scholarly journals R-Process Nucleosynthesis in MHD Jet Explosions of Core-Collapse Supernovae

2013 ◽  
Vol 2013 ◽  
pp. 1-13
Author(s):  
Motoaki Saruwatari ◽  
Masa-aki Hashimoto ◽  
Ryohei Fukuda ◽  
Shin-ichiro Fujimoto
Keyword(s):  
Magnetic Field ◽  
Heavy Element ◽  
Initial Conditions ◽  
Core Collapse ◽  
Combined Effects ◽  
Two Dimensional ◽  
The Third ◽  
R Process ◽  
Helium Star ◽  
Hydrodynamic Code

We investigate the r-process nucleosynthesis during the magnetohydrodynamical (MHD) explosion of a supernova in a helium star of 3.3 M⊙, where effects of neutrinos are taken into account using the leakage scheme in the two-dimensional (2D) hydrodynamic code. Jet-like explosion due to the combined effects of differential rotation and magnetic field is able to erode the lower electron fraction matter from the inner layers. We find that the ejected material of low electron fraction responsible for the r-process comes out from just outside the neutrino sphere deep inside the Fe-core. It is found that heavy element nucleosynthesis depends on the initial conditions of rotational and magnetic fields. In particular, the third peak of the distribution is significantly overproduced relative to the solar system abundances, which would indicate a possible r-process site owing to MHD jets in supernovae.

scholarly journals Anisotropy in MHD turbulence due to a mean magnetic field

1983 ◽  
Vol 29 (3) ◽  
pp. 525-547 ◽  
Author(s):  
John V. Shebalin ◽  
William H. Matthaeus ◽  
David Montgomery
Keyword(s):  
Magnetic Field ◽  
Reynolds Numbers ◽  
Combined Effects ◽  
Two Dimensional ◽  
Mhd Turbulence ◽  
Magnetohydrodynamic Turbulence ◽  
High Wavenumbers

The development of anisotropy in an initially isotropie spectrum is studied numerically for two-dimensional magnetohydrodynamic turbulence. The anisotropy develops through the combined effects of an externally imposed d.c. magnetic field and viscous and resistive dissipation at high wavenumbers. The effect is most pronounced at high mechanical and magnetic Reynolds numbers. The anisotropy is greater at the higher wavenumbers.

scholarly journals Magnetically assisted explosions of weakly magnetized stars

2017 ◽  
Vol 12 (S331) ◽  
pp. 125-130
Author(s):  
Hidetomo Sawai ◽  
Shoichi Yamada
Keyword(s):  
Magnetic Field ◽  
Angular Momentum ◽  
High Resolution ◽  
Stellar Evolution ◽  
Positive Impact ◽  
Core Collapse ◽  
Two Dimensional ◽  
Magnetorotational Instability ◽  
The Magnetic Field ◽  
Large Angular Momentum

AbstractWe carried out high resolution simulations of weakly-magnetized core-collapse supernovae in two-dimensional axisymmetry in order to see the influence of the magnetic field and rotation on the explosion. We found that the magnetic field amplified by magnetorotational instability (MRI) has a great positive impact on the explosion by enhancing the neutrino heating, provided that the progenitor has large angular momentum close to the highest value found in stellar evolution calculations. We also found that even for progenitors neither involving strong magnetic flux nor large angular momentum, the magnetic field is greatly amplified by the convection aand rotation, and this leads to the boost of the explosion again by enhancing the neutrino heating.

scholarly journals Towards a realistic explosion landscape for binary population synthesis

2020 ◽  
Vol 499 (2) ◽  
pp. 2803-2816 ◽  
Author(s):  
Rachel A Patton ◽  
Tuguldur Sukhbold
Keyword(s):  
Initial Conditions ◽  
Massive Stars ◽  
Core Structure ◽  
Core Collapse ◽  
Population Synthesis ◽  
Diverse Range ◽  
Sample Application ◽  
Helium Star ◽  
Crucial Ingredient

ABSTRACT A crucial ingredient in population synthesis studies involving massive stars is the determination of whether they explode or implode in the end. While the final fate of a massive star is sensitive to its core structure at the onset of collapse, the existing binary population synthesis studies do not reach core collapse. Instead, they employ simple prescriptions to infer their final fates without knowing the pre-supernova core structure. We explore a potential solution to this problem by treating the carbon-oxygen (CO) core independently from the rest of the star. Using the implicit hydrodynamics code $\mathrm{\tt {KEPLER}}$, we have computed an extensive grid of 3496 CO-core models from a diverse range of initial conditions, each evolved from carbon ignition until core collapse. The final core structure, and thus the explodability, varies non-monotonically and depends sensitively on both the mass and initial composition of the CO core. Although bare CO cores are not perfect substitutes for cores embedded in massive stars, our models compare well both with $\mathrm{\tt {MESA}}$ and full hydrogenic and helium star calculations. Our results can be used to infer the pre-supernova core structures from population synthesis estimates of CO-core properties, thus to determine the final outcomes based on the results of modern neutrino-driven explosion simulations. A sample application is presented for a population of Type-IIb supernova progenitors.

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

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