Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session C11: Numerical Relativity: Black Hole Binaries 
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Sponsoring Units: DGRAV Chair: Carlos Lousto, Rochester Institute of Technology Room: Sheraton Governor's Square 17 
Saturday, April 13, 2019 1:30PM  1:42PM 
C11.00001: Numerical Relativity in the LISA era Deirdre Shoemaker, Deborah Ferguson, Karan P Jani, Pablo Laguna Gravitational waveforms generated by numerical relativity were critical to the success of groundbased gravitational wave detection. In this talk, we illustrate some of the important factors for numerical relativity as groundbased detectors improve their sensitivity and spacebased detectors prepare for first light. We focus on binary black holes. 
Saturday, April 13, 2019 1:42PM  1:54PM 
C11.00002: The BlackHoles@Home Project: Black Hole Binaries on the Desktop Computer Zachariah Etienne, Ian Ruchlin, Thomas W Baumgarte Current numerical relativity (NR) gravitational waveform catalogs sample the 7dimensional blackhole binary parameter space extremely sparsely, and will need to be expanded by orders of magnitude to maximize the science from upcoming gravitational wave detectors. We report on BlackHoles@Home, a proposed SETI@Homelike project that focuses on generating NRbased black hole binary waveform catalogs and followups at unprecedentedly large scales. Through our recent extensions of the BSSNinsphericalcoordinates reference metric formulation to comoving, bisphericallike numerical grids, the project aims to reduce the cost of numerical relativistic black hole and neutron star binary simulations by ~100x. With this cost savings, stateoftheart black hole binary merger simulations may be performed entirely on a consumergrade computer, enabling the general public to participate directly in this critical science. 
Saturday, April 13, 2019 1:54PM  2:06PM 
C11.00003: An update on the Simulating Extreme Spacetimes (SXS) simulation catalog for binary black holes CJ Woodford The coalescence of two black holes as well as gravitational waves cannot be calculated analytically, and so numerical solutions yielding numerical waveforms are arguably the most accurate gravitational waveforms. Numerical waveforms are the basis for numerous inspiralmergerringdown waveform models used to detect gravitational waves from coalescing black holes, to estimate the properties of the coalescing binaries, to test general relativity with the observed gravitational waves, and to study systematic errors of parameter estimation. The Simulating Extreme Spacetimes collaboration (SXS) has computed a comprehensive public catalog of numerical waveforms, bolstering the original SXS catalog from 2013 to ~1300 waveforms with mass ratios up to 10.0, effective spins up to 0.998, and averaging 44 cycles long. This talk summarises the current status of the SXS online catalog, including details of its parameter space coverage, assessments of the uncertainties and accuracy of the numerical waveforms, and novel methods for waveform extraction and postprocessing. 
Saturday, April 13, 2019 2:06PM  2:18PM 
C11.00004: The NCSA eccentric gravitational waveform catalog Roland Haas, Eliu Antonio Huerta, Sarah Habib, Anushri Gupta, Adam Rebei, Vishnu Chavva, Daniel Johnson, Shawn Rosofsky, Erik Wessel, Bhanu Agarwal, Diyu Luo, Wei Ren Gravitational wave observations of eccentric binary black hole mergers will provide unequivocal 
Saturday, April 13, 2019 2:18PM  2:30PM 
C11.00005: Surrogate modeling of binary black hole waveforms with rapid spins Marissa B Walker Gravitationalwave signals from merging binary black holes carry information about their sources' masses and spins. Accurately recovering these parameters requires comparing the detected signals with many modeled waveforms. Numerical relativity (NR) produces the most accurate waveforms, but at a great computational cost. The technique of surrogate modeling allows for rapid construction of interpolated waveforms from a model trained with NR simulations. Prior SXS Collaboration surrogate models have not included black hole waveforms with spins greater than 0.8, although rapidly spinning black hole systems may be present in potential future observations. I will present an analysis of the performance of surrogate models for high spin black hole mergers. Specifically, I will evaluate the performance of onedimensional models for equal mass and spin binary black hole systems in this parameter space, using mismatches with NR waveforms. I will also compare these results with the extrapolation of current NR surrogate models to high spin. 
