Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session L16: Gravitational Waveform Modeling of Compact Binaries ILive

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Sponsoring Units: DGRAV Chair: Gaurav Khanna, Univ. of Rhode Island 
Sunday, April 18, 2021 3:45PM  3:57PM Live 
L16.00001: Imprint of KozaiLidov Mechanism on Gravitational Waves Rohit Chandramouli, Nicolas Yunes Gravitational waves emitted by inner binaries in hierarchical triples are interesting astrophysical candidates for spacebased detectors like LISA. In the presence of a third body, the inner binary undergoes oscillations in eccentricity and inclination angle due to the KozaiLidov (KL) mechanism. In this talk, I will discuss how to construct analytic gravitational waveforms in the Fourier domain, with this effect included. Using multiplescale analysis, we make use of the separability of timescales in the system to combine the effects of KL oscillations and radiation reaction. The imprint on the waveform, due to this combined evolution, can then be analytically computed in the stationary phase approximation. I will also discuss our analysis of the parameters of the hierarchical triple which can produce a detectable (by LISA) imprint of KL oscillations on the waveform and outline potential implications for gravitational wave data analysis and tests of GR. [Preview Abstract] 
Sunday, April 18, 2021 3:57PM  4:09PM Live 
L16.00002: Evolution of Highly Eccentric Binary Orbits with Radiation Reaction: An Analytic Approach Alexandria Tucker, Clifford 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, resulting from 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 useful 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 of general mass ratios, incorporating gravitational radiation reaction at 4.5 postNewtonian order, including leading tail effects. We have developed accurate analytic expressions for the binary’s eccentricity and total inspiral time as a function of its latetime gravitational wave frequency, and of its initial energy and angular momentum. We will discuss our results and their implications for eccentric binary gravitational wave detection. [Preview Abstract] 
Sunday, April 18, 2021 4:09PM  4:21PM Live 
L16.00003: A New Waveform Model for Eccentric Binary White Dwarf Systems Shu Yan Lau, Kent Yagi, Phil Arras Close white dwarf binaries are promising sources of gravitationalwave signals for Laser Interferometer Space Antenna (LISA). The eccentricity of such a system decays over time due to gravitationalwave emission and tidal friction. In some scenarios, however, the orbits can have a high eccentricity even at the late stage of inspiral. Examples are hierarchical triple systems involving gravitational interactions between the binary and a distant third body. Analyzing the gravitationalwave signals from these systems requires accurate waveform templates. In this talk, I will describe a new waveform model for eccentric binary white dwarf systems taking tides into account. We propose a semianalytical ``kludge model'' which gives the quadrupole radiation from a postKeplerian orbit (obtained numerically) including the post1Newtonian effect on point masses as well as the quadrupolar tidal force. We also separately compare the effects on orbital evolution due to various factors including gravitationalwave emission, the additional force on the orbit due to tidallyinduced quadrupoles, and the effect of tidal friction. The model aims to provide accurate and efficient templates to study eccentric binary white dwarf systems with LISA. [Preview Abstract] 
Sunday, April 18, 2021 4:21PM  4:33PM Live 
L16.00004: Eccentric binary black hole surrogate models for the gravitational waveform: comparable mass, nonspinning case Tousif Islam, Vijay Varma, Jackie Lodman, Scott Field, Gaurav Khanna, Mark Scheel, Harald Pfeiffer, Davide Gerosa, Lawrence Kidder We develop new strategies to build numerical relativity surrogate models for eccentric binary black hole systems, which are expected to play an increasingly important role in current and future gravitationalwave detectors. We introduce a new surrogate waveform model, \texttt{NRSur2dq1Ecc}, using 47 nonspinning, equalmass waveforms with eccentricities up to $0.2$ when measured at a reference time of $5500M$ before merger. This is the first waveform model that is directly trained on eccentric numerical relativity simulations and does not require that the binary circularizes before merger. The model includes the $(2,2)$, $(3,2)$, and $(4,4)$ spinweighted spherical harmonic modes. We show that our waveform model can accurately predict numerical relativity waveforms with mismatches $\approx10^{3}$. We demonstrate that the waveform model can also recover subtle effects like modemixing in the ringdown signal without any special adhoc modeling steps. Finally, we show that despite being trained only on equalmass binaries, \texttt{NRSur2dq1Ecc} can be reasonably extended up to mass ratio $q\approx3$ with mismatches $\simeq 10^{2}$ for eccentricities smaller than $\sim 0.05$ as measured at a reference time of $2000M$ before merger. [Preview Abstract] 
Sunday, April 18, 2021 4:33PM  4:45PM Live 
