scholarly journals Production of Aluminium and the Heavy Magnesium Isotopes in Asymptotic Giant Branch Stars

2003 ◽  
Vol 20 (3) ◽  
pp. 279-293 ◽  
Author(s):  
A. I. Karakas ◽  
J. C. Lattanzio
Keyword(s):  
Globular Cluster ◽  
Main Sequence ◽  
Stellar Mass ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Magnesium Isotopes ◽  
Wide Range ◽  
Abundance Anomalies ◽  
Stellar Models ◽  
Giant Branch Stars

AbstractWe investigate the production of aluminium and magnesium in asymptotic giant branch models covering a wide range in mass and composition. We evolve models from the pre-main sequence, through all intermediate stages, to near the end of the thermally-pulsing asymptotic giant branch phase. We then perform detailed nucleosynthesis calculations from which we determine the production of the magnesium and aluminium isotopes as a function of the stellar mass and composition. We present the stellar yields of sodium and the magnesium and aluminium isotopes. We discuss the abundance predictions from the stellar models in reference to abundance anomalies observed in globular cluster stars.

scholarly journals Globular cluster abundances: the role of asymptotic giant branch stars

2009 ◽  
Vol 5 (S266) ◽  
pp. 161-168
Author(s):  
Amanda I. Karakas
Keyword(s):  
Globular Cluster ◽  
Globular Clusters ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Modelling Uncertainties ◽  
Low Metallicity ◽  
Abundance Anomalies ◽  
Giant Branch Stars

AbstractOne of the more popular theories to account for the abundance anomalies in globular cluster stars is the ‘self-pollution scenario,’ where the polluters were a previous generation of intermediate-mass asymptotic giant branch (AGB) stars. This idea has proved attractive because: (i) the hot-bottom burning experienced by these objects qualitatively provides an ideal proton-capture environment to produce helium and convert C and O to N, Ne to Na and Mg to Al, and (ii) the slow winds from these stars allow their retention by the cluster's gravitational potential. New stellar yields from low-metallicity AGB models are presented and compared to abundances derived in globular clusters. We also discuss external pollution and inhomogeneous-pollution models that use AGB stars as polluters. Current models of AGB stars cannot match all observational features of globular cluster stars. However, stellar modelling uncertainties are considerable and suggest AGB stars should not be ruled out just yet.

scholarly journals Stellar Models and Yields of Asymptotic Giant Branch Stars

2007 ◽  
Vol 24 (3) ◽  
pp. 103-117 ◽  
Author(s):  
Amanda Karakas ◽  
John C. Lattanzio
Keyword(s):  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Population Synthesis ◽  
Intermediate Phases ◽  
Structural Details ◽  
Solar Metallicity ◽  
Stellar Models ◽  
Giant Branch Stars

AbstractWe present stellar yields calculated from detailed models of low and intermediate-mass asymptotic giant branch (AGB) stars. We evolve models with a range of mass from 1 to 6 M⊙, and initial metallicities from solar to 1/200th of the solar metallicity. Each model was evolved from the zero age main sequence to near the end of the thermally pulsing (TP) AGB phase, and through all intermediate phases including the core He-flash for stars initially less massive than 2.5 M⊙. For each mass and metallicity, we provide tables containing structural details of the stellar models during the TP-AGB phase, and tables of the stellar yields for 74 species from hydrogen through to sulfur, and for a small number of iron-group nuclei. All tables are available for download. Our results have many applications including use in population synthesis studies and the chemical evolution of galaxies and stellar systems, and for comparison to the composition of AGB and post-AGB stars and planetary nebulae.

scholarly journals The origin of dust in galaxies across cosmic time

2020 ◽  
Vol 493 (2) ◽  
pp. 2490-2505 ◽  
Author(s):  
Dian P Triani ◽  
Manodeep Sinha ◽  
Darren J Croton ◽  
Camilla Pacifici ◽  
Eli Dwek
Keyword(s):  
Grain Growth ◽  
Galaxy Formation ◽  
Cosmic Time ◽  
Mass Function ◽  
Stellar Mass ◽  
Asymptotic Giant Branch ◽  
Scaling Relations ◽  
Asymptotic Giant Branch Stars ◽  
Wide Range ◽  
Dust Mass

