Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session S15: Gravitational Waveform Modeling |
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Room: 103 |
Monday, April 7, 2014 1:30PM - 1:42PM |
S15.00001: Applying Late-Merger IRS Multi-Mode Templates to Parameter Estimation Bernard Kelly, John Baker The IRS picture [Baker et al. PRD 78:044046 (2008); Kelly et al. 84:084009 (2011)] visualises black-hole-binary late-inspiral/merger/ringdown gravitational waveforms as being generated by a single ``implicit rotating source,'' with the most important waveform angular modes being locked in phase through merger into ringdown. This led to the development of late-merger/ringdown waveform templates for the dominant modes of the binary for nonspinning black holes, and for holes with aligned (non-precessing) spins. We report on the current status of the original IRS model as used in multi-mode templates. We consider its performance for the most important $|m| = \ell$ modes. We also consider the inconvenient behavior of $|m| < \ell$ waveform modes, focusing on their physicality, how they may be treated in the IRS picture, and implications for other approaches to constructing template banks that reach beyond the dominant quadrupole radiation for black-hole binary mergers. [Preview Abstract] |
Monday, April 7, 2014 1:42PM - 1:54PM |
S15.00002: Extending empirical models for binary black hole merger-ringdown waveforms to include late inspiral John Baker, Bernard Kelly Analytic and empirical models for gravitational merger waveforms are a valuable tool for efficiently encoding the information from expensive numerical relativity simulations. Such models can be applied as a practical intermediary for gravitational-wave data analysis studies and may provide interesting heuristics for interpretation of waveform phenomenology. In the Implicit Rotating Source description of waveforms, we exploit the simple structure of computed spherical harmonic components for near-circular mergers, to represent the waveforms through the secular development of a circularly polarized waveform. We have previously presented waveform models for the most powerful merger-ringdown portions of these waveforms following an approach which first describes rotational frequency as a function of time, then treats amplitude in terms of the phasing behavior. A parametric representation of time and frequency allows useful extension of the waveforms back through the late insprial. We present results showing precise fits for numerical relativity $(\ell=2,m=2)$ waveform phasing with the extended model. [Preview Abstract] |
Monday, April 7, 2014 1:54PM - 2:06PM |
S15.00003: Effective-one-body modeling of generic black-hole binaries Andrea Taracchini We report on the current status of the effective-one-body description of gravitational-wave emission from black-hole binaries. An ongoing effort at the interface between analytical and numerical relativity aims at the construction of an accurate model that could be used for detection and parameter estimation with advanced ground-based detectors. We will show how the effective-one-body model has been extended to generic mass ratios and spin magnitudes in nonprecessing systems by calibrating it to a large catalog of numerical-relativity waveforms. We will also discuss how to build precessing waveforms starting from such accurate nonprecessing model, and show comparisons with numerical relativity. [Preview Abstract] |
Monday, April 7, 2014 2:06PM - 2:18PM |
S15.00004: Spin Precession: Breaking the degeneracy between Neutron Stars and Black Holes Katerina Chatziioannou, Neil Cornish, Antoine Klein, Nicolas Yunes Gravitational waves from spin-precessing compact binaries carry a lot of information about the system that emitted them. However, our ability to extract the system's parameters, is related to the accuracy of the models we use when analyzing the data. More specifically, models that do not capture the information that comes from the precession of the orbital plane due to spin-orbit coupling lead to degeneracies between neutron stars and black holes. In this talk I will describe how if one includes such precessional effects in the models, this degeneracy breaks, allowing us to distinguish between standard neutron stars and alternative possibilities, such as black holes or exotic neutron stars with large masses and spins. [Preview Abstract] |
Monday, April 7, 2014 2:18PM - 2:30PM |
S15.00005: Surrogate models for EOB gravitational waveforms Scott Field, Chad Galley, Jan Hesthaven, Jason Kaye, Manuel Tiglio Parameterized gravitational waves models specified through ordinary differential equations often carry large evaluation costs. These costs constitute a major bottleneck for many important applications such as Bayesian parameter estimation which can require thousands or millions of model evaluations. In these multi-query contexts the cost per model evaluation dominates the overall simulation time. I will describe how surrogate models can be used to quickly evaluate an underlying parameterized waveform model. Surrogate models are built by accumulating model evaluations at a representative few parameter values and tying together these samples. This offline building stage needs to be performed only once, while its subsequent online use is computationally inexpensive to evaluate. I will show how surrogates can be used to speed up the generation of effective one body waveforms by many orders of magnitude without sacrificing accuracy. [Preview Abstract] |
