Importance of Prolate Neutrino Radiation in Core-Collapse Supernovae: The Reason for the Prolate Geometry of SN1987A?

We have carried out 2-D simulations of core-collapse supernova explosions. The local neutrino radiation field is assumed to have its maximum value either at the symmetry (polar) axis or on the equatorial plane. These lead to the prolate and oblate explosions, respectively. We find that the gain of the explosion energy in the prolate explosion evolves more predominately than that in the oblate one when the total neutrino luminosity is given. Namely, the prolate explosion is more energetic than the oblate one. One of the authors (Shimizu et al. 2001) showed for the first time that globally anisotropic neutrino radiation produces more powerful explosion than the spherical neutrino radiation does. In our previous study (Madokoro et al. 2003), we improved the numerical code of Shimizu et al. and demonstrated that the globally anisotropic neutrino radiation yields more energetic explosion than spatially-fluctuated neutrino radiation does. Together with the result of this paper, we conclude that the globally anisotropic (prolate) neutrino radiation is the most effective way of increasing the explosion energy among various types of explosions investigated in these studies. We discuss the reason for this. Our result is suggestive of the fact that the expanding materials of SN1987A is observed to have a prolate geometry.Comment: 15 pages, including 7 figures, to appear in PAS

Required precision of mass and half-life measurements for r-process nuclei planned at future RI-beam facilities

In order to understand the r-process nucleosynthesis, we suggest precision required for mass and beta-decay half-life measurements planned at future RI-beam facilities. To satisfy a simple requirement that we put on nuclear model predictions, it is concluded that the detectors for the mass measurements must have a precision of 1sigma ~< 250 keV, and that the detectors for the half-life measurements demand a precision of 1sigma ~< 0.15 ms. Both the above precisions are required at the neutron richness of A/Z = 3.0 at the N=82 shell closure and A/Z = 2.9 at the N=50 shell closure. For the doubly magic nuclide 78Ni, a precision of 1sigma ~< 300 keV and 1sigma ~< 5 ms are required, respectively, for mass and half-life measurements. This analysis aims to provide a first rough guide for ongoing detector developments.Comment: 8 pages, 2 figures. in Proceedings of Int. conf. The Future Astronuclear Physics, From microscopic puzzles to macroscopic nightmares, Eds. H.M.J. Boffin et al., EAS Publication Series, EDP Sciences, in press (2004

Global Anisotropy Versus Small-Scale Fluctuations in Neutrino Flux in Core-Collapse Supernova Explosions

Effects of small-scale fluctuations in the neutrino radiation on core-collapse supernova explosions are examined. Through a parameter study with a fixed radiation field of neutrinos, we find substantial differences between the results of globally anisotropic neutrino radiation and those with fluctuations. As the number of modes of fluctuations increases, the shock positions, entropy distributions, and explosion energies approach those of spherical explosion. We conclude that global anisotropy of the neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This supports the previous statement on the explosion mechanism by Shimizu and coworkers.Comment: 14 pages, including 12 figures. To be published in the Astrophysical Journa

Radioactivity of the Key Isotope 44Ti in SN 1987A

We investigate radioactivity from the decay sequence of 44Ti in a young supernova remnant SN 1987A. We perform Monte-Carlo simulations of degradation of the nuclear lines to explain a late-time bolometric luminosity which is estimated from optical and near-infrared observation at 3600 days after the explosion. Assuming the distance to LMC in between 45.5 and 52.1 kpc, we have obtained the initial 44Ti mass of (0.82-2.3) 10^{-4} solar mass within the current uncertainty of the physical quantities. The resulting fluxes of gamma- and hard X-rays emerged from the 44Ti decay are estimated and compared with the line sensitivity of the INTEGRAL/SPI on board and that of NeXT X-ray satellite planned to be launched in 2010. The effect of 44Ti ionization on the estimated fluxes is briefly remarked.Comment: 6 pages, 2 figures; Invited talk, in Proceedings of Tours Symposium on Nuclear Physics V (Tours2003), Tours, France, August 2003, eds. H. Utsunomiya et al., AIP Conference Series, in pres

Magnetic excitations in antiferromagnetic Bi₂CuO₄

Magnetic excitations in the antiferromagnetic Bi₂CuO₄ (TN=42K) are investigated on the basis of anisotropic exchange interaction between spins of Cu²⁺ ions. We calculate the dispersion curves and evaluate the intensity of the inelastic neutron scattering by spin wave excitations. The results are discussed in connection with observations. Spin contraction at 0K, temperature dependence of the sublattice magnetization and field dependence of the antiferromagnetic resonance frequency are calculated. Furthermore, the effect of spin wave interaction on the spin wave dispersions is investigated in the framework of the random phase approximation.Article信州大学理学部紀要 29(1): 9-20(1994)departmental bulletin pape

Core-Collapse Supernovae Induced by Anisotropic Neutrino Radiation

We demonstrate the important role of anisotropic neutrino radiation on the mechanism of core-collapse supernova explosions. Through a new parameter study with a fixed radiation field of neutrinos, we show that prolate explosions caused by globally anisotropic neutrino radiation is the most effective mechanism of increasing the explosion energy when the total neutrino luminosity is given. This is suggestive of the fact that the expanding materials of SN 1987A has a prolate geometry.Comment: in Proceedings of Int. conf. in hohour of the 60th birthday of Marcel Arnould, The Future Astronuclear Physics, From microscopic puzzles to macroscopic nightmares, Eds. H.M.J. Boffin et al., EAS Publication Series, EDP Sciences, in press (2004

Magnetic Phase Diagram of Bi₂CuO₄

The ground state spin configuration in Bi₂CuO₄-type crystal having two magnetic ions in the unit cell is studied on the basis of the Heisenberg model with four kinds of superexchange interaction. The magnetic phase diagram is found to be composed of five regions: four of wich are collinear spin arrangement and one is of double helical spin arrangement. The values of exchange integrals of Bi₂CuO₄ estimated by Aïn et al from their own neutron scattering data are in the region where the observed collinear spin arrangement is stabilized.Article信州大学理学部紀要 30(2): 55-67(1996)departmental bulletin pape

Avaliação do tratamento de fraturas toracolombares tipo explosão com fixação com pinos de Schanz intermediários pela via posterior

Orientador : Prof. Dr. Xavier SolerMonografia (especialização) - Universidade Federal do Paraná. Setor de Ciências da Saúde. Curso de Especialização em Cirurgia e Patologia da Coluna VertebralInclui referênciasObjetivo: Avaliação radiográfica de pacientes com fraturas explosão toracolombares tratados com fixação transpedicular não convencional, o que inclui a fixação adicional da vértebra fraturada associada ao uso da barra de conexão transversal - cross-link. Métodos: Trabalho retrospectivo com 68 pacientes operados no Hospital do Trabalhador de Curitiba, serviço de Ortopedia, dos quais 15 deles foram elegíveis para a pesquisa. Todos tratados com fixação pedicular posterior com parafuso intermediário. Foi realizada a avaliação pelo método do ângulo de Cobb das radiografias pré-operatória, pós-operatória imediata e pós-operatória tardia (01 ano de evolução). Resultados: No estudo foi constatado uma redução média da cifose de 8,3º (77%), com uma perda no pós-operatório tardio em relação ao pós-operatório imediato de 1,34º. Conclusão: O método de fixação via posterior com parafuso intermediário de fraturas tipo explosão da coluna toracolombar mostrou-se eficaz na manutenção da redução obtida no pós-operatório imediato após um (01) ano de evolução