Fragment Distribution in Coexistence Phase of Supernova Matter

We propose a new nucleosynthesis process in which various nuclei are formed through the liquid-gas phase transition of supernova matter as a preprocess of the standard r-process, and study its possibility of realization qualitatively. In the relativistic mean field and statistical model calculations, we find that this process may take place and help the later r-process to proceed.Comment: 5 pages, 3 figures, proceedings of Yukawa International Seminar 2001 (YKIS01), Physics of Unstable Nuclei, November 5-10, 2001, Kyoto, Japan. (v2: minor package change to adapt ptptex style file.

EOSDB: The Database for Nuclear EoS

Nuclear equation of state (EoS) plays an important role in understanding the formation of compact objects such as neutron stars and black holes. The true nature of the EoS has been a matter of debate at any density range not only in the nuclear physics but also in the astronomy and astrophysics. We have constructed a database of EoSs by compiling data from the literature. Our database contains the basic properties of the nuclear EoS of symmetric nuclear matter and of pure neutron matter. It also includes the detailed information about the theoretical models, for example the adopted methods and assumptions in individual models. The novelty of the database is to consider new experimental probes such as the symmetry energy, its slope relative to the baryon density, and the incompressibility, which enables the users to check their model dependences. We demonstrate the performance of the EOSDB through the examinations of the model dependence among different nuclear EoSs. It is reveled that some theoretical EoSs, which is commonly used in astrophysics, do not satisfactorily agree with the experimental constraints.Comment: 30 pages, 5 figures, submitted to Publications of the Astronomical Society of Japan (revised

Statistical double Lambda hypernuclear formation from Xi(-) absorption at rest in light nuclei

We investigate double Lambda hyperfragment formation from the statistical decay of double Lambda compound nuclei produced in the Xi(-) absorption at rest in the light nuclei C-12, N-14, and O-16. We examine the target and the Lambda Lambda bond energy dependence of the double Lambda hyperfragment formation probabilities, especially of those double hypernuclei observed in experiments. For the 12C (N-14) target, the formation probabilities of 6 He and 10 Be (B-13(Lambda Lambda)) are found to be reasonably large as they are observed in the KEK-E373 (KEK-E176) experiment. By comparison, for the O-16 target, the formation probability of Be-11(Lambda Lambda) is calculated to be small with Delta B-Lambda Lambda consistent with the Nagara event. We also evaluate the formation probability of H-5(Lambda Lambda) from a Xi(-)-He-6 bound state, H-7(Xi)

Statistical double Λ\Lambda hypernuclear formation from Ξ−\Xi^- absorption at rest in light nuclei

We investigate double $\Lambda$ hyperfragment formation from the statistical decay of double $\Lambda$ compound nuclei produced in the $\Xi^-$ absorption at rest in light nuclei, $^{12}\mathrm{C}$, $^{14}\mathrm{N}$ and $^{16}\mathrm{O}$. We examine the target and the $\Lambda\Lambda$ bond energy dependence of the double $\Lambda$ hyperfragment formation probabilities, especially of those double hypernuclei observed in experiments. For the $^{12}\mathrm{C}$ ($^{14}\mathrm{N}$) target, the formation probabilities of $^{6}_{\Lambda\Lambda}\mathrm{He}$ and $^{10}_{\Lambda\Lambda}\mathrm{Be}$ ($^{13}_{\Lambda\Lambda}\mathrm{B}$) are found to be reasonably large as they are observed in the KEK-E373 (KEK-E176) experiment. By comparison, for $^{16}\mathrm{O}$ target, the formation probability of $^{11}_{\Lambda\Lambda}\mathrm{Be}$ is calculated to be small with $\Delta B_{\Lambda\Lambda}$ consistent with the Nagara event. We also evaluate the formation probability of ${}^{5}_{\Lambda\Lambda}\mathrm{H}$ from a $\Xi^-$-${}^{6}\mathrm{He}$ bound state, ${}^{7}_{\Xi}\mathrm{H}$.Comment: 19 pages, 10 figures (revision is made in v3

