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.

S-process Elements in Binary Central Stars of Planetary Nebulae

2018 ◽  
Vol 14 (S343) ◽  
pp. 452-453
Author(s):  
Lisa Löbling ◽  
Henri Boffin
Keyword(s):  
Neutron Capture ◽  
Planetary Nebulae ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Intermediate Mass ◽  
Element Abundances ◽  
Evolved Stars ◽  
Intermediate Mass Stars ◽  
Process Elements ◽  
Central Stars

AbstractLow- and intermediate-mass stars experience a phase of carbon enrichment and slow neutron-capture nucleosynthesis (s-process) on the asymptotic giant branch. An interesting element is the radioactive technetium, whose presence is a clear indication that nucleosynthesis happened recently. Analysing the element abundances not only in the hot evolved stars at the center of planetary nebulae helps to derive constraints for the evolution of these stars. Doing so also in their companions if they are in a binary, provides information on the mass-transfer history.

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.

scholarly journals Evolutionary timescales from the AGB to the CSPNe phase

2018 ◽  
Vol 14 (S343) ◽  
pp. 36-46
Author(s):  
Marcelo M. Miller Bertolami
Keyword(s):  
White Dwarf ◽  
New Physics ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars

AbstractThe transition from the asymptotic giant branch (AGB) to the final white dwarf (WD) stage is arguably the least understood phase in the evolution of single low- and intermediate-mass stars (0.8 ≲ MZAMS/M⊙ ≲ 8…10). Here we briefly review the progress in the last 50 years of the modeling of stars during the post-AGB phase. We show that although the main features, like the extreme mass dependency of post-AGB timescales were already present in the earliest post-AGB models, the quantitative values of the computed post-AGB timescales changed every time new physics was included in the modeling of post-AGB stars and their progenitors. Then we discuss the predictions and uncertainties of the latest available models regarding the evolutionary timescales of post-AGB stars.

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 Monash Chemical Yields Project (Monχey) Element production in low- and intermediate-mass stars

2015 ◽  
Vol 11 (A29B) ◽  
pp. 164-165
Author(s):  
Carolyn Doherty ◽  
John Lattanzio ◽  
George Angelou ◽  
Simon W. Campbell ◽  
Ross Church ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Heavy Element ◽  
Internal Surface ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Galactic Chemical Evolution ◽  
Intermediate Mass ◽  
Mixing Processes ◽  
Intermediate Mass Stars ◽  
Solar Metallicity

AbstractThe Monχey project will provide a large and homogeneous set of stellar yields for the low- and intermediate- mass stars and has applications particularly to galactic chemical evolution modelling. We describe our detailed grid of stellar evolutionary models and corresponding nucleosynthetic yields for stars of initial mass 0.8 M⊙ up to the limit for core collapse supernova (CC-SN) ≈ 10 M⊙. Our study covers a broad range of metallicities, ranging from the first, primordial stars (Z = 0) to those of super-solar metallicity (Z = 0.04). The models are evolved from the zero-age main-sequence until the end of the asymptotic giant branch (AGB) and the nucleosynthesis calculations include all elements from H to Bi. A major innovation of our work is the first complete grid of heavy element nucleosynthetic predictions for primordial AGB stars as well as the inclusion of extra-mixing processes (in this case thermohaline) during the red giant branch. We provide a broad overview of our results with implications for galactic chemical evolution as well as highlight interesting results such as heavy element production in dredge-out events of super-AGB stars. We briefly introduce our forthcoming web-based database which provides the evolutionary tracks, structural properties, internal/surface nucleosynthetic compositions and stellar yields. Our web interface includes user- driven plotting capabilities with output available in a range of formats. Our nucleosynthetic results will be available for further use in post processing calculations for dust production yields.

