scholarly journals The Dawes Review 2: Nucleosynthesis and Stellar Yields of Low- and Intermediate-Mass Single Stars

2014 ◽  
Vol 31 ◽  
Author(s):  
Amanda I. Karakas ◽  
John C. Lattanzio
Keyword(s):  
Chemical Evolution ◽  
Surface Composition ◽  
Theoretical Calculations ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Intermediate Mass ◽  
Capture Process ◽  
Intermediate Mass Stars ◽  
Low Metallicity ◽  
The Universe

AbstractThe chemical evolution of the Universe is governed by the chemical yields from stars, which in turn are determined primarily by the initial stellar mass. Even stars as low as 0.9 M⊙can, at low metallicity, contribute to the chemical evolution of elements. Stars less massive than about 10 M⊙experience recurrent mixing events that can significantly change the surface composition of the envelope, with observed enrichments in carbon, nitrogen, fluorine, and heavy elements synthesized by the slow neutron capture process (thes-process). Low- and intermediate-mass stars release their nucleosynthesis products through stellar outflows or winds, in contrast to massive stars that explode as core-collapse supernovae. Here we review the stellar evolution and nucleosynthesis for single stars up to ~ 10 M⊙from the main sequence through to the tip of the asymptotic giant branch (AGB). We include a discussion of the main uncertainties that affect theoretical calculations and review the latest observational data, which are used to constrain uncertain details of the stellar models. We finish with a review of the stellar yields available for stars less massive than about 10 M⊙and discuss efforts by various groups to address these issues and provide homogeneous yields for low- and intermediate-mass stars covering a broad range of metallicities.

scholarly journals Stellar yields for chemical evolution modelling

2013 ◽  
Vol 9 (S298) ◽  
pp. 142-153 ◽  
Author(s):  
Amanda I. Karakas
Keyword(s):  
Chemical Evolution ◽  
Surface Composition ◽  
Slow Neutron ◽  
Surface Enrichment ◽  
Intermediate Mass ◽  
Capture Process ◽  
Stellar Outflows ◽  
Evolved Stars ◽  
Intermediate Mass Stars ◽  
Low Metallicity

AbstractStellar yields are a key ingredient in chemical evolution models. Stars with masses as low as 0.9M⊙, which have an age less than that of our Galaxy at low metallicity, can contribute to the chemical evolution of elements. Stars less than about 8–10M⊙ experience recurrent mixing events that can significantly change the surface composition of the envelope. Evolved stars are observed with surface enrichment in carbon, nitrogen, fluorine, and heavy elements synthesized by the slow neutron capture process (the s-process). These stars release their nucleosynthesis products through stellar outflows or winds, in contrast to massive stars that explode as core-collapse supernovae. Here I review stellar yields for stars up to 10M⊙, including a brief discussion of their uncertainties and shortcomings. Finally, I discuss efforts by various groups to address these issues and to provide homogeneous yields for low and intermediate-mass stars covering a broad range of metallicities.

Nucleosynthesis in stars: The Origin of the Heaviest Elements

2018 ◽  
Vol 14 (S343) ◽  
pp. 79-88 ◽  
Author(s):  
Amanda I. Karakas
Keyword(s):  
Chemical Evolution ◽  
Neutron Capture ◽  
Recent Progress ◽  
Agb Stars ◽  
Intermediate Mass ◽  
Capture Process ◽  
Intermediate Mass Stars ◽  
Intermediate Neutron ◽  
Heaviest Elements ◽  
The Universe

AbstractThe chemical evolution of the Universe is governed by the nucleosynthesis contribution from stars, which in turn is determined primarily by the initial stellar mass. The heaviest elements are primarily produced through neutron capture nucleosynthesis. Two main neutron capture processes identified are the slow and rapid neutron capture processes (s and r processes, respectively). The sites of the r and s-process are discussed, along with recent progress and their associated uncertainties. This review is mostly focused on the s-process which occurs in low and intermediate-mass stars which have masses up to about 8 solar masses (M⊙). We also discuss the intermediate-neutron capture process (or i-process), which may occur in AGB stars, accreting white dwarfs, and massive stars. The contribution of the i-process to the chemical evolution of elements in galaxies is as yet uncertain.

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 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 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 The Chemical Evolution of Magnesium Isotopic Abundances in the Solar Neighbourhood

2003 ◽  
Vol 20 (4) ◽  
pp. 340-344 ◽  
Author(s):  
Y. Fenner ◽  
B. K. Gibson ◽  
H.-c. Lee ◽  
A. I. Karakas ◽  
J. C. Lattanzio ◽  
...  
Keyword(s):  
Chemical Evolution ◽  
Galactic Disk ◽  
Asymptotic Giant Branch ◽  
Solar Neighbourhood ◽  
Asymptotic Giant Branch Stars ◽  
Intermediate Mass ◽  
Intermediate Mass Stars ◽  
Isotopic Abundances ◽  
First Time ◽  
Giant Branch Stars