ABSTRACT We study the dust evolution in galaxies by implementing a detailed dust prescription in the SAGE semi-analytical model (SAM) for galaxy formation. The new model, called Dusty SAGE, follows the condensation of dust in the ejecta of Type II supernovae and asymptotic giant branch stars, grain growth in the dense molecular clouds, destruction by supernovae shocks, and the removal of dust from the interstellar medium (ISM) by star formation, reheating, inflows, and outflows. Our model successfully reproduces the observed dust mass function at redshift z = 0 and the observed scaling relations for dust across a wide range of redshifts. We find that the dust mass content in the present Universe is mainly produced via grain growth in the ISM. By contrast, in the early Universe, the primary production mechanism for dust is the condensation in stellar ejecta. The shift of the significant production channel for dust characterizes the scaling relations of dust-to-gas (DTG) and dust-to-metal (DTM) ratios. In galaxies where the grain growth dominates, we find positive correlations for DTG and DTM ratios with both metallicity and stellar mass. On the other hand, in galaxies where dust is produced primarily via condensation, we find negative or no correlation for DTM and DTG ratios with either metallicity or stellar mass. In agreement with observation showing that the circumgalactic medium contains more dust than the ISM, our model also shows the same trend for z < 4. Our SAM is publicly available at https://github.com/dptriani/dusty-sage.

scholarly journals Thermally-pulsing asymptotic giant branch stars in the Magellanic Clouds

2008 ◽  
Vol 4 (S256) ◽  
pp. 385-390
Author(s):  
Paola Marigo ◽  
Léo Girardi ◽  
Alessandro Bressan ◽  
Martin A. T. Groenewegen ◽  
Bernhard Aringer ◽  
...  
Keyword(s):  
Magellanic Clouds ◽  
Asymptotic Giant Branch ◽  
Circumstellar Dust ◽  
Stellar Winds ◽  
Asymptotic Giant Branch Stars ◽  
Stellar Clusters ◽  
Agb Stars ◽  
Wide Range ◽  
Giant Branch Stars ◽  
Theoretical Project

AbstractWe present the latest results of a theoretical project aimed at investigating the properties of thermally-pulsing asymptotic giant branch (TP-AGB) stars in different host systems. For this purpose, we have recently calculated calibrated synthetic TP-AGB tracks — covering a wide range of metallicities (0.0001 ≤ Z ≤ 0.03) up to the complete ejection of the envelope by stellar winds (Marigo & Girardi 2007) — and used them to generate new sets of stellar isochrones (Marigo et al. 2008). The latter are converted to about 25 different photometric systems, including the mid-infrared filters of Spitzer and AKARI as the effect of circumstellar dust from AGB stars is taken into account. First comparisons with AGB data in the MC field and stellar clusters are discussed.

scholarly journals Lithium production by thermohaline mixing in low-mass, low-metallicity asymptotic giant branch stars

2009 ◽  
Vol 5 (S268) ◽  
pp. 405-410
Author(s):  
Richard J. Stancliffe ◽  
George C. Angelou ◽  
John C. Lattanzio
Keyword(s):  
Main Sequence ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Low Metallicity ◽  
Low Mass ◽  
Thermal Pulses ◽  
Giant Branch Stars

AbstractWe examine the effects of thermohaline mixing on the composition of the envelopes of low-metallicity asymptotic giant branch (AGB) stars. We have evolved models of 1, 1.5 and 2M⊙ and of metallicity Z = 10−4 from the pre-main sequence to the end of the thermal pulsing asymptotic giant branch with thermohaline mixing applied throughout the simulations. We find that the small amount of 3He that remains after the first giant branch is enough to drive thermohaline mixing on the AGB and that the mixing is most efficient in the early thermal pulses, with the efficiency dropping from pulse to pulse. We note a surprising increase in the 7Li abundance, with log10ϵ(7Li) reaching values of over 2.5 in the 1.5M⊙ model. It is thus possible to get stars which are both C- and Li-rich at the same time. We compare our models to measurements of carbon and lithium in carbon-enhanced metal-poor stars which have not yet reached the giant branch. These models can simultaneously reproduced the observed C and Li abundances of carbon-enhanced metal-poor turn-off stars that are Li-rich.

