scholarly journals Galactic Chemical Evolution of Radioactive Isotopes with an s-process Contribution

2022 ◽  
Vol 924 (1) ◽  
pp. 10
Author(s):  
Thomas C. L. Trueman ◽  
Benoit Côté ◽  
Andrés Yagüe López ◽  
Jacqueline den Hartogh ◽  
Marco Pignatari ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Average Length ◽  
Asymptotic Giant Branch ◽  
Radioactive Isotopes ◽  
Agb Stars ◽  
Galactic Chemical Evolution ◽  
Early Solar System ◽  
Self Consistent ◽  
Consistent Solution ◽  
The Mean

Abstract Analysis of inclusions in primitive meteorites reveals that several short-lived radionuclides (SLRs) with half-lives of 0.1–100 Myr existed in the early solar system (ESS). We investigate the ESS origin of 107Pd, 135Cs, and 182Hf, which are produced by slow neutron captures (the s-process) in asymptotic giant branch (AGB) stars. We modeled the Galactic abundances of these SLRs using the OMEGA+ galactic chemical evolution (GCE) code and two sets of mass- and metallicity-dependent AGB nucleosynthesis yields (Monash and FRUITY). Depending on the ratio of the mean-life τ of the SLR to the average length of time between the formations of AGB progenitors γ, we calculate timescales relevant for the birth of the Sun. If τ/γ ≳ 2, we predict self-consistent isolation times between 9 and 26 Myr by decaying the GCE predicted 107Pd/108Pd, 135Cs/133Cs, and 182Hf/180Hf ratios to their respective ESS ratios. The predicted 107Pd/182Hf ratio indicates that our GCE models are missing 9%–73% of 107Pd and 108Pd in the ESS. This missing component may have come from AGB stars of higher metallicity than those that contributed to the ESS in our GCE code. If τ/γ ≲ 0.3, we calculate instead the time (T LE) from the last nucleosynthesis event that added the SLRs into the presolar matter to the formation of the oldest solids in the ESS. For the 2 M ⊙, Z = 0.01 Monash model we find a self-consistent solution of T LE = 25.5 Myr.

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 Galactic Chemical Evolution of the s Process from AGB Stars

2009 ◽  
Vol 26 (3) ◽  
pp. 153-160 ◽  
Author(s):  
Alessandra Serminato ◽  
Roberto Gallino ◽  
Claudia Travaglio ◽  
Sara Bisterzo ◽  
Oscar Straniero
Keyword(s):  
Solar System ◽  
Chemical Evolution ◽  
Asymptotic Giant Branch ◽  
Heavy Elements ◽  
Agb Stars ◽  
Galactic Chemical Evolution ◽  
Element Analysis ◽  
Residual Method ◽  
The Galaxy ◽  
Process Element

AbstractWe follow the chemical evolution of the Galaxy for the s elements using a Galactic chemical evolution (GCE) model, as already discussed by Travaglio et al. (1999, 2001, 2004), with a full updated network and refined asymptotic giant branch (AGB) models. Calculations of the s contribution to each isotope at the epoch of the formation of the solar system is determined by following the GCE contribution by AGB stars only. Then, using the r-process residual method we determine for each isotope their solar system r-process fraction, and recalculate the GCE contribution of heavy elements accounting for both the s and r process. We compare our results with spectroscopic abundances at various metallicities of [Sr,Y,Zr/Fe], of [Ba,La/Fe], of [Pb/Fe], typical of the three s-process peaks, as well as of [Eu/Fe], which in turn is a typical r-process element. Analysis of the various uncertainties involved in these calculations are discussed.

scholarly journals Galactic Chemical Evolution of Radioactive Isotopes

2019 ◽  
Vol 878 (2) ◽  
pp. 156 ◽  
Author(s):  
Benoit Côté ◽  
Maria Lugaro ◽  
Rene Reifarth ◽  
Marco Pignatari ◽  
Blanka Világos ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Radioactive Isotopes ◽  
Galactic Chemical Evolution

scholarly journals Dynamics, temperature, chemistry, and dust: Ingredients for a self-consistent AGB wind

2018 ◽  
Vol 14 (S343) ◽  
pp. 129-133
Author(s):  
J. Boulangier ◽  
D. Gobrecht ◽  
L. Decin
Keyword(s):  
Life Time ◽  
Vital Role ◽  
Asymptotic Giant Branch ◽  
Nucleation Theory ◽  
Agb Stars ◽  
Low Mass Stars ◽  
Chemical Enrichment ◽  
Self Consistent ◽  
Evolutionary Phase ◽  
Almost All

AbstractUnderstanding Asymptotic Giant Branch (AGB) stars is important as they play a vital role in the chemical life cycle of galaxies. AGB stars are in a phase of their life time where they have almost ran out of fuel and are losing vast amounts of material to their surroundings, via stellar winds. As this is an evolutionary phase of low mass stars, almost all stars go through this phase making them one of the main contributors to the chemical enrichment of galaxies. It is therefore important to understand what kind of material is being lost by these stars, and how much and how fast. This work summarises the steps we have taken towards developing a self-consistent AGB wind model. We improve on current models by firstly coupling chemical and hydrodynamical evolution, and secondly by upgrading the nucleation theory framework to investigate the creation of TiO2, SiO, MgO, and Al2O3 clusters.

scholarly journals Barium Stars: Theoretical Interpretation

2009 ◽  
Vol 26 (3) ◽  
pp. 176-183 ◽  
Author(s):  
Laura Husti ◽  
Roberto Gallino ◽  
Sara Bisterzo ◽  
Oscar Straniero ◽  
Sergio Cristallo
Keyword(s):  
Binary Systems ◽  
Main Sequence ◽  
Mass Transfer Process ◽  
Asymptotic Giant Branch ◽  
Theoretical Interpretation ◽  
Evolutionary Stage ◽  
Elemental Distribution ◽  
Red Giants ◽  
Agb Stars ◽  
Consistent Solution

AbstractBarium stars are extrinsic Asymptotic Giant Branch (AGB) stars. They present the s-enhancement characteristic for AGB and post-AGB stars, but are in an earlier evolutionary stage (main sequence dwarfs, subgiants, red giants). They are believed to form in binary systems, where a more massive companion evolved faster, produced the s-elements during its AGB phase, polluted the present barium star through stellar winds and became a white dwarf. The samples of barium stars of Allen & Barbuy (2006) and of Smiljanic et al. (2007) are analysed here. Spectra of both samples were obtained at high-resolution and high S/N. We compare these observations with AGB nucleosynthesis models using different initial masses and a spread of 13C-pocket efficiencies. Once a consistent solution is found for the whole elemental distribution of abundances, a proper dilution factor is applied. This dilution is explained by the fact that the s-rich material transferred from the AGB to the nowadays observed stars is mixed with the envelope of the accretor. We also analyse the mass transfer process, and obtain the wind velocity for giants and subgiants with known orbital period. We find evidence that thermohaline mixing is acting inside main sequence dwarfs and we present a method for estimating its depth.

scholarly journals Gas and dust from metal-rich AGB stars

2020 ◽  
Vol 641 ◽  
pp. A103
Author(s):  
P. Ventura ◽  
F. Dell’Agli ◽  
M. Lugaro ◽  
D. Romano ◽  
M. Tailo ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Main Sequence ◽  
Carbon Star ◽  
Asymptotic Giant Branch ◽  
Chemical Compositions ◽  
Agb Stars ◽  
Dust Production ◽  
Lower Mass ◽  
Nuclear Burning ◽  
Physical And Chemical

Context. Stars evolving through the asymptotic giant branch (AGB) phase provide significant feedback to their host system, which is both gas enriched in nuclear-burning products, and dust formed in their winds, which they eject into the interstellar medium. Therefore, AGB stars are an essential ingredient for the chemical evolution of the Milky Way and other galaxies. Aims. We study AGB models with super-solar metallicities to complete our vast database, so far extending from metal-poor to solar-chemical compositions. We provide chemical yields for masses in the range 1−8 M⊙ and metallicities Z = 0.03 and Z = 0.04. We also study dust production in this metallicity domain. Methods. We calculated the evolutionary sequences from the pre-main sequence through the whole AGB phase. We followed the variation of the surface chemical composition to calculate the chemical yields of the various species and model dust formation in the winds to determine the dust production rate and the total dust mass produced by each star during the AGB phase. Results. The physical and chemical evolution of the star is sensitive to the initial mass: M >  3 M⊙ stars experience hot bottom burning, whereas the surface chemistry of the lower mass counterparts is altered only by third dredge-up. The carbon-star phase is reached by 2.5−3.5 M⊙ stars of metallicity Z = 0.03, whereas all the Z = 0.04 stars (except the 2.5 M⊙) remain O-rich for the whole AGB phase. Most of the dust produced by metal-rich AGBs is in the form of silicate particles. The total mass of dust produced increases with the mass of the star, reaching ∼0.012 M⊙ for 8 M⊙ stars.

scholarly journals Stellar yields – theory and observations

2015 ◽  
Vol 11 (A29B) ◽  
pp. 162-163
Author(s):  
Amanda I. Karakas
Keyword(s):  
Chemical Evolution ◽  
Stellar Evolution ◽  
Theoretical Calculations ◽  
Theoretical Models ◽  
Asymptotic Giant Branch ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Chemically Peculiar ◽  
Essential Tool

AbstractStellar yields are an essential tool for studies of chemical evolution. For low and intermediate-mass stars (0.8 up to 8-10M⊙) the richest nucleosynthesis occurs when the stars are on the asymptotic giant branch (AGB) of stellar evolution. We discuss the main nucleosynthesis outcomes, along with the uncertainties that affect the theoretical calculations. The uncertainties in the physics can be improved by comparing theoretical models to observations, including chemically peculiar metal-poor stars, along with AGB stars and their progeny.

scholarly journals Asymptotic Giant Branch Stars and presolar grains

2020 ◽  
Vol 227 ◽  
pp. 01002
Author(s):  
Maurizio Busso ◽  
Sara Palmerini ◽  
Diego Vescovi
Keyword(s):  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Radioactive Isotopes ◽  
Red Giants ◽  
Asymptotic Giant Branch Stars ◽  
Heavy Nuclei ◽  
Early Solar System ◽  
Stable Species ◽  
The Galaxy ◽  
Circumstellar Environments

Starting from the recognition that radioactive isotopes were present alive in the Early Solar System, inducing composition anomalies from their decay, and through the discovery that other important anomalies affected also stable species, we shall discuss how the carriers of these abundance peculiarities were identified in very refractory pre-solar dust grains, formed in circumstellar environments. We shall outline how groups of such grains and subsequently in-dividual single crystals of C-rich or O-rich materials (like, e.g., SiC and Al2O3) could be analyzed, providing a new tool to verify the composition of stellar winds. This is so especially for AGB stars, which are the primary factories of dust in the Galaxy. For this reason, pristine meteorites open a crucial window on the details of nucleosynthesis processes occurring in such evolved red giants, for both intermediate-mass elements and rare heavy nuclei affected by slow neutron captures (the s-process).

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