Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session LD: Nuclear Astrophysics VI |
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Chair: Nicole Vassh, Notre Dame Room: The Loft |
Wednesday, October 13, 2021 2:00PM - 2:12PM |
LD.00001: Impact of EoS on Neutrino Opacities in Core-collapse supernovae Zidu Lin, Andrew W Steiner Neutrinos radiate 99% of the energy and play a crucial role in the explosion mechanism and nucleosynthesis of core-collapse supernovae. The neutrino interactions in hot and dense matter is a complex problem due to bound nuclei and the strong nuclear forces. In this work we calculate the dynamic and static response of the neutral current and charged current neutrino-nucleon interactions, from low-density region near the neutrino sphere to high-density region up to approximately 1.5 saturation densities at finite T, by applying random phase approximation (RPA). We emphasize on the consistency between an equation of state (EoS) and the neutrino opacity, by using the density-dependent residual interactions, effective mass, single nucleon potentials directly derived from given EoSs in the RPA calculations. We further analyze the effect of EoSs on neutrino opacities by calculating the statistical uncertainties of neutrino opacities. The EoSs we used in this work naturally evolve to a model-independent virial EoS at low density, and are consistent with empirical constraints from (i) nuclear mass measurements, (ii) p-p scattering phase shifts, and (iii) neutron star observations. We found that our neutral current static response based on RPA is close to the results from model-independent virial approximation at low density, and our description of neutrino opacities at high densities have large uncertainties due to still unclear strong (especially spin-dependent) nuclear forces. |
Wednesday, October 13, 2021 2:12PM - 2:24PM |
LD.00002: Effect of the Nuclear Equation of State and Relativistic Turbulence on Core-Collapse Supernovae Luca Boccioli, Grant J Mathews, Evan P O'Connor The nuclear Equation of State (EOS) is an important component in the evolution and subsequent explosion of core collapse supernovae. We make a survey of various equations of state in the literature and analyze their effect on the explosion. To simulate the supernova, we use the general relativistic spherically-symmetric code GR1D, modified to take into account the effects of three-dimensional turbulence by using a new mixing length theory approach (STIR). We show that the viability of the explosion is quite EOS dependent and that the strength of explosions correlates best with the central entropy at bounce and the onset of turbulent mixing in the proto-neutron star. In particular, we find that EOSs calculated using the liquid drop model and the ones calculated using a relativistic mean field approach have a different influence on the explosion and on the proto-neutron star convection. |
Wednesday, October 13, 2021 2:24PM - 2:36PM |
LD.00003: A Nuclear Equation of State Inferred from Stellar r-process Abundances Erika M Holmbeck, Richard W O'Shaughnessy, Vera E Delfavero Binary neutron star mergers (NSMs) have been confirmed as one source of the heaviest observable elements made by the rapid neutron-capture (r-) process. However, modeling NSM outflows---from the total ejecta masses to their elemental yields---depends on the unknown nuclear equation of state (EOS) that governs neutron-star structure. In this work, we derive a phenomenological EOS by assuming that NSMs are the dominant sources of the heavy-element material in metal-poor stars that display r-process abundance patterns. We start with a population synthesis model to obtain a set of merging neutron-star binaries and calculate their EOS-dependent elemental yields. We then find the EOS such that the yields calculated from these mergers reproduces the abundances of r-process elements derived from observations of metal-poor stars. This EOS therefore represents our best prediction for what neutron stars should look like if they are to be the main progenitors of r-process material in the early universe. We present this EOS and comment on how it compares to both existing EOS models and results from the Neutron Star Interior Composition Explorer. |
Wednesday, October 13, 2021 2:36PM - 2:48PM |
LD.00004: Binary neutron star mergers of quark matter based nuclear equations of state Atul S Kedia, Hee Il Kim, Grant J Mathews, In-Saeng Suh With recent observations of gravitational wave signals from binary neutron star(BNS) mergers and observations by NICER, the nuclear equation of state(EoS) is becoming increasingly testable by numerical simulations. Numerous simulations currently exist exploring the equations of state at different density regimes for the constituent neutron stars. In this work we perform full GR three-dimensional hydrodynamics simulations of BNS mergers for parameterized EoSs based on quark matter at the highest nuclear densities. We construct our initial data using Lorene followed by simulating the merger with Einstein Toolkit. The goal of this study is to extract the effects on the observed GW waveform as the merger happens caused by quark matter. |
