Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session G12: Nuclear Astrophysics I.Live
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Sponsoring Units: DNP Chair: Amber Lauer, Duke University |
Sunday, April 18, 2021 8:30AM - 8:42AM Live |
G12.00001: Constraints on Neutron Star Masses and Radii in This Era of Multi-Messenger Astronomy Mohammad Al-Mamun We performed a Bayesian analysis which constrains the neutron star mass-radius relation using observations from quiescent low-mass X-ray binaries, photospheric radius expansion X-ray bursters, merger event GW170817, and J0030+0451 from NICER. This observational data set provides tight constraints on mass-radius relation and the equation of state with a small dependence on the prior choice of equation of state distribution. Analyzing the hidden uncertainties of electromagnetic data, performing intrinsic scattering on the given systematic uncertainties, does not provide a significant change on mass-radius constraints except a slight broadening of the posteriors. Our inferences suggest that both the gravitational wave and the electromagnetic observations of neutron stars are consistent with one another. [Preview Abstract] |
Sunday, April 18, 2021 8:42AM - 8:54AM Live |
G12.00002: Placing Bounds on Nuclear Matter Parameters using NICER Measurements of J0030 Josef Zimmerman, Zack Carson, Andrew Steiner, Kent Yagi The NICER telescope recently made the first direct simultaneous measurement of the mass $M$ and radius $R$ of the neutron star PSR J0030+0451. We utilize this measurement to place bounds on the supranuclear equation of state (EoS). We construct a population of theory-agnostic EoSs by expressing the binding energy per nucleon as a Taylor expansion in nucleon number density and isospin symmetry. By randomly sampling each of the parameters in the Taylor expansion and excluding non-physical combinations, we generate a population of 100,000 possible EoSs. By numerically solving the properties of the NS described by each EoS, we construct conditional probability distributions relating the measurable quantities $M$ and $R$ to the nuclear parameters such as $K_{sym,0}$ that govern the EoS. A marginalization routine is used to place bounds on the values of $K_{sym,0}$ that are consistent with measurements of J0030. [Preview Abstract] |
Sunday, April 18, 2021 8:54AM - 9:06AM Live |
G12.00003: Reconstructing Neutron Star Merger Masses from Metal-poor Stars Erika Holmbeck, Anna Frebel, G. McLaughlin, Rebecca Surman, Rodrigo Fernandez, Brian Metzger, Matthew Mumpower, Trevor Sprouse Neutron star mergers (NSMs) are promising astrophysical sites for the rapid neutron-capture (``$r$") process, but can their integrated yields explain the majority of heavy-element material in the Galaxy, especially those present in metal-poor stars? One method to address this question implements a forward approach that propagates NSM rates and yields along with stellar formation rates and compares with the observed elemental abundances of metal-poor stars. In this work, we take the inverse approach by utilizing $r$-process signatures of metal-poor stars as input to reconstruct the masses of the neutron star (NS) binary progenitors that would have merged to create those elements. Notably, with our model assumptions and the studied stellar sample, we postulate that the most $r$-process-enhanced stars on their own would require progenitor NSMs of asymmetric systems that are distinctly different from present ones in the Galaxy. However, we find that NSMs can still account for all $r$-process material in metal-poor stars that display $r$-process signatures, while simultaneously reproducing the present-day distribution of double-NS systems. [Preview Abstract] |
Sunday, April 18, 2021 9:06AM - 9:18AM Live |
G12.00004: Strangeness-changing Rates and Hyperonic Bulk Viscosity in Neutron Star Mergers Alexander Haber, Mark Alford In this talk we present a computation of the rates of strangeness-changing processes and the resultant bulk viscosity in matter at the densities and temperatures typical of neutron star mergers. We include processes where quarks move between baryons via meson exchange: these have generally been omitted in previous analyses but provide the dominant contribution to the rates of strangeness-changing processes and the bulk viscosity. The calculation of these rates is an essential step towards any calculation of dissipation mechanisms in hyperonic matter in mergers. As one application, we present the dissipation times for density oscillations at the frequencies seen in merger simulations. [Preview Abstract] |