Monday, April 7, 2014 2:30PM - 2:42PM |
S15.00006: Surrogate models for numerical relativity waveforms Chad Galley, Jonathan Blackman, Scott Field, Mark Scheel, Bela Szilagyi, Manuel Tiglio Simulating binary black hole coalescences involves solving Einstein's equations with large-scale computing resources that can take months to complete for a single numerical solution. This engenders a computationally intractable problem for multiple-query applications related to parameter space exploration, data analysis for gravitational wave detectors like LIGO, and semi-analytical waveform fits. Recently, reduced order modeling techniques were used to build surrogate models that substitute having to solve the original ordinary/partial differential equations which generate the waveform itself. Whereas the original waveform computation can carry large evaluation costs, the surrogate can be evaluated very quickly and often without loss of accuracy. I discuss a surrogate model for numerical relativity waveforms of non-spinning binary black hole coalescences. This surrogate can be used to generate numerical relativity waveforms with about 15 cycles for mass ratios in the range of 1 to 10 in the matter of milli-seconds as opposed to months compared to the Spectral Einstein Code. The results of this work represent a significant advance in using numerical relativity waveforms for multiple-query applications. [Preview Abstract] |
Monday, April 7, 2014 2:42PM - 2:54PM |
S15.00007: Self--force gravitational waveforms for extreme and intermediate mass ratio inspirals: importance of spin--orbit coupling Gaurav Khanna, Lior M. Burko We consider the importance of spin--orbit coupling for gravitational-wave dephasing for an extreme or intermediate mass ratio system moving along a quasi-circular Schwarzschild orbit. For the first-order self force we use the fully relativistic force in the Lorenz gauge for eternally circular geodesics. The second-order self force is modeled with its 3.5 post Newtonian counterpart, and spin--orbit coupling is calculated with the Papapetrou equations. We evolve the system using the osculating orbits method, and obtain the gravitational waveforms, whose phase includes all the terms ---within our approximation (and using the self force along circular geodesics)--- that are independent of the system's mass ratio. We find the partial dephasing due to the following terms, all of which contribute at the same order in the mass ratio (i.e., at order unity): the first-order conservative self force, the second-order dissipative self force, and spin--orbit coupling. We discuss the relative importance of each of these effects. [Preview Abstract] |
Monday, April 7, 2014 2:54PM - 3:06PM |
S15.00008: Self-forced evolutions for comparable and intermediate mass ratio coalescences Eliu Huerta, Prayush Kumar, Jonathan Gair, Sean McWilliams The quest for intermediate mass black holes (IMBHs) has been revived by the recent detection of hyper-luminous X-ray sources. To confirm that these sources host IMBHs, we require a robust measurement of the mass of the central object. Advanced gravitational wave detectors may detect from 1-30 events per year that involve the coalescence of stellar mass black holes with IMBHs in globular clusters. Furthermore, it is expected that neutron star-black hole mergers will have electromagnetic counterparts, whose detection will provide important information about the astrophysical properties of their progenitors. Detecting these events and learning about the stellar dynamics of their environments require accurate waveform models. After discussing the inadequacy of post-Newtonian calculations and black hole perturbation theory to capture the true dynamics of these sources, we introduce a waveform model that includes the inspiral, merger and ringdown in a physically consistent way. We show that our self-forced evolution model provides a robust and accurate framework to model these type of events, and explore the information that could be extracted from the observation of these events using a four detector network in the context of second and third generation gravitational wave detectors [Preview Abstract] |
Monday, April 7, 2014 3:06PM - 3:18PM |
S15.00009: Post-newtonian approach for spin effects in compact objects binaries Sylvain Marsat The upcoming new generation of ground-based detectors such as LIGO and VIRGO is likely to allow for the first direct detections of gravitational waves, opening a new window on the universe and on extreme events in the regime of strong-field gravity. Compact object mergers are the most promising sources for these detectors, as for the future space-based experiments. The faintness of the signal has driven a lot of effort to model it as accurately as possible, which is done using a combination of analytical and numerical methods. In this talk, we will address the question of the analytical modelling of spin-orbit effects in the inspiral of compact binaries, within the post-Newtonian approach. From astrophysical observations, black holes spins are expected to be generically close to maximal, and they play an important role by causing orbital plane precession modulating the signal. After a presentation of the formalism, we will report results recently obtained for the spin-orbit dynamics at higher order, as well as the new corresponding contributions to the emitted flux and phasing of the binary, and discuss briefly their importance. [Preview Abstract] |
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