scholarly journals Binary Central Stars of Planetary Nebulae

Galaxies ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 28 ◽  
Author(s):  
David Jones
Keyword(s):  
Planetary Nebulae ◽  
Current Understanding ◽  
Intermediate Mass ◽  
Single Star ◽  
Intermediate Mass Stars ◽  
Binary Evolution ◽  
Central Stars

It is now clear that a vast majority of intermediate-mass stars have stellar and/or sub-stellar companions, therefore it is no longer appropriate to consider planetary nebulae as a single-star phenomenon, although some single, isolated stars may well lead to planetary nebulae. As such, while understanding binary evolution is critical for furthering our knowledge of planetary nebulae, the converse is also true: planetary nebulae can be valuable tools with which to probe binary evolution. In this brief review, I attempt to summarise some of our current understanding with regards to the role of binarity in the formation of planetary nebulae, and the areas in which continued study of planetary nebulae may have wider ramifications for our grasp on the fundaments of binary evolution.

scholarly journals Constraining ν-process production of fluorine through cosmic ray nucleosynthesis

2019 ◽  
Vol 490 (3) ◽  
pp. 4307-4316 ◽  
Author(s):  
Keith A Olive ◽  
Elisabeth Vangioni
Keyword(s):  
Stellar Evolution ◽  
Massive Star ◽  
Cosmic Ray ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Star Production ◽  
Low Metallicity ◽  
Galactic Cosmic Ray

ABSTRACT Fluorine is massive enough that it is not considered to be a light (Z ≤ 5) element, yet compared to its near neighbours, C, N, O, and Ne, it is far underproduced in the course of stellar evolution, making its origin more complex. In fact, the abundance of fluorine is the lowest among all elements between Z = 5 and 21 and is roughly 3–4 orders of magnitude below that of C, N, O, and Ne. There are several plausible sources for F beyond standard stellar evolution. These include the production in the asymptotic giant branch phase (AGB) in intermediate-mass stars, production in Wolf–Rayet stars, and the production through neutrino spallation in supernovae. The latter, known as the ν-process, is an important source for 11B, and may contribute to the abundance of 7Li as well. We combine a simple model of Galactic chemical evolution with a standard Galactic cosmic ray nucleosynthesis model to treat self-consistently the evolution of the Li, Be, and B isotopes. We include massive star production of F, as well as contributions from AGB stars, and the ν-process. Given the uncertainties in neutrino energies in supernovae, we normalize the ν-process using the observed 11B/10B ratio as a constraint. As a consequence, we are able to determine the relative importance of each contribution to the F abundance. We find that although the ν-process dominates at early times (low metallicity), the present-day F abundance is found to originate primarily from AGB stars.

scholarly journals Silicon Carbide as the Carrier of the 21μm Feature

2003 ◽  
Vol 209 ◽  
pp. 315-315
Author(s):  
A. K. Speck ◽  
A. M. Hofmeister
Keyword(s):  
Silicon Carbide ◽  
Solid State ◽  
Ir Spectra ◽  
Planetary Nebulae ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Transient Species ◽  
Physical Conditions ◽  
Show Evidence ◽  
Central Stars

Some proto-planetary nebulae (PPNe) exhibit an enigmatic feature in their infrared (IR) spectra at ~21 μm. PPNe which display this feature are all C-rich and all show evidence for s-process enhancements in their photospheres, indicative of efficient dredge-up during the ascent of the asymptotic giant branch (AGB). Furthermore, this 21 μm feature is not seen in the spectra of either the precursors to PPNe, the AGB stars, or the successors of PPNe, planetary nebulae (PNe). However the 21 μm feature has been seen in the spectra of PNe with Wolf-Rayet central stars. Therefore the carrier of this feature is unlikely to be a transient species that only exists in the PPNe phase. It is more likely that the physical conditions in the AGB stars and PNe conspire against the observation of an IR feature at 21 μm. This feature has been attributed to various molecular and solid state species, none of which satisfy all constraints, although TiC and PAHs have seemed the most viable.

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