Sunday, April 18, 2021 9:18AM - 9:30AM Live |
G12.00005: Improved treatment of neutron star cooling via modified Urca Process Ziyuan Zhang, Mark Alford Most neutron stars cool predominately via the modified Urca process, in which emitted neutrinos carry away energy. The traditional treatment for the in-medium nucleon propagator in the modified Urca process uses crude approximations. We reformulate the propagator by including the nucleon self-energy and examine the effect of this new propagator on the neutrino emissivity due to the modified Urca process. [Preview Abstract] |
Sunday, April 18, 2021 9:30AM - 9:42AM Live |
G12.00006: The Neutrino Opacities in Core-collapse supernovae: a Systematic Way to Describe Neutrino Interactions for a Wide Range of Densities at Finite Temperature Zidu Lin, Andrew Steiner We derived both neutrino neutral current and charged current interactions based on random phase approximation (RPA). The RPA is treated as an extendable platform where other “many body effect modules”, such as nucleon potential mean field corrections and collisional broadening, can be easily added. Furthermore, the RPA consistently relates the neutrino response with an equation of state (EoS). In this work, we employed density-dependent nucleon effective mass, Landau Fermi liquid parameters and nucleon potential, which are all derived from a Skyrme type EoS (NRAPR), in the RPA approximation. We further discuss the possibilities of estimating the uncertainties of neutrino response coming from the Skyrme EoS parameters. Finally, we discuss approximations beyond RPA at low densities to find an appropriate method to describe the dynamic neutrino response that is consistent with the model-independent virial approximation of neutrino static response. [Preview Abstract] |
Sunday, April 18, 2021 9:42AM - 9:54AM Live |
G12.00007: Response functions for hot and dense nuclear nuclear matter from chiral nuclear forces Eunkyoung Shin, Jeremy Holt, Ermal Rrapaj, Sanjay Reddy Response function gives an idea to understand interaction in the matter. We derived density density response and spin spin response function, which is including up to 1st order perturbation(mean field correction and vertex correction). We studied neutrino interaction(neutrino scattering and neutrino absorption) in the nuclear matter(pure neutron matter and nuclear matter with small proton fraction) with response function. The nuclear potential is derived from chiral effective field theory. We use three different cutoff energies (414, 450, 500 MeV). Finally, we calculate the dynamic structure function with response function. Since the scattering rate can be calculated using structure function, the study gives a hint for the neutrino process on core collapsing supernova simulation. [Preview Abstract] |
Sunday, April 18, 2021 9:54AM - 10:06AM Live |
G12.00008: Variational and Parquet-diagram Calculations for Neutron Matter. III. S-wave Pairing Jiawei Wang, Eckhard Krotscheck We apply parquet-diagram summation methods for the calculation of the superfluid gap in $S$-wave pairing in neutron matter for realistic nucleon-nucleon interactions such as the Argonne $v_6$ and the Reid $v_6$ potentials. It is shown that diagrammatic contributions that are outside the parquet class play an important role. These are, in variational theories, identified as so-called ``commutator contributions''. Moreover, using a particle-hole propagator appropriate for a superfluid system results in the suppression of the spin-channel contribution to the induced interaction. Applying these corrections to the pairing interaction, our results agree quite well with Quantum Monte Carlo data. [Preview Abstract] |
Sunday, April 18, 2021 10:06AM - 10:18AM Live |
G12.00009: Measuring the Weak Charge Radius of Pb$^{208}$ with PREX-II Brendan Reed, Charles Horowitz Parity-violating electron scattering is a strong tool that can be used to probe the elusive neutron density in atomic nuclei. Recently, the parity-violating electron scattering experiment PREX-II made measurements of the weak charge radius of Pb$^{208}$. This measurement is a strong improvement over the results of the PREX experiment, now measuring the weak charge radius with an uncertainty of 1.4%. In this talk, I will detail the results of the PREX-II experiment and their implications on various nuclear matter systems. These include neutron stars, pure neutron matter, and on the saturation density of symmetric nuclear matter. [Preview Abstract] |
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