Stellar Models and Yields of Asymptotic Giant Branch Stars

Karakas, Amanda I.; Lattanzio, John C.

doi:10.1071/as07021

Cited by 315 publications

(521 citation statements)

References 71 publications

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“…In Figure 1 we show the yields of 12 C, 14 N, 17 O and 19 F as a function of initial stellar mass from the Z = 0.0001 models of Karakas (2009) compared to the yields from Karakas & Lattanzio (2007). The new yields of 14 N from the intermediate-mass AGB models have been reduced, while the yields of 12 C are reasonably consistent with the previous calculations.…”

Section: Yields From Asymptotic Giant Branch Starssupporting

confidence: 75%

“…In Figure 2 we show the yields of 23 Na from the Z = 0.0001 models of Karakas (2009) compared to the yields from Karakas & Lattanzio (2007). Here we can see a huge reduction in the sodium yields, by a few orders of magnitude for the most massive models.…”

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 93%

“…Stellar nucleosynthesis predictions from low-metallicity, intermediate-mass AGB stars are available in the literature (e.g., Herwig 2004;Karakas & Lattanzio 2007;Ventura & D'Antona 2009). Here, we compare GC abundance trends using new AGB yields that are an update to the stellar yields presented in Karakas & Lattanzio (2007).…”

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 99%

“…Here, we compare GC abundance trends using new AGB yields that are an update to the stellar yields presented in Karakas & Lattanzio (2007). These new yields are discussed in detail in Karakas (2009); in summary, these models use updated reaction rates and provide yields from scaled-solar initial abundances for the Z = 0.008 and 0.004 models.…”

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 99%

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Globular cluster abundances: the role of asymptotic giant branch stars

Karakas

2009

Proc. IAU

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Abstract.One 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 inhomogeneouspollution 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.

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Section: Yields From Asymptotic Giant Branch Starssupporting

confidence: 75%

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 93%

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 99%

Section: Yields From Asymptotic Giant Branch Starsmentioning

confidence: 99%

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Globular cluster abundances: the role of asymptotic giant branch stars

Karakas

2009

Proc. IAU

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“…The chemical content of the expelled material depends critically on the physical properties of the pulses (e.g., pulse duration and interpulse mass-loss rate). The duration of the pulse limits the time for nucleosynthesis to occur inside the star 18 , while the mass-loss rate between pulses limits the number of thermal pulses an AGB star will experience 17 . These properties will affect the stellar yields of new elements returned to the ISM, as well as eventually lead to the termination of the AGB phase.…”

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confidence: 99%

Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris

Maercker

Mohamed

Vlemmings

et al. 2012

Nature

161

204

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The asymptotic giant branch star R Sculptoris is surrounded by a detached shell of dust and gas 1,2 . The shell originates from a thermal pulse during which the star undergoes a brief period of increased mass loss 3,4 . It has hitherto been impossible to constrain observationally the timescales and mass-loss properties during and after a thermal pulse − parameters that determine the lifetime on the asymptotic giant branch and the amount of elements returned by the star. Here we report observations of CO emission from the circumstellar envelope and shell around R Sculptoris with an angular resolution of 1.3". What was hitherto thought to be only a thin, spherical shell with a clumpy structure, is revealed to contain a spiral structure. Spiral structures associated with circumstellar envelopes have been seen previously, from which it was concluded that the systems must be binaries 5,6,7,8 . Using the data, combined with hydrodynamic simulations, we conclude that R Sculptoris is a binary system that underwent a thermal pulse ≈1800 years ago, lasting ≈200 years. About 3×10 !3 M ! of mass was ejected at a velocity of 14.3 km s −1 and at a rate ≈30 times higher than the prepulse mass-loss rate. This shows that ≈3 times more mass is returned to the interstellar medium during and immediately after a pulse than previously thought. The detached shell around R Sculptoris was observed in CO(J = 3 − 2) emission at 345 GHz using the Atacama Large Millimeter/submillimeter Array (ALMA) during Cycle 0 operations (Fig.1, and supplementary information). The data clearly show the well-centered detached shell with a radius of 18.5", and reveal a spiral structure extending from the central star outwards to the shell. Previous observations of R Sculptoris show structure in the form of clumps. However, this was interpreted as clumpy material within the shell itself, and not as a structure interior to the shell 2 . Until now no clear signs of binary companions have been observed in the detached shell sources (with a possible exception for the detached shell around TT Cyg 9 ). The observed structure around R Sculptoris, however, indicates the presence of a companion, shaping the stellar wind into a spiral shell structure 8 . Smoothed particle hydrodynamics (SPH) models show that a wide binary companion can have a significant effect in the shaping of the wind, leading to elliptical and spiral structures (e.g. as observed in the case of the envelope of AFGL 3068) 5,6 . The observed shapes of the circumstellar envelopes (CSEs) around binary AGB stars depend on the physical parameters of the binary system (e.g., separation and mass ratio 10 ), the density contrasts imprinted on the wind, the temperatures in the CSE, the viewing angle, and, in the case of the gas, the chemistry and excitation 11 . The temporal variations of the mass-loss-rate and the expansion velocity further affect the structure of the CSE. Hence, the observed spiral structure and detached shell allow us to measure these important properties, and to directly link them to th...

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Chemodynamical Simulations of Galaxies

Kobayashi

2010

Galaxies and Their Masks

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Abstract. We simulate the formation and evolution of galaxies with a self-consistent 3D hydrodynamical model including star formation, supernova feedback, and chemical enrichment. Hypernova feedback plays an essential role not only in solving the [Zn/Fe] problem, but also reproducing the cosmic star formation rate history and the mass-metallicity relations. In a MilkyWay type galaxy, kinematics and chemical abundances are different in bulge, disk, and thick disk because of different star formation histories and the contribution of Type Ia Supernovae.

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Stellar Models and Yields of Asymptotic Giant Branch Stars

Cited by 315 publications

References 71 publications

Globular cluster abundances: the role of asymptotic giant branch stars

Globular cluster abundances: the role of asymptotic giant branch stars

Unexpectedly large mass loss during the thermal pulse cycle of the red giant star R Sculptoris

Chemodynamical Simulations of Galaxies

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