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

On the Neutrino Distributions in Phase Space for the Rotating Core-collapse Supernova Simulated with a Boltzmann-neutrino-radiation-hydrodynamics Code

With the Boltzmann-radiation-hydrodynamics code, which we have developed to solve numerically the Boltzmann equations for neutrino transfer, the Newtonian hydrodynamics equations, and the Newtonian self-gravity simultaneously and consistently, we simulate the collapse of a rotating core of the progenitor with a zero-age-main-sequence mass of $11.2\,M_\odot$ and a shelluler rotation of $1\,{\rm rad\,s^{-1}}$ at the center. We pay particular attention in this paper to the neutrino distribution in phase space, which is affected by the rotation. By solving the Boltzmann equations directly, we can assess the rotation-induced distortion of the angular distribution in momentum space, which gives rise to the rotational component of the neutrino flux. We compare the Eddington tensors calculated both from the raw data and from the M1-closure approximation. We demonstrate that the Eddington tensor is determined by complicated interplays of the fluid velocity and the neutrino interactions and that the M1-closure, which assumes that the Eddington factor is determined by the flux factor, fails to fully capture this aspect, especially in the vicinity of the shock. We find that the error in the Eddington factor reaches $\sim 20\%$ in our simulation. This is due not to the resolution but to the different dependence of the Eddington and flux factors on the angular profile of the neutrino distribution function, and hence modification to the closure relation is needed.Comment: 24 pages, 23 figures, 0 explosion, published in Ap

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.

CCD Photometry of a Newly Confirmed SU UMa-Type Dwarf Nova, NSV 4838

We present time-resolved CCD photometry of a dwarf nova NSV 4838 (UMa 8, SDSS J102320.27+440509.8) during the 2005 June and 2007 February outburst. Both light curves showed superhumps with a mean period of 0.0699(1) days for the 2005 outburst and 0.069824(83) days for the 2007 outburst, respectively. Using its known orbital period of 0.0678 days, we estimated the mass ratio of the system to be $q$=0.13 based on an empirical relation. Although the majority of SU UMa-type dwarf novae having similar superhump periods show negative period derivatives, we found that the superhump period increased at $\dot{P}$ / $P_{\rm sh}$=+7(+3, -4)$\times10^{-5}$ during the 2007 superoutburst. We also investigated long-term light curves of NSV 4838, from which we derived 340 days as a supercycle of this system.Comment: 8 pages, 9 figures, accepted for PAS

Quantum Molecular Dynamics Approach to the Nuclear Matter Below the Saturation Density

Quantum molecular dynamics is applied to study the ground state properties of nuclear matter at subsaturation densities. Clustering effects are observed as to soften the equation of state at these densities. The structure of nuclear matter at subsaturation density shows some exotic shapes with variation of the density.Comment: 21 pages of Latex (revtex), 9 Postscript figure