scholarly journals High-resolution spectroscopy of globular cluster post-Asymptotic Giant Branch stars

2004 ◽  
Vol 419 (3) ◽  
pp. 1123-1132 ◽  
Author(s):  
C. J. Mooney ◽  
W. R. J. Rolleston ◽  
F. P. Keenan ◽  
P. L. Dufton ◽  
J. V. Smoker ◽  
...  
Keyword(s):  
High Resolution ◽  
Globular Cluster ◽  
Asymptotic Giant Branch ◽  
High Resolution Spectroscopy ◽  
Asymptotic Giant Branch Stars ◽  
Giant Branch Stars

scholarly journals Oxygen loss from simulated galaxies and the metal flow main sequence: predicting the dependence on mass and environment

2020 ◽  
Vol 496 (4) ◽  
pp. 4433-4441
Author(s):  
Philip Taylor ◽  
Chiaki Kobayashi ◽  
Lisa J Kewley
Keyword(s):  
Galaxy Evolution ◽  
Main Sequence ◽  
Metal Flow ◽  
Stellar Mass ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Strong Constraint ◽  
Massive Galaxies ◽  
Star Forming ◽  
Ia Supernovae

ABSTRACT We predict the mass fraction of oxygen lost from galaxies in a cosmological simulation as a function of stellar mass and environment at the present day. The distribution with stellar mass is bimodal, separating star-forming and quenched galaxies. The metallicity of gas and stars is self-consistently calculated using a chemical evolution model that includes Type II and Ia supernovae, hypernovae, and asymptotic giant branch stars. The mass of oxygen lost from each galaxy is calculated by comparing the existing oxygen in gas and stars in the galaxy to the oxygen that should have been produced by the present-day population of stars. More massive galaxies are able to retain a greater fraction of their metals (∼100 per cent) than low-mass galaxies (∼40–70 per cent). As in the star formation main sequence, star-forming galaxies follow a tight relationship also in terms of oxygen mass lost – a metal flow main sequence – whereas massive quenched galaxies tend to have lost a greater fraction of oxygen (up to 20 per cent), due to active galactic nucleus-driven winds. The amount of oxygen lost by satellite galaxies depends on the details of their interaction history, and those in richer groups tend to have lost a greater fraction of their oxygen. Observational estimates of metal retention in galaxies will provide a strong constraint on models of galaxy evolution.

Final evolution of super-AGB stars and supernovae triggered by electron capture

2019 ◽  
Vol 36 ◽  
Author(s):  
Shing-Chi Leung ◽  
Ken’ichi Nomoto
Keyword(s):  
Electron Capture ◽  
Asymptotic Giant Branch ◽  
Asymptotic Giant Branch Stars ◽  
Core Electron ◽  
The Core ◽  
Wide Range ◽  
Curve Model ◽  
Theoretical Question ◽  
Giant Branch Stars ◽  
Final Evolution

AbstractStars of 8–10 M⊙ form a strongly electron-degenerate oxygen–neon–magnesium core which is more massive than ∼1.1 M⊙, and become super-Asymptotic Giant Branch stars. The oxygen–neon–magnesium core increases its mass through H and He shell burning. The core contracts accordingly and the central density increases. In the high density core, electron capture takes place and further boosts the core contraction. When electron capture on 20Ne starts, it induces oxygen–neon deflagration. It remains a theoretical question whether neutron star can be formed after the deflagration has started. If the star collapses, the following explosion is known as an electron capture supernova. In this article, we give a brief overview on the development of idea in the presupernova evolution and the hydrodynamics behaviour of electron capture supernovae. Using standard stellar evolutionary models that show rather high ignition density, we show that the collapse can occur in a wide range of model parameter. However, future study remains important. We also review the possible observables of electron capture supernovae and discuss their applications to the light curve model for the Crab supernova 1054.

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