Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session L16: Gravitational Waves: Source Modeling 
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Sponsoring Units: DGRAV Chair: Tanja Hinderer, University of Amsterdam Room: Sheraton Grand Ballroom I 
Sunday, April 14, 2019 3:30PM  3:42PM 
L16.00001: Evolution of highly eccentric binary orbits with radiation reaction Alexandria Tucker, Clifford M Will To date, gravitational wave detections have been limited to those from quasicircular binary mergers. However, a significant percentage of mergers could have measurable residual eccentricities because of either external perturbations of the system or short timescales between formation and merger of the binary. Understanding how the orbits of such binaries evolve could aid in creating eccentric gravitational waveform templates as well as provide astrophysical information about the environment and formation channels of these systems. We have analyzed the longterm evolution of nonspinning highly eccentric binaries together with a relativistic criterion for capture, focussing on gravitational radiation reaction to high postNewtonian orders. We will report on the current status of this work. 
Sunday, April 14, 2019 3:42PM  3:54PM 
L16.00002: Analytic blackhole binary mergers: waveforms and kicks from first principles Sean T McWilliams We present a highly accurate, fully analytical model for the late inspiral, merger, and ringdown of blackhole binaries with arbitrary mass ratios and spin vectors, including the contributions of harmonics beyond the fundamental mode. This model assumes only that nonlinear effects remain small throughout the entire coalescence, and is developed based on a physical understanding of the dynamics of late stage binary evolution, in particular on the tendency of the dynamical binary spacetime to behave like a linear perturbation of the stationary mergerremnant spacetime, even at times before the merger has occurred. We demonstrate that the waveforms predicted by our model agree with the most accurate numerical relativity results to within their own uncertainties throughout the mergerringdown phase, and do so for example cases spanning the full range of binary parameter space that is currently testable with numerical relativity. In addition, we combine the waveform model with an improved physical understanding of spinning binary mergers to fully explain the origin of “superkicks”, and compare our predictions to numerical relativity. Finally, we highlight some novel predictions from our model that have not yet been observed in numerical relativity simulations. 
Sunday, April 14, 2019 3:54PM  4:06PM 
L16.00003: Highaccuracy remnant kicks, spins, and masses from precessing binaries with NR surrogate modeling Leo C Stein, Vijay Varma, Davide Gerosa, Francois Hebert, Hao Zhang Gravitational waves (GWs) carry energy, angular momentum, and linear momentum; the black hole remnant from a binary merger has its mass, spin, and recoil "kick" velocity determined by the emitted GWs. These quantities are astrophysically important for binary population synthesis, waveform modeling, and developing GWbased tests of GR. We present accurate fits for the remnant properties of generically precessing binary black holes, trained directly on large banks of numericalrelativity simulations, using modern machinelearning techniques. Our model is at least an order of magnitude more accurate than all previous fits, and changes the paradigm to avoid using manuallyconstructed fitting formulas. We make our models available in a fast, easytouse python package, surfinBH.

Sunday, April 14, 2019 4:06PM  4:18PM 
L16.00004: Numerical relativity surrogate waveform model for precessing binary black holes Vijay Varma, Scott E Field, Davide Gerosa, Leo C Stein, Mark A Scheel Numerical relativity (NR) simulations are required to accurately predict the gravitational waveform from the merger of binary black holes. Unfortunately, NR simulations are very expensive and cannot be used directly in parameter estimation. Surrogate modeling is a datadriven approach to modeling, that has been shown to be both fast and accurate in reproducing NR simulations. We present a new 7dimensional surrogate model for the waveforms of generically precessing binary black holes, with mass ratios as high as 4. Trained directly against hundreds of NR simulations, these models are shown to reproduce the simulations nearly as accurately as the simulations themselves. 