Connection of four-dimensional Langevin model and Hauser-Feshbach theory to describe statistical decay of fission fragments

We developed a method superposing two different fission modes calculated in a four-dimensional Langevin model to obtain more accurate fission fragment yield and total kinetic energy (TKE). The two fission modes correspond to the standard I and standard II modes reported by Brosa et al., and parameters in the Langevin model and the superposing ratio were determined to reproduce the fission fragment yield of $^{240}$Pu of spontaneous fission. We also investigated the fission fragment yields and the TKEs of other Pu isotopes by using the same Langevin parameters and different superposing ratios, such as spontaneous fission of $^{238,242}$Pu and neutron-induced fission of $^{239}$Pu. The prompt fission observables, such as the neutron multiplicity, the prompt fission neutron spectrum, and the independent fission product yield were calculated in the Hauser-Feshbach statistical decay model implemented in a nuclear reaction code TALYS with $^{239}$Pu(n,f) in the incident energies ranging from thermal energy up to 5 MeV. The calculated fission observables qualitatively reproduce several known trends while calculated results have quantitative discrepancies between reported data. Although more improvements are needed for the most important nuclides, it turned out that our approach has the capability to provide prompt fission observables for difficult-to-measure nuclides.Comment: 19 pages, 10 figures, Under review in Journal of Nuclear Science and Technolog

The Stellar Abundances for Galactic Archeology (SAGA) Database - Compilation of the Characteristics of Known Extremely Metal-Poor Stars

We describe the construction of a database of extremely metal-poor (EMP) stars in the Galactic halo whose elemental abundances have been determined. Our database contains detailed elemental abundances, reported equivalent widths, atmospheric parameters, photometry, and binarity status, compiled from papers in the recent literature that report studies of EMP halo stars with [Fe/H] < -2.5. The compilation procedures for this database have been designed to assemble the data effectively from electronic tables available from online journals. We have also developed a data retrieval system that enables data searches by various criteria, and permits the user to explore relationships between the stored variables graphically. Currently, our sample includes 1212 unique stars (many of which are studied by more than one group) with more than 15000 individual reported elemental abundances, covering all of the relevant papers published by December 2007. We discuss the global characteristics of the present database, as revealed by the EMP stars observed to date. For stars with [Fe/H] < -2.5, the number of giants with reported abundances is larger than that of dwarfs by a factor of two. The fraction of carbon-rich stars (among the sample for which the carbon abundance is reported) amount to ~30 % for [Fe/H] < -2.5. We find that known binaries exhibit different distributions of orbital period, according to whether they are giants or dwarfs, and also as a function of metallicity, although the total sample of such stars is still quite small.Comment: 24 pages, 10 figures, accepted by PASJ, final version. The SAGA database is available at http://saga.sci.hokudai.ac.j

Tables of Hyperonic Matter Equation of State for Core-Collapse Supernovae

We present sets of equation of state (EOS) of nuclear matter including hyperons using an SU_f(3) extended relativistic mean field (RMF) model with a wide coverage of density, temperature, and charge fraction for numerical simulations of core collapse supernovae. Coupling constants of Sigma and Xi hyperons with the sigma meson are determined to fit the hyperon potential depths in nuclear matter, U_Sigma(rho_0) ~ +30 MeV and U_Xi(rho_0) ~ -15 MeV, which are suggested from recent analyses of hyperon production reactions. At low densities, the EOS of uniform matter is connected with the EOS by Shen et al., in which formation of finite nuclei is included in the Thomas-Fermi approximation. In the present EOS, the maximum mass of neutron stars decreases from 2.17 M_sun (Ne mu) to 1.63 M_sun (NYe mu) when hyperons are included. In a spherical, adiabatic collapse of a 15$M_\odot$ star by the hydrodynamics without neutrino transfer, hyperon effects are found to be small, since the temperature and density do not reach the region of hyperon mixture, where the hyperon fraction is above 1 % (T > 40 MeV or rho_B > 0.4 fm^{-3}).Comment: 23 pages, 6 figures (Fig.3 and related comments on pion potential are corrected in v3.