Bernard J. Kelly

Toward faithful templates for non-spinning binary black holes using the effective-one-body approach

im izing only overtim eofarrivaland initialphase.W eobtain thisresultby sim ply adding a 4-post- Newtonian ordercorrection in theEO B radialpotentialand determ iningthe(constant)coecientby im posing high-m atching perform anceswith num ericalwaveform sofm assratios m 1=m 2 = 1;3=2;2 and 4, m 1 and m 2 being the individualblack-hole m asses. Thenalblack-hole m ass and spin predicted by the num ericalsim ulations are used to determ ine the ringdown frequency and decay tim eofthreequasi-norm al-m ode dam ped sinusoidsthatare attached to theEO B inspiral-(plunge) waveform at the EO B light-ring. The EO B waveform s m ight be tested and further im proved in thefutureby com parison with extrem ely long and accurateinspiralnum erical-relativity waveform s. They m ay already be em ployed for coherent searches and param eter estim ation ofgravitational wavesem itted by non-spinningcoalescing binary black holeswith ground-based laser-interferom eter detectors.

Black-hole binaries, gravitational waves, and numerical relativity

Understanding the predictions of general relativity for the dynamical interactions of two black holes has been a long-standing unsolved problem in theoretical physics. Black-hole mergers are monumental astrophysical events, releasing tremendous amounts of energy in the form of gravitational radiation, and are key sources for both ground- and space-based gravitational-wave detectors. The black-hole merger dynamics and the resulting gravitational wave forms can only be calculated through numerical simulations of Einsteins equations of general relativity. For many years, numerical relativists attempting to model these mergers encountered a host of problems, causing their codes to crash after just a fraction of a binary orbit could be simulated. Recently, however, a series of dramatic advances in numerical relativity has allowed stable, robust black-hole merger simulations. This remarkable progress in the rapidly maturing field of numerical relativity and the new understanding of black-hole binary dynamics that is emerging is chronicled. Important applications of these fundamental physics results to astrophysics, to gravitational-wave astronomy, and in other areas are also discussed.

Testing gravitational-wave searches with numerical relativity waveforms: results from the first Numerical INJection Analysis (NINJA) project

The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave data analysis communities. The purpose of NINJA is to study the sensitivity of existing gravitational-wave search algorithms using numerically generated waveforms and to foster closer collaboration between the numerical relativity and data analysis communities. We describe the results of the first NINJA analysis which focused on gravitational waveforms from binary black hole coalescence. Ten numerical relativity groups contributed numerical data which were used to generate a set of gravitational-wave signals. These signals were injected into a simulated data set, designed to mimic the response of the initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this data using search and parameter-estimation pipelines. Matched filter algorithms, un-modelled-burst searches and Bayesian parameter estimation and model-selection algorithms were applied to the data. We report the efficiency of these search methods in detecting the numerical waveforms and measuring their parameters. We describe preliminary comparisons between the different search methods and suggest improvements for future NINJA analyses.

A data-analysis driven comparison of analytic and numerical coalescing binary waveforms: nonspinning case

We compare waveforms obtained by numerically evolving nonspinning binary black holes to postNewtonian (PN) template families currently used in the search for gravitational waves by groundbased detectors. We find that the time-domain 3.5PN template family, which includes the inspiral phase, has fitting factors (FFs) ≥ 0.96 for binary systems with total mass M = 10–20M⊙. The timedomain 3.5PN effective-one-body template family, which includes the inspiral, merger and ring-down phases, gives satisfactory signal-matching performance with FFs ≥ 0.96 for binary systems with total mass M = 10–120M⊙. If we introduce a cutoff frequency properly adjusted to the final black-hole ring-down frequency, we find that the frequency-domain stationary-phase-approximated template family at 3.5PN order has FFs ≥ 0.96 for binary systems with total mass M = 10–20M⊙. However, to obtain high matching performances for larger binary masses, we need to either extend this family to unphysical regions of the parameter space or introduce a 4PN order coefficient in the frequencydomain GW phase. Finally, we find that the phenomenological Buonanno-Chen-Vallisneri family has FFs ≥ 0.97 with total mass M = 10–120M⊙. The main analyses use the noise spectral-density of LIGO, but several tests are extended to VIRGO and advanced LIGO noise-spectral densities.

Modeling Kicks from the Merger of Nonprecessing Black Hole Binaries

Several groups have recently computed the gravitational radiation recoil produced by the merger of two spinning black holes. The results suggest that spin can be the dominant contributor to the kick, with reported recoil speeds of hundreds to even thousands of kilometers per second. The parameter space of spin kicks is large, however, and it is ultimately desirable to have a simple formula that gives the approximate magnitude of the kick given a mass ratio, spin magnitudes, and spin orientations. As a step toward this goal, we perform a systematic study of the recoil speeds from mergers of black holes with mass ratio q ? m1/m2 = 2/3 and dimensionless spin parameters of a1/m1 and a2/m2 equal to 0 or 0.2, with directions aligned or antialigned with the orbital angular momentum. We also run an equal-mass a1/m1 = -a2/m2 = 0.2 case, and find good agreement with previous results. We find that, for currently reported kicks from aligned or antialigned spins, a simple kick formula inspired by post-Newtonian analyses can reproduce the numerical results to better than ~10%.

Binary black hole late inspiral: Simulations for gravitational wave observations

Coalescing binary black hole mergers are expected to be the strongest gravitational wave sources for ground-based interferometers, such as the LIGO, VIRGO, and GEO600, as well as the space-based interferometer LISA. Until recently it has been impossible to reliably derive the predictions of general relativity for the final merger stage, which takes place in the strong-field regime. Recent progress in numerical relativity simulations is, however, revolutionizing our understanding of these systems. We examine here the specific case of merging equal-mass Schwarzschild black holes in detail, presenting new simulations in which the black holes start in the late-inspiral stage on orbits with very low eccentricity and evolve for

Consistency of post-Newtonian waveforms with numerical relativity.

\ensuremath{\sim}1200M

Mergers of non-spinning black-hole binaries: Gravitational radiation characteristics

through

Samurai project: Verifying the consistency of black-hole-binary waveforms for gravitational-wave detection

\ensuremath{\sim}7

Status of NINJA: the Numerical INJection Analysis project

orbits before merging. We study the accuracy and consistency of our simulations and the resulting gravitational waveforms, which encompass