Search Talks

The dynamics of black-hole binaries is a very complex problem which has been solved only very recently through time-expensive numerical-relativity calculations. In spite of this mathematical complexity many results of these calculations can be accurately reproduced with phenomenological approaches based on test particles combined with Post-Newtonian theory and black-hole perturbation theory. In this talk I will focus on effective-one-body models, which have proved a useful and fast tool to accurately reproduce numerical-relativity waveforms. In particular I will present a novel, self-consistent effective-one-body model for spinning black-hole binaries, and show that this model does not suffer from the shortcomings of the existing models which have been put forward in the literature.

The quest for gravitational waves from binary inspiral is performed via matched filtering and thus requires a detailed knowledge of the signal. For non-precessing binaries complete analytic waveforms exist from inspiral to merger and ring-down. Here we present complete waveforms for generically spinning equal mass systems.They have been constructed by bridging the gap between the analytically known inspiral phase described by spin Taylor (T4) approximants in the restricted waveform approximation and the ring-down phase. These two phases are connected by a phenomenological intermediate phase calibrated by confrontation with numerically generated waveforms.The values of the overlap integral between numerical waveforms and our semi-analitic ones range between 0.96 and 0.99.

Recently generated asymptotic expansions zanolin et al. arXiv:0912.0065 [gr-qc] showa frequentist approach to go beyond Fisher information assessments of the accuracy for maximum likelihood parameter estimations. In this talk we describe the application of these techniques to directional reconstruction fornumerical relativity waveforms.

Most searches with ground-based detectors for gravitational-wave signals from the inspirals of stellar-mass compact binaries use template based methods. Those work well for non-spinning systems but since the dimensionality of the parameter space of spinning waveforms is large a template bank search is not feasible. We describe Bayesian and Markov-chain Monte-Carlo methods for parameter estimation of spinning waveforms using hybrid spinning waveforms matching the ringdown from Numerical Relativity results. We compare those results when using post-Newtonian only waveforms. We explore the parameter space and discuss different ways to overcome its high dimensionality and multi-modality.

Black hole-neutron star binary (BHNS) mergers are likely sources for detectable gravitational radiation and candidate engines for short-hard gamma-ray bursts. However, accurate modeling of these mergers requires fully general relativistic simulations, incorporating both relativistic hydrodynamics for the matter and Einstein's field equations for the (strong) gravitational fields. I will review techniques and results from recent fully general relativistic BHNS merger simulations. These simulations examine the effects of the BH:NS mass ratio, BH spin, and NS equation of state, focusing on both the gravitational waveforms and remnant disk.

The familiar post-Newtonian inspiral description of a binary neutron star system is sufficient for detection in current instruments. However, as we consider making astrophysical measurements using advanced detectors, the effects of matter and strong gravity on gravitational wave signals may become significant. I will review recent work modelling the waveforms produced by the inspiral and coalescence of binary neutron stars. In the mid-to-late inspiral this includes modifications to the post-Newtonian waveform models from tidal deformations. In the late inspiral and coalescence, numerical simulations are exploring a range of masses, mass ratios, equations of state, and magnetic fields. In some circumstances a hypermassive remnant produces significant additional signal after the merger. Numerical simulation results also link neutron-star merger to potential counterpart signals.

A coherent multi-site search is expected to be more powerful than itscoincident counterpart in discriminating gravitational wave (GW) signals fromthe noise background. This is because the former tests the consistency of thesignals' amplitudes phases and time-delays across the sites with those expected from a real GW source. However the coherent statistic that is optimalin Gaussian noise is not guaranteed to perform as well in real data which arenon-Gaussian. Here we introduce an alternative coherent statistic for searchingcompact binary coalescence (CBC) signals that includes chi-square andnull-stream discriminators for non-Gaussian features in the data. Thisstatistic has been found to perform better than coincident statistics exploredin real data. This alternative coherent statistic is being used in ongoinginspiral-merger-ringdown searches in LIGO-Virgo data and is expected to beuseful in bridging the performance gap between the coincident CBC searchpipeline and the coherent burst search pipeline for detecting signalshigh-mass CBCs especially for systems with total-mass tending toward ahundred solar masses that have only a few signal cycles in band. We planto use this statistics in future NINJA analysis.

In this talk we present the motivation behind our implementation of and results from a coherent search for spinning compact binary coalescences. Our method uses the Physical template family of waveforms which describe binaries where only one of the objects has spin. In addition we discuss the possibility of extending thissearch to incorporate template waveforms for precessing black hole mergers derived from numerical relativity.

We present simulations of non-spinning unequal mass black-hole binaries with mass ratio q=1/4 covering approximately 11 orbits prior to coalescence and merger obtained with the moving puncture technique. Accuracy of the simulations and matching to post-Newtonian waveforms is discussed.