Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session C3: Gravitational-wave Astrophysics: Neutron Stars and Core Collapse Supernovae |
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Sponsoring Units: DAP DGRAV Chair: Jocelyn Read, California State University, Fullerton Room: Maryland C |
Saturday, January 28, 2017 1:30PM - 1:42PM |
C3.00001: Prospects for Gravitational Wave Searches for Core-Collapse Supernovae within the Local Universe Kiranjyot Gill, Marica Branchesi, Michele Zanolin, Marek Szczepanczyk We present an updated estimate of the intrinsic (vs observed) core collapse supernovae (CCSNe) rate within 20 Mpc from Earth, which is roughly the largest distance of interest for the searches for gravitational waves (GWs) from CCSNe with laser interferometers. Recognizing that CCSN galaxy host models are morphologically dependent, we separate the galaxies within 20 Mpc into the local field and Virgo cluster and account for biases, such as galactic plane absorption. The improved estimation of the CCSNe rate within 20 Mpc is 430 $\pm$ 21 CCSNe $\mathrm{Century}$ $^{-1}$ $\mathrm{Mpc}^{-1}$. We also discuss the Feldman-Cousins and GRB methodologies for detecting CCSNe when there are multiple CCSNe optical triggers, as predicted for advanced LIGO data science runs. Illustrative examples of the sensitivity improvement with respect to the single-event current approaches are provided for rapidly rotating semi-analytical models of GW emissions and real (publicly released) LIGO data. [Preview Abstract] |
Saturday, January 28, 2017 1:42PM - 1:54PM |
C3.00002: Gravitational Wave Signals from Core-Collapse Supernova Explosions Anthony Mezzacappa, Konstantin Yakunin, Noah Frere, Pedro Marronetti, Stephen Bruenn, W. Raphael Hix, Eric J. Lentz, J. Austin Harris, Eirik Endeve, O. E. Bronson Messer, John Blondin We present gravitational wave signals produced in two- and three-dimensional simulations of core-collapse supernova explosions. We perform our first-principles simulations with the neutrino hydrodynamics code CHIMERA. The code is based on Newtonian hydrodynamics and MGFLD neutrino transport with realistic neutrino interactions. It includes a nuclear equation of state, general relativistic corrections to the gravitational potential and neutrino transport, and a nuclear reaction network. Our simulations cover a wide range of progenitors from light (9.6M$_\odot$) to heavy (30M$_\odot$) mass. We compute the complete gravitational wave signals for all of these models. In this talk, we present the results and analyze the similarities and differences between the signals. [Preview Abstract] |
Saturday, January 28, 2017 1:54PM - 2:06PM |
C3.00003: Impact of the tidal p-g instability on the gravitational wave signal from coalescing binary neutron stars Reed Essick, Salvatore Vitale, Nevin Weinberg Recent studies suggest that coalescing neutron stars are subject to a fluid instability involving the nonlinear coupling of the tide to $p$-modes and $g$-modes. The instability's influence on the inspiral dynamics and thus the gravitational wave signal is, however, uncertain because we do not know precisely how the it saturates. I discuss recent work in which we construct a simple, physically motivated model of the saturation and explore the instability's impact as a function of the model parameters. We find that for plausible assumptions about the saturation, current gravitational wave detectors might miss more than 70\% of events if only point particle waveforms are used. Parameters such as the chirp mass, component masses, and luminosity distance might also be significantly biased. On the other hand, we find that relatively simple modifications to the point particle waveform can alleviate these problems and enhance the science that emerges from the detection of binary neutron stars. [Preview Abstract] |
Saturday, January 28, 2017 2:06PM - 2:18PM |
C3.00004: Resonant tidal excitation of superfluid neutron stars in coalescing binaries Hang Yu, Nevin Weinberg We study the resonant tidal excitation of g-modes in coalescing superfluid neutron star (NS) binaries and investigate how such tidal driving impacts the gravitational-wave signal of the inspiral. Previous studies treated the NS core as a normal fluid and did not account for its superfluidity. The source of buoyancy that supports the g-modes is fundamentally different in the two cases: in a normal fluid core the buoyancy is due to gradients in the proton-to-neutron fraction whereas in a superfluid core it is due to gradients in the muon-to-electron (or hyperon) fraction. The latter yields a stronger stratification and a superfluid NS has a denser spectrum of g-modes. As a result, many more g-modes undergo resonant tidal excitation during the inspiral. We find that $\simeq 10$ times more orbital energy is transferred into g-mode oscillations if the NS has a superfluid core rather than a normal fluid core. However, because this energy is transferred later in the inspiral when the orbital decay is faster, the accumulated phase error in the gravitational waveform is comparable for a superfluid and normal fluid NS ($\sim 10^{-3}-10^{-2}\textrm{ rad}$). A phase error of this magnitude is too small to be measured with the current generation of gravitational wave detectors. [Preview Abstract] |
Saturday, January 28, 2017 2:18PM - 2:30PM |
