Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session 2WC: Neutron Stars and Properties of Nuclear Matter at High Densities |
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Chair: Kenji Fukushima, University of Tokyo Room: Kohala 3 |
Tuesday, October 7, 2014 2:00PM - 2:30PM |
2WC.00001: Astrophysical observations and future projects of neutron stars and magnetars Invited Speaker: Teruaki Enoto Neutron stars are enigmatic compact objects characterized by dense nuclear matter, rapid stellar rotation, and strong magnetic fields. Such an extreme environment has provided an accessible astrophysical laboratory to test fundamental physics. Recent astronomical observations from radio to gamma-rays have revealed a remarkable diversity of neutron stars: e.g., rotation-powered pulsars, accretion-powered pulsars, and magnetically-powered sources. Among important physical parameters of neutron stars, a wide range of magnetic field from $10^4$\,T to $10^{11}$\,T is thought to be one principal cause of the diversity. Especially, enigmatic X-ray sources, Soft Gamma Repeater (SGRs) and Anomalous X-ray Pulsar (AXPs), are now considered to have extremely strong magnetic field reaching $10^{10}$--$10^{11}$\,T, and thus, dubbed as ``magnetars.'' They emerge mainly in the X-ray frequency with intense giant flares, short bursts, and X-ray outbursts. Unlike for rotation-powered or accretion-powered pulsars, the bulk of their X-ray emission appears to be powered by their super-strong magnetic fields. At this talk, I will review recent high energy astrophysical observations of strongly-magnetized neutron stars, and also overview approved future missions to approach the neutron star science, for example, Astro-H (launch in 2015) which realizes the high energy resolution and the Neutron star Interior Composition ExploreR Mission (NICER, launch in late 2016) mission which is dedicated to determine the equation of state of neutron stars. [Preview Abstract] |
Tuesday, October 7, 2014 2:30PM - 3:00PM |
2WC.00002: From neutron-rich nuclei to low-mass neutron stars Invited Speaker: Atsushi Tamii In the first part of this talk, Atsushi Tamii will discuss on the experimental determination on the equation of state (EOS) of neutron rich nucleonic matter, especially on the symmetry energy term and its density dependence at around the nuclear saturation density. A special focus is placed on the precise measurements of the neutron density distribution in neutron rich nuclei as well as the neutron skin thickness, electric dipole polarizability, and pygmy dipole resonance. In the second part of this talk, Kei Iida would like to discuss condensed matter aspects of neutron star matter, particularly matter in the crustal portion of neutron stars. In this portion, with increasing depth, nuclei present become more and more neutron rich in the presence of a neutralizing background of electrons, and eventually drip neutrons. These nuclei and free neutrons, which can be regarded as a liquid-gas mixture of nuclear matter, play a role in controlling various properties as astrophysical condensed matter. These properties include a peculiar lattice structure of nuclei, superfluidity of dripped neutrons and vortices in this lattice, and liquid crystalline structures of the liquid-gas mixture in the deepest region of the crust. Near normal nuclear density, the system melts into uniform nuclear matter, of which the EOS controls the mass-radius relation of low-mass neutron stars. This EOS is thus expected to be constrained from possible simultaneous determinations of neutron star masses and radii. [Preview Abstract] |
Tuesday, October 7, 2014 3:00PM - 3:30PM |
2WC.00003: Heating and Cooling in Accreting Neutron Stars Invited Speaker: Hendrik Schatz In accreting neutron stars, material in the crust undergoes complex nuclear reaction sequences that involve a broad range of nuclei ranging from stability to the neutron drip line and beyond. It was recently shown that these reactions not only heat the crust, but can also lead to efficient cooling through an Urca process that involves electron capture and beta decay between pairs of nuclei. Urca cooling and crustal heating depend sensitively on the properties of neutron rich nuclei that in many cases are only poorly known. I will review observations, models, and experimental efforts to constrain the relevant nuclear physics, and discuss the key nuclear physics questions that arise from these new effects. [Preview Abstract] |
Tuesday, October 7, 2014 3:30PM - 4:00PM |
2WC.00004: COFFEE BREAK
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Tuesday, October 7, 2014 4:00PM - 4:30PM |
2WC.00005: Simultaneous determinations of neutron star radii and masses, and the equation of state Invited Speaker: Feryal Ozel Neutron stars offer the unique possibility of probing the equation of state of cold, ultradense matter in a region of the QCD phase diagram that is otherwise inaccessible. I will describe a technique that allows simultaneous determinations of neutron star radii and masses and show recent measurements that tightly constrain the radius of 10 neutron stars. Combined with mass measurements from pulsar timing, these radii measurements allows for the first astrophysical inference of the pressure of cold matter above nuclear saturation density. [Preview Abstract] |
Tuesday, October 7, 2014 4:30PM - 5:00PM |
2WC.00006: Hadronic Stars versus Hybrid stars: how can we identify them? Invited Speaker: Mark Alford The properties of high-density hadronic matter have been investigated for some time to predict properties of neutron stars including mass/radius and the maximum mass of a neutron star. Recent results indicate the properties of dense hadronic matter up to several times saturation density may be strongly constrained by properties of three-nucleon interactions and hyperon-nucleon interactions. We review some of these results and their comparison to observations. At high pressure, nuclear matter will undergo a transition to quark matter, so sufficiently heavy neutron stars may really be ``hybrid stars'' with quark matter cores. We will discuss the ``Constant Sound Speed'' (CSS) parameterization of the quark matter EoS, and show how it provides a generic way of understanding the topology of the mass-radius relation, as well as more specific features like the maximum mass and typical radius. CSS provides a fairly general framework or language for comparing different quark matter models with each other and with data, and for expressing experimental constraints in model-independent terms. [Preview Abstract] |
Tuesday, October 7, 2014 5:00PM - 5:30PM |
2WC.00007: Neutron star merger, gravitational waves, and the dense matter equation of state Invited Speaker: Yuichiro Sekiguchi The equation of state of dense matter that determines properties of the neutron star also characterizes the dynamics and gravitational waveforms emitted during binary neutron-star mergers. Understanding the effects of the equation of state on them requires numerical-relativity simulations of the mergers and a number of strategies for extracting information of equation of sate from gravitational waves have been proposed. Furthermore, recent numerical-relativity simulations also clarified that the neutron-star equation of state has a significant impact on the r-process nucleosynthesis which proceeds in the neutron-rich ejecta of the mergers. The r-process in the mergers has been accumulated wide interests both as a possible origin of heavy nuclei and a promising electro-magnetic counterpart to gravitational waves. I will review these topics and discuss possible feedbacks to the nuclear physics. [Preview Abstract] |
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