Engineering topics

Kotake, K

Publications and source records attributed to Kotake, K.

4 records

DOE OSTI2012

Nucleosynthesis in a massive star associated with magnetohydrodynamical jets from collapsars

We investigate the nucleosynthesis during the stellar evolution and the jet-like supernova explosion of a massive star of 70 M{sub Circled-Dot-Operator} having the solar metallicity in the main sequence stage. The nucleosynthesis calculations have been performed with large nuclear reaction networks, where the weak s-, p-, and r-processes are taken into account. As a result s-elements of 60 > A > 90 and r-elements of 90 > A > 160 are highly overproduced relative to the solar system abundances. We find that the Sr-Y-Zr isotopes are primarily synthesized in the explosive nucleosynthesis which could be one of the sites of the lighter element primary process (LEPP).

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

Nucleosynthesis in neutrino-driven, aspherical supernova explosion of a massive star

We examine explosive nucleosynthesis of p-nuclei during a delayed neutrino-driven, aspherical supernova explosion aided by standing accretion shock instability, based on two-dimensional hydrodynamic simulations of the explosion of a 15M{sub {center_dot}} star. We find that p-nuclei are mainly produced through {gamma}-processes, and that the nuclei lighter than {sup 92}Mo are abundantly synthesized in slightly neutron-rich bubbles with electron fractions of Y{sub e}{<=}0.48. {sup 94}Mo, {sup 96}Ru, and {sup 98}Ru, are underproduced compared with the solar system, as in the spherical model.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

Nucleosynthesis in Magnetohydrodynamical Jets from Collapsars

We investigate the heavy-element nucleosynthesis of a massive star whose mass in the main sequence stage is M{sub ms} = 70 M{sub {center_dot}}. Detailed calculations of the nucleosynthesis are performed during the hydrostatic stellar evolution until the core composed of iron-group nuclei begins to collapse. As a supernova explosion model, a collapsar model is constructed whose jets are driven by magnetohydrodynamical effects of a differentially rotating core. The heavy-element nucleosynthesis inside the jet of a collapsar model is followed along the trajectories of stream lines of the jet. We combine the results of both hydrostatic and heavy-element nucleosyntheses to compare with the solar abundances. We find that neutron-rich elements of 70<A<140 are highly overproduced relative to the solar abundances. Therefore, we conclude that this scenario should be rare and elements of A < or approx. 70 are compensated for other supernova explosion models. We find also that different mass formula changes significantly the production of elements of A>140.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2011

R-process Nucleosynthesis in Supernova Explosion

We investigate the possibility of the r-process during the magnetohydrodynamical (MHD) explosion of supernova in a massive star of 13 M{sub {center_dot}} with the effects of neutrinos included. Contrary to the case of the spherical explosion, jet-like explosion due to the combined effects of rotation and magnetic field lowers the electron fraction significantly inside the layers. We find that the ejected material of low electron fraction responsible for the r-process comes out from the inner deep region of the core that is made up of iron-group nuclei. This leads to the production of the second to third peak in the solar r-process elements. We suggest that there are some variations in the r-process nucleosynthesis according to the initial conditions of rotational and magnetic fields.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