C3.00005: Measuring neutron star tidal deformability with Advanced LIGO: black hole - neutron star binaries Prayush Kumar, Michael Pürrer, Harald Pfeiffer The pioneering observations of gravitational waves (GW) by Advanced LIGO have ushered us into an era of \textit{observational} GW astrophysics. Compact binaries remain the primary target sources for GW observations, of which black hole - neutron star (BHNS) binaries form an important subset. GWs from coalescing BHNS systems carry signatures of the tidal distortion of the neutron star by its companion black hole during inspiral, as well as of its disruption close to merger. In this talk, I will discuss how well we can measure tidal effects from individual and populations of LIGO observations of disruptive BHNS mergers. I will also talk about how our measurements of non-tidal parameters can get affected by ignoring tidal effects in BHNS parameter estimation. [Preview Abstract] |
Saturday, January 28, 2017 2:30PM - 2:42PM |
C3.00006: Determining the Hubble Constant from Gravitational-wave Observations of Merging Binary Neutron Stars and Electromagnetic Observations of Galaxies Hong Qi, Patrick Brady, Chris Pankow, David Kaplan, Angela Van Sistine Active research has been made in the past few decades on measuring the Hubble constant $H_0$. Most of the research use electromagnetic observations only. In our research, we propose a different method of determining the Hubble constant more accurately with both electromagnetic observations of galaxies and gravitational-wave observations of signals that happen in these galaxies. Our method is based on the method proposed by Bernard Schutz in 1986, in which one uses information from galaxy surveys as prior information for the location of a gravitational wave source. Since the first direct detection of gravitational waves in 2015, this approach has been made more supported and useful. We show how accurate we can constrain $H_0$ by combining the results from a couple of hundreds of simulated gravitational-wave observations of merging binary neutron stars from a network of two advanced interferometers. This accuracy will be expectedly dramatically improved when we use a network of three advanced detectors. We also show various systematic effects on the measurements of $H_0$ due to the incompleteness of galaxy catalog, the uncertainty in the measurements of the redshifts of galaxies, and so forth. We will also review the ongoing work. [Preview Abstract] |
Saturday, January 28, 2017 2:42PM - 2:54PM |
C3.00007: Appplications of the post-Tolman-Oppenheimer-Volkoff formalism Hector O. Silva, Kostas Glampedakis, George Pappas, Emanuele Berti Besides their astrophysical interest, neutron stars are promising candidates for testing theories of gravity in the strong-field regime. It is known that, generically, modifications to general relativity affect the bulk properties of neutron stars, e.g. their masses and radii, in a way that depends on the specific choice of theory. In this presentation we review a theory-agnostic approach to model relativistic stars, called the post-Tolman-Oppenheimer-Volkoff formalism. Drawing inspiration from the parametrized post-Newtonian formalism, this framework allows us to describe perturbative deviations from general relativity in the structure of neutrons stars in a parametrized manner. We show that a variety of astrophysical observables (namely the surface redshift, the apparent radius, the Eddington luminosity and the orbital frequency of particles in geodesic motion around neutron stars) can be parametrized using only two parameters. [Preview Abstract] |
Saturday, January 28, 2017 2:54PM - 3:06PM |
C3.00008: R-mode frequencies of rapidly and differentially rotating relativistic neutron stars Cecilia Chirenti, Michael Jasiulek R-modes are a promising source of gravitational waves for ground based detectors. If the precise frequency is known, guided gravitational wave searches with higher detectability are possible. Many authors have calculated the r-mode frequency because of its physical importance. For the dominant mode its value is 4/3 times the angular velocity of the star, subject to various corrections, of which the most important are relativistic and rotational corrections. Here we extend the results from previous works and investigate the effect of rapid rotation and differential rotation on the r-mode frequency. We evolve the perturbation equations in Cowling approximation in time using finite differencing methods to compute the r-mode frequency for sequences of rotating neutron stars with polytropic equations of state. The results presented here are relevant to the design of gravitational wave and electromagnetic r-mode searches. [Preview Abstract] |
Saturday, January 28, 2017 3:06PM - 3:18PM |
C3.00009: General Relativistic Non-radial Oscillations of Compact Stars Zack Hall, II, Prashanth Jaikumar Currently, we lack a means of identifying the type of matter at the core of compact stars, but in the future, we may be able to use gravitational wave signals produced by fluid oscillations inside compact stars to discover new phases of dense matter. To this end, we study the fluid perturbations inside compact stars such as Neutron Stars and Strange Quark Stars, focusing on modes that couple to gravitational waves. Using a modern equation of state for quark matter that incorporates interactions at moderately high densities, we implement an efficient computational scheme to solve the oscillation equations in the framework of General Relativity, and determine the complex eigenfrequencies that describe the oscillation and damping of the non-radial fluid modes. We discuss the significance of our results for future detection of these modes through gravitational waves. [Preview Abstract] |
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