Bulletin of the American Physical Society
APS April Meeting 2020
Volume 65, Number 2
Saturday–Tuesday, April 18–21, 2020; Washington D.C.
Session H16: Modeling Eccentric and Spinning Compact BinariesLive

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Sponsoring Units: DAP DGRAV Chair: Sean McWilliams, West Virginia University Room: Virginia C 
Sunday, April 19, 2020 10:45AM  10:57AM Live 
H16.00001: Integrability of eccentric, spinning blackhole binaries at the second postNewtonian order Sashwat Tanay, Leo Stein The LISA mission is projected to observe eccentric binaries of spinning compact objects, which inspiral very slowly. Modeling gravitational waveforms from these systems is challenging because of the interplay of orbital, precession, and inspiral dynamics. Here we report on the integrability of the postNewtonian (PN)Hamiltonian for eccentric, spinning blackhole binaries (BHBs), without resorting to averaging. Integrability is exact at 1.5PN, with 5 constants of motion in a 10 dimensional phase space. We show that the system is also integrable at the 2PN order in the PN perturbative sense. Integrability gives hope to finding longterm analytic solutions for the conservative motion. We then report progress in finding the action integrals and then proceed to show how to solve for the spin and orbital angular momentum vectors of a circular BHB in terms of elliptic functions. [Preview Abstract] 
Sunday, April 19, 2020 10:57AM  11:09AM Live 
H16.00002: Eccentricorbit extrememassratio inspirals: Analytically expanding black hole perturbation theory quantities to high PN order Christopher Munna, Charles Evans We present new advances in determining analytic PN series for various orbital features of nonspinning extrememassratio inspirals. We pursue quantities in both the dissipative and conservative sectors using an expansion procedure for the MST solutions in the RWZ formalism. On the dissipative side, these solutions immediately yield PN series for the timeaveraged fluxes using standard formulas. Because the process requires only a finite number of modes, the results can be taken to high PN order, as well as high (if not arbitrary) order in the eccentricity of the orbit. However, local conservative changes involve an infinite number of modes, increasing the computational complexity by an order of magnitude. Nevertheless, we employ several computational simplifications to advance the state of the art for the redshift invariant. We conclude by discussing the spin precession invariant and local selfforce, as well as future application to the more complicated case where the central black hole has spin. [Preview Abstract] 
Sunday, April 19, 2020 11:09AM  11:21AM Live 
H16.00003: Effective FlyBy Waveforms Nicholas Loutrel Binary black holes may be formed dynamically in globular clusters, with large (close to unity) orbital eccentricity and emitting gravitational waves within the detection band of ground based detectors. The gravitational waves from such sources resemble more a discrete set of bursts than the continuous signal of their quasicircular counterparts. I here present new analytic waveform models to accurately capture the bursts of radiation from such systems by treating the leading postNewtonian order orbital evolution as a perturbation of a parabolic flyby, leading to an effective flyby (EFB) formalism. I discuss the comparison of these EFB waveforms to flyby waveforms from numerical relativity, and the prospect of using them for detection. [Preview Abstract] 
Sunday, April 19, 2020 11:21AM  11:33AM Live 
H16.00004: Neutron Stars in Effective FlyBys Jose Arredondo, Nicholas Loutrel Eccentric compact object (CO) binaries, such as black hole  neutron star binaries, pose not only a challenge for gravitational wave detectors, but also provide a probe into the structure of COs. At closest approach between the objects, an fmode is excited in the neutron star while a burst of gravitational radiation is emitted. In order to model the signals from these eccentric binaries falling in the LIGO band, we have developed an effective flyby (EFB) waveform for a black hole  neutron star binary in the postNewtonian formalism. This waveform model captures the gravitational wave emission from the fmode and its effect on the orbital phase. We discuss the prospect of constraining the neutron star equation of state with these EFB waveforms. [Preview Abstract] 
Sunday, April 19, 2020 11:33AM  11:45AM On Demand 
H16.00005: Evolution of Highly Eccentric Binary Orbits with Radiation Reaction 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 due to 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 of general mass ratios, focussing on gravitational radiation reaction to high postNewtonian orders. We will report on the current status of this work. [Preview Abstract] 
Sunday, April 19, 2020 11:45AM  11:57AM 