Saturday, April 13, 2019 2:30PM  2:42PM 
C11.00006: Induced Spins from Hyperbolic and NearHyperbolic Encounters of Initially Nonspinning Black Holes Patrick Nelson, Zachariah Etienne, Sean T McWilliams When two nonspinning, equalmass black holes pass by one another on hyperbolic or nearhyperbolic trajectories, we would expect their tidal interaction to induce spins on each black hole. However, neither perturbative (e.g. postNewtonian) treatments nor numerical relativity simulations to date have explored tidally induced spins from such nonmerging encounters. We have performed a number of numerical relativity simulations to study this potential effect. The basic setup for the simulations involves two equalmass, nonspinning black holes (BowenYork initial data) at 100M initial separation. We vary two parameters: the initial boost and shooting angle 𝜃 of the black holes. As the shooting angle 𝜃 decreases toward the bound/unbound limit (corresponding to marginally bound zoomwhirl orbits), tidally induced spinups increase exponentially. We find that initial boosts of 0.265c lead to interactions that spin up each black hole to a dimensionless spin parameter of at most 0.0197 (corresponding to the bound/unbound limit). With initial boosts of 0.488c, this grows to 0.199. Based on these results, we anticipate that much higher spinups will be possible with larger initial boosts. 
Saturday, April 13, 2019 2:42PM  2:54PM 
C11.00007: Improved initial Lapse and Shift for Binary Black Hole Simulations Nicole C Rosato, Carlos Lousto, James Healy We present a new set of initial lapse and shift for binary black hole (BBH) evolutions by constructing analytic formulas that mimic the settled behavior of those metric components in the moving puncture gauge. These initial values allow for substantial improvements in the initial shape of both the lapse and the shift. Current simulations set initial shift β=0 and lapse α to be isotropic asymptotically. Our new initial construction sets these initial values to be closer to the settled shape of α and β for boosted, spinning black holes. To evaluate the effects of the initial lapse and shift on evolutions, we monitor both the Hamiltonian and Momentum constraint violations. This method shows explicit improvements in a simulation of a 1:3 mass ratio, nonspinning BBH system and also in an equalmass system with spins a=0.8. We explore the extent in the binary’s parameter space where this method reduces the amount of time required for the settling of the lapse and shift, while improving the satisfaction of the constraints and thus making simulations of both high massratio and near extremally spinning systems computationally more efficient. 
Saturday, April 13, 2019 2:54PM  3:06PM 
C11.00008: "The LIGO/Virgo BinaryBlackHole Orrery" Teresita D Ramirez, Geoffrey Lovelace On September 14 2015, Advanced LIGO (Laser Interferometer Gravitationalwave Observatory) successfully made the first gravitational wave detection. Since then, LIGO and Virgo have published nine additional observations of gravitational waves from merging black holes. This poster presents a visualization, developed for education and public outreach, illustrating the different merging black holes that LIGO and Virgo have observed so far. The animation uses numerical relativity (specifically, the Spectral Einstein Code) to model the black holes’ horizons and the emitted gravitational waves. Each calculation is consistent with one of the LIGOVirgo observations. 
Saturday, April 13, 2019 3:06PM  3:18PM 
C11.00009: Quick BBH merger visualizations: Interpolating numerical apparent horizons Akshay Khadse, Leo C Stein
Binary black hole(BBH) coalescences are often visualized by rendering their apparent horizon(AH) surfaces over time. The information for plotting these AH surfaces is obtained through numerical simulations of BBH mergers. However, numerical simulations are available only for a finite number of points in parameter space (mass ratio and spin configurations) and also for a limited number of time slices within these parameter values. We, therefore, develop an approach which interpolates the existing AH data available from these numerical simulations not only in time but also between different parameter values of the binary. Such an approach will provide us with a quick and accurate way to generate BBH merger visualizations for any point in parameter space without running a full numerical simulation.

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