Due to its importance as an astronomical observable in core-collapse supernovae (CCSNe), the reactions producing and destroying $^{44}$Ti must be well constrained. Generally, statistical model calculations such as Hauser-Feshbach are employed when experimental cross sections are not available, but the variation in such adopted rates can be large. Here, data from the literature is compared with statistical model calculations of the $^{44}$Ti($α$,p)$^{47}$V reaction cross section and used to constrain the possible reaction rate variation over the temperatures relevant to CCSNe. Suggestions for targeted future measurements are given.
Uncertainties in the production of iron-group nuclides in core-collapse supernovae from Monte Carlo variations of reaction rates
Kogakuin University（工学院大学）；The University of Tokyo（东京大学）；RIKEN Pioneering Research Institute (PRI)（理化学研究所先导研究本部）；National Astronomical Observatory of Japan (NAOJ)（日本国立天文台）；North Carolina State University（北卡罗来纳州立大学）；University of Basel（巴塞尔大学）；University of Hertfordshire（赫特福德大学）
The work reported in this dissertation will concern the study of kinetics, cycles and quantum mechanic processes of nuclear reactions involved in massive stars together with explosive nucleosynthesis phenomena having a key role in supernovae explosion. Four main fields will be explored: physics of nuclear reaction, hydrogen burning, CNO cycles and explosive supernovae phenomena. The first chapter will provide an overview of the background of the nuclear physics and of the potential approaches to the field as quantum mechanic aspects, cross section and Maxwell-Boltzmann distribution. The next c…
We propose a $(p,xn)$ mechanism with dynamic production as a new set of nuclear reactions that could produce high density neutrons and explain the r- and rp-elements. We calculate the rate of thorium and uranium produced by our proposed mechanism and show that it is compatible with different stellar conditions found in explosive events at an initial temperature of $T \geq 3\times 10^{9} K$ with a "freeze-out" by a neutrino-driven wind. We show that charged particle reactions could explain the discrepancies in the abundances of ${}^{232}Th$ and ${}^{235,238}U$ nucleochronometers. We extend the …
Reducing Uncertainties in the Production of the Gamma Emitting Nuclei 26Al, 44Ti, and 60Fe in Core Collapse Supernovae by Using Effective Helium Burning Rates
Type Ia supernovae (SNe Ia) are thought to be thermonuclear explosion of white dwarfs (WDs). Their progenitors are not well understood. One popular scenario is the double-degenerate (DD) scenario, which attributes SNe Ia to WD-WD binary mergers. The fates of the WD mergers depend on the rate of $^{12}$C+$^{12}$C reaction. Recently, the $^{12}$C+$^{12}$C cross sections have been measured and the analysis of the data using the Trojan Horse Method suggested that the astrophysical reaction rate is larger than conventional rates at astrophysical temperatures due to possible resonances. The resonanc…
Temperature-resolved sensitivities of $^{56}{\rm Ni}$ production to helium-burning reactions in pair-instability supernovae
The University of Tokyo（东京大学）；RIKEN Nishina Center for Accelerator-Based Science, RIKEN（理化学研究所加速器科学研究中心）；Kogakuin University（工学馆大学）；Center for Nuclear Study, The University of Tokyo（东京大学核研究分中心）；Astrophysical Big-Bang Laboratory, Pioneering Research Institute, RIKEN（理化学研究所先驱研究院天体大爆炸实验室）；Yukawa Institute for Theoretical Physics (YITP), Kyoto University（京都大学汤川理论物理研究所）
In the late stages of stellar core-collapse, prior to core bounce, electron captures on medium-heavy nuclei drive deleptonization and simulations require the use of accurate reaction rates. Nuclei with neutron number near $N=50$, just above atomic number $Z=28$, play an important role, but rates used in astrophysical simulations rely primarily on a relatively simple single-state approximation. In order to improve the accuracy of astrophysical simulations, experimental data are needed to test the electron-capture rates and to guide the development of better theoretical models. This work present…
The $(n,α)$ reaction contributes in many processes of energy generation and nucleosynthesis in stellar environment. Since experimental data are available for a limited number of nuclei and in restricted energy ranges, at present only theoretical studies can provide predictions for all astrophysically relevant $(n,α)$ reaction cross sections. The purpose of this work is to study $(n,α)$ reaction cross sections for a set of nuclei contributing in the weak s-process nucleosynthesis. Theory framework is based on the statistical Hauser-Feshbach model implemented in TALYS code with nuclear masses an…
Neutrino induced reactions are a basic ingredient in astrophysical processes like star evolution. The existence of neutrino oscillations affects the rate of nuclear electroweak decays which participates in the chain of events that determines the fate of the star. Among the processes of interest, the production of heavy elements in core-collapse supernovae is strongly dependent upon neutrino properties, like the mixing between different species of neutrinos. In this work we study the effects of neutrino oscillations upon the electron fraction as a function of the neutrino mixing parameters, for…
We infer the expected detection number of pair instability supernovae (PISNe) during the operation of the Euclid space telescope based on binary population models. Our models reproduce the global maximum of the rate at the primary BH mass of $\sim 9-10$ $M_\odot$, and the overall gradient of the primary BH mass distribution in the binary BH merger rate consistent with recent observations. We consider different PISN conditions depending on the $^{12}$C$(α, γ)^{16}$O reaction rate. The fiducial and $3σ$ models adopt the standard and $3σ$-smaller reaction rate, respectively. Our fiducial model pr…
Calculations of Maxwellian-averaged Cross Sections and Astrophysical Reaction Rates Using the ENDF/B-VII.0, JEFF-3.1, JENDL-3.3 and ENDF/B-VI.8 Evaluated Nuclear Reaction Data Libraries
