
Keyword(s):  
Molecular Hydrogen ◽  
Near Infrared ◽  
Infrared Imaging ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Preliminary Results ◽  
Near Ir ◽  
Intermediate Mass Stars ◽  
Hydrogen Lines

It is not really known how low and intermediate mass stars eject mass to form PNs. We present preliminary results from a programme of near–IR imaging, in which we study a sequence of objects, from extreme AGB stars through proto–planetaries to young, compact PNs. We aim to study the sequence of morphologies, to see where the onset of bipolar shaping occurs, and to use the IR molecular hydrogen lines to map neutral regions around ionized nebulae.

scholarly journals AGBs, Post-AGBs and the Shaping of Planetary Nebulae

Galaxies ◽  
2018 ◽  
Vol 6 (3) ◽  
pp. 99 ◽  
Author(s):  
Eric Lagadec
Keyword(s):  
Angular Resolution ◽  
Hubble Space Telescope ◽  
Planetary Nebulae ◽  
High Angular Resolution ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Shaping Process ◽  
Huge Variety ◽  
Isotropic Radiation

During the last decades, observations, mostly with the Hubble Space Telescope, have revealed that round Planetary Nebulae were the exception rather than rule. A huge variety of features are observed, such as jets, discs, tori, showing that the ejection of material is not due to isotropic radiation pressure on a spherical shell and that more physics is involved. This shaping process certainly occur early in the evolution of these low and intermediate mass stars and must leave imprints in the evolutionary stages prior the PN phase. Thanks to news instruments on the most advanced telescopes (e.g., the VLTI, SPHERE/VLT and ALMA), high angular resolution observations are revolutionising our view of the ejection of gas and dust during the AGB and post-AGB phases. In this review I will present the newest results concerning the mass loss from AGB stars, post-AGB stars and related objects.

Magnetic fields in PNe and other evolved low-mass and intermediate-mass stars

2016 ◽  
Vol 12 (S323) ◽  
pp. 136-140
Author(s):  
Laurence Sabin ◽  
Qizhou Zhang ◽  
Gregg A. Wade ◽  
Agnès Lèbre ◽  
Roberto Vázquez
Keyword(s):  
Magnetic Fields ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Efficient Mechanism ◽  
Intermediate Mass Stars ◽  
Low Mass

AbstractMagnetic fields are likely to be an efficient mechanism which can affect evolved intermediate mass stars (i.e. post-AGB stars and planetary nebulae) in different ways such as via the shaping of their envelope. However, observational probes for the presence of those fields are still scarce. I will present a summary of the works, including those from our group, on the detection and measurement of magnetic fields in various evolved objects.

scholarly journals New models for the evolution of central stars of planetary nebulae: Faster and Brighter

2016 ◽  
Vol 12 (S323) ◽  
pp. 179-183
Author(s):  
Marcelo M. Miller Bertolami
Keyword(s):  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Short Article ◽  
Intermediate Mass Stars ◽  
New Models ◽  
Central Stars

AbstractThe post-asymptotic giant branch (AGB) phase is arguably one of the least understood phases of the evolution of low- and intermediate- mass stars. The recent post-AGB evolutionary sequences computed by Miller Bertolami (2016) are at least three to ten times faster than those previously published by Vassiliadis & Wood (1994) and Blöcker (1995) which have been used in a large number of studies. This is true for the whole mass and metallicity range. The new models are also ~0.1–0.3 dex brighter than the previous models with similar remnant masses. In this short article we comment on the main reasons behind these differences, and discuss possible implications for other studies of post-AGB stars or planetary nebulae.

scholarly journals Star – Gas Cycle in Galaxies

2006 ◽  
Vol 2 (S235) ◽  
pp. 268-270
Author(s):  
Jan Palouš
Keyword(s):  
Mass Loss ◽  
Stellar Mass ◽  
Stellar Winds ◽  
Intermediate Mass ◽  
Evolution Of Galaxies ◽  
Intermediate Mass Stars ◽  
Ob Associations

AbstractThe importance of the star-gas cycle for the evolution of galaxies is discussed. We describe three different ways of stellar mass loss: a) the gas return from low and intermediate mass stars, b) the stellar winds from OB associations; c) the superwinds from superstar clusters.

scholarly journals Asymptotic Giant Branch Evolution and the Initial-Final Mass Relation of Single CO White Dwarfs

2011 ◽  
Vol 7 (S281) ◽  
pp. 36-43
Author(s):  
Paola Marigo
Keyword(s):  
Mass Loss ◽  
White Dwarfs ◽  
Asymptotic Giant Branch ◽  
Mass Relation ◽  
Evolutionary Models ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Final Mass ◽  
The Impact

AbstractCombining recent mass determinations of Galactic CO white dwarfs and their progenitors with the latest evolutionary models for Asymptotic Giant Branch (AGB) stars, I review the initial-final mass relation (IFMR) of low- and intermediate-mass stars. In particular, I analyze the impact on the IFMR produced by a few critical processes characterizing the AGB phase, namely: the second and third dredge-up events, hot-bottom burning, and mass loss. Their dependence on metallicity and related theoretical uncertainties are briefly discussed.

scholarly journals Parameterizing the Third Dredge up in AGB Stars

2003 ◽  
Vol 209 ◽  
pp. 82-82 ◽  
Author(s):  
A. I. Karakas ◽  
J. C. Lattanzio ◽  
O. R. Pols
Keyword(s):  
Mass Loss ◽  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
The Third ◽  
Intermediate Mass Stars

We present new evolutionary sequences for low and intermediate mass stars (1M⊙ to 6M⊙) for three different metallicities, z = 0.02, 0.008 and 0.004. We evolve the models from the pre-main sequence to the thermally-pulsing asymptotic giant branch (AGB) phase. We have two sequences of models for each mass, one which includes mass-loss and one without mass-loss. For an overview of AGB evolution and nucleosynthesis, see Herwig (2002) and Lattanzio (2002).

scholarly journals Quantitative Spectral Analysis of hot Post-AGB Stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 356-357
Author(s):  
Daniel R. Costa-Mello ◽  
Simone Daflon ◽  
Claudio B. Pereira
Keyword(s):  
Spectral Analysis ◽  
Chemical Composition ◽  
High Resolution ◽  
Planetary Nebulae ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Quantitative Spectral Analysis ◽  
Luminous Objects

AbstractPost-AGB (PAGB) stars are luminous objects of low and intermediate mass in a final and short stage of evolution in the transition between AGB stars and planetary nebulae (PNe). In this work we present a quantitative spectral analysis of some hot PAGBs based on high resolution spectra. The stellar parameters and chemical composition were obtained from the synthesis of non-LTE spectra.

Variability, Pulsations and Mass Loss of Evolved Stars

2017 ◽  
Vol 14 (S339) ◽  
pp. 95-97
Author(s):  
S. Höfner
Keyword(s):  
Mass Loss ◽  
Chemical Elements ◽  
Building Blocks ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Long Period ◽  
Evolved Stars ◽  
Intermediate Mass Stars ◽  
Recent Developments

AbstractEvolved low- and intermediate-mass stars that have reached the Asymptotic Giant Branch (AGB) phase tend to show pronounced long-period variability due to large-amplitude pulsations. Those pulsations are considered to play a key role in triggering mass loss through massive dusty winds. The winds enrich the surrounding interstellar medium with newly-produced chemical elements and dust grains, providing building blocks for new generations of stars and planets. Considerable efforts are being made to understand the physics of AGB stars, and to develop quantitative models. This talk gave a brief summary of recent developments, with references to the literature.

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