Bulletin of the American Physical Society
2011 Fall Meeting of the APS Division of Nuclear Physics
Volume 56, Number 12
Wednesday–Saturday, October 26–29, 2011; East Lansing, Michigan
Session MG: Astrophysics VI: EoS and Neutron Stars |
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Chair: Grant Mathews, University of Notre Dame Room: 105AB |
Saturday, October 29, 2011 8:30AM - 8:42AM |
MG.00001: Quark matter in neutron stars and core-collapse supernovae Irina Sagert, Tobias Fischer, Matthias Hempel, Giuseppe Pagliara, Juergen Schaffner-Bielich, Thomas Rauscher, Friedrich-K. Thielemann, Roger Kaeppeli, Gabriel Martinez-Pinedo, Matthias Liebendoerfer Recent neutron star mass measurements point to compact star maximum masses of at least $1.97\pm 0.04$ solar masses and represent thereby a challenge for soft nuclear equations of state, which often go hand in hand with the presence of hyperons or quarks. In this talk I will discuss such high neutron star masses regarding the nuclear equation of state from heavy ion experiments. Furthermore, I will introduce equations of state for core-collapse supernova and binary merger simulations, which include a phase transition to strange quark matter. As was recently shown, neutrino signals from supernova explosions can provide a probe for the low density appearance of quark matter. The compatibility of the latter with high neutron star masses is an interesting and important question and will be addressed in the talk. [Preview Abstract] |
Saturday, October 29, 2011 8:42AM - 8:54AM |
MG.00002: Laboratory Tests of Low Density Astrophysical Equations of State Joseph Natowitz Clustering in low density nuclear matter has been investigated using the NIMROD multi-detector at Texas A{\&}M University. Thermal coalescence models were employed to extract densities, $\rho$, and temperatures, T, for evolving systems formed in collisions of 47A MeV $^{40}$Ar + $^{112}$Sn, $^{124}$Sn and $^{64}$Zn + $^{112}$Sn, $^{124}$Sn. The yields of d, t, $^{3}$He and $^{4}$He have been determined at $\rho$ = .002 to .032 nucleons/fm$^{3}$ and T= 5 to 10 MeV. Symmetry energy coefficients and equilibrium constants for alpha production have been derived from these data. The data provide an important constraint on astrophysoical equation of state models at low density. [Preview Abstract] |
Saturday, October 29, 2011 8:54AM - 9:06AM |
MG.00003: Bulk viscosity for high amplitude oscillations and its effect on spin-down evolution of compact stars Simin Mahmoodifar, Mark G. Alford, Kai Schwenzer I will present our results for the bulk viscosity of dense matter taking into account non-linear effects that arise in the supra-thermal regime, $\Delta\mu \gg T$, where the bulk viscosity grows with the oscillation amplitude. This regime is relevant to unstable modes such as r-modes in neutron stars, which grow in amplitude until saturated by non-linear effects. Then I will discuss the effects of the high amplitude bulk viscosity on damping of the r-modes and spin-down evolution of rapidly rotating compact stars. I will present our results for different cases of hadronic stars and strange stars. [Preview Abstract] |
Saturday, October 29, 2011 9:06AM - 9:18AM |
MG.00004: An Updated Nuclear Equation of State for Neutron Stars and Supernova Simulations M.A. Meixner, G.J. Mathews, H.E. Dalhed, N.Q. Lan We present an updated and improved Equation of State based upon the framework originally developed by Bowers \& Wilson. The details of the EoS and improvements are described along with a description of how to access this EOS for numerical simulations. Among the improvements are an updated compressibility based upon recent measurements, the possibility of the formation of proton excess ($Y_e > 0.5$) material and an improved treatment of the nuclear statistical equilibrium and the transition to pasta nuclei as the density approaches nuclear matter density. The possibility of a QCD chiral phase transition is also included at densities above nuclear matter density. We show comparisons of this EOS with the other two publicly available equations of state used in supernova collapse simulations. The advantages of the present EoS is that it is easily amenable to phenomenological parameterization to fit observed explosion properties and to accommodate new physical parameters. [Preview Abstract] |
Saturday, October 29, 2011 9:18AM - 9:30AM |
MG.00005: Chemical separation in accreting Neutron Stars Andre da Silva Schneider, Joe Hughto, Charles Horowitz, Don Berry Matter accreted by a Neutron star in a binary system undergoes a variety of nuclear reactions. The ash left over from these nuclear reactions include a complex range of chemical elements which form the ocean and crust of the neutron star. Amongst the elements produced are heavy elements such as Selenium and light elements such as Oxygen. We used large molecular dynamics simulations to study Oxygen Selenium mixtures and the chemical separation that occurs when the ash freezes. We found that the liquid ocean is enriched in light elements while the crust, solid phase, is greatly enriched in heavier elements. Understanding this phase separation is important to determine the thermal conductivity and temperature profile of the star. [Preview Abstract] |
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