Bulletin of the American Physical Society
APS April Meeting 2016
Volume 61, Number 6
Saturday–Tuesday, April 16–19, 2016; Salt Lake City, Utah
Session H15: Neutron Star and Supernova Gravity Wave Astrophysics 
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Sponsoring Units: GGR DAP Chair: Steven Liebling, Long Island University Room: 251C 
Sunday, April 17, 2016 8:30AM  8:42AM 
H15.00001: Probing the Internal Composition of Neutron Stars with Gravitational Waves Katerina Chatziioannou, Kent Yagi, Antoine Klein, Neil Cornish, Nicolas Yunes Gravitational waves from neutron star binaries carry information about the equation of state of supranuclear matter through a parameter called tidal deformability. This parameter measures the quadrupole deformation of a neutron star in the presence of an external field. Its measurability has been assessed in a number of studies, concluding it could provide important information about the equation of state of neutron star matter. In this talk, I will describe a complimentary approach to the problem of equation of state determination, one which focuses on how information from gravitational waves can be translated in ways that could be of direct benefit to nuclear physicists. Specifically, I will talk about what gravitational waves can tell us about the internal composition of neutron stars, information that is directly applicable to equation of state modeling. I will also briefly discuss the importance of spininduced precession in the quality of information extracted. [Preview Abstract] 
Sunday, April 17, 2016 8:42AM  8:54AM 
H15.00002: Gravitational Wave Physics with Binary Love Relations Kent Yagi, Nicolas Yunes Gravitational waves from the late inspiral of neutron star binaries encode rich information about their internal structure at supranuclear densities through their tidal deformabilities. However, extracting the individual tidal deformabilities of the components of a binary is challenging with future groundbased gravitational wave interferometers due to degeneracies between them. We overcome this difficulty by finding new, approximate universal relations between the individual tidal deformabilities that depend on the mass ratio of the two stars and are insensitive to their internal structure. Such relations have applications not only to gravitational wave astrophysics, but also to nuclear physics as they improve the measurement accuracy of tidal parameters. Moreover, the relations improve our ability to test extreme gravity and perform cosmology with gravitational waves emitted from neutron star binaries. [Preview Abstract] 
Sunday, April 17, 2016 8:54AM  9:06AM 
H15.00003: Improved Universal NoHair Relations for Neutron Stars Barun Majumder, Kent Yagi, Nicolas Yunes The exterior gravitational field of an astrophysical body can be characterized by its multipole moments. Nohair theorems for black holes state that the exterior gravitational field can be completely described in terms of their mass and spin angular momentum. Similar nohair like relations have been recently found for neutron stars which are approximately independent of the internal structure of the star. Missions like NICER and LOFT will observe the pulse profiles of millisecond pulsars and thermonuclear bursters. The equationofstate (EoS) independent relations may break degeneracies among the relevant observables in the modeling of Xray pulse and atomic line profiles. The amount of EoS independence of these approximately universal relations depends on how one adimensionalizes the multipole moments of the star with stellar mass, spin and radius. We show that for slowlyrotating neutron stars in both nonrelativistic limit and full General Relativity, the optimal normalization of the multipole moments exist that minimizes the EoS dependence in the universal relations. The relations among the moment of inertia and higher order moments can be improved from the original ones approximately by a factor of two. [Preview Abstract] 
Sunday, April 17, 2016 9:06AM  9:18AM 
H15.00004: Lowmass neutron stars: universal relations, the nuclear symmetry energy and gravitational radiation Hector O. Silva, Emanuele Berti, Hajime Sotani Compact objects such as neutron stars are ideal astrophysical laboratories to test our understanding of the fundamental interactions in the regime of supranuclear densities, unachievable by terrestrial experiments. Despite recent progress, the description of matter (i.e., the the equation of state) at such densities is still debatable. This translates into uncertainties in the bulk properties of neutron stars, masses and radii for instance. Here we will consider lowmass neutron stars. Such stars are expected to carry important information on nuclear matter near the nuclear saturation point. It has recently been shown that the masses and surface redshifts of lowmass neutron stars smoothly depend on simple functions of the central density and of a characteristic parameter $\eta$ associated with the choice of equation of state. Here we extend these results to slowlyrotating and tidally deformed stars and obtain empirical relations for various quantities, such as the moment of inertia, quadrupole moment and ellipticity, tidal and rotational Love numbers, and rotational apsidal constants. We discuss how these relations might be used to constrain the equation of state by future observations in the electromagnetic and gravitationalwave spectra. [Preview Abstract] 