H16.00006: Analytic Modeling of Eccentric Binary Black Holes: from Inspiral to Merger and Ringdown Dillon Buskirk, Dr. Maria BabiucHamilton Binary black hole (BBH) are primary sources of gravitational waves (GW). Their evolution is highly nonlinear and numerical relativity (NR) is required to simulate this problem. However, this is computationally expensive, and it is imperative for GW modeling to create analytic formulations that produce results comparable to NR simulations. BBH dynamics are separated into three phases: inspiral, merger, and ringdown. In a recent work, we used the postNewtonian (PN) theory for the inspiral phase, and the generic implicit rotating source (gIRS) formulation for the merger, to build complete analytical GW templates for BBH evolution. Here we expand our work to include eccentric orbits in the inspiral phase, which greatly complicates the calculations. We develop an analytic method to speed up the evaluation of the Bessel functions without loss of accuracy. For the merger and ringdown we use the Backwardsonebody (BOB) approach. This new model, introduced by S. McWilliams, provides analytic GW based on physical principles. We match the BOB model with the circularized eccentric inspiral, to obtain a complete waveform. Next, we compare our waveforms with the gIRS model and the Simulating Extreme Spacetimes (SXS) data produced using numerical relativity simulations, finding agreement. [Preview Abstract] 
Sunday, April 19, 2020 11:57AM  12:09PM 
H16.00007: Lining Up Your Shots: Capturing the Interesting Part of Highly Eccentric EMRI Gravitational Wave Snapshots Aaron Johnson, Daniel Oliver, Daniel Kennefick Extreme mass ratio inspirals (EMRIs) with highly eccentric orbits, while not individually resolvable, collectively will constitute a noise source for LISA, the proposed spacebased gravitational wave detector. Previous characterizations of the noise source have used a Newtonian order approximation. We seek to improve this estimate by using a frequency domain, Teukolsky based approach or semirelativistic approximation. At high eccentricities, the largest mode may reside at the 10,000th or even the 100,000th radial harmonic mode for eccentricities of 0.999 and 0.9999 respectively, but fortunately the lower modes are mostly negligible compared to the peak modes. Here we present a method to predict where the peak mode is going to be so that the negligible modes can be skipped and discuss the methods currently implemented in our Teukolsky based code. [Preview Abstract] 
Sunday, April 19, 2020 12:09PM  12:21PM Not Participating 
H16.00008: Imprint of the KozaiLidov Mechanism on the Gravitational Waveform Rohit Chandramouli, Nicolas Yunes Gravitational waves emitted by an inner binary in a hierarchical triple are interesting astrophysical candidates for future detectors like LISA. In the presence of the third body, the inner binary can undergo oscillations in eccentricity due to the KozaiLidov (KL) mechanism, which is one of the astrophysical channels for the formation of eccentric binaries. In this talk, I will present our efforts towards an analytic calculation of the effect of KL oscillations on the gravitational waveform. The separability of timescales of the system implies that multiplescale analysis can be used to combine the effects of both radiation reaction and KL oscillations. 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. [Preview Abstract] 
Sunday, April 19, 2020 12:21PM  12:33PM Not Participating 
H16.00009: Probing Astrophysics and Fundamental Physics with Accurate Gravitational Waveforms for Eccentric Compact Binary Inspirals Nicolas Yunes, Blake Moore The growing number of gravitational wave observations suggests the possibility of detecting signals from binaries with nonnegligible orbital eccentricity in the near future. Models that incorporate the effects of small eccentricities ($e < 0.2$) exit, but they may not be sufficient to analyze waves from systems with moderate eccentricity. We recently developed a model that faithfully accounts for eccentric corrections in the moderate eccentricity regime ($e < 0.8$ for certain source masses) at 3rd postNewtonian order. In this talk, I will first review the waveform construction, and then focus on the astrophysical and fundamental physics that can be probed if we detect such eccentric signal, based on a Bayesian parameter estimation study. I will first discuss the accuracy to which eccentricity can be measured given a moderately eccentric signal, as well as the smallest eccentricity that can be measured given a slightly eccentric signal, and the systematic biases that can be incurred if a quasicircular model is used to extract an eccentric signal. I will conclude with a discussion of how eccentricity enhances our ability to test General Relativity, focusing on tests of scalartensor theory and EinsteindilatonGaussBonnet gravity. [Preview Abstract] 
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