L16.00005: A New Effective Spin for Modelling Precessing Higher Modes in the StrongField Lucy M. Thomas, Patricia Schmidt, Geraint Pratten Gravitational wave data analysis relies on accurate and efficient waveform models which incorporate physical phenomena such as precession and higherorder modes. Current semianalytical models for precessing binary black holes are not calibrated to numerical relativity in the precessing sector, in part due to the highdimensionality of the parameter space. One possibility lies in dimensional reduction of the precessing spinspace, previously done with $\chi_p$, but it has been shown that $\chi_p$ does not accurately represent precessing higherorder modes, which are crucial for modelling a complete precessing waveform. In this talk, I will present an alternative 2D effective precession spin $\vec{\chi}_{\perp}$. I will show that it reproduces the precession dynamics and higherorder modes of strongfield precessing waveforms much more accurately than $\chi_p$, as well as the remnant spin. This could be a promising avenue towards meaningful calibration of semianalytic precessing, higherorder mode waveforms to numerical relativity. [Preview Abstract] 
Sunday, April 18, 2021 4:45PM  4:57PM Live 
L16.00006: Testing Compact Binary Waveforms Using Memory and Angular Momentum Neev Khera, Badri Krishnan, Abhay Ashtekar Accurate modelling of gravitational waves from compact binaries is essential for their detection and parameter estimation. The accuracy is generally measured by comparison to Numerical Relativity (NR). We present supplementary methods to test for consistency with exact General Relativity using balance laws: an infinite tower of supermomentum balance laws and the angular momentum balance law. These methods do not rely on NR and can thus be used all across parameter space. The supermomentum balance law cannot be applied directly, however, since currently the memory effect is not modeled. Instead we use it indirectly to first \emph{infer} the memory and then compare the systematic differences of the inferred memory to their statistical uncertainties. We apply these methods to some recent models and binary black hole events. [Preview Abstract] 
Sunday, April 18, 2021 4:57PM  5:09PM Live 
L16.00007: Multipolar effectiveonebody waveforms for eccentric, spinaligned binary black holes Mohammed Khalil, Alessandra Buonanno, Serguei Ossokine, Antoni RamosBuades, Jan Steinhoff, Justin Vines While most binary mergers are expected to circularize when they enter the LIGO/Virgo frequency band, a small fraction of those binaries could have nonnegligible orbital eccentricity depending on their formation channel. Hence, it is important to accurately model eccentricity effects in waveform models to detect those binaries, infer their properties and shed light on their astrophysical environment. In this talk, I will present a multipolar effectiveonebody (EOB) eccentric waveform model for spinaligned black holes. In the quasicircular orbit limit, it reproduces the stateoftheart EOB model currently used in LIGO/Virgo analyses (SEOBNRv4HM). The waveform model contains eccentricity effects in the radiationreaction force and gravitational modes through second postNewtonian order, including tail effects, spinorbit, and spinspin couplings. I will also present results that validate such an eccentric waveform model against numericalrelativity simulations. [Preview Abstract] 
Sunday, April 18, 2021 5:09PM  5:21PM Live 
L16.00008: Error estimation and bounds for gravitationalwave surrogate models Feroz Shaik, Scott Field In the era of highprecision gravitational wave (GW) astronomy, modeling error may routinely dominate over statistical error as GW detectors approach design sensitivity. Due to the expected increase in the signaltonoise ratio of future detections, models that provide uncertainty estimates across the parameter space should play an increasingly important role in the analysis effort. For example, the inclusion of these uncertainties into the analysis will improve confidence in parameter estimates of future GW events. In this talk, I will discuss current efforts in the development of an error estimation methodology for surrogate waveform models. We apply this methodology to a set of benchmark test cases to verify the theoretical framework and implement the framework to nonspinning surrogate models. [Preview Abstract] 
Sunday, April 18, 2021 5:21PM  5:33PM Live 
L16.00009: Targeted Numerical Relativity Surrogate Waveform Model for GW190814 Jooheon Yoo, Vijay Varma, Matthew Giesler, Mark Scheel, Lawrence Kidder, Harald Pfeiffer The recent detection of GW190814 highlights the need for reliable, highaccuracy gravitational waveform templates for binary black holes of high mass ratios. We describe NRHybSur2dq15, a surrogate model for hybridized, nonprecessing numerical relativity (NR) waveforms, extending the previously explored mass ratio ranges. In this model, we train the surrogate over two parameters: the mass ratio, $q\in[1,15]$, and the spin of the highermass black hole, $\left\chi^1_z\right\leq 0.8$. For the training, we use hybrid waveforms generated from the NR simulations. The new surrogate model reproduces the hybrid waveforms with reasonable mismatches over the entire LIGO band for stellarmass binaries. The surrogate model also is quite robust to extrapolations of the parameters. Finally, we use templates generated from the surrogate model for parameter estimation of GW190814. [Preview Abstract] 
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