Sunday, April 14, 2019 4:18PM  4:30PM 
L16.00005: Black hole ringdown: the importance of overtones Matthew Giesler, Maximiliano Isi, Mark A Scheel, Saul A Teukolsky It is possible to infer the mass and spin of the remnant black hole of binary mergers by comparing the ringdown gravitationalwave signal to results from studies of perturbed Kerr spacetimes. Typically these studies are based on the fundamental quasinormal mode (QNM) of the dominant l=m=2 harmonic. Using the ringdown from numerical relativity simulations, we find that the fundamental mode alone is insufficient to recover the true underlying mass and spin, unless the analysis is started very late in the ringdown. Including higher overtones associated with this l=m=2 harmonic appears to resolve this issue, and provides an unbiased estimate of the true remnant parameters. Further, including overtones allows for the modeling of the ringdown signal for all times beyond the peak strain amplitude, with good agreement even before the peak amplitude, indicating the linear quasinormal regime has a start time much earlier than previously expected. Moreover, we explore the possibility of using the l=m=2 fundamental QNM and its first overtone as a twomode test of general relativity, as opposed to the conventional approach of relying on the fundamental QNMs from two different angular harmonics. 
Sunday, April 14, 2019 4:30PM  4:42PM 
L16.00006: Signature of horizon dynamics in binary black hole gravitational waveforms Ssohrab Borhanian, K. G. Arun, Harald P. Pfeiffer, Bangalore S. Sathyaprakash Gravitational waves from merging binary black holes carry the signature of the strong field dynamics of the newly forming common horizon. This signature presents itself in the amplitudes and phases of various spherical harmonic modes as deviations from the point particle description provided by postNewtonian theory. Understanding the nature of these departures will aid in (a) formulating better models of the emitted waveforms in the strong field regime of the dynamics, and (b) relating the waveforms observed at infinity to the common horizon dynamics. We use a combination of numerical relativity simulations and postNewtonian theory to search for the modes of radiation whose amplitude is most affected by the strong field phase. We find that modes with large amplitudes or spherical harmonic indices l = m are least modified from their dominant postNewtonian behavior, while the weaker l ≠ m modes are affected to the greatest extent. The addition of spins to the binary components only affects currentmultipole modes with l + m = odd at the order of interest and seems to stabilize some mode amplitudes against deviations from postNewtonian theory. 
Sunday, April 14, 2019 4:42PM  4:54PM 
L16.00007: Hybrid Waveforms for Precessing binary black holes for LIGO data analysis Jam Sadiq, Yosef Zlochower, Richard O'Shaughnessy We construct hybrid waveforms of precessing binary black holes by 
Sunday, April 14, 2019 4:54PM  5:06PM 
L16.00008: Hybrid Gravitational Wave Systematics and Model Comparisons for Binary Neutron Star Systems Eric Flynn, Jocelyn Read Compact binary systems are a source of many anticipated signals for current and future gravitational wave detectors. The detectability and measurement of any gravitational wave (GW) source is dependent on models of the inspiral, merger, and post merger of a compact binary system. Hybrid gravitational waves join analytical models of the insprial and numerical simulations of the merger and post merger to make a single model. Hybrid accuracy depends on a set of construction parameters, and can contribute to waveform systematic error when using hybrid models. We identify and study the effect construction parameters have on hybrid waveforms modeling binary neutron star (BNS) mergers used for waveform detection and parameter estimation to leading order. By minimizing the error contributions from these sources for nonspinning BNS simulations from the Computational Relativity (CoRe) library, we identify limitations to hybrid accuracy and determine, given these limitations, if a family of hybrids can be constructed within accuracy bounds needed by the LIGO detectors. 
Sunday, April 14, 2019 5:06PM  5:18PM 
L16.00009: Gravitational Waves from ChargedBlack Hole Binaries Justin Y. J. Burton, Ruomin Zhu, Thomas Osburn We model the dynamics of a binary black hole system with electrically charged components and the gravitational waves emitted. Systems with extreme and intermediate massratios are investigated using black hole perturbation theory. Through this procedure we solve the linearized EinsteinMaxwell equations numerically. The rate of radiative energy dissipation from gravitational and electromagnetic waves is used to incorporate radiation reaction into the equations of motion through adiabatic and quasicircular approximations. We observe that the gravitational waveforms are most strongly affected by electric charge when the two binary components have opposite chargetomass ratios, and we quantify the effect of electric charge in various scenarios. 
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