Sunday, April 17, 2016 9:18AM  9:30AM 
H15.00005: Effects of neutronstar dynamic tides on gravitational waveforms within the effectiveonebody approach Tanja Hinderer, Andrea Taracchini, Francois Foucart, Alessandra Buonanno, Jan Steinhoff, Matthew Duez Extracting the unique information on ultradense nuclear matter from the gravitational waves emitted by merging neutronstar binaries requires robust theoretical models of the signal. I will discuss a novel effectiveonebody waveform model that includes for the first time dynamic (instead of only adiabatic) tides of the neutron star and also describes the merger signal for neutronstarâ€“blackhole binaries. We demonstrate the importance of the dynamic tides by comparing the predictions of this model against results from numerical relativity simulations. I will also show that the impact of the dynamical tidal effects can be approximately captured by a simple effective description that makes explicit the influence of the neutron star matter through two key parameters (for each multipole): tidal deformability and fundamental oscillation frequency. [Preview Abstract] 
Sunday, April 17, 2016 9:30AM  9:42AM 
H15.00006: Nonlinear Tides in Coalescing Binary Neutron Stars Nevin Weinberg Coalescing binary neutron stars are among the most promising sources for groundbased gravitational wave detectors such as Advanced LIGO. Tidal interactions in such systems extract energy from the orbit and, at some level, modify the gravitational wave signal. Previous studies found that tidal effects are probably too small to be detected from individual systems with LIGO. However, these studies typically assumed that the tide can be treated as a linear perturbation to the star. I will show that the linear approximation is invalid even during the early stages of inspiral and that nonlinear fluid effects in the form of tideinternal wave interactions become important around the time the binary first enters LIGO's bandpass (at gravitational wave frequencies around 30 Hz). Although the precise influence of nonlinear fluid effects is not yet well constrained, I will show that they may significantly modify the gravitational wave signal and electromagnetic emission from coalescing binary neutron stars. [Preview Abstract] 

H15.00007: ABSTRACT WITHDRAWN 
Sunday, April 17, 2016 9:54AM  10:06AM 
H15.00008: Gravitational Wave Signals from 2D and 3D Core Collapse Supernova Explosions Konstantin Yakunin, Anthony Mezzacappa, Pedro Marronetti, Stephen Bruenn, W. Raphael Hix, Eric J. Lentz, O. E. Bronson Messer, J. Austin Harris, Eirik Endeve, John Blondin We study two and threedimensional (2D and 3D) corecollapse supernovae (CCSN) using our firstprinciples CCSN simulations performed with the neutrino hydrodynamics code CHIMERA. The following physics is included: Newtonian hydrodynamics with a nuclear equation of state capable of describing matter in both NSE and nonNSE, MGFLD neutrino transport with realistic neutrino interactions, an effective GR gravitational potential, and a nuclear reaction network. Both our 2D and 3D models achieve explosion, which in turn enables us to determine their complete gravitational wave signals. In this talk, we present them, and we analyze the similarities and differences between the 2D and 3D signals. [Preview Abstract] 
Sunday, April 17, 2016 10:06AM  10:18AM 
H15.00009: Equation of State Dependence of Gravitational Waves from Rapidly Rotating CoreCollapse Sherwood Richers, Christian D. Ott, Ernazar Abdikamalov We carry out axisymmetric simulations of rotating corecollapse, exploring over 92 precollapse rotational configurations and 18 different finitetemperature microphysical equations of state (EOS) using the generalrelativistic hydrodynamical code CoCoNuT. Our focus is on gravitational wave (GW) emission. We find that the GW wave signature depends systematically on the rotation rate of the inner core at bounce and the compactness of the protoneutron star (PNS), set by the EOS and rotation. The GW signal from core bounce is almost independent of the EOS. However, the frequency of the postbounce ring down signal from the fundamental quadrupole oscillation mode of the PNS is dependent on both rotation and the EOS, increasing with rotation rate and compactness. We will discuss the origin of the EOSdependent fmode frequency variation and its potential observability with Advanced LIGO. [Preview Abstract] 
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