s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Abstract

In the past years the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the socalled Asymptotic Giant Branch (or AGB) could not be explained by self-consistent models, forcing researchers to extensive parameterizations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding the formation of 13C and then the activation of the 13C(a,n)16O reaction. Only recently, attempts to solve this problem started to consider quantitatively physically-based mixing mechanisms. Among them, MHD processes in the plasma were suggested to yield mass transport through magnetic buoyancy. In this framework, we compare results of nucleosynthesis models for Low Mass AGB Stars (M<=3Mo), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the 13C reservoir. We find that n-captures driven by magnetically-induced mixing can indeed account for the SiC data quite well and that this is due to the fact that our 13C distribution fulfils the above constraints rather accurately. We suggest that similar tests should be now performed using different physical models for mixing. Such comparisons would indeed improve decisively our understanding of the formation of the neutron source.

16 page, 10 figures

References in corpus (51)

• The s Process: Nuclear Physics, Stellar Models, Observations
• Updated stellar yields from Asymptotic Giant Branch models
• The Dawes Review 2: Nucleosynthesis and stellar yields of low and intermediate-mass single stars
• Nucleosynthesis and mixing on the Asymptotic Giant Branch. III. Predicted and observed s-process abundances
• Evolution, nucleosynthesis and yields of low mass AGB stars at different metallicities (II): the FRUITY database
• Evolution, nucleosynthesis and yields of AGB stars at different metallicities (III): intermediate mass models, revised low mass models and the ph-FRUITY interface
• Stellar yields from metal-rich asymptotic giant branch models
• Galactic Chemical Evolution and solar s-process abundances: dependence on the 13C-pocket structure
• Thermohaline instability and rotation-induced mixing. I - Low- and intermediate-mass solar metallicity stars up to the end of the AGB
• The s process in asymptotic giant branch stars of low metallicity and the composition of carbon-enhanced metal-poor stars
• Short-lived Nuclei in the Early Solar System: Possible AGB Sources
• Deep Mixing of He-3: Reconciling Big Bang and Stellar Nucleosynthesis
• Convective-reactive proton-C12 combustion in Sakurai's object (V4334 Sagittarii) and implications for the evolution and yields from the first generations of stars
• NuGrid stellar data set I. Stellar yields from H to Bi for stars with metallicities Z = 0.02 and Z = 0.01
• Stellar Evolution with Rotation and Magnetic Fields IV: The Solar Rotation Profile
• Chemistry of the Sagittarius Dwarf Galaxy: a Top-Light IMF, Outflows and the R-Process
• Asteroseismology Can Reveal Strong Internal Magnetic Fields in Red Giant Stars
• Rotational mixing in low-mass stars II. Self-consistent models of Pop II RGB stars
• s-Process Nucleosynthesis in Carbon Stars
• Dynamos in Asymptotic-Giant-Branch Stars As the Origin of Magnetic Fields Shaping Planetary Nebulale
• Numerically determined transport laws for fingering ("thermohaline") convection in astrophysics
• Deep Mixing in Evolved Stars: I. The Effect of Reaction Rate Revisions from C to Al
• Low mass AGB stellar models for 0.003 < Z < 0.02: basic formulae for nucleosynthesis calculations
• H ingestion into He-burning convection zones in super-AGB stellar models as a potential site for intermediate neutron-density nucleosynthesis
• VLBA determination of the distance to nearby star-forming regions V. Dynamical mass, distance and radio structure of V773 Tau A
• Magnetic Mixing in Red Giant and Asymptotic Giant Branch Stars
• 3D hydrodynamical simulations of a proton ingestion episode in a low-metallicity asymptotic giant branch star
• s-Processing in the Galactic Disk. I. Super-Solar Abundances of Y, Zr, La, Ce in Young Open Clusters
• Barium Isotopic Composition of Mainstream Silicon Carbides from Murchison: Constraints for s-Process Nucleosynthesis in AGB Stars
• News on the s process from young open clusters
• $s$-Processing in AGB Stars Revisited. II. Enhanced ${}^{13}$C Production Through MHD-Induced Mixing
• Thermohaline Mixing: Does It Really Govern the Atmospheric Chemical Composition of Low-Mass Red Giants?
• Application of a Theory and Simulation based Convective Boundary Mixing model for AGB Star Evolution and Nucleosynthesis
• Correlated Strontium and Barium Isotopic Compositions of Acid-Cleaned Single Silicon Carbides from Murchison
• The effects of thermohaline mixing on low-metallicity asymptotic giant branch stars
• New determination of the 13C(a, n)16O reaction rate and its influence on the s-process nucleosynthesis in AGB stars
• Merging Binary Stars and the magnetic white dwarfs
• MHD and deep mixing in evolved stars. 1. 2D and 3D analytical models for the AGB
• The impact of updated Zr neutron-capture cross sections and new asymptotic giant branch models on our understanding of the s process and the origin of stardust
• s-Processing in AGB Stars Revisited. I. Does the Main Component Constrain the Neutron Source in the 13C-Pocket?
• The 13C-Pocket Structure in AGB Models: Constraints from Zirconium Isotope Abundances in Single Mainstream SiC Grains
• Tungsten isotopic compositions in stardust SiC grains from the Murchison meteorite: Constraints on the s-process in the Hf-Ta-W-Re-Os region
• Barium and Yttrium abundance in intermediate-age and old open clusters
• Local associations and the barium puzzle
• Luminosities of Carbon-rich Asymptotic Giant Branch stars in the Milky Way
• The $Gaia$-ESO Survey: the inner disk intermediate-age open cluster NGC 6802
• Intermediate-mass asymptotic giant branch stars and sources of ${}^{26}$Al, ${}^{60}$Fe, ${}^{107}$Pd, and ${}^{182}$Hf in the solar system
• A Deep Mixing Solution to the Aluminum and Oxygen Isotope Puzzles in Presolar Grains
• First determination of s-process element abundances in pre-main sequence clusters: Y, Zr, La, and Ce in IC 2391, the Argus association and IC 2602
• Detailed modelling of a large sample of Herschel sources in the Lockman Hole: identification of cold dust and of lensing candidates through their anomalous SEDs
• Chemical composition of evolved stars in the young open clusters NGC 4609 and NGC 5316

Cited by in corpus (10)

• Magnetic-buoyancy Induced Mixing in AGB Stars: Presolar SiC Grains
• The importance of the 13C(alpha,n)16O reaction in Asymptotic Giant Branch stars
• Re-evaluation of the ${}^{22}$Ne($\alpha ,\gamma$)${}^{26}$Mg and ${}^{22}$Ne($\alpha ,n$)${}^{25}$Mg reaction rates
• s-Processing in AGB Stars Revisited. III. Neutron captures from MHD mixing at different metallicities and observational constraints
• Presolar grain isotopic ratios as constraints to nuclear and stellar parameters of AGB nucleosynthesis
• Magnetic-buoyancy-induced mixing in AGB Stars: fluorine nucleosynthesis at different metallicities
• On the Origin of the Early Solar System Radioactivities. Problems with the AGB and Massive Star Scenarios
• Origin of large meteoritic SiC stardust grains in metal-rich AGB stars
• New constraints on the major neutron source in low-mass AGB stars
• Modeling the formation of the ${}^{13}$C neutron source in AGB stars