Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session L12: Nuclear Astrophysics I |
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Sponsoring Units: DNP Chair: Carolyn Raithel, University of Arizona Room: Sheraton Plaza Court 1 |
Sunday, April 14, 2019 3:30PM - 3:42PM |
L12.00001: Multi-messenger Neutron Star Astrophysics and Determining the Composition of the Neutron Star Core Andrew W Steiner, Spencer Beloin, Sophia Han, Khorgolkhuu Odbadrakh Using a model for the equation of state and composition of dense matter and the magnitude of singlet proton superconductivity and triplet neutron superfluidity, we perform the first simultaneous fit of neutron star masses and radii with neutron star luminosities and ages determined from observations of isolated neutron stars. We also simultaneously fit the charge radii and binding energies of heavy nuclei and find agreement with the tidal deformability obtained in GW 170817. We find that the threshold density for the direct Urca process lies between the central density of 1.7 and 2 solar mass neutron stars, but that 2 solar mass stars are unlikely to cool principally by the direct Urca process because of the suppression by neutron triplet superfluidity. This is the first quantitative constraint on the composition of matter above the saturation density. |
Sunday, April 14, 2019 3:42PM - 3:54PM |
L12.00002: Imprints of the nuclear symmetry energy on the tidal deformability of neutron stars Plamen G Krastev, Bao-An Li Applying an equation of state (EOS) constrained by heavy-ion reaction data, we calculate the tidal deformability of neutron stars in coalescing binary systems. We investigate the effects of the high-density behavior of the nuclear symmetry energy on the tidal properties of neutron stars, and discuss their implications for the EOS of dense matter, and the interpretation of recent and future gravitational-wave signals from inspiraling neutron star binaries. |
Sunday, April 14, 2019 3:54PM - 4:06PM |
L12.00003: Dilute Fermi gas at fourth order in effective field theory Christian Drischler, Corbinian Wellenhofer, Kai Hebeler, Achim Schwenk Microscopic calculations of nuclear matter have important consequences for nuclear astrophysics as well as finite nuclei. We present an efficient Monte-Carlo framework for perturbative calculations of infinite nuclear matter based many-body forces derived within chiral effective field theory. It enables to incorporate all many-body contributions in a transparent and also straightforward way, making it well-suited for pushing the limits of current state-of-the-art calculations to high orders in both the chiral as well as the many-body expansion. Furthermore, uncertainty estimates can systematically be extracted by order-by-order calculations, which provides important insights into the rate of convergence of each of the two expansions. Taking advantage of the novel framework, we report here on our complete calculation of the fourth-order term in the Fermi-momentum or $k_{\rm F} a_s$ expansion for the ground-state energy of a dilute Fermi gas. The convergence behavior of the expansion for spin one-half fermions is assessed by comparing to quantum Monte-Carlo results. |
Sunday, April 14, 2019 4:06PM - 4:18PM |
L12.00004: Bulk viscosity in neutrino-transparent nuclear matter Steven P Harris, Mark Alford In nuclear matter, bulk viscosity arises from a phase lag between an imposed density oscillation and beta reequilibration of the particle content of the nuclear matter, which proceeds via the Urca process. When bulk viscosity is sufficiently strong, which happens when the reequilibration rate nearly matches the frequency of the density oscillation, it can noticeably dampen the oscillation. Consequently, it might be necessary to consider bulk viscosity in neutron star merger simulations, depending on the temperature where bulk viscosity attains its maximum value. Traditionally, the bulk viscosity calculation assumes that only particles near their Fermi surfaces participate in the Urca process (termed the "Fermi surface approximation"). We recalculate the bulk viscosity, computing the Urca rates with a complete phase space integral instead of using the Fermi surface approximation, and find that the temperature at which bulk viscosity is important changes by about 1 MeV compared to the results using the Fermi-surface approximation. |
Sunday, April 14, 2019 4:18PM - 4:30PM |
L12.00005: Properties of Hypothetical Quark-Hadron Coulomb Lattices in the Cores of Neutron Stars Fridolin Weber, William Spinella The tremendously high pressures in the cores of neutron We use relativistic mean-field equations of state to model hadronic |
Sunday, April 14, 2019 4:30PM - 4:42PM |
L12.00006: (Color-)Magnetic Defects in Dense Nuclear and Quark Matter Alexander Haber Nucleons and possibly quarks in compact stars form an interacting multicomponent system of a (color-)superconductor and a superfluid. Due to the strong magnetic field in most neutron stars, magnetic defects like flux tubes form. By starting from a field-theoretical, bosonic model, the phase structure of these multicomponent systems can be studied. Special emphasis is put on the type-I/type-II transition using lattice calculations. Additionally, new defects in color flavor locked quark matter are studied within the presented model. |
Sunday, April 14, 2019 4:42PM - 4:54PM |
L12.00007: Remeasuring the resonance strength of the 21Ne(p,gamma)22Na reaction at DRAGON Matthew A Lovely, Jonathan Karpesky, Devin S Connolly, Charlie Akers, Greg Christian, Barry Davids, Jennifer Fallis, Dave Hutcheon, Uwe Greife, Alex Rojas, Chris Ruiz, Ulrike Hager Novae are explosive astrophysical events which provide a unique environment for nucleosynthesis. Oxygen-Neon(O-Ne) novae caused by the thermonuclear runaway of accreted material on the white dwarf of a close binary system can reach peak temperatures of 0.1-0.4 GK. These novae are particularly important for the production of higher mass nuclides through cycles such as the Ne-Na cycle. The 21Ne(p,gamma)22Na reaction of the Ne-Na cycle is of great interest in studying these events due to the beta decay and subsequent release of a characteristic gamma ray at 1.275 MeV and the relatively long half-life of 2.6 years. Current satellites have the capability to detect gammas of this energy but to date, no gammas from the 22Na decay have been detected and this remains a problem in understanding novae nucleosynthesis. The 21Ne(p,gamma)22Na reaction was measured at Ecm=258.6 keV in inverse kinematics at the DRAGON recoil separator as a part of the commissioning measurements and yielded a resonance strength over twice the literature value measured by Gorres et al.. This reaction was then remeasured in order to resolve this discrepancy. Preliminary results and analysis will be discussed. |
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