AbstractThe abundance of the neutron-rich magnesium isotopes observed in metal-poor stars is explained quantitatively with a chemical evolution model of the local Galaxy that considers — for the first time — the metallicity-dependent contribution from intermediate mass stars. Previous models that simulate the variation of Mg isotopic ratios with metallicity in the solar neighbourhood have attributed the production of 25Mg and 26Mg exclusively to hydrostatic burning in massive stars. These models match the data well for [Fe/H] > –1.0 but severely underestimate 25,26Mg/24Mg at lower metallicities. Earlier studies have noted that this discrepancy may indicate a significant role played by intermediate mass stars. Only recently have detailed calculations of intermediate mass stellar yields of 25Mg and 26Mg become available with which to test this hypothesis. In an extension of previous work, we present a model that successfully matches the Mg isotopic abundances in nearby Galactic disk stars through the incorporation of nucleosynthesis predictions of Mg isotopic production in asymptotic giant branch stars.

scholarly journals The slow-neutron capture process in low-metallicity asymptotic giant branch stars

2009 ◽  
Vol 5 (S265) ◽  
pp. 57-60
Author(s):  
Amanda I. Karakas ◽  
Maria Lugaro ◽  
Simon W. Campbell
Keyword(s):  
Neutron Capture ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Observational Constraints ◽  
Asymptotic Giant Branch Stars ◽  
Agb Stars ◽  
Capture Process ◽  
Low Metallicity ◽  
Giant Branch Stars ◽  
Full Network

AbstractElements heavier than iron are produced in asymptotic giant branch (AGB) stars via the slow neutron capture process (s process). Recent observations of s-process-enriched Carbon Enhanced Metal-Poor (CEMP) stars have provided an unprecedented wealth of observational constraints on the operation of the s-process in low-metallicity AGB stars. We present new preliminary full network calculations of low-metallicity AGB stars, including a comparison to the composition of a few s-process rich CEMP stars. We also discuss the possibility of using halo planetary nebulae as further probes of low-metallicity AGB nucleosynthesis.

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 Constraining nucleosynthesis in two CEMP progenitors using fluorine

2020 ◽  
Vol 498 (3) ◽  
pp. 3549-3559
Author(s):  
Aldo Mura-Guzmán ◽  
D Yong ◽  
C Abate ◽  
A Karakas ◽  
C Kobayashi ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Slow Neutron ◽  
Asymptotic Giant Branch ◽  
Capture Process ◽  
Upper Limit ◽  
Infrared Spectrometer ◽  
Binary Evolution ◽  
Vibration Rotation ◽  
R Process ◽  
Process Elements

ABSTRACT We present new fluorine abundance estimations in two carbon enhanced metal-poor (CEMP) stars, HE 1429−0551 and HE 1305+0007. HE 1429−0551 is also enriched in slow neutron-capture process (s-process) elements, a CEMP-s, and HE 1305+0007 is enhanced in both, slow and rapid neutron-capture process elements, a CEMP-s/r. The F abundances estimates are derived from the vibration–rotation transition of the HF molecule at 23358.6 Å  using high-resolution infrared spectra obtained with the Immersion Grating Infrared Spectrometer (IGRINS) at the 4-m class Lowell Discovery Telescope. Our results include an F abundance measurement in HE 1429−0551 of A(F) = +3.93 ([F/Fe] = +1.90) at [Fe/H] = −2.53, and an F upper limit in HE 1305+0007 of A(F) < +3.28 ([F/Fe] < +1.00) at [Fe/H] = −2.28. Our new derived F abundance in HE 1429−0551 makes this object the most metal-poor star where F has been detected. We carefully compare these results with literature values and state-of-the-art CEMP-s model predictions including detailed asymptotic giant branch (AGB) nucleosynthesis and binary evolution. The modelled fluorine abundance for HE 1429−0551 is within reasonable agreement with our observed abundance, although is slightly higher than our observed value. For HE 1429−0551, our findings support the scenario via mass transfer by a primary companion during its thermally pulsing phase. Our estimated upper limit in HE 1305+0007, along with data from the literature, shows large discrepancies compared with AGB models. The discrepancy is principally due to the simultaneous s- and r-process element enhancements which the model struggles to reproduce.

scholarly journals The s-process in stellar sites

2018 ◽  
Vol 184 ◽  
pp. 01004
Author(s):  
Sergio Cristallo
Keyword(s):  
Solar System ◽  
Neutron Capture ◽  
Slow Neutron ◽  
Heavy Elements ◽  
The Sun ◽  
Capture Process ◽  
The Universe ◽  
Pollution Episodes

Stars are marvellous caldrons where all the elements of the Universe (apartfrom hydrogen and helium) have been synthesized. The solar system chemical distri-butionis the result of many pollution episodes from already extinct stellar generations, occurred at different epochs before the Sun formation. Main nucleosynthesis channels re-sponsiblefor the formation of heavy elements are the rapid neutron capture process (ther-process) and the slow neutron capture process (the s-process). Hereafter, I will describethe theory of the s-process and the stellar sites where it is active.

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