Wednesday, October 13, 2021 2:48PM - 3:00PM |
LD.00005: Transport in Neutron Star Mergers Alexander Haber, Mark Alford, Steven P Harris, Ziyuan Zhang Transport properties of compact stars have been computed in the past mostly for the conditions in old, isolated and therefore cold neutron stars. Gravitational wave observations of binary neutron star mergers allow us to examine dense matter in even denser, but more importantly significantly hotter matter. This requires a careful reexamination of nuclear and exotic transport properties of dense matter. In this talk I will present our work on nuclear and exotic bulk viscosity and Urca like processes in these environments. |
Wednesday, October 13, 2021 3:00PM - 3:12PM |
LD.00006: Insights on the peak in the speed of sound of ultradense matter Maurício Hippert, Eduardo S Fraga, Jorge Noronha In this work we investigate the minimal physical requirements needed for generating a speed of sound that surpasses its asymptotic conformal limit. It is shown that a peak in the speed of sound of homogeneous matter naturally emerges in the transition from a phase with broken chiral symmetry to one with a gapped Fermi surface. We argue that this could be relevant for understanding the peak in the speed of sound displayed by some of the current models for cold ultradense matter. A minimal model implementation of this mechanism is presented, based on the spontaneous breakdown of an approximate particle-antiparticle symmetry, and its thermodynamic properties are determined. |
Wednesday, October 13, 2021 3:12PM - 3:24PM |
LD.00007: From Nuclei to Neutron Stars: Combining Nuclear Physics and Multi-Messenger Observations Ingo Tews Neutron stars contain the largest reservoirs of degenerate fermions, reaching the highest densities we can observe in the cosmos, and probe matter under conditions that cannot be recreated in terrestrial experiments. Throughout the Universe, a large number of high-energy, cataclysmic astrophysical collisions of neutron stars are continuously occurring. These collisions provide an excellent testbed to probe the properties of matter at densities exceeding the density inside atomic nuclei, are an important site for the production of elements heavier than iron, and allow for an independent measurement of the expansion rate of our Universe. |
Wednesday, October 13, 2021 3:24PM - 3:36PM |
LD.00008: Numerical Enhancements for the Chiral Mean Field Model Nikolas Cruz Camacho, Jacquelyn Noronha-Hostler, Veronica Dexheimer A very successful model for the equation of state at large baryon densities that has been used to describe neutron stars, neutron star mergers, and heavy-ion collisions is the Chiral Mean Field model \cite{Dexheimer:2009hi}. Currently, the Chiral Mean Field model has a very slow execution time that lasts on the order of one month to construct 3D tables. Because heavy-ion collisions require 4D tables (baryon, strangeness, and electric charge are conserved) reduced running time is a high priority. In this work, we significantly reduce this time by employing program optimization techniques at the source, build, and compilation levels. Dynamic analysis was done by time profiling with Gprof and analyzing memory issues with Valgrind. For numerical integration, the QUADPACK library was linked. Finally, the execution was parallelized in constant temperature slices. Either for stellar mater or isospin symmetric matter, the execution time is reduced from months to hours. |
Wednesday, October 13, 2021 3:36PM - 3:48PM |
LD.00009: Nuclear Reaction Rates in Highly Magnetized Relativistic Plasmas: Effects on Pulsational Pair-Instability Supernovae, Magnetar Nucleosynthesis, and Other Sites Michael A Famiano, A. Baha Balantekin, Kanji Mori, Toshitaka Kajino, Yudong Luo If an astrophysical environment is hot enough, screening in the associated nuclear reactions can be modified by the presence of a relativistic electron-positron plasma. Additionally, strong magnetic fields can create an additional enhancement as the electron and positron energy distribution is modified by the altered Landau level occupancy. This can result in a further enhancement of nuclear reaction rates, and the reaction rate enhancement factor is studied in several relevant scenarios. Nearly every astrophysical site may undergo shifts in nuclear reaction rates due to electron-positron screening at high temperatures and magnetic fields. Massive stars that undergo pulsational pair-instability can be affected by the relativistic plasma in the core, and results are presented including affects on the final black-hole mass, composition of matter ejected in the pulse, and stellar dynamical effects. In addition, results pertaining to r-process nucleosynthesis in collapsar and magnetar environments will be presented. In addition to relativistic thermal effects, strong magnetic fields can enhance weak rates, resulting in dramatically different r-process distributions. Effects on the the final r-process abundance and potential galactic chemical evolution results